Radiographic Evaluation of the Wrist: a Vanishing Art Rebecca A

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Radiographic Evaluation of the Wrist: A Vanishing Art Rebecca A. Loredo, MD,* David G. Sorge, MD, Lt. Colonel,† and Glenn Garcia, MD‡

he intricate anatomy and compartmentalization of struc- interpretation of standard or MR arthrograms and for identi- Ttures in the wrist are somewhat daunting. As in other joints, fying various patterns of arthritic involvement.2 The com- the radiographic appearance of disease processes affecting the partments are as follows: wrist is very much dependent on the articular and periarticular soft tissue and osseous anatomy. Therefore, abbreviated discus- 1. Radiocarpal compartment sions of the pertinent anatomy are included within the introduc- 2. Midcarpal compartment tion with more speciﬁc anatomic discussions within the text as a 3. Pisiform-triquetral compartment prelude to certain conditions affecting the wrist. 4. Common carpometacarpal compartment 5. First carpometacarpal compartment 6. Intermetacarpal compartments Anatomy of the Wrist 7. Inferior (distal) radioulnar compartment

Osseous Anatomy In daily clinical practice, the most important compart- The osseous structures of the wrist are the distal portions of the ments are the radiocarpal, midcarpal, and distal radioulnar radius and ulna, the proximal and distal rows of carpal bones, compartments. The radiocarpal compartment (Fig. 2) lies and the bases of the metacarpals (Fig. 1). The proximal row of between the proximal carpal row and the distal radius and carpal bones consists of the scaphoid, lunate, triquetrum, and the triangular fibrocartilage, which is fibrocartilaginous tis- the pisiform. The distal row of carpal bones contains the trape- sue that extends from the ulnar side of the distal aspect of the zium, trapezoid, capitate, and hamate bones. The distal row of radius to the base of the ulnar styloid. A meniscus attaches to bones articulates with the metacarpal bases. The bases of the the triquetrum and is located between the radiocarpal and metacarpals articulate with the distal row of carpal bones and pisiform-triquetral compartments, in most cases. In the coro- with each other. The proximal carpal row is termed an interca- nal plane, the radiocarpal compartment forms a C-shaped lated segment because forces acting on its proximal and distal cavity bordered by the radial collateral ligament on the radial articulations determine its position.1 This aspect of the osseus side and the point at which the meniscus is attached to the anatomy becomes important when considering the pattern of triquetrum on the ulnar side.2 On its ulnar side, two projec- collapse that occurs in the different types of wrist instability. tions are noted from the joint space, a proximal prestyloid recess between the meniscus and the triangular fibrocartilage Articular Compartmental Anatomy and a distal recess that extends to the triquetrum; these latter The wrist joint is separated into a number of compartments projections form a Y-shaped area toward the ulnar wrist. The by the many ligaments that attach to the carpal bones (Fig. 2). prestyloid recess abuts the ulnar styloid and, on its radial These compartments are of considerable significance for the aspect, the radiocarpal compartment contacts the “bare area” (area unprotected by articular cartilage) of the scaphoid and the radial styloid.2 These relationships become important *Department of Radiology, University of Texas Health Science Center, San when articular diseases such as rheumatoid arthritis affect the Antonio, TX. wrist.2 †Department of Radiology, Wilford Hall Medical Center, Lackland AFB, TX. ‡Department of Radiology, University of Texas Health Science Center, San The midcarpal compartment (Fig. 2) includes articulations Antonio, TX. between the proximal and the distal carpal rows. The distal The opinions and assertions expressed herein are the private views of the pole of the scaphoid articulates with the two trapezial bones, authors and are not to be construed as official or as representing the termed the trapezioscaphoid space. The proximal end of the views of the Air Force or the Department of Defense. scaphoid combines with the lunate and triquetrum to form a Address reprint requests to Rebecca A. Loredo, MD, Associate Professor and Chief of Musculoskeletal Imaging, Department of Radiology, University concavity that articulates with the combined capitate and 2 of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, hamate. Texas 78284. E-mail: [email protected] The inferior radioulnar compartment (Fig. 2) lies between

extrinsic ligaments because they connect the distal portion of the radius and the carpal bones. Two intrinsic ligaments join the bones of the proximal carpal row, the scapholunate interosseous ligament (joining the proximal surfaces of the scaphoid and lunate) and the lunotriquetral interosseous ligament (joining the proximal surfaces of the lunate and triquetrum) (Fig. 3).1 These ligaments connect the bones from their palmar to dorsal surfaces. The intrinsic scapholunate ligament complex and the lunotriquetral complex each con- sist of dorsal, palmar, and proximal (membranous) components.3 When intact, they separate the radiocarpal and midcarpal compartments of the wrist. The ulnar ligamentous complex (ulnocarpal ligaments) is largely synonymous with the triangular fibrocartilage com- Figure 1 Gross anatomic section through the wrist illustrating the plex (TFCC), comprising the triangular fibrocartilage (TFC) osseous anatomy. The proximal row consists of the scaphoid (S), proper (the articular disk) and the dorsal radioulnar liga- lunate (L), triquetrum (tq), and pisiform (not shown). The distal ment, volar radioulnar ligament, ulnolunate ligament, ul- row includes the trapezium (tm), trapezoid (tz), capitate (C) and notriquetral ligament, ulnar collateral ligament, and the me- hamate (H). R ϭ radius, U ϭ ulna, 1st ϭ base of thumb metacarpal, niscus homologue.4 The literature includes the sheath of the ϭ 5th base of small finger metacarpal. (Color version of figure is extensor carpi ulnaris tendon in the description of the available online.) TFCC.5 The distal radioulnar joint is stabilized by the TFCC.5 The complex arises from the medial margin of the distal radius to the cartilage-covered surfaces of the radius (sigmoid notch) insert in the fovea at the base of the ulnar styloid process. and the ulnar head, surrounded by a loose capsule. When the From the ulnar side, the ulnocarpal ligaments arise and insert articulating surface between the ulna and the sigmoid notch strongly on the triquetrum (the ulnotriquetral ligament) and is intact, the radius translates on the seat of the ulnar head. weakly on the lunotriquetral interosseous ligament and on The synovial cavity of this compartment is described as L- the lunate (the ulnolunate ligament). Further ulnarly, the shaped in coronal section, as it extends between the distal TFCC becomes thickened again as it is joined by fibers of the radius and ulna and then across the distal ulna.2 This com- ulnar collateral ligament to form the meniscus homologue, partment is separated from the radiocarpal joint by the trian- and it courses distally to insert on the triquetrum, hamate, gular fibrocartilage. and base of the fifth metacarpal bone (meniscus reflection). Ligamentous Anatomy On its dorsolateral side, the TFCC is incorporated into the floor of the sheath of the extensor carpi ulnaris tendon. The Detailed review of the ligamentous anatomy of the wrist is beyond the scope of this article. Rather, the discussion will be limited to the scapholunate ligament, lunotriquetral ligament, and the triangular fibrocartilage complex. The ligaments of the wrist have been classified into intrinsic ligaments because they arise and insert on carpal bones and

Figure 3 Intrinsic ligaments. Joining the proximal surfaces of the scaphoid (S) and lunate (L) is the scapholunate interosseous ligament; and, joining the proximal surfaces of the lunate (L) and triquetrum (T) is the lunotriquetral interosseous ligament. They separate the radiocarpal and midcarpal compartments. In the distal Figure 2 Articular compartmental anatomy. The wrist is separated carpal row, three intrinsic ligaments unite the trapezium (TR) and into compartments by ligaments that attach to carpal bones. The trapezoid (TZ) bones, the trapezoid and capitate bones, and the radiocarpal, midcarpal, pisiform-triquetral, common carpometacar- capitate with the hamate bones. These distal interosseous ligaments pal, ﬁrst carpometacarpal, intermetacarpal, and inferior radioulnar do not prohibit midcarpal and common carpometacarpal compart- compartments are shown. (Reproduced with permission.19) ment communication. (Reproduced with permission.1) 250 R.A. Loredo, D.G. Sorge, and G. Garcia

Figure 4 Standard radiographic evaluation of the wrist. The routine radiographic evaluation includes (from left to right) posteroanterior, lateral, and oblique radiographs.

TFC may be fenestrated centrally, especially in middle-aged at 90° to the arm.6 With the forearm in this pronated posi- and elderly persons. It functions as a cushion between the tion, the ulnar styloid is seen in profile. When views are taken ulna proximally and the carpus, primarily the triquetrum, in supination, the ulnar styloid overlaps the central portion of distally. It is a major stabilizer of the distal radioulnar joint.2,5 the distal ulna. With the wrist in the neutral position, one- half or more of the lunate should contact the distal radial Imaging of Osseous articular surface.1 and Articular Structures Normal Arcs of the Wrist Three smooth carpal arcs are formed on the neutral PA view Radiographic Views along the radiocarpal and midcarpal joints (Fig. 6). Arc 1 In most situations, standard radiographic evaluation of the follows the proximal surfaces of the scaphoid, lunate, and wrist includes posteroanterior, oblique, and lateral radio- triquetrum; arc 2 is along the distal surfaces of these same graphs (Fig. 4). Additional exams may include radial or ulnar carpal bones, and arc 3 follows the curvature of the proximal deviation views, carpal tunnel view, carpal bridge view, spe- surfaces of the capitate and hamate.7 In the normal situation, cial scaphoid views, or other specialized techniques.1,6 To on a neutral PA view, these curvilinear arcs are roughly par- avoid diagnostic errors, the routine and specialized tech- allel, without disruption, and the interosseous spaces are niques and significant points of plain film evaluation are re- nearly equal in size. Disruption of these arcs or abnormal viewed. overlapping of adjacent bones on the PA view commonly indicates carpal subluxation or dislocation. There are, how- Posteroanterior Projection ever, two common normal variants that mimic step-offs The posteroanterior (PA) projection (Fig. 5) is obtained with within the carpal arcs (Fig. 7): (1) a triquetrum shorter in its the arm abducted 90° from the trunk and the forearm flexed proximal-distal dimension than the adjacent lunate creates a Radiographic evaluation of the wrist 251

Figure 7 Two common normal variants that mimic step-offs within the carpal arcs: (A) a triquetrum (tq) shorter in its proximal-distal Figure 5 Posteroanterior (PA) views. (A) With the forearm in a dimension than the adjacent lunate (L) creating a lunotriquetral pronated position, the ulnar styloid is seen in profile. (B) When step-off (arrow) of the first carpal arc and a normal second carpal views are taken in supination, the ulnar styloid overlaps the central arc, and (B) a proximally prominent hamate (H) with an apposing portion of the distal ulna. With the wrist in a neutral position, hamate facet on the lunate (L ϭ type II lunate) that produces a one-half or more of the lunate (L) should contact the distal radial bilobate second and third carpal arc using the capitate (C) facet and articular surface. hamate (H) facet along the distal lunate articular surface to create the second carpal arc and the proximal capitate and hamate facets to create the third carpal arc (shown). lunotriquetral step-off of the first carpal arc and a normal second carpal arc and (2) a proximally prominent hamate with an apposing hamate facet on the lunate (type II lunate) Ulnar Variance that produces a bilobate third carpal arc and a smooth second Changes in the length of the ulna relative to the length of the carpal arc if the radial portion (“capitate facet”), rather than radius, designated ulnar variance (Fig. 8), alter the distribu- the hamate facet, of the distal lunate articular surface is used tion of compressive forces across the wrist. Ulnar variance is to create the second carpal arc.7,8 found by extending a line along the distal articular surface of the radius toward the ulna and measuring the distance from Normal Scapholunate Joint Space this line to the distal ulna2 (Fig. 8A). Normally, the radius and The normal scapholunate joint space width is the same as the ulna are almost the same length, although wrist and forearm width between pairs of the other carpal bones. It is measured position and centering of the x-ray tube have been noted to at the center of the scapholunate joint with the beam angled influence the measurements obtained.1 When the ulna is from the dorsal ulnar aspect of the wrist approximately 10°.9 shorter than the radius, the term negative ulnar variance is In its midportion, this space normally measures 2 mm or less and usually remains constant even within the normal range of radial or ulnar deviation of the wrist.9

Figure 8 Ulnar variance on PA wrist views. (A) Normal or neutral variance. Perpendicular to the long axis of the radius, tangential lines are drawn along the ulnar-most extent of the subchondral Figure 6 PA view illustrating the normal three arcs of the wrist. Arc white line of the distal radius and the distal-most extent of the 1 spans the proximal articular surfaces of the scaphoid (S), lunate articular surface of the ulnar dome. The shortest distance between (L), and triquetrum (tq). Arc 2 connects the distal concave surfaces these two lines is the measure of ulnar variance. (B) Negative ulnar of these same bones. Arc 3 outlines the proximal articular surfaces of variance or ulna minus variance (measurement of dotted line). (C) the capitate (C) and hamate (H). Positive ulnar variance (measurement of dotted line). 252 R.A. Loredo, D.G. Sorge, and G. Garcia

Figure 9 Carpal height relative measurements in the left and right hands of the same patient. (A) Left hand carpal height is shown as a line (a) that spans the distance between the base of the third metacarpal and the distal radial articular surface on a PA radiograph. (B) In the right hand, the carpal height (b) is comparatively shorter than that measured in the left hand due to chronic arthritis affecting the right Ͼ left hand. used (Fig. 8B). The consequences of negative ulnar variance Figure 10 Normal lateral views of the wrist. (A) Normal. The distal are increased force applied to the radial side of the wrist and pole of the scaphoid (S) is seen. (B) Example of parallelism of the long axis of the radius with the long axis of the third metacarpal. The to the lunate bone, which may explain the association of pisiform (P) is overlying the distal pole of the scaphoid. negative ulnar variance and Kienböck’s disease.2 With such variance, the TFC is thicker, and abnormalities of the TFCC are uncommon. A consequence of a long ulna, or positive ulnar variance, is the ulnar impaction or ulnar abutment syndrome, with resulting limitation of rotation. The TFC is thinner in instances of positive ulnar variance, and degenerative perforation of this structure (as well as disruption of the lunotriquetral interosseous ligament) may be observed.2 Carpal Height Carpal height is the distance between the base of the third metacarpal and the distal radial articular surface as determined on a PA radiograph of the wrist (Fig. 9). Measurement of carpal height allows comparative quantiﬁcation of carpal collapse in an individual patient over time.7 The carpal height ratio allows com- parison between individuals and it is the carpal height divided by the length of the third metacarpal. Similarly, a carpal height index may be obtained by dividing the carpal height ratio of the diseased wrist by that of the normal hand. Some investigators believe the carpal height index to be the most sensitive for detection of abnormal carpal height in a speciﬁc hand.7 Lateral Projection On a true lateral view of a normal wrist (Fig. 10), the long axis of Figure 11 Normal lateral views illustrating measurements. (A) The the third metacarpal should be coaxial (parallel) with the long axes of the radius, lunate, and capitate should superimpose, with 0 axis of the radius. Another clue to a true lateral view is that the to 30° described as the capitate-lunate angle in normal patients. The pisiform projects directly over the dorsal pole of the scaphoid.5 axis of the capitate (C) is drawn from the center of its head to the Longitudinal Axes of the center of its distal articular surface. The lunate axis (L) is drawn as perpendicular to a line through the center of its proximal and distal Radius, Lunate, and Capitate poles. (B) The scapholunate angle formed between the long axis of In neutral position, the longitudinal axes through the third the lunate and that of the scaphoid (the scapholunate angle) ranges metacarpal, the capitate, the lunate, and the radius all fall on between 30 and 60°. The axis of the scaphoid (S) is shown as a line the same line (Fig. 11A). This ideal situation is actually un- connecting the proximal and distal convex margins. The lunate (L) common, but in most cases the axes are within 10° of this axis is shown as a perpendicular to a line through the center of the line. The axis of the radius is constructed as a line parallel to proximal and distal poles. Radiographic evaluation of the wrist 253

Oblique View The standard oblique view (Fig. 13) is taken in the PA position, with the hand in partial pronation. This view is helpful in detection of scaphoid tuberosity and waist fractures and dorsal margin triquetral fractures. It profiles the scaphotra- pezial, trapeziotrapezoidal, and capitolunate joints and will show the first carpometacarpal and the scaphotrapezoidal joints to best advantage.12 Radial and Ulnar Deviation Views Radiographs obtained with radial and ulnar deviation of the wrist (Fig. 14) are useful for visualizing the carpal bones, Figure 12 Normal measurements of the distal radius. (A) Palmar or particularly the scaphoid, and for assessing carpal mobility. volar tilt of the radius can be measured by obtaining the angle of As the wrist is radially deviated, palmar flexion of the proxi- intersection between a line drawn tangentially across the most distal mal carpal row occurs and the distal pole of the distal scaph- points of the radial articular surface and a perpendicular to the oid rotates into the palm. This causes the normal scaphoid to midshaft of the radius. Normal range is 11° of volar tilt to 4° of dorsal tilt. (B) Radial inclination is measured on PA radiographs and appear foreshortened and exhibit a ring-like appearance of its averages 22° (range ϭ 13 to 30°). (C) Radial length is the distance distal pole as the distal aspect of the scaphoid is seen end-on. between the tip of the radial styloid and the ulnar head articular As the wrist is placed in ulnar deviation, the scaphoid rotates surface. Radial length averages 11 to 22 mm. its distal pole dorsally and ulnarly and it appears to elongate.1 The distances between the carpal bones are normally equal throughout and are unchanged by radial or ulnar deviation. Although widening of the scapholunate distance to between the center of the radial shaft (Fig. 11A). The axis of the lunate 2 and 4 mm may be abnormal, more than 4 mm is definitely can be drawn through the midpoints of its proximal and abnormal.1,6 distal articular surfaces (Fig. 11A). The axis of the capitate is drawn through the centers of its head and its distal articular Radiocarpal Joint View surface (Fig. 11A). The axes of the radius, lunate, and capitate Radiographs obtained by angulating the beam along the axis should superimpose, with 0 to 30° described as the capitolu- of the radiocarpal joint (Fig. 15) allow better visualization of nate angle in normal patients.1

Longitudinal Axis of the Scaphoid The long axis of the scaphoid is represented by a line drawn through the midpoints of its proximal and distal poles (Fig. 11B).1 Another method, proposed by Gilula and Weeks, consists of connecting the ventral convexities of the scaphoid that are visible on the lateral view.10 Normally, the angle formed between the long axis of the radius, the lunate, and the capitate and that of the scaphoid (the scapholunate angle) ranges between 30 and 60° and averages 47°.1

Distal Radial Measurements on Lateral and Posteroanterior Views There are three radiographic measurements that are commonly used to assess the anatomy of the distal radius, namely, palmar tilt, radial inclination, and radial length (Fig. 12).1,11 The normal palmar or volar tilt of the radius can be measured on lateral views by noting the angle of intersection between a line drawn tangentially across the most distal points of the radial articular surface and a perpendicular to the midshaft of the radius (Fig. 12A). This normally ranges from 11° of volar tilt to 4° of dorsal tilt.1 Radial inclination (Fig. 12B) is measured on PA radiographs and averages 22° (range ϭ 13 to 30°). Radial length (Fig. 12C) can be measured along the longitudinal axis of the radius. It is the dis- Figure 13 Normal semipronated oblique radiograph: this view al- tance between the tip of the radial styloid and the ulnar head lows examination of the radial aspect of the wrist, particularly the articular surface. Radial length averages 11 to 22 mm.11 scaphoid (S) and radial styloid (RS). 254 R.A. Loredo, D.G. Sorge, and G. Garcia

Figure 14 Normal radial and ulnar deviation views. (A) Radial and Figure 16 Normal oblique views. (A) Normal AP semisupinated (B) ulnar deviation. In radial deviation, the scaphoid (S) rotates oblique radiograph: in this view, the pisiform bone is separated toward the palm and appears foreshortened. The distal scaphoid is from the remaining carpal bones. The hamate (H), pisiform (P), projected end-on and appears as a circular density (asterisk). The triquetrum (tq), and pisiform-triquetral joint (arrow) are speciﬁcally scapholunate distance remains normal (less than 2 mm). In ulnar seen on this view when evaluating for inﬂammatory disease. (B) deviation, the scaphoid is seen in full length. The scaphoid rotates Normal semipronated oblique radiograph: This view allows exam- (its distal pole moving dorsally and toward the ulna) and appears to ination of the radial aspect of the wrist, particularly the scaphoid (S) elongate (arrows). The scapholunate interval may increase slightly. and radial styloid (arrow).

AP Projection this articulation; a PA roentgenogram may be obtained with To more reliably profile the scapholunate and lunotriquetral the beam angulated 10° proximally, and a lateral radiograph interspaces, an AP view can be obtained. The dorsum of the from the radial side of the joint may be obtained with the hand and wrist are flat against the cassette and the central beam angulated 15° proximally. The PA view elongates the beam is perpendicular to the cassette, centered over the head scaphoid and shortens the capitate, and it may provide better of the capitate. The ulnar styloid projects over the ulnar head 12 visualization of abnormalities of the scaphoid. on an adequate examination.6,9 Semisupinated Oblique View In some cases, oblique projections are taken in both a semipronated oblique and a semisupinated oblique position (Fig. 16). The latter is an anteroposterior oblique view that is taken in partial supination. Synonymous names for this view include the Norgaard view, the “ball-catcher’s” or “You’re in good hands with Allstate” view. It shows the pisiform, palmar aspect of the triquetrum, palmar ulnar surface of the hamate, and it profiles the pisiform-triquetral joint. The Norgaard view is optimal for evaluation of early erosive changes in the hands and wrists of patients with inflammatory arthritides.1,12,13 Lateral Flexion and Extension Views These views demonstrate extension and flexion at the radiocarpal and midcarpal joints in normal wrists (Fig. 17). They can be used in evaluation of carpal instability patterns. In particular, these views can assist in distinguishing between a Figure 15 Normal radiocarpal joint view. (A) The wrist and palm are true instability pattern versus normal variance.12 Extension placed flat on the cassette, as in the PA view. The central beam is angled 25 to 30° toward the elbow and is centered just distal to and flexion of the wrist is recognized by observation of the Lister’s tubercle.12 (B) This view elongates the scaphoid and short- long axis of the third metacarpal extended dorsally and flexed ens the capitate. The radiocarpal (R-C) joint should demonstrate volarly, respectively, relative to the long axis of the radius and minimum bony overlap with parallelism at the (R-C) joint still vis- ulna. In extension, the pisiform remains closely apposed to ible. (Reproduced with permission.12) the triquetrum and projects over the scaphoid as in the neu- Radiographic evaluation of the wrist 255

Figure 19 Normal carpal tunnel view. (A) The long axis of the hand is placed in a vertical direction (hyperextended) and the central ray is directed along the volar aspect at an angle of 25 to 30° to the long 6 Figure 17 (A) Normal lateral volar flexion and (B) dorsiflexion (ex- axis. (B) and (C) In the normal situation, the trapezium (tm), tension) of the wrist occur with motion at the radiocarpal and the scaphoid (S), triquetrum (tq), pisiform (P), and the hook of the 1 midcarpal joints. The distal pole of the scaphoid (S) rotates toward hamate (h) can be delineated. (Reproduced with permission. ) the palm in volar flexion. tral lateral view. In flexion, the pisiform moves away from the The view is taken with the ulnar side of the wrist on the triquetrum, projecting anterior to the scaphoid.12 cassette, in slight ulnar deviation and with approximately 30° supination. The central beam passes tangent to the Carpal Boss View or Off-Lateral View dorsal prominence.12 A slightly supinated off-lateral view (Fig. 18) shows the dorsal carpal boss on a tangent and enables distinction of (1) a separate os styloideum, (2) a bony prominence at- Scaphoid Views tached to the second or third metacarpal base or apposing The standard pronated oblique view generally shows frac- surface of the trapezoid or capitate bones, (3) degenerative tures of the scaphoid tubercle. However, the detection of osteophytes, or (4) a fracture of the dorsal prominence.12 non-displaced scaphoid fractures can be significantly improved with the use of dedicated scaphoid views. These may include magnification views or any combination of the following: PA or AP ulnar deviation view, semipronated oblique view with ulnar deviation, lateral scaphoid view, “stecher position” view, ulnar oblique scaphoid view, 30-degree semipronated oblique PA view, 60-degree semipronated oblique PA view, and elongated oblique view.12 For a more detailed technical discussion of these projections, the reader is referred to standard imaging texts that detail the position and technique for obtaining these views.12

Carpal Tunnel View The carpal tunnel view (Fig. 19) is obtained with the wrist dorsiflexed and either the ventral aspect of the wrist (inferosuperior view) or the palm (superoinferior view) placed on the film cassette. The x-ray beam is angled to Figure 18 Carpal boss view. (A) The wrist is slightly ulnar-deviated profile the carpal tunnel. This view shows the palmar soft with the ulnar side of the wrist on the cassette. Approximately 30° tissues and the palmar aspects of the trapezium, scaphoid supination of the wrist is performed to place the dorsal prominence of the second to third CMC joints tangent to a vertical central ray. tuberosity, capitate, hook of the hamate, triquetrum, and 6,12 The central beam is passed through or tangent to the dorsal prom- the entire pisiform. It should be noted that the carpal inence. (Reproduced with permission.12) (B) In this case, the dorsal tunnel view obtained using the inferosuperior projection, prominence is profiled to show a separate bone, the carpal boss the Gaynor–Hart method, may create a confusing ring (arrow), in tangent. artifact representing an end-on view of the fifth metacarpal 256 R.A. Loredo, D.G. Sorge, and G. Garcia

Figure 20 Normal carpal bridge view. (A) The wrist is flexed to approximately 90° and the central ray is angled at 45° in a superoinferior direction (Reproduced with permission.12) (B) This view Figure 21 Normal clenched fist view. With a tight fist, the contract- demonstrates the scaphoid (S) and lunate (L) and triquetrum (tq) ing tendons and muscles create a force within the wrist that drives and is useful for diagnosing fractures, foreign bodies, and soft-tissue the capitate (C) proximally toward the scapholunate joint. In wrists swelling within the dorsum of the wrist. with a lax or disrupted scapholunate ligament, the joint will widen. In this case, the S-L interval did not abnormally widen. superimposed on the carpal bones, with the central radiolucent area corresponding to the medullary canal.6 First Carpometacarpal Joint View A dedicated anteroposterior projection with beam angula- Carpal Bridge View tion has been used to define changes in the first carpometacarpal joint (Fig. 23).12 Coned frontal and lateral This view profiles dorsal surface fractures of the scaphoid, views of the first carpometacarpal joint allow a more pre- chip fractures of the dorsum of other carpal bones, and it cise analysis of arthritis and traumatic lesions, such as the demonstrates calcifications and foreign bodies in the dorsal Bennett’s fracture.6 soft tissues. On an adequate examination, there is tangential view of the dorsal aspect of the scaphoid, lunate, and triquetrum (Fig. 20). The superimposed capitate should be visible.12

Clenched Fist View The clenched ﬁst view (Fig. 21) is used to widen the scapholunate joint in cases of scapholunate joint diastasis. It can be obtained in a PA or AP position as the central beam passes through the center of the capitate head. With a tight ﬁst, the contracting tendons and muscles create a force within the wrist that drives the capitate proximally toward the scapholunate joint.3,12 In wrists with a lax or disrupted scapholunate ligament, the joint will widen.

Distal Tilt View Figure 22 Normal distal tilt view. (A) The wrist is placed flat on the If there is suspicion of a capitate waist fracture that is not cassette, as it is for a PA view. The central beam is angled 25 to 30° demonstrated on the standard PA view, the distal tilt view toward the fingers, centered on the capitate. (B) This view is used for (Fig. 22) may be utilized. It is a PA projection with the central optimal evaluation of the capitate waist. The capitate (C) is elon- beam angled 25 to 30° toward the fingers, centered on the gated and the scaphoid (S) is foreshortened. (Reproduced with per- capitate.12 mission.12) Radiographic evaluation of the wrist 257

Figure 23 Normal first carpometacarpal joint: specialized view. (A) The hand is hyperextended and the thumb is placed in a horizontal position. The central ray is angled approximately 45° toward the elbow. (Reproduced with permission.6) (B) The ra- Figure 24 The pronator quadratus fat pad. The pronator quadratus diograph shows that the axis of the thumb differs from the other fat stripe is seen on the lateral radiograph of the wrist as a linear or digits. crescent-shaped lucency just anterior to the distal radius and ulna (arrowheads). Fractures involving the distal radius or ulna often show volar displacement (arrows), blurring, irregularity, or obliteration of this fat plane. Radiographic Evaluation of Soft Tissues Wrist Pain — Differential Diagnosis Deep and Superficial Fat Planes Many wrist disorders are readily identified during the initial There are two deep fat planes that are useful in the radio- clinical evaluation. Alternatively, the patient’s history may be graphic evaluation of wrist trauma: the pronator quadra- pathognomonic of a certain injury, such as acute volar ulnar tus fat pad and the scaphoid fat pad. The pronator quad- wrist pain in a golfer after a “dubbed swing”; this being a ratus fat pad (Fig. 24) lies between the pronator quadratus history that is typically associated with fracture of the hook of muscle and the volar tendon sheaths. It is seen on the the hamate. However, some disorders such as carpal instabil- lateral radiograph of the wrist as a linear or crescent- shaped lucency just anterior to the distal radius and ulna. Fractures involving the distal radius or ulna often show volar displacement, blurring, irregularity, or obliteration of this fat plane. The scaphoid fat plane or fat stripe (Fig. 25) is a triangular or linear collection of fat that is bounded by tendons of the abductor pollicis longus and the extensor pollicis brevis and by the radial collateral ligament.1 This fat plane is seen on the PA radiograph as a lucent stripe extending from the radial styloid to the trapezium and almost paralleling the radial aspect of the scaphoid. Fractures of the scaphoid, the radial styloid, and the first metacarpal often result in displacement or obliteration of this fat stripe. On the ulnar aspect of the wrist, fat along the extensor carpi ulnaris tendon is often visible. Inflammatory processes Figure 25 Scaphoid fat stripe. (A) The normal fat stripe is seen par- such as rheumatoid arthritis may obliterate this fat stripe and alleling the lateral aspect of the scaphoid (arrows). (B) A non-dis- thicken the tendon shadow, increasing the amount of soft- placed fracture of the scaphoid is associated with obliteration of the tissue density along the ulnar styloid.1 fat stripe (circle). 258 R.A. Loredo, D.G. Sorge, and G. Garcia

ponents or parts of an articular fracture: (1) the radial shaft, (2) the radial styloid, (3) a dorsal medial fragment, and (4) a palmar medial fragment (Fig. 26). The two medial fragments, along with their ligamentous attachments to the carpus and the ulnar styloid, are termed the medial complex. Anatomic preservation of this medial complex is recognized as an ab- solute requirement for optimal fracture reduction and management. Displacement of these strategically positioned medial fragments also forms the basis for categorizing articular fractures into a classification system (type I, II, III, IV), taking into account features of previous classification systems.15 Type I fractures are minimally displaced, stable after closed reduction, and effectively treated by a short period of cast immobilization (Fig. 27). More commonly, an articular fracture is Type II, which is the dorsally displaced “die-punch fracture”. In such a fracture, the lunate selectively impacts the dorsal medial component, resulting in an unstable fracture characterized by varying degrees of comminution of the dorsal metaphysis, marked dorsal tilting, and considerable shortening of the radius.15 In the majority of type II fractures, the medial complex components are neither widely separated nor rotated (Type IIA), and they are generally amenable to closed reduction and skeletal fixation (Fig. 28). Less commonly, a more comminuted and displaced pattern of dorsal or palmar displacement, the type IIB fracture (Fig. 29), is seen, irreducible by closed methods.15 Figure 26 Basic components of an articular fracture of the radius. A third type of pattern, the type III “spike fracture,” dem- The basic fracture parts are (1) the radial shaft, (2) the radial styloid, onstrates articular disruption similar to that in type II injuries (3) a dorsal medial fragment, and (4) a palmar medial fragment. with added displacement of a “spike fragment,” from the volar metaphysis (Fig. 30). Displacement of the spike fragment may occur at the time of injury or during fracture ma- ity and ulnar-sided wrist pain are less specific; and these conditions are conclusively diagnosed only after careful examination supported by appropriate imaging studies. There are many varied causes of wrist pain and methods of radiographic evaluation, as will be discussed throughout the following pages of this writing.

Traumatic Fractures of the Radius and Ulna—Patterns of Injury Fractures of the distal aspect of the radius are one of the most common skeletal injuries treated by orthopedic surgeons and they account for 17% of all fractures seen in emergency de- partments.14 A multitude of classification systems have been devised based on extraarticular or intraarticular involvement, fracture complexity (degree of displacement and angulation), management issues, mechanism of injury, and treatment op- tions.15 Intraarticular fractures of the distal portion of the radius have been described as two-, three-, four-, or five-part (or more) fractures. Based on stability and reducibility of the fracture, consistent radiographic observations have led to a more universally accepted description of articular injuries (discussion of fracture parts), whereby analysis of the fracture pattern and creation of a subset of articular injury classification has facilitated their treatment.15 Figure 27 Type I fractures are minimally displaced and stable after Despite frequent comminution, there are four basic com- closed reduction. Radiographic evaluation of the wrist 259

Figure 28 Type IIA “die-punch” fracture. The medial complex components are neither widely separated nor rotated and are generally amenable to closed reduction and/or skeletal external ﬁxation. nipulation, which worsens fracture stability and may cause injury to adjacent nerves and tendons.15 The type IV fracture pattern is characterized by wide separation or rotation of the dorsal and palmar medial fragments Figure 30 with severe disruption of the distal radius articulations15 (Fig. Type III “spike fracture.” The articular disruption is similar to that in type II injuries with the added displacement of a “spike 31). A more violent injury accounts for the occurrence of the fragment” (arrow), from the volar metaphysis. type V explosion fracture. This severe injury results from an enormous force, composed of both axial compression and direct crush, with resultant severe comminution often extending from the articular surface of the radius to the diaph- ysis.15 The latter two patterns usually occur in association with severe surrounding soft-tissue trauma.

Figure 29 Type IIB “die-punch” fracture. (A) PA view and (B) oblique Figure 31 Type IV fracture. (A) PA view and (B) lateral view show view show a more comminuted and displaced pattern of dorsal wide separation or rotation of the dorsal and palmar medial frag- displacement. ments with severe disruption of the distal radius articulation. 260 R.A. Loredo, D.G. Sorge, and G. Garcia

impaction (Fig. 33); (2) angulation or tilting of the radial articular surface exceeding 20° in the sagittal plane, which causes a serious disturbance of radiocarpal collinear alignment as well as incongruity of the distal radioulnar joint; and (3) metaphyseal comminution involving both the volar and the dorsal radial cortices as this eliminates an intact bony buttress on which a stable reduction must hinge. Recognition of these radiographic signs of instability is essential for satis- factory management of these injuries.15

Smith’s Fracture The less common Smith’s fracture is a fracture of the distal radial metaphysis or epiphysis, with or without articular involvement, demonstrating palmar displacement or angula- Figure 32 Colles’ fracture. (A) PA oblique and (B) lateral views show tion. The mechanism of injury is hyperﬂexion from a fall on a metaphyseal fracture of the radius (arrows) in mild dorsal angu- the palmar-ﬂexed wrist (Fig. 34). Complications of Smith’s lation with associated ulna styloid tip avulsion fracture (arrowhead). fractures are similar to those of Colles’ fractures and may include injury to the extensor tendons.16

The classification system described above is not meant to Barton’s Fracture replace the common fracture descriptions and use of their A Barton’s fracture is a marginal fracture of the dorsal rim of eponyms; it is a method of discussion that increases under- the radius that displaces along with the carpus, producing a standing of fracture reducibility, stability, and ultimate man- fracture-subluxation (Fig. 35). The fracture results from a fall agement. Common eponyms are consistently used to de- causing dorsiflexion and forearm pronation on a fixed wrist. scribe fractures of the distal end of the radius. Examples A variant of the Barton’s fracture involves the palmar rim of include Colles’ fracture (fracture of the distal aspect of the the distal end of the radius (Fig. 36) and may be more com- radius with dorsal displacement), Smith’s fracture (fracture mon than its dorsal counterpart. It is sometimes referred to as of the distal portion of the radius with palmar displacement), a reverse Barton’s or a palmar Barton’s fracture. Complica- Barton’s fracture (fracture of the dorsal rim of the radius), tions of fractures of the dorsal or palmar rim of the radius are palmar or reverse Barton’s fracture (fracture of the palmar rim of the radius), and Hutchinson’s or chauffeur’s fracture (fracture of the radial styloid process). Colles’ Fracture The well-known Colles’ fracture (Fig. 32) is the most common injury to the wrist caused by a fall on an outstretched hand causing axial compression together with a bending mo- ment. The combination leads to dorsiflexion of the joint.16 The frequency of this fracture increases with advancing age of the patient. The classic Colles’ fracture is a transverse fracture, with or without comminution, with or without intraarticular extension, accompanied by impaction and dorsal displacement of the distal surface of the radius.16 Complications of Colles’ fractures are diverse and fairly common. Such complications include unstable reduction, articular incongruity, subluxation or dislocation of the distal radioulnar joint, median nerve compression resulting in carpal tunnel syndrome, ulnar nerve injury, entrapment of flexor tendons, reflex sympathetic dystrophy, carpal malalignment or fracture, posttraumatic osteolysis of the ulna, and malunion, delayed union, or nonunion.16 Therefore, measurement of such parameters as radial tilt, radial inclination, and ulnar variance on routine radiographs assumes some importance17 in evaluation of fracture stability. Markers of fracture instability are (1) radial shortening in Figure 33 Result of Colles’ fracture instability. A PA view demon- excess of 6 to 10 mm, as this predisposes to further collapse, strates radial shortening resulting in both disabling distal radioulnar resulting in distal radioulnar instability and ulnocarpal joint instability and ulnocarpal joint impaction (ellipse). Radiographic evaluation of the wrist 261

Figure 36 Reverse Barton’s fracture. (A) Lateral and (B) PA views Figure 34 Smith’s fracture. (A) PA view and (B) lateral view of a demonstrate a volar rim fracture with palmar displacement of the fracture of the distal radial metaphysis that is angulated in the pal- carpus with the rim fragment (arrow), consistent with a fracture mar direction. subluxation pattern. similar to those of a Colles’ fracture with increased difficulty line may enter the space between the scaphoid and lunate in maintaining stable reduction.15 fossae, thereby causing scapholunate dissociation and lesser 16 Hutchinson’s or Chauffeur’s Fracture arc injury of the wrist. It is critical to restore the articular surface to anatomic Fracture of the styloid process of the radius is often referred congruency following the described various fracture patterns to as a Hutchinson’s fracture or a chauffeur’s fracture (origi- nally described as a fracture that occurred when the starting crank of an engine suddenly reversed during an engine back- fire) (Fig. 37). It is an avulsion injury related to the sites of attachment of the radiocarpal ligaments or the radial collateral ligament. It may also result from a direct blow.18 Because the fragment is most often non-displaced, this fracture is often difficult to visualize. The fracture is best identified on a PA radiograph and may not be apparent on a lateral radiograph. On the PA view, it should not be confused with the normal irregularity along the lateral surface of the radius at the expected site of previous physeal closure. The fracture

Figure 37 Hutchinson’s fracture or chauffeur’s fracture. (A) PA and Figure 35 Barton’s fracture. (A) Lateral and (B) AP oblique views (B) PA oblique views demonstrate a fracture through the base of the show a marginal fracture of the dorsal rim of the radius that is radial styloid (arrows). The fracture approaches the space between displaced along with the carpus, producing a fracture-subluxation. the scaphoid and lunate fossae (arrowheads). 262 R.A. Loredo, D.G. Sorge, and G. Garcia

Figure 39 Figure 38 Ulna styloid fractures. (A) PA view shows a fracture of the Torus fracture. (A) PA view and (B) lateral views show a ulna styloid (arrow). This fracture is associated with a scaphoid unicortical fracture of the metaphysis of the radius (arrow). fracture (arrowheads). (B) Oblique view demonstrating hypertrophy of the ulna fragment with ulna fracture nonunion.

tures commonly occur (Fig. 39). The radiographs of children should be inspected carefully in at least two orthogonal to prevent the development of instability and late posttrau- planes in an effort to avoid misdiagnosis or incomplete diag- matic arthritis. In addition to diagnostic PA, lateral and nosis of fractures. Physeal fractures are usually Salter–Harris oblique plain x-rays, thin-section computed tomography type II (Fig. 40). (CT) scans with multiplanar reconstruction of images can be used to assess the intraarticular extent and fracture fragment morphology in preparation for percutaneous pinning and Occult Wrist Fractures other methods of reduction. In particular, coronal and sagit- There are a number of common and not-so-common carpal tal images are especially helpful in measuring cortical depres- bone fractures that are more often missed than others. In- sion or offset. MR imaging has been useful in evaluation of creasing awareness of these injuries and more consistent use ligamentous, nerve, tendon, and surrounding soft-tissue pa- of CT scanning and MR imaging have improved their diag- thology associated with wrist fractures. nosis. Ulna Styloid Fracture When an ulnar styloid fracture is present, another fracture should be sought (Fig. 38A), because only 6% of ulnar styloid fractures occur alone.19 In isolation, an ulna styloid fracture is perhaps related to an avulsion produced by the ulnar collateral ligament or triangular fibrocartilage complex. The resulting ossific fragment should not be confused with the anatomic variant appearance of the normal ossification center (lunula) that may appear in the meniscus homologue of the wrist. The irregular contour of the fracture fragment, as well as the irregularity of the donor site along the styloid process, generally allows accurate diagnosis of the fracture. Hypertro- phy of the fragment with fracture nonunion is encountered infrequently and may be a source of chronic wrist pain16 (Fig. 38B). Childhood Fractures In children, injuries may result from acute trauma or chronic overuse. Due to the fact that the capsule and ligaments are Figure 40 Salter Harris, type II fracture of the radius. (A) PA and (B) two to five times stronger than the growth plate, the growth lateral views of the wrist demonstrate fracture of the metaphysis plate is more often involved. Acute fractures typically involve (arrows) that extends into the physis (arrowhead) with dorsal dis- the radial and ulnar physes; in younger children, torus frac- placement of the epiphysis with the dorsal metaphyseal fragment. Radiographic evaluation of the wrist 263

that the entire blood supply to the scaphoid enters through its distal pole, avascular necrosis (AVN) may occur following fractures through the waist of the scaphoid and it is an expected sequela of proximal pole fractures. Increased density of the proximal fragment, indicating avascular necrosis, has been noted on radiographs in about 30% of patients.1 How- ever, sclerosis alone does not indicate inevitable nonunion, and both the fracture and the avascular area may go on to heal. Nonunion of scaphoid fractures is due primarily to a delay in diagnosis or lack of adequate immobilization, or both.21 Contributing factors include anatomical features such as the presence of articular cartilage covering five of the six scaph- Figure 41 Scaphoid fracture avascular necrosis (AVN) and non- oid surfaces, healing by endosteal reaction only, failure to union. (A) Avascular necrosis of the proximal fragment (arrow) is achieve anatomical reduction, and a tenuous blood supply in more prevalent in fractures that involve the proximal third of the some cases.21,22 scaphoid and less frequent with fractures that involve the middle Radiographic abnormalities of scaphoid nonunion include third. (B) A PA view of the wrist demonstrates a chronic fracture through the waist of the scaphoid, consistent with nonunion (ar- bone sclerosis, cyst formation, widening of the scapholunate row). space, bone resorption, and, subsequently, osteoarthritis. Tendon ruptures may occur as a complication of scaphoid nonunion, and CT may reveal hypertrophy of Lister’s tuber- Scaphoid Fracture cle in the dorsum of the radius, which may predispose to The majority of fractures of the wrist involve the scaphoid tendon disruption.16 (65%). However, radiographic diagnosis may be difficult. Seventy percent of these fractures occur through the waist; 20% involve the proximal third, and 10% occur in the distal pole. In children, avulsion fractures of the distal portion of the scaphoid are typical. Unusual patterns of scaphoid injury include dorsal avulsion fractures and fractures of the osteo- chondral interface in young children.16 Radiographically, multiple views of the wrist are indicated in patients with suspected scaphoid fractures. In addition to PA, lateral and oblique projections, angled and magnification views, and views with the wrist in ulnar deviation will show the waist of the scaphoid to best advantage. Soft-tissue signs of fracture include dorsal swelling and scaphoid fat pad changes. Obliteration, distortion, or displacement of the “scaphoid fat stripe” may occur (Fig. 25B). In the case of a displaced scaphoid fracture or suboptimal healing, there may be dorsal tilting of the lunate (“humpback deformity”) simu- lating that occurring in dorsal segmental instability.16 The major factor leading to nonunion of scaphoid fractures is delayed or inadequate immobilization. Therefore, treatment is often begun even when radiographic confirmation is lacking. Individuals without radiographically demonstrable fractures who are clinically suspected of having non-displaced scaphoid fractures are immobilized in a cast for several weeks and then reexamined. Ganel and coworkers, who noted that a negative bone scan 24 to 72 hours after injury excludes fracture at this site, have suggested an alternative course.20 In clinically suspicious cases with negative radiographs, a bone scan (with the cast on) is performed and, if this is negative, immobilization is discontinued. Complications of a scaphoid fracture (Fig. 41) include avascular necrosis of the proximal pole, delayed or nonunion, and an unusual form of osteoarthritis, termed scaph- Figure 42 Triquetral dorsal avulsion fracture. A lateral view shows a oid nonunion advanced collapse16 (SNAC). Due to the fact dorsal-avulsion fracture of the triquetrum (ellipse). 264 R.A. Loredo, D.G. Sorge, and G. Garcia

Figure 44 Hamate fracture. (A) A pronated oblique view of the wrist Figure 43 Fracture of the body of the triquetrum. (A) A conventional demonstrates a fracture of the hook of the hamate (arrow). (B) lateral x-ray may not show this rare type of triquetral injury. It is Corresponding CT scan image shows the fracture to best advantage better diagnosed with (B), computed tomography (arrow). (arrow). (Courtesy of Donald Resnick, MD, San Diego, CA.)

Fractures of Other Carpal Bones a direct blow to the volar surface of the wrist. The fracture may be transverse (usually a chip fracture of the distal end of The triquetrum is the second most commonly injured carpal the bone) or longitudinal. Occasionally, the fracture is com- bone (3 to 4% of all carpal bone injuries). The dorsal fracture minuted. The fracture is best visualized on a 30° supinated (Fig. 42) may be caused by forceful contact of the triquetral AP view, carpal tunnel view, lateral oblique view, or a radial with the hamate or ulnar styloid process or to avulsion of the deviation PA view. When no other soft-tissue swelling is dorsal radiotriquetral ligaments.16 The dorsal-avulsion type seen, paraulnar fat pad swelling suggests a pisiform fracture. of injury is not often missed on the lateral or oblique projec- A complication of fractures involving the pisiform is ulnar tions. However, a less common triquetral fracture that is of- nerve damage.16,24 ten missed involves the body of the triquetrum (Fig. 43), Isolated fractures of the capitate, trapezium, and trapezoid caused by a direct blow in most cases.16 This rare type of are infrequent. Capitate fractures (Fig. 47) usually involve triquetral injury may be missed on conventional radiography the neck of the bone and may be associated with metacarpal and better diagnosed with CT. fractures, scaphoid fractures, and trans-scaphoid perilunate Fractures of the hamate make up 2 to 4% of all carpal dislocations, at times resulting in the scaphocapitate syn- fractures.16 Sagittal or coronal fractures through the body drome (Fig. 48).16 In scaphocapitate syndrome, the head of may occur and these may be detected on plain x-ray or with CT. CT scans are often necessary to define the fracture plane. It is more difficult to clinically and radiographically detect the more common fracture involving the hook of the hamate (Fig. 44). Therefore, this injury deserves attention. Fractures of the hook often occur in association with a dubbed golf swing or in sports that use rackets or bats. The grip may place the end of the club handle or bat against the hook, thereby predisposing the hook to direct trauma. These injuries may also result from a fall on a dorsiflexed wrist, with the force transmitted through the transverse carpal and pisohamate ligaments.16 Aside from standard radiographs, a carpal tunnel view, computed tomography, or a bone scan may be helpful in detecting fractures of the hook of the hamate, as is MR imaging (Fig. 45). Complications of these fractures include nonunion, osteonecrosis, injuries to the ulnar or median nerve, tenosynovitis or tendon rupture, and chronic pain. A bipartite hook or os hamuli proprium (incomplete fusion of the ossification center of the hook) may mimic a 16 fracture. On an MR imaging study, it is recommended that Figure 45 Hamate hook fracture. (A) Sagittal T1-weighted MR image the axial and sagittal images be completely reviewed before of a hamate hook fracture (arrows). (B) T1-weighted axial image and excluding a fracture of the hamate.23 (C) T2-weighted axial image show the fracture line (circle and ar- Fractures of the pisiform (Fig. 46) are usually the result of row). Radiographic evaluation of the wrist 265

Figure 48 Scaphocapitate syndrome status post transscaphoid, tran- scapitate perilunate fracture dislocation. (A) The “squared-off” appearance of the proximal end of the capitate, best seen on a PA view, is the key to making the proper diagnosis of the syndrome. C ϭ capitate. (B) A lateral view shows the perilunate fracture dislocation Figure 46 Pisiform fracture. A 30° supinated AP view demonstrates a pattern. The lunate (L), capitate (C), and two scaphoid fragments (S) transverse fracture (chip fracture) of the distal end of the bone are labeled. (arrows).

capitate, best seen on a PA view, is the key to making the the capitate is fractured and rotated 180°. Difficulty inter- proper diagnosis.24 preting the radiographs in this situation can result in im- The trapezium may fracture in various places, the vertical proper treatment of a fracture fragment that is considerably body, dorsoradial tubercle, dorsoulnar tubercle, and anterior displaced or a fracture fragment that is markedly rotated. (palmar) ridge.25,26 The vertical split fracture of the body of Proper radiographic interpretation often requires multiple the trapezium is associated with lateral subluxation of the projections, including PA, lateral, and oblique views, often first metacarpal, which remains attached to the lateral trape- supplemented with CT scan images. When interpreting the zial fragment. The fracture of the palmar trapezial ridge, al- films, the “squared-off” appearance of the proximal end of the though rare, is important to recognize as these fractures are prone to nonunion27 if not promptly diagnosed and treated. The anatomy is such that a portion of the transverse carpal ligament attaches to this ridge and extends across the carpal tunnel to the hook of the hamate. In a setting of trauma, an avulsion fracture of the trapezial ridge may be produced26 (Fig. 49). Because the ridge is not well visualized on routine radiographs, the diagnosis can be easily overlooked. Trape- zial ridge fractures can best be seen on the carpal tunnel view (Fig. 49B). CT scans also are very useful in evaluation of these fractures. Carpometacarpal Injuries Anatomically, the osseous structures of the wrist include the bases of the metacarpals. Within the first carpometacarpal compartment of the wrist, relatively common injuries include the Bennett’s fracture-dislocation and Rolando’s fracture that occur at the base of the thumb metacarpal (Fig. 50). The Bennett’s fracture and Rolando’s fracture are two-part Figure 47 Capitate fracture. (A) A Capitate (C) neck fracture is not and three-part (or comminuted) fractures, respectively, and well seen on a PA view. (B) An axial T1-weighted MR image illustrates a low signal intensity fracture line within the capitate (arrows). they are usually well recognized on radiographs. A more (C) In the same patient, a coronal T2-weighted MR image demon- challenging diagnosis is that of a beak ligament avulsion frac- strates high marrow signal intensity within the capitate (circle) and ture. a subtle high signal intensity fracture line within the waist of the The beak ligament avulsion fracture (Fig. 51) occurs at the capitate (arrow). level of the thumb carpometacarpal joint. At this articulation, 266 R.A. Loredo, D.G. Sorge, and G. Garcia

Figure 49 Trapezial ridge fracture. (A) A PA wrist view does not Figure 51 Beak ligament avulsion fracture. (A) The ﬁrst carpometa- clearly demonstrate the fracture of the trapezium (circle). (B) A carpal (CMC) joint is subluxed (circle) and an adjacent bone frag- carpal tunnel view clearly illustrates a trapezial ridge fracture (ar- ment is seen (arrow). (B) Pinning of the ﬁrst CMC joint is necessary row). The trapezium (tm), scaphoid (S), and hamate hook (h) are for adequate reduction and prevention of instability. labeled.

fragment(s) adjacent to the metacarpal base unless there is there is a major strong ligament that connects the beak of the pure ligamentous avulsion. metacarpal base to the anterior tubercle of the trapezium. This ligament has been referred to as the anterior oblique, the Stress Fracture of the ulnar, the ulnar-volar, and the beak ligament.28 Two other Radial Epiphyseal Plate ligaments in the capsule include the lateral ligament beneath In the skeletally immature, a stress reaction can develop pri- the abductor pollicis longus tendon insertion, and the poste- marily at the distal radial growth plate and to a lesser degree rior oblique ligament that is under the extensor pollicis lon- in the distal end of the ulna. Gymnastics is the major cause of gus.2 Although rare, pure dislocation of the ﬁrst metacarpal this injury; hence it bears the name, “gymnast’s wrist”29 (Figs. without fracture can occur. The dislocations are always dor- 52 and 53). The condition is due to chronic compression and sal and the beak ligament strips subperiosteally along the rotational forces that are applied as the upper extremity be- metacarpal. The ligament is lax in the dislocated position, but comes the weight-bearing limb during this sport activity. it becomes tight again if the thumb is reduced. Chronic in- Radiographically, the changes at the physis resemble those stability can result if unrecognized and not treated with rigid seen in rickets. The physeal plate shows irregularity, cystic reduction (pinning) for a 6- to 8-week time interval.2 Careful change, and widening, consistent with a Salter–Harris type I radiographic examination may demonstrate the tiny avulsed or II injury. There may be adjacent bone fragmentation. If not treated, the condition can lead to early physeal closure and positive ulnar variance with dysfunction of the distal radio-

Figure 50 Fracture of the base of the thumb metacarpal. (A) A Ben- nett’s fracture is consistent with a two-part fracture-dislocation (cir- Figure 52 “Gymnast’s wrist (SH I injury).” (A) PA and (B) lateral wrist cle). (B) A Rolando’s fracture is consistent with a comminuted views demonstrate widening of the physis of the radius (arrows) (three-part) fracture (circle). secondary to chronic stress reaction in a gymnast. Radiographic evaluation of the wrist 267

Figure 53 “Gymnast’s wrist”—SH II injury of radius and ulna. (A) A PA view shows mild widening of the physes of the ulna and radius Figure 54 Perilunate dislocation. (A and B) Widening of the (arrows) with possible minimal metaphyseal sclerosis. (B) The cor- scapholunate joint (arrow) secondary to ligamentous injury and responding coronal T2-weighted image shows high signal intensity dorsal perilunate dislocation (arrows) are shown. The anterior-most metaphyseal bands that are consistent with stress reaction or stress line depicts the lunate (L) sitting within the radial (R) articular fractures of the radius and ulna (arrows). surface with the second line spanning the dorsally displaced carpus.

24 ulnar joint and abnormalities of the triangular fibrocartilage ligaments. The final stage IV injury is associated with dis- complex.29 ruption of the dorsal radiocarpal ligaments, which frees the lunate and allows it to become volarly displaced (lunate dis- Wrist Instability Carpal instability occurs when there is symptomatic malalignment between the rows of carpal bones and between the carpal bones and the radius. Figuratively speaking, the proximal carpal row is termed an intercalated segment because forces acting on its proximal and distal articulations determine its position.30 Collapse is normally prevented by link- age of the proximal and the distal carpal rows by the scaphoid and its connecting ligaments.1 When the system is com- pressed, a zigzag pattern of collapse occurs, analogous to what happens to cars in a train if the first car stops short. The resultant instability may be due to traumatic injuries (fractures or ligamentous disruption) or to inflammatory conditions such as rheumatoid arthritis. When the term carpal instability was first coined, it was almost synonymous with scapholunate instability. Since then, descriptions of progressive perilunate instabilities have evolved with scapholunate instability representing the first stage of perilunate injuries.3 Perilunate Dislocation Most wrist injuries, including dislocations, result from forced dorsiflexion of the wrist. The resultant lesions are predictable as they are all progressive stages of the same injury pattern. A stage I injury is secondary to scapholunate ligamentous failure and dissociation with rotatory subluxation of the scaphoid.16 Stage II injury is characterized by perilunar instability resulting from capitolunate failure of the palmar radioscaphocapitate ligament or a fracture of the radial styloid process, leading to perilunate dislocation16 (Fig. 54). The stage III injury results from lunotriquetral partial or complete Figure 55 A lateral x-ray depicts palmar lunate dislocation (arrow) failure or avulsion of the volar and dorsal radiotriquetral with minimal dorsal tilt of the capitate (lines drawn). 268 R.A. Loredo, D.G. Sorge, and G. Garcia

1. A wide scapholunate distance (“Terry Thomas sign”). Normally, the scapholunate distance is less than 2 mm. Ligamentous disruption is suggested when the distance between the scaphoid and lunate is greater than 2 mm and can be diagnosed almost unequivocally when this distance is 4 mm or more.1,16 2. Foreshortened appearance of the scaphoid. On a PA view, this appearance is due to rotation of the distal pole of the scaphoid toward the palm. In contrast to the normal wrist, this foreshortening does not appear on ulnar deviation. 3. Ring sign. This sign refers to the density produced by the cortex of the distal pole of the scaphoid seen end-on because of the abnormal scaphoid rotation. Normal individuals may exhibit this finding on PA views taken with the hand in radial deviation; however, this appearance should not persist when the hand is in ulnar deviation.1 4. Dorsiflexion instability. On a continuum of progressive Figure 56 A PA view demonstrates marked scapholunate joint space severity of scapholunate injury or dissociation is the widening (double arrow), a foreshortened scaphoid with a ring sign occurrence of secondary changes such as capsular con- (circle) due to palmar rotary subluxation of the scaphoid, consistent tracture, scaphoid and midcarpal fixation, dorsal inter- with scapholunate dissociation. Incidentally noted is first carpo- calary segment instability (DISI), scapholunate ad- metacarpal osteoarthritis. vanced collapse (SLAC), and pancarpal degenerative arthritis.1,16 Radiographic findings of DISI include (1) on a PA view, overlap of the lunate and the capitate and location)16 (Fig. 55). When the perilunate dislocation pattern (2) on a lateral view (Fig. 57), scapholunate angle Ͼ80° is associated with fractures, these injuries are then called greater arc injuries as the arc of injury passes through the scaphoid, capitate, hamate, and/or triquetrum. The lesser arc injuries affect the ligaments and joint spaces about the cir- cumference of the lunate and begin with scapholunate injury.16 Scapholunate (SL) Instability Scapholunate instability or scapholunate dissociation may accompany tears of the palmar radiocarpal ligaments and scapholunate interosseous ligament complex. Scapholunate dissociation (rotatory subluxation of the scaphoid) may occur as a complication of lunate or perilunate dislocation, rheumatoid arthritis, and other articular diseases, or as an isolated injury.16 Although characteristic abnormalities are typically identified on routine radiographic examination, patients who are suspected of having ligamentous instability may require additional views. The full series may include (1) PA views in neutral, ulnar deviation, and radial deviation; (2) AP clenched fist view; (3) an oblique view; (4) lateral views with the wrist in neutral, flexion, and extension; and (5) lateral view in neutral position with the fist clenched.1 The views in flexion and extension and in radial and ulnar deviation help to demonstrate the dynamics of wrist motion. The clenched-fist views compress the wrist, tending to force the capitate into the space between the scaphoid and the lunate, and to rotate the scaphoid toward the palm, thus revealing any tendency for abnormal scaphoid rotation or scapholu- Figure 57 A lateral view demonstrates dorsal tilt of the lunate and a nate separation.1,3 widened scapholunate angle to near 90° (normal 30 to 60°) suggest- Abnormal findings on standard radiographic views or on ing disruption of the scapholunate ligament resulting in a DISI the additional views include the following1 (Fig. 56): deformity. Radiographic evaluation of the wrist 269

(normal ϭ 30 to 60°), lunate dorsally tilted, and scaphoid ﬂexed toward the palm.1,16 A wrist with SLAC has a pattern of osteoarthritis, characterized by narrowing of both the radioscaphoid and the capitolunate spaces.1

During videofluoroscopy, widening of the scapholunate space may be demonstrated, as the wrist is observed during a range of motion.30 Conventional arthrography can confirm disruption of the scapholunate ligament by demonstrating extension of contrast medium into the midcarpal joint space following radiocarpal joint injection. CT scanning and MR imaging can be useful for the diagnosis of scapholunate dissociation. Aside from the expected observations that can be extrapolated from radiographs (scapholunate gap Ͼ2 mm, palmar flexion of scaphoid, dorsal tilting of lunate), abnormalities of the intrinsic and extrinsic components of the scapholunate ligament can be visualized with the use of specific MR imaging parameters. T2- weighted image findings include hyperintense linear signal intensity in partial or complete ligament tears, complete ligamentous disruption with a hyperintense fluid-filled gap, hyperintense synovial fluid communication between the radiocarpal and midcarpal compartments, disruption of the dorsal component of the SL ligament, synovitis of the extrinsic volar radiocarpal ligaments, and degenerative perforations in the membranous (proximal) ligamentous portion. MR arthrogra- Figure 58 A lateral view demonstrates capitolunate angle Ͼ30° (nor- phy has been successful in identification of flap tears, perfo- mal ϭ 0 to 30°), lunate tilted volarly, capitate directed dorsally, ration, and assessment of the integrity of the dorsal compo- volar tilting of the lunate most consistent with a VISI (volar interca- nent of the SL ligament.23 With all methods of assessment for lated segment instability) often due to disruption of the lunotrique- instability, caution must be exercised as improper position- tral ligament. ing of the wrist during routine radiography, CT scanning, or 16 MR imaging may simulate the instability patterns. ulnar deviation, producing overlapping of the lunate and triquetrum.31 On the lateral view, the lunate is tilted volarly, Lunotriquetral Instability capitate directed dorsally, and the triquetrum dorsiflexed in Lunotriquetral instability may be seen after sprain or disrup- relation to the lunate compared with the other wrist.1,18,31 tion of the lunotriquetral interosseous ligament, with perilu- With progressive instability, volar intercalated segmental in- nate injury, excision of the triquetrum, sprains of the mid- stability (VISI) deformity occurs and radiographic findings carpal joint that attenuate the extrinsic ligaments, with ulnar include the following: (1) PA views show that the lunate positive variance associated with degenerative lunotriquetal overlaps the capitate and (2) lateral views (Fig. 58) demon- membranous tears, and in patients using wheelchairs.16,23 strate a scapholunate angle Ͻ30° (normal ϭ 30 to 60°), Patients with this injury usually progress from minimal increased capitolunate angle to Ͼ30° (normal ϭ 0 to 30°), symptoms to ulnar wrist pain and the sensation of instability. lunate tilted volarly, capitate directed dorsally, and the tri- They develop ulnar nerve paresthesias and eventual midcar- quetrum dorsiflexed in relation to the lunate compared with pal instability. A similar pattern of instability is seen as a the other wrist.1,16,30 normal variant in persons with ligamentous laxity and in Standard arthrography is probably the most helpful diag- those with various articular disorders, including rheumatoid nostic aid in the evaluation of lunotriquetral tears30 (sprains). arthritis and calcium pyrophosphate dihydrate crystal depo- Sequential injection of the midcarpal and radiocarpal spaces sition disease.14 has been shown to be the best method of evaluation.16 A Standard radiographs may appear normal in patients with positive study demonstrates communication between the lunotriquetral tears or sprains and in those with lunotrique- midcarpal and radiocarpal joints through the lunotriquetral tral dissociation and dynamic instability.16 Stress radio- space. Patients with isolated lunotriquetral tears need to be graphs, ie, clenched-fist AP view in pronation or ulnar devi- differentiated from those with ulnar impaction syndrome. ation or the clenched-fist lateral view, may be necessary to Ulnar impaction syndrome is discussed more extensively elicit the abnormality in patients with dynamic instability. elsewhere in this writing. The abnormalities encountered include disruption of the normal smooth convexity of the proximal carpal row with the Midcarpal Instability—Intrinsic to Carpus triquetrum displaced proximally on the AP radiograph. Dis- In midcarpal instability, laxity of certain carpal ligaments ruption of the normal arc is particularly pronounced with results in lack of support for the proximal carpal row and 270 R.A. Loredo, D.G. Sorge, and G. Garcia midcarpal joint, which in turn leads to a loss of the normal itate on the lunate and the scaphoid on the scaphoid fossa of joint reactive forces between the proximal and distal carpal the radius could be demonstrated. These patients have fea- rows. The proposed etiology is injury to—or laxity of—the tures similar to those of patients with DMCI.17 ulnar arm of the arcuate ligament (a major stabilizer of the midcarpal joint) and laxity of the dorsal radiolunotriquetral Midcarpal Instability—Extrinsic to Carpus (RLT) ligament.32 A dynamic flexion deformity (VISI) occurs in the proximal row as the distal row translates palmarly Extrinsic midcarpal instability is often associated with rever- owing to the lax ligament. As the wrist moves from radial to sal of the normal volar tilt of the distal articulating surface of ulnar deviation, there is no longer the normal coupled rota- the radius. This is most often observed in patients with mal- tion of the carpus and smooth transition from flexion (VISI) union of a distal radial fracture. Subsequently, the lunate and to extension (DISI). Instead, the proximal row remains flexed capitate are tilted dorsally; however, they maintain a collinear in a “VISI-like” pattern for a period with “the head of the relationship with each other on neutral lateral views. With capitate [subluxed] volarly into the space of Poirier.”32,33 As ulnar deviation, the capitate rotates volarly and becomes par- the distal row/capitate abruptly reduces, the proximal row allel and slightly dorsally displaced, relative to the shaft of the snaps into extension in a “DISI-like” pattern creating the radius on the lateral view. However, the lunate remains dor- clinical finding called the “catch-up clunk.” This is accentu- sally tilted. The inability of the lunate to rotate volarly with ated by increasing the load on the capitolunate joint when the the capitate is thought to cause the pain and clunk associated 32 fist is clenched and relieved by either splints which apply with extrinsic midcarpal instability. pressure in a dorsal direction to the pisiform or by surgery to strengthen the volar arcuate ligament and dorsal ligaments or Radiocarpal or Proximal Carpal Instabilities 33 by fusion of the lunate-triquetrum-capitate-hamate bones. Although a rare occurrence, proximal carpal instabilities are The dynamic pattern of instability described above is characterized by subluxation or dislocation of the entire car- named “palmar midcarpal instability (PMCI)” because of the pus in a dorsal, palmar, ulnar, or radial direction relative to palmar translation of the distal row. In earlier reports, this the distal radius. Dorsal and palmar instabilities are most 34 entity was termed “ulnar midcarpal instability.” Dorsiflex- commonly related to trauma and ulnar dislocations are re- ion injury, compression, rotation, and distraction injuries lated to ligamentous laxity. Radial translocations have not 35 and ulnar minus variance have been associated with PMCI. been reported.32 36 PMCI is the most common pattern of midcarpal instability. Dorsal carpal instabilities may appear as an isolated find- A much less common variant of midcarpal instability, in ing or in association with Colles’ or Barton’s fractures, which which the proximal carpal row is extended (DISI) and the result in either dorsal tilt of the distal radial articular surface distal carpal row is subluxed dorsally when the wrist is in or dorsal displacement of the dorsal lip. Palmar carpal insta- 32 neutral, is termed dorsal midcarpal instability (DMCI). bilities are less common, as one might expect, given their The radiographs may be normal as PMCI is a dynamic association with the rare palmar or reverse Barton’s fracture. condition. Lateral radiographs in neutral, radial, and ulnar This results in increased palmar tilt or displacement of the deviation may demonstrate VISI deformity and mild palmar articular surface. Both are treated with osteotomy to correct translation of the distal carpal row. Videofluoroscopy in PA the malalignment.18,38 and lateral planes may show the dynamic palmar flexion Ulnar carpal instabilities are generally from capsular injury instability (VISI) with wrist motions from radial to ulnar de- or any type of synovitis, such as rheumatoid arthritis result- 32 viation. CT scan and MR image findings include VISI de- ing in weakening and laxity of the extrinsic ligaments.32 This formity with volar tilt of the scaphoid and the lunate, palmar allows the carpus to “migrate down the inclined plane of the translocation of the distal row, sclerosis between the distal distal radius in an ulnar direction”33 (Fig. 59). A diagnostic lunate and proximal capitate, and dorsal tilting of the distal feature is an abnormally wide space between the radial pole of the capitate. The T2-weighted MR images show an styloid process and the scaphoid29 as the carpus begins to attenuated or disrupted lunotriquetral ligament with hyper- slide ulnarly along the radius. The scapholunate angle is less intense fluid extending across the lunotriquetral (LT) or than 30°. PA views show that the lunate overlaps the capitate. scapholunate (SL) interval. There may be hyperintense syno- Shift of the entire carpus dorsal to the midpoint of the distal vitis versus ligament attenuation associated with the ulnar radial articular surface is seen.1 arm of the arcuate ligament and the dorsal radiotriquetral (or radiolunotriquetral) ligament. MR arthrography will show contrast directly communicating across the SL or LT inter- Distal Radioulnar Joint Instability val.32 Anatomically, in full supination, the ulnar head rests on the The natural history of midcarpal instability is that the dy- palmar aspect of the notch, and in full pronation, it rests namic instability becomes a fixed VISI deformity with loss of against the dorsal lip of the notch.2 Acute injuries of the distal the normal physiologic VISI to DISI wrist motion with wrist radioulnar joint (DRUJ) frequently go undiagnosed or misdi- motion from radial to ulnar deviation. Louis and associates37 agnosed. Early recognition of DRUJ injury is crucial to effec- have described the capitolunate instability pattern (CLIP tive treatment because chronic DRUJ conditions are much wrist) where there is laxity of the palmar radioscaphocapitate more difficult to manage.39 Injuries to the DRUJ can involve ligament in patients in whom dorsal subluxation of the cap- trauma to the bone, joint, and the surrounding soft tissues. Radiographic evaluation of the wrist 271

PA radiograph; (2) widening of the radioulnar distance on the PA view in ulna dorsal dislocations; (3) superimposition of the radius and ulna on the PA view in ulna ventral dislocations; and (4) posterior or anterior (less common) displacement of the ulna on lateral radiographs.27 Unfortunately, detection of subluxation on radiographs may be quite difficult because slight variations in wrist position alter the relationship of the radius and ulna. Because of the difficulty in demonstrating the anatomy of the distal radioulnar joint on routine radiographs, the associated complex injuries that occur, and the infrequent occurrence of isolated subluxations or dislocations, CT of the bilateral wrists in neutral, pronated, and supinated positions may be utilized to confirm the diagnosis.46 Due to the fact that DRUJ dislocation or subluxation may not occur until the patient reaches the extremes of pronation or supination, most institutions study the DRUJ in full pronation, neutral position, and in full supination. The asymptomatic wrist is included in the same positions.5 On transax-

Figure 59 A coronal T1-weighted MR image with scapholunate widening, proximal migration of the capitate (C), and ulnar translocation of the carpus.

DRUJ Dislocation/Subluxation DRUJ dislocations have been reported as isolated injuries as well as with Galleazzi fractures, Essex-Lopresti injuries, both bone forearm fractures, distal radius fractures, fracture-dislocation of the elbow, and in plastic deformation of the forearm.39 DRUJ dislocation can be categorized as simple (reduces spontaneously or with minimal manipulation), or complex (irreducible, incomplete reduction, or interposition of soft tissue or bone). Isolated dislocations of the inferior radioulnar joint are uncommon, usually resulting from significant rotatory force applied to the forearm about a fixed hand, as in a fall or twisting injury. At the distal radioulnar articulation, dislocations of the ulna most often occur in a distal, dorsal, and medial direction; volar dislocation is less frequent.16 Most dislocations of this articulation occur in conjunction with Galeazzi fractures, short oblique, or transverse fractures that occur at the junction of the middle and distal third of the radius accompanied by dislocation of the DRUJ. An Essex-Lopresti injury is a fracture or fracture-dislocation of the radial head associated with disruption of the interosseous membrane between the radius and ulna and dislocation of the DRUJ.40 DRUJ injuries also occur with distal radius fractures. Poor results following treatment of distal radius fractures with symptoms at the distal radioulnar joint are typically from chronic disruption of the TFCC, ulnar abutment due to radial shortening, posttraumatic arthritis of Figure 60 Distal radioulnar joint (DRUJ) dorsal dislocation. A PA the distal radioulnar joint, and/or persistent instability or view demonstrates widening of the radioulnar distance (diamond), 39 dislocation of the DRUJ. abnormal rotation of the ulna with the ulnar styloid (arrow) overly- Radiographic findings of distal radioulnar dislocation (Fig. ing the central portion of the distal ulna. Incidentally noted is soft- 60) include (1) abnormal rotation of the ulna with the ulnar tissue calcification in the expected location of the flex carpi ulnaris styloid overlying the central portion of the distal ulna on the tendon (asterisk). 272 R.A. Loredo, D.G. Sorge, and G. Garcia

Figure 61 Objective methods of evaluation of normal DRUJ on CT. Figure 62 A coronal T1-weighted fat suppressed postgadolinium MR (A) With the forearm in neutral rotation, the congruent ulnar head image following radiocarpal contrast injection demonstrating a tear should lie between the two divergent lines drawn.46 (B) In supina- (arrow) just ulnar to the cartilaginous attachment of the TFC (trian- tion, a perpendicular line drawn from the midpoint between the gular fibro-cartilage) onto the radius with contrast spilling into the center of the ulnar head and the ulnar styloid (center of DRUJ distal radioulnar joint from a radiocarpal injection. rotation) to the chord of the sigmoid notch falls in the center of the sigmoid notch. (C) With the arm in pronation, the arcs of the sigmoid notch and the ulnar head should be congruous. (Reprinted contrast opacification of the radiocarpal joint will be associ- with permission.5) ated with filling of the inferior radioulnar joint as a result of perforation or detachment of the intervening articular cartilage (Fig. 62). ial images, there are methods of objective CT or MR evaluation of the position of the ulna relative to the radius. Triangular Fibrocartilage Complex Tears The methods (Fig. 61) require construction of a number of Pathologic conditions affecting the TFCC can be categorized lines that are drawn along the radius and ulna. In one as traumatic or degenerative and Palmer has devised a system method, a line is drawn through the dorsoulnar and dorso- for categorizing the abnormalities42 (Table 1). Lesions of the radial aspects of the radius and another line is drawn through TFCC are variable in location; they may be confined to the the palmoulnar and palmoradial aspects of the radius; the horizontal, or flat, portion of the TFCC (referred to as the congruent ulnar head should lie between these two divergent TFC or articular disc) or involve one or more components of lines5,46 (Fig. 61A). If the ulnar head crosses the respective the TFCC with or without instability of the distal radioulnar dorsal or palmar line, subluxation in a dorsal or palmar direction is diagnosed. Another method is the epicenter method.41 In this method, with the DRUJ in supination, a Table 1 Palmer Classification of TFCC Abnormalities42 perpendicular line is drawn from the midpoint between the Class 1. Traumatic center of the ulnar head and the ulnar styloid (center of DRUJ A. Central perforation rotation) to the chord of the sigmoid notch (Fig. 61B). If this B. Ulnar avulsion line is in the center of the sigmoid notch, the joint is consid- C. Distal avulsion ered congruous.5 With the arm in pronation, the arcs of the D. Radial avulsion sigmoid notch and the ulnar head should be congruous (Fig. Class 2. Degenerative (ulnocarpal abutment syndrome) 61C). CT and MR imaging share diagnostic advantages in A. TFCC wear (B. TFCC wear (lunate ؉/or ulnar chondromalacia assessment of this joint. However, MR imaging has the added (C. TFCC perforation (lunate ؉/or ulnar chondromalacia advantage of evaluation of the surrounding soft-tissue struc- D. TFCC perforation (chondromalacia ؉ lunotriquetral tures. ligament perforation) In equivocal cases, arthrography of the radiocarpal joint E. TFCC perforation (chondromalacia, ligament can be helpful in establishing the diagnosis, as disruption of perforation, ulnocarpal arthritis) the inferior radioulnar joint requires injury to one or more Traumatic and degenerative TFCC abnormalities/tears exist and are components of the TFCC, the major stabilizing structure of listed according to the most often used classification system the distal portion of the ulna.16 On arthrographic images, described by Palmer.42 Radiographic evaluation of the wrist 273 joint.2 Degenerative lesions of the TFCC are more common than traumatic lesions and are thought of as chronic injuries resulting from load on the ulnar side of the wrist. Anatomic studies have shown that perforation of the TFCC occurs in approximately one-third to one-half of cadaveric specimens, perhaps due to degenerative changes.1 Radiography is not useful in characterization of TFCC abnormalities. However, there are radiographic findings that are associated with abnormalities of the complex, such as positive ulnar variance, the presence of an ulnar base fracture associated with proximal detachment of the TFCC, and avulsion fracture of the fovea of the ulna indicating injury at the site of attachment of the proximal lamina of the TFCC.43 The role of arthrography in the diagnosis of TFCC defects is well established, although there is some disagreement re- garding the optimal technique for compartmental injection. Nonetheless, the terms communicating (full-thickness) and noncommunicating (partial thickness) defects are used in discussion of TFCC abnormalities. The presence of contrast material in the DRUJ after radiocarpal opacification or in the radiocarpal compartment after DRUJ injection is diagnostic Figure 64 A coronal T2-weighted fat suppressed MR image demon- of a communicating defect in the TFC (articular disc) (see strates negative ulnar variance and cystic degenerative changes at Fig. 62). Noncommunicating, or partial, defects involving the distal radioulnar joint consistent with distal radioulnar impinge- the proximal and distal aspects of the TFC can be demon- ment. strated following injection of the DRUJ and radiocarpal joint, respectively. Other traumatic abnormalities that involve the TFCC attachments, as described by Palmer, may be associated with distinctive arthrographic findings.42 At this time, often due to altered mechanics from ulnar elongation relative arthrography and state-of-the-art MR imaging can be consid- to the radius (positive ulnar variance). Patients present with ered equally accurate in assessment of defects of the TFCC.2 ulnar wrist pain, swelling, crepitus, and limited wrist motion. The condition is caused by chronic impaction of the ulnar Ulnar Abutment Syndrome head against the TFCC and ulnar-sided carpal bones resulting in progressive deterioration of the TFCC, chondromala- The ulna abutment syndrome, also termed ulnocarpal abut- cia of the lunate and ulna, and attrition of the lunotriquetral ment, ulnar impaction syndrome, and ulnolunate impaction interosseous ligament.44 The ulnar impaction syndrome is syndrome, is a degenerative condition related to excessive almost always associated with a positive ulnar variance. Pos- 44 load-bearing across the ulnar side of the wrist. It is most itive ulnar variance is often idiopathic but can be caused by malunion of a distal radial fracture, premature physeal arrest of the distal radius, or an Essex-Lopresti injury.31 Although the ulnar impaction syndrome has been identified in patients with neutral or positive ulnar variance, it is not associated with negative ulnar variance.31 A routine PA radiograph may demonstrate positive ulnar variance (Fig. 63) and degenerative changes such as joint space narrowing, subchondral sclerosis, or cystic changes in the ulnar head, sigmoid notch, lunate, or triquetrum.45 An excellent radiographic study for ulnar abutment is to obtain a PA view with the fist clenched in addition to the routine PA view. With a load across the wrist, the ulna moves distal relative to the radius, and this change is often quite noticeable on plain radiographs.5 Videofluoroscopy can be used to determine whether there truly is an abutment between the distal ulna and the carpus in ulnar impaction syndrome.5 MR imaging may dem- Figure 63 A PA x-ray demonstrates positive ulnar variance and cystic onstrate chondromalacia or degenerative arthritis of the changes of the radial aspect of the distal ulna and ulnar aspect of the ulnar head or carpus, and the lunotriquetral ligament may proximal lunate consistent with ulnolunate abutment or impaction be perforated.37,45 (see arrows). The syndrome of ulnar abutment or impaction should 274 R.A. Loredo, D.G. Sorge, and G. Garcia

wrist. The destruction of the trapezioscaphoid and trapezoid- oscaphoid joints results from disruptions in the ligamentous support of the scaphoid distally. The radial column collapse allows the trapezium and trapezoid to migrate proximally and come to rest on the nonarticular dorsum of the distal scaphoid, immediately proximal to the distal articular cartilage. This, along with any rotational changes and lateral displacement of the distal scaphoid, leads to abnormal shear stresses that result in the degeneration observed.

Congenital/Developmental Conditions The following topics are congenital or developmental conditions that may lead to wrist pain. The discussion of each entity is brief, and interested readers may consult standard reference textbooks for more detailed information. Figure 65 A PA view shows a more advanced case of SLAC wrist (circle). Carpal Coalition Coalition, or carpal fusion, is relatively common and may occur as an isolated phenomenon or as part of a generalized be differentiated from the syndrome of ulna impingement, congenital malformation syndrome. As a rule, isolated fu- which is generally associated with negative ulnar variance sions involve bones in the same carpal row (proximal or (Fig. 64). Impingement at the level of the DRUJ can occur distal); fusions related to syndromes may affect bones in dif- following surgical resection of the distal ulna, following ferent rows (proximal and distal) and massive carpal fusion is fracture of the ulnar head or secondary to a malunited usually associated with congenital malformations and anom- 5 sigmoid notch as a sequela of a distal radius fracture. The alies.31 Coalition may be fibrous (Fig. 67) or bony (Fig. 68). syndrome of impingement may be seen in chronic insta- The most common type of isolated fusion is between the bility of the DRUJ, infection, inflammatory arthritis, crys- triquetrum and the lunate bones, occurring in 0.1 to 1.6% of 7,46 talline disease, and primary osteoarthritis. Ulna im- the general population. The condition is bilateral in approx- pingement syndrome is a degenerative process that leads imately 60% of cases.31 The scapholunate interosseous space to DRUJ pathology and pain with supination. is frequently widened in cases of lunotriquetral coalition, and, although the SL ligament is generally intact,31 abnormal Posttraumatic/Postinstability Arthrosis (SLAC) A wrist with scapholunate advanced collapse (Fig. 65) has a pattern of osteoarthritis, occurring either spontaneously or after trauma, characterized by narrowing of both the radioscaphoid and the capitolunate spaces. Some investigators believe that it is one of the most common patterns of degenerative joint disease in the wrist. The most common etiology of SLAC wrist is rotary subluxation of the scaphoid (RSS) due to scapholunate or periscaphoid dissociation. In addition to RSS, SLAC wrist may be caused by other conditions such as Kienbock’s disease, scaphoid fracture nonunion or malunion, radioscaphoid and capitolunate intraarticular fractures, Preiser’s disease (spontaneous osteonecrosis of the scaphoid), and crystalline pyrophosphate deposition disease (CPPD).5 The presence of chondrocalcinosis or other types of intraarticular calcification, the absence of a history of injury, or the presence of radiolunate joint space narrowing, alone or in combination, strongly suggests the diagnosis of CPPD crystal deposition disease.

Triscaphe Arthritis Figure 66 PA x-ray with variant of triscaphe arthritis (arrows) in Triscaphe arthritis (Fig. 66) occurs as a result of load changes addition to distal radioulnar fractures and trapezium-trapezoid-cap- and articular abnormalities analogous to those in the SLAC itate coalition. Radiographic evaluation of the wrist 275

Figure 69 A PA radiograph shows slight increased density of the lunate (arrow) suggestive of early Kienbock’s disease.

Figure 67 A coronal T2-weighted fat suppressed MR image confirms partial fibrous lunotriquetral coalition (arrows) with surrounding such as juvenile chronic arthritis, and rheumatoid arthritis, marrow edema suggesting minimal motion at the partial coalition trauma, and surgery.31 site. Osteonecrosis and Osteochondrosis Kienböch’s Disease widening to more than 3 to 4 mm suggests a scapholunate The various synonyms used for this condition (lunatomala- 7 ligament tear or laxity. Less common isolated fusions have cia, aseptic necrosis, avascular necrosis, osteochondritis, been described in almost all possible combinations, includ- traumatic osteoporosis, osteitis) are most likely a reflection of ing two or more bones. the fact that its exact etiology remains unclear. Early descrip- Bone cysts adjacent to the coalition are sometimes seen. tions of Peste and, later on, Kienböck, supported the belief The changes can usually be differentiated from the acquired that the lesion is a fracture with a traumatic etiology.36,38 ankylosis that may accompany infection, certain arthritides Kienböck believed that repeated sprains, contusions, or subluxations led to ligamentous and vascular injury resulting in loss of blood supply to the lunate.36 Since then, numerous authorities have described the pathologic changes as avascular necrosis. The exact cause and pathogenesis is not definitely known. However, there is the finding of ulna minus variance that has been associated with Kienbock’s disease. Theoretically, a short ulna causes increased shear forces on the ulnar side of wrist and particularly on the lunate. This is thought to be a contributing factor in the development of avascular necrosis.35 Early in the course of Kienböck’s disease, the radiographs may appear normal to slightly dense (Fig. 69). However, a linear or compression fracture can be delineated with CT scanning and MR imaging. Subsequently, increased density of the lunate is noted, followed by altered shape and dimin- ished size of the bone. Eventually, the lunate may collapse and fragment. Later on, complications may develop such as disruption of carpal architecture, scapholunate separation, or dissociation, with disruption of the scapholunate interosseous ligament, ulnar deviation of the triquetrum, and secondary degenerative joint disease in the radiocarpal and midcarpal compartments of the wrist.35 Tendon rupture resulting from erosion by the irregular and collapsed lunate has been Figure 68 A coronal T1-weighted MR image shows osseous lunotri- reported.47 quetral coalition. tq ϭ triquetrum, L ϭ lunate. Many classification systems of Kienböck’s disease have 276 R.A. Loredo, D.G. Sorge, and G. Garcia

steosis, enchondromatosis, hereditary multiple exostoses (HME) (Fig. 70), mesomelic dwarfism, and Turner syndrome. Degenerative Osteoarthritis Osteoarthritis (OA) is the most common arthropathy seen today. In primary osteoarthritis, the radiographic features include normal mineralization, nonuniform loss of joint space, subchondral new bone formation, osteophyte formation, cysts, subluxation, absence of erosions, and unilateral or bilateral asymmetrical distribution.15 Primary OA is virtually limited to the first carpometacarpal and the trapezioscaphoid joints. Characteristic findings are seen (Fig. 71) as follows: (1) at the first carpometacarpal joint, there is radial subluxation of the metacarpal base; (2) osteophyte formation occurs between the base of the first and second metacarpals; and (3) at the trapezioscaphoid area, joint space narrowing and ebur- nation may be the only findings.13,50 Osteoarthritic changes involving any other joint in the wrist should be considered secondary to another arthropathy Figure 70 Madelung deformity in a patient with HME. or to accidental or occupational trauma. In the posttraumatic setting, more widespread involvement of the wrist may be observed. Abnormalities of the radiocarpal and midcarpal compartments can follow a scaphoid fracture or Kienbock’s been proposed. The most popular is a four-stage system de- disease; changes at the DRUJ can appear following subluxa- scribed by Lichtman and coworkers that is based on radio- tion or dislocation, and abnormalities of the radiocarpal and 48 graphic abnormalities. In stage I, radiographs are usually midcarpal areas can be observed in pneumatic tool operators normal except for possible visualization of a fracture. Unless or professional athletes.50 As the degenerative joint disease a compression fracture is visible, this stage is clinically indis- worsens and becomes more widespread, there may be even- tinguishable from a wrist sprain. Stage II is when there are tual development of SLAC. abnormalities of radiodensity that are not accompanied by In secondary osteoarthritis, the joint space loss is uniform changes in size, shape, and relationships of the carpal bones. as this type of arthritis develops secondary to an underlying In stage III, the lunate bone is collapsed on the PA or AP view cartilage problem. The uniform involvement distinguishes and is elongated in the lateral view with abnormalities in carpal bone relationships. The capitate migrates proximally secondary to scapholunate dissociation. To assess the extent of collapse in stage III, the carpal height ratio can be measured (normal ratio ϭ 0.54 Ϯ 0.03). Carpal height ratio is becoming more important, because the results of treatment in stage III are related to the extent of collapse. Stage III is divided into stage IIIA (lunate collapse without fixed rotation of the scaphoid) and stage IIIB (lunate collapse with fixed rotation of the scaphoid and other secondary derangements). Stage IV is when there are changes of osteoarthritis.49 Madelung Deformity Madelung deformity is a developmental growth disturbance of the distal radial physis that manifests clinically during adolescence. The primary deformity is a bowing of the distal end of the radius typically in a volar direction while the ulna continues to grow in a straight fashion. The result is a short radius and a long ulna. It predominantly affects females and is usually bilateral, although one side may be symptomatic. Clinically, the carpus and hand appear to be displaced anterior to the forearm and the distal ulna is dorsally subluxed, forming a prominence that is most marked in pronation. Figure 71 Osteoarthritis of the wrist. Characteristic areas of involve- Potential causes of Madelung deformity include dyschondro- ment (arrows) are well demonstrated on this PA view. Radiographic evaluation of the wrist 277

wrist through the hand. Three routes of wrist extension of infection are via tendon sheaths, fascial planes, or lymphat- ics, with the tendon sheaths being the primary route of contamination.19 Particularly in the first and fifth digits, the synovial sheaths surrounding the flexor tendons of the hand allow extension of infection to the radial and ulnar bursae. As a result of contamination of the fifth finger, ulnar bursa, radial bursa, and first finger, a characteristic “horseshoe abscess” may develop.19 In the dorsum of the wrist, infection usually occurs in the subcutaneous or subaponeurotic space. However, the less frequent occurrence of infected extensor tenosynovitis can contaminate the wrist19 (Fig. 72). On radiographs, diffuse soft-tissue swelling (Fig. 73), osteoporosis, and articular and osseous destruction are evident. Infections in the fascial planes of the hand are numerous. However, they result in wrist joint or bone alterations less Figure 72 Abscess and tenosynovitis demonstrated with MR imag- frequently than those via the synovial sheaths.19 Lymphangi- ing. (A) Coronal T2-weighted MR image of the hand and wrist tis may result from superficial injuries with rapid extension demonstrating heterogeneous high signal intensity tenosynovitis (circle) with synovial sheath extension of synovitis and infection producing widespread swelling. In some cases, tenosynovi- from the hand into the wrist (arrows). (B) Sagittal T1-weighted MR tis, septicemia, osteomyelitis, and septic arthritis may result. image following intravenous administration of a gadolinium compound shows rim-enhancing flexor synovial sheath and adjacent Bacterial Osseous Infection abscess (box). In acute hematogenous osteomyelitis, males are affected more commonly, and a history of trauma or recent infection is often obtained.51 In the neonate or infant, Staphylococcus secondary osteoarthritis from primary OA where there is aureus, group B streptococcus, and Escherichia coli are the nonuniform joint space loss. bone isolates recovered most frequently; in children older than 1 year of age, S. aureus, Streptococcus pyogenes, and Hae- Infectious Diseases mophilus influenzae are responsible for most cases of hematogenous osteomyelitis. Gram-negative organisms assume Bacteria Soft-Tissue Infection importance as pathogens in bone and joint infections in Infection may be derived from hematogenous seeding, adults and in intravenous drug abusers. An acute or chronic spread from a contiguous source, direct implantation, or operative contamination. An infection can gain access to the

Figure 73 Dorsal hand infection. (A) Lateral view of the hand in a patient with dorsal soft-tissue cellulitis demonstrated as dorsal soft- tissue swelling (asterisks). (B) In a different patient, an infection has Figure 74 Radiographic ﬁndings in osteomyelitis and septic arthritis. progressed to involve the extensor carpi ulnaris with associated A PA wrist view shows soft-tissue swelling and obliteration of tissue soft-tissue swelling (asterisks) identiﬁed on a PA view. Osteopenia planes. Joint space loss, osteolysis, and marginal and central osseous of the ulnar styloid is consistent with early osseous destruction erosions involve the distal aspect of the radius and ulna and multiple (arrow). carpal bones. 278 R.A. Loredo, D.G. Sorge, and G. Garcia

than adults. The usual presentation is as a chronic extensor or flexor tenosynovitis, with joint involvement in some cases. There is a firm or boggy swelling with minimal tenderness and inflammation. Diagnosis may be delayed for several months.52,53 Infection with Mycobacterium fortuitum can occur following penetrating wounds and steroid injections,54 whereas infection with Mycobacterium marinum or Mycobac- terium terrae may occur following exposure to a marine or farm environment, respectively.53 Mycobacterium kansasii and Mycobacterium aviumintracellulare appear to be the most commonly isolated pathogens in deep mycobacterial infections.54,55 Mycobacterium tuberculosis infection occurs less commonly at the wrist than at other sites, such as the spine and hip, although the clinical presentation is similar. In cases of wrist involvement, dactylitis involving the metacarpals may present as a swollen wrist. Successful treatment of my- Figure 75 Septic arthritis and osteomyelitis. (A) Early and (B) late cobacterial infection consists of surgical debridement in con- disease radiographs. The PA wrist views show pancompartmental junction with long-term antibiotic therapy. narrowing of the wrist joints with progressive periarticular erosions Besides atypical mycobacterial infections, cutaneous, ten- (arrows). don sheath, and joint infection may be caused by Sporothrix schenckii.56 Bacteroides infection may follow a human bite respiratory tract infection is important in the pathogenesis of wound.57 In the immunocompromised patient, a variety of tuberculous, fungal, and pneumococcal osteomyelitis.19 unusual bacterial, myocobacterial, and fungal infections may The route of hematogenous bacterial seeding very much occur and are often difficult to eradicate (Fig. 75). depends on the age of the patient. In a child, a metaphyseal Chronic recurrent multifocal osteomyelitis is an inflamma- focus is frequent as the growth plate acts as a barrier. From tory disorder of unknown origin affecting the skeletally im- this site, cortical penetration can result in a subperiosteal mature. It is characterized by repeated episodes of fever, local abscess in those locations in which the growth plate is ex- pain, and swelling over the metaphyseal region of tubular traarticular or in a septic joint in those locations in which the bones and the clavicle. The radiographic appearance is sim- growth plate is intraarticular. Because the distal radial and ilar to that of osteomyelitis (Fig. 77). Antibiotics produce no ulnar metaphyses are extraarticular, secondary joint involve- response. The condition is treated with anti-inflammatory ment does not occur as a rule. In children, the radius and agents and it usually shows eventual spontaneous remis- ulna are affected in 5 to 9% of cases. In the infant (Ͻ1-year- sion.58 old), a metaphyseal focus may be complicated by epiphyseal extension owing to the vascular anatomy in this age group. In the adult, a subchondral focus in an epiphysis is not unusual owing to the vascular anatomy in this older age group19 (Fig. 74). In general, carpal bone osteomyelitis is extremely rare. The radiographic findings of osteomyelitis (Figs. 74 and 75) (including abscess, involucrum, and sequestration), septic arthritis (including joint space loss and marginal and central osseous erosions), and soft-tissue suppuration (including swelling, radiolucent streaks, and periostitis) are generally delayed for a variable period after the clinical onset of infection. Radiographs are nonspecific in the early stages, showing soft-tissue swelling and obliteration of tissue planes. After 10 days or so, diffuse or focal osteopenia, periosteal elevation, and new bone formation are seen. Localized cortical and medullary abscesses may be seen as single or multiple radiolucent cortical or medullary lesions with surrounding sclerosis. Cortical necrosis and sequestra formation may occur Figure 76 MR image findings in osteomyelitis and septic arthritis. (A) followed by sinus tract formation. Other diagnostic tech- T1-weighted coronal image shows abnormal intermediate signal niques, including scintigraphy and MR imaging (Fig. 76), intensity within the epiphysis of the ulna (U) and radius (R) and in allow accurate diagnosis at an earlier stage of the process. multiple carpal bones (C). (B) The corresponding T2-weighted coronal image shows abnormal increased signal intensity in the same areas within the ulna (U) and radius (R) and in the carpus. (C) Atypical Infections A T1-weighted coronal image following intravenous administration The wrist is the most commonly affected site in atypical my- of a gadolinium compound illustrates enhancement within these cobacterial infections. Children are affected less frequently same areas of involvement. Radiographic evaluation of the wrist 279

Figure 77 Chronic recurrent multifocal osteomyelitis. (A) A PA wrist view in a skeletally immature patient shows focal osteolysis of the Figure 78 Enchondroma. (A) Magnification view of the ulna shows a metaphysis of the radius (arrow). (B) In the same patient, an AP lucent lesion with a well-circumscribed nonsclerotic margin (ar- radiograph of the knee demonstrates focal areas of tibial osteomy- row). The matrix appears nonmineralized. (B) A coronal fluid-sen- elitis (arrows). sitive MR image illustrates a homogeneously bright matrix (arrow). (C) The corresponding axial T1-weighted image following administration of a gadolinium compound shows a rim-enhancing margin and intermediate signal intensity matrix (arrow). Tumors and Tumor-like Diseases Osteoblastic lesions vary from the benign bone island or With the exception of ganglion cysts, tumors and tumor-like osteoma to aggressive, fortunately rare, osteosarcoma. Bone conditions of the wrist are uncommon. As is true of the hand, islands (enostoses) are common, can occur in any carpal most tumors that occur in or about the wrist are benign, bone, are usually asymptomatic, and are picked up as inci- although malignancies do appear on occasion. All ages may dental findings. Occasionally, one may show increased radio- be affected and the size of the lesion is not a clue as to whether pharmaceutical uptake on a bone scan. However, more com- the lesion is benign or malignant. Tumor-like lesions may be monly, increased uptake represents a more active process, associated with a generalized metabolic disorder, such as in such as an osteoid osteoma. gout or xanthomatosis; or may develop following trauma as Osteoid osteoma (Fig. 81) is not an infrequent finding in in a foreign body reaction or granuloma.59 the wrist area. It usually manifests as pain that is relieved by salicylates. Conventional radiography, CT scanning, or MR Osseous—Benign Lytic lesions are very common in the carpal bones. If cystic, radiographically, they usually appear as rounded lucencies that are sharply demarcated by a thin margin of sclerosis. They usually contain mucinous material and probably represent degenerative cysts. Occasionally, they are called “in- traosseous ganglia” because they originate in the same location as the routine ganglia and represent remodeling of the bone and capsular tissues.60 Cartilaginous lesions, such as enchondromas, are relatively common (Fig. 78) and are often seen in conjunction with enchondromas in the hand. A variety of bone lesions occur in the radius and ulna. The distal aspect of the radius is one of the more common locations for occurrence of a giant cell tumor; the ulna is somewhat less common. Radiographically, extensive osteoclastic resorption and remodeling is seen with an irregular, thin shell of expanded bone and periosteum (Fig. 79). Osteo- chondromas can occur in the wrist and may involve the ra- Figure 79 Giant cell tumor. (A) PA view illustrating an expansile, dius, ulna, or carpal bones. Multiple osteochondromas may lytic lesion within the radius (arrow) that spans the metaphysis and be seen in the hereditable condition of osteochondromatosis the epiphysis in this skeletally mature patient. (B) A lateral view (Fig. 70). Rarely, epiphyseal osteochondromas (Trevor’s dis- shows extensive osteoclastic resorption and remodeling with an ease) may be a source of wrist pain (Fig. 80). irregular, thin shell of expanded bone and periosteum. 280 R.A. Loredo, D.G. Sorge, and G. Garcia

Figure 80 Trevor’s disease. PA wrist view shows enlargement and sclerosis/calciﬁcation of the radial epiphysis due to the presence of an osteochondroma (arrow).

imaging may delineate the nidus. It is not unusual for symptoms to be present for a year or more before a diagnosis is Figure 81 Osteoid osteoma. A PA view illustrates a focal sclerotic made. Radiothermal ablation of the nidus is curative. nidus of an osteoid osteoma within the capitate (arrow), surrounded by dense-appearing bone. C ϭ capitate, H ϭ hamate. Osseous—Malignant Primary skeletal malignancies of the carpus are rare. As in malignancies elsewhere, control of the primary tumor is usu- mass in patients of any age; however, it tends to occur during ally surgical. However, due to the central location of the the third to ﬁfth decades. Women are more commonly af- wrist, in terms of structures passing from the forearm to the fected and there may be a history of prior trauma. On the hand, a localized limb-sparing resection is seldom feasible.59 volar side, most ganglia originate from the joint capsule (Fig. MR imaging has become essential in staging of primary ma- 82) and some originate from the trapezioscaphoid joint. Fre- lignancies to determine whether the tumor is retained within a compartment or if metastasis is present. Although reports of metastatic tumors of the bones of the wrist and hand are quite uncommon, a large number of malignant tumors of the wrist are metastatic.61 There is no spe- ciﬁc predilection for any given primary tumor to metastasize to the bones of the wrist. The incidence of any type tends to match that of the tumors that metastasize to bone (ie, breast, lung, kidney). When tumors do metastasize to the carpus, they tend to cause destruction in several bones simulta- neously, which is often a clue to the aggressive nature of the process. Generally, the tumor is treated systemically, although occasionally, a local approach may be necessary for diagnostic reasons and for stabilization or pain relief.59 Soft Tissue—Benign In all reported series, the dorsal wrist ganglion cyst arising from the capsule over the scapholunate joint is the most Figure 82 Volar soft-tissue ganglion cyst. (A) Lateral and (B) PA common tumor of the hand/wrist. It may appear as a painless views of the wrist depict a volar, radial side soft tissue mass (arrows). Radiographic evaluation of the wrist 281

Figure 83 Lipoma. (A) A T1-weighted coronal image of the wrist Figure 84 Giant cell tumor of the tendon sheath. (A) Within the demonstrates extension of a high signal intensity soft-tissue mass dorsum of the ulnar wrist, there is an inhomogeneous mildly in- from the hand into the wrist (arrows). The mass follows fat signal creased signal intensity mass that is shown on a T2-weighted sagittal intensity (asterisk) on the (B) T1-weighted axial and (C) T2- MR image (arrow). (B) The mass appears as inhomogeneous inter- weighted fat suppressed axial images (asterisk). mediate signal intensity (asterisk) on a corresponding T1-weighted axial image. (C) The T1-weighted axial fat-suppressed image shows bright homogeneous enhancement of the lesion (asterisk). quently, they appear near the radial artery and cause compression of the artery or distort its path. These lesions may be found in the carpal tunnel or in Guyon’s canal.59 The exact type and a myxomatous or cystic type, and they are easily re- etiology of ganglia is still unknown. The most commonly moved. On the other hand, neurofibromas originate from the accepted theory involves remodeling of the fibrous capsular fibrous tissue of the epineurium or endoneurium, are more in- tissue of the joint. Collagen fiber breakdown products and filtrative between nerve bundles, and are difficult to remove intercellular mucin collect and as these collections coalesce, without causing damage to the nerve of origin.59 expand, and dissect their way toward the subcutaneous tis- Fibrous lesions can occur in the skin or subdermal soft tissues, a fibrous pseudocapsule is created.63 sues. They are relatively common lesions, may be single or mul- Lipomas may involve the wrist by way of extension from the tiple, and are locally invasive. They may or may not have fine hand or the forearm and appear as deep or superficial lesions stippled calcifications.59 A not-so-common, but interesting le- (Fig. 83). Not uncommonly they may be found during carpal tunnel release procedures. There are reports of large lipomas in the median nerve.64 Radiographically, lipomas in the wrist have the typical density of fat, unless they undergo metaplastic change and appear as a mixture of fat and myxoid material, or undergo osseous metaplasia following trauma.59 Giant cell tumors of the tendon sheath are slow growing, painless masses that may arise in association with synovial tissue of the joints or tendon sheaths on the flexor or extensor side of the wrist (Fig. 84). These benign growths contain numerous histiocytes and foreign body giant cells adjacent to hemosiderin deposits from minor bleeding episodes secondary to trauma.59 Vascular lesions more commonly include hemangiomas (Fig. 85), arteriovenous shunts (congenital or acquired), thromboses (after intravenous infusions or following trauma), or aneurysms (following repetitive trauma).59 Glomus tumors have been described in the carpal area.62 One of the more common lesions in the wrist is a neuroma Figure 85 Venous hemangioma. (A) A serpiginous intermediate in- caused by trauma following operative section of a nerve, pre- homogeneous signal intensity mass is seen on a T1-weighted coro- senting as a tender mass. Neuromas of the superficial radial and nal MR image of the wrist (circle). (B) The axial T2-weighted fat- palmar cutaneous branch of the median nerve are particularly suppressed image shows the mass to be inhomogeneous increased problematic.59 A neurofibroma or a neurilemoma may occur in signal intensity (arrows). (C) Following gadolinium administration, any of the nerves at the wrist. Neurilemomas arise from the mass (arrows) shows inhomogeneous enhancement on an axial Schwann cells and are composed of two types of tissue, a cellular T1-weighted MR image. 282 R.A. Loredo, D.G. Sorge, and G. Garcia

inflammatory problem. On the PA view, early erosions in the wrist may be seen in specific locations, namely, the waist of the navicular, the waist of the capitate, the articulation of the hamate with the base of the small finger metacarpal, the articulation of the thumb metacarpal with the trapezium, the radial styloid, and the ulnar styloid.13 As the disease progresses (Fig. 87), there is pancompartmental loss of cartilage and joint spaces of the wrist; the soft-tissue swelling decreases, and the juxta-articular osteoporosis becomes diffuse. The initial subtle marginal erosions eventually become large subchondral erosions. Subcutane- ous rheumatoid nodules may develop in 25% of the patients, without bone destruction.13 As arthritis mutilans develops (Fig. 88), there is lack of any recognizable joint space as bone ankylosis occurs. One interesting finding that occurs at the wrist in patients Figure 86 Fibrolipomatous hamartoma in a 22-year-old male. (A) A with rheumatoid arthritis is the “caput ulnae syndrome.” The T1-weighted axial MR image shows marked enlargement of the syndrome consists of pain, limited motion, and dorsal prom- median nerve with multiple intermediate and low signal intensity inence of the distal end of an eroded ulna. The eroded and longitudinal tubular regions (arrows), creating the appearance of a abnormally located ulnar head impinges into the extensor cable. (B) The corresponding T2-weighted axial image demonstrates the tubular regions as high signal intensity (arrows) with inter- tendon compartments on the dorsum of the wrist. This pro- spersed areas of low signal intensity. (C) A gadolinium enhanced duces fraying of the surfaces of the tendons in association axial image shows inhomogeneous bright enhancement of the lesion with tenosynovitis, a situation that leads to weakening of the (arrows). (Courtesy of Donald Resnick, MD San Diego, CA.) tendons with subsequent rupture of the tendons beginning on the ulnar side of the wrist.67 In evaluation of the wrist, MR imaging has not yet replaced quality conventional radiography, although rheumatoid ar- sion, called a fibrolipoma (Fig. 86), is a hamartomatous enlargement of the median nerve. It has been associated with macro- dactyly of the fingers or overgrowth of portions of the hand, a condition known as, “macrodystrophia lipomatosa.”65,66

Synovial/Inflammatory Diseases: Arthritis Imaging modalities that may be utilized for the evaluation of articular disease include conventional radiography, computed tomography, scintigraphy, ultrasonography, and magnetic resonance imaging. Evaluation of articular disease should always begin with conventional radiography. If quality films are obtained (appropriate patient positioning in at least two orthogonal planes), the extent and severity of joint involvement, and the disease progression or regression may be documented. In some cases, special views may be utilized to evaluate for specific joint involvement. Although PA and AP oblique (Norgaard) radiographs of the hands are the most informative for evaluation of arthritis, the wrist may show characteristic changes on these views as well. The PA view provides for evaluation of mineralization and soft-tissue involvement. In the Norgaard view of the wrist, the pisiform and the hamate are well demonstrated, and this view profiles the triquetrum-pisiform joint.13,50 Rheumatoid Arthritis In rheumatoid arthritis, the earliest radiographic changes are Figure 87 Progressive changes in rheumatoid arthritis. A PA view of symmetric periarticular soft-tissue swelling and juxta-articu- the wrist in a patient with RA shows progressive marginal erosions lar osteoporosis. Although these changes are nonspecific, that progressively involved more and more of the articular surface to they help support any clinical suspicion of an underlying become large subchondral erosions. Radiographic evaluation of the wrist 283

Figure 89 Psoriatic arthritis. An AP oblique (Norgaard) view of the wrist illustrates a few hallmarks of this disorder: joint space loss, bone proliferation, and erosions (ellipse) in each bone that is out- lined above.

Figure 88 Arthritis mutilans. There is lack of any recognizable radiocarpal and intercarpal joints as bone ankylosis (box) has occurred. Similar changes involve multiple carpometacarpal joints (within box). other features will distinguish psoriatic arthritis from rheumatoid arthritis (ie, usually DIP and/or PIP involvement and/or evidence of bone proliferation in psoriatic arthropa- 13 thritis has been the arthropathy most extensively studied by thy). MR imaging. MR imaging can demonstrate synovitis, tenosynovitis, erosion, synovial cyst formation, bursitis, tendon Reiter’s Disease rupture, and fibrocartilaginous degeneration associated with The classic radiographic features of Reiter’s disease (Fig. 90) rheumatoid arthritis.15 The literature states that MR imaging are identical to those of psoriatic arthritis with the erosive may show erosions earlier than plain films and offers the disease and bone formation being the predominant findings. potential of directly demonstrating the extent of synovial hy- However, the hands and wrists are less frequently involved in pertrophy and cartilage destruction.68 The MR image dem- Reiter’s than in psoriatic arthropathy. When the upper ex- onstration of the synovium may be very important to the tremity is affected, the hand is the most common area of rheumatologist, if the physical examination is equivocal in involvement.13 determining the effect of a particular treatment regimen. Sy- novium may demonstrate intermediate signal intensity on T1-weighted images relative to the low signal intensity of adjacent fluid and show intermediate signal intensity on T2- weighted images compared with the relatively high signal of an effusion.68 However, frequently, synovium cannot be differentiated from effusion without use of intravenous gadolinium. Active synovitis enhances following the administration of gadolinium. However, the affected joint must be imaged immediately, as gadolinium will diffuse into the joint if imaging is delayed.68 Psoriatic Arthritis In the hands or wrists, the hallmarks of this disorder are bilateral asymmetrical distribution of soft-tissue swelling, normal mineralization (following the initial stage of the disease), joint space loss (sometimes dramatic), bone proliferation (adjacent to erosions, along shafts, across joints, and at tendon and ligament insertions), and erosions (usually DIP or PIP joints) (Fig. 89).13 In the wrist, psoriatic arthritis may appear in the carpal bones in conjunction with ray involve- Figure 90 Reiter’s disease. A PA wrist view shows multiple erosive ment or it may appear only in the wrist in a pattern similar to defects (arrows) along the ulnar head and styloid and at the level of that observed in rheumatoid arthritis. In the latter pattern, the distal radioulnar joint. 284 R.A. Loredo, D.G. Sorge, and G. Garcia

Figure 91 Chondrocalcinosis in CPPD. Chondrocalcinosis is most frequently encountered in the triangular fibrocartilage (arrow) and/or the hyaline cartilage between the lunate and the triquetrum (double arrow) and that between the scaphoid and lunate (hatched arrow). scaphoid ϭ S, lunate ϭ L, triquetrum ϭ tq, capitate ϭ C. Figure 92 Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease. There is typically uniform joint space loss, subchondral new bone formation, and cyst formation (arrows), with the changes Crystal-Induced and Related Diseases in a distribution different from that of primary OA. CPPD crystal deposition disease is a common disorder and the most common crystal arthropathy. CPPD crystals deposit In the wrist, gout affects the bone, joint, or soft tissue in a in hyaline and fibrous cartilage, producing a radiographic sporadic, asymmetrical fashion. The radiographic changes of picture of calcified cartilage (chondrocalcinosis). It is seen the disease occur in response to urate crystals that deposit in most frequently in the knee, pubic symphysis, and wrist, tissues such as cartilage, tendon sheaths, and bursa. If the with the hips, shoulder, and elbow involved in decreasing urate crystals deposit in cartilage, the primary radiographic order of frequency.13 The radiographic diagnosis can be picture is that of osteoarthritis. Mineralization is maintained. made when two or more different joints (one wrist and one There may be pancompartmental involvement of the wrist; knee, not two wrists or two knees) in the skeleton demon- however, frequently there is preferential involvement of the strate chondrocalcinosis.13 The radiographic picture varies carpometacarpal joints with erosive change (Fig. 93). Many from chondrocalcinosis alone to severe arthropathy (Figs. 91 of the erosions have sclerotic borders and often there are and 92). When arthropathy occurs, the radiographic picture overhanging edges of cortex (Fig. 94). The joint space may or of CPPD crystal deposition disease resembles that of osteoar- may not be preserved, although gout is one of the few arthritis. The arthropathy of the wrist most commonly affects thropathies that is known for causing significant changes the radiocarpal joint. There is typically uniform joint space around the joint while maintaining the joint space.69 One loss, subchondral new bone formation, and cyst formation, with the changes in distribution different from that of primary OA. Normal mineralization, variable osteophyte formation, cyst formation (more prominent than in OA), and bilateral distribution are other typical features of the arthropathy. The wrist arthropathy is found in 70% of patients with the disease and chondrocalcinosis is found in 65% of the patients.13 Chondrocalcinosis is most frequently encountered in the triangular fibrocartilage and/or the hyaline cartilage between the lunate and the triquetrum and between the navicular and the lunate. This may lead to SL ligamentous disruption with subsequent SL disassociation.13 If there is SL dissociation, there may be associated narrowing of the capitolunate joint space. The characteristic appearance of these latter findings has been described as a “stepladder” configu- ration.13 The only other two diseases known to cause deposition of CPPD crystals in cartilage, other than idiopathic Figure 93 Gout. There is preferential involvement of the carpometa- CPPD crystal deposition disease, are hyperparathyroidism carpal joints with erosive changes (arrows) seen in this patient with and hemochromatosis.13 longstanding gout. Radiographic evaluation of the wrist 285

Figure 94 Erosion and gouty tophi. Dense soft-tissue swelling (calcified tophus) about the ulna styloid (arrow) and thumb (hatched arrow) are noted. The thumb metacarpal shows a large para-articular erosion (arrowhead) with an overhanging edge of cortex. Note Figure 96 the enlarged ends of the thumb metacarpal and proximal phalanx. Extensive hydroxyapatite deposition in a patient with renal osteodystrophy. may see irregular bone spicules at sites of tendon and ligamentous attachment. Enlargement of ends of bones may also ous systemic diseases, such as scleroderma, dermatomyositis, occur. If urate deposits in soft tissue, chronic tophaceous renal osteodystrophy (Fig. 96), hypervitaminosis D, and gout will result (Fig. 94). A tophus deposited on the extensor milk-alkali syndrome.13 When there is no underlying aspect of a joint may cause significant erosive change of the systemic disease, the entity is known as hydroxyapatite dep- dorsal aspect of the joint while preserving the flexor side.13 osition disease (HADD). In the triangular fibrocartilage Hydroxyapatite depositional disease is an extremely com- complex, hydroxyapatite deposition may simulate the ap- mon disorder that primarily causes periarticular disease. The pearance of CPPD crystal deposition.70 Possible complica- wrist is involved more frequently than the hand. There may tions of calcium hydroxyapatite deposition within the tendon be bilateral, polyarticular involvement. Calcium hydroxyap- sheaths or tendons include tendon rupture and intraarticular atite crystals may deposit in bursae, tendons, musculotendi- extension of the calcification, resulting in articular disease, nous junctions, ligaments, and within soft tissues of the wrist on rare occasion.13 producing bursitis, tendinopathy, or carpal tunnel syn- Rare deposition diseases that may affect the wrist are drome.70,71 Calcific deposits may be seen, most commonly, in hemochromatosis and Wilson’s disease. These disorders have or about the tendon of the flexor carpi ulnaris (adjacent to the all been associated with chondrocalcinosis. Whether or not it pisiform) (Fig. 95).72 Deposits also occur in or near the ten- is true that CPPD crystal deposits in the hyaline or fibrous dons of the flexor carpi radialis (on the volar side of the cartilage or some other substance, degeneration and second- radiocarpal joint), common flexors (near the volar aspect of ary osteoarthritis occur.13 Radiographically, each of the dis- the wrist), and the extensor carpi ulnaris (adjacent to the eases has distinguishing features. distal end of the ulna).70 The crystals may be poorly defined Hemochromatosis, a rare disease leading to marked iron or well defined. Calcific deposits are often described in vari- deposition throughout the body, is almost identical to that of CPPD crystal deposition in that there is osteoarthritis in atypical sites compared with primary OA. Characteristic findings in the hand specifically involve the second and third meta- carpophalangeal joints. There may or may not be involvement of the wrist. However, if the wrist is involved (Fig. 97), there is usually involvement of the common carpometacarpal, midcarpal, and/or the first carpometacarpal compartments, with sparing of the radiocarpal compartment.13 The changes observed are those of atypical OA or CPPD crystal deposition disease. Wilson’s disease is extremely rare. Copper is the substance that is abnormally deposited in various tissues. Radiograph- Figure 95 Hydroxyapatite deposition on the radial aspect of the ically, chondrocalcinosis may be observed. However, it re- wrist. (A) A lateral view shows calcification (arrows) adjacent to the mains unclear whether the calcification seen is secondary to pisiform within the tendon of the flexor carpi ulnaris muscle. (B) true CPPD crystals or bone fragmentation in the joint.13 In Calcification (arrow) on the radial side of the wrist is seen on a PA approximately 50% of patients, an arthropathy occurs. The oblique view. arthropathy is distinctive as there is marked irregularity of 286 R.A. Loredo, D.G. Sorge, and G. Garcia

(during the acute phase) and central gull wing erosions. Eventual ankylosis may ensue.

Connective Tissue Disorders The collagen vascular diseases (connective tissue diseases) are a group of conditions that have multisystem involvement. For the most part, the articular symptoms play a minor role in each condition. However, there are distinctive features in each disease.

Systemic Lupus Erythematosus Systemic lupus erythematosus (SLE) is the most common of the collagen vascular diseases and it is associated with articular symptoms in 75 to 90% of affected individuals.13,73 Most often, this disease is described as a bilateral deforming nonerosive arthritis (Fig. 99). Soft-tissue swelling may be seen early in the disease, followed by soft-tissue atrophy. Juxta- Figure 97 Hemochromatosis affecting the hand and wrist. The meta- articular osteoporosis is observed with eventual diffuse demi- carpophalangeal joints show osteoarthritic changes with character- neralization. Reducible subluxation and/or dislocation with- istic “hook osteophytes” (arrows). out erosions are the hallmark of SLE.13,73 Osteonecrosis is a feature of SLE, whether or not the pa- the cortex and subchondral bone giving a “paint brush” ap- tient is receiving or has received steroid treatment. It usually 13 pearance.15 Due to significant subchondral bone fragmenta- occurs bilaterally and asymmetrically. As in osteonecrosis tion, the condition may appear as osteochondritis dissecans. secondary to other etiologies, the radiographic findings are Ossicles may be seen in the joint (Fig. 98).13 The arthropathy similar. Initial osteoporosis may or may not be appreciated otherwise resembles primary osteoarthritis in an atypical dis- radiographically. The first radiographic change that may be tribution. observed is an ill-defined increased bone density surrounded by osteoporosis creating a “smudgy” appearance.13 As the Erosive Osteoarthritis condition progresses, a subchondral lucency is seen due to subchondral fragmentation. This is followed by articular sur- Erosive osteoarthritis (OA) is an inflammatory condition that is superimposed on underlying osteoarthritic changes. It is most often described in postmenopausal females. Radio- graphically, erosive osteoarthritis is similar to primary OA in distribution in the wrist. However, the inflammatory component of erosive OA causes periarticular soft-tissue swelling

Figure 98 Wilson’s disease. Ossicles (arrows) are seen within, and Figure 99 Systemic lupus erythematosus. A deforming, nonerosive adjacent to, multiple joints. arthritis is shown on a lateral view. Radiographic evaluation of the wrist 287

disease, juvenile-onset adult-type (seropositive) rheumatoid arthritis, and Still’s disease (seronegative chronic arthritis).74 All of these disorders, except for Still’s disease, tend to occur in older children and therefore usually behave like their adult counterpart. Juvenile-onset adult-type (seropositive) rheumatoid arthritis differs from adult rheumatoid arthritis in two ways. First, a periostitis is frequently present in the metaphyses of the phalanges, metacarpals, and metatarsals. Second, there is significant erosive disease without joint space loss.13,74 Still’s disease (seronegative chronic arthritis) makes up 70% of the cases of JCA. The radiographic changes are those of chronic inflammation and hyperemia in a joint that is undergoing growth and change; the radiographic changes are as follows:13 1. Periarticular soft-tissue swelling 2. Osteoporosis—juxta-articular, metaphyseal lucent bands, and/or diffuse. 3. Periostitis 4. Overgrown or ballooned epiphyses Figure 100 Scleroderma. Amorphous subcutaneous calcification (ar- 5. Advanced skeletal maturation—premature fusion rows) within the ulnar side soft tissues is demonstrated on a PA 6. Late joint space loss view. 7. Late erosive disease 8. Ankylosis 9. Bilateral and symmetrical distribution in polyarticular face deformity, collapse, and eventual secondary osteoarthri- disease; sporadic in pauciarticular or monoarticular tis. disease Calcification is the third typical but nonspecific feature of 10. Distribution in hand and wrist, foot, knee, ankle, hip, SLE. It may be present in the subcutaneous tissues and may cervical spine, and mandible, in decreasing order, in appear as linear and streaky density. polyarticular disease; distribution in knee, ankle, elbow, and wrist in pauciarticular or monoarticular Scleroderma and Dermatomyositis disease. Approximately 46% of patients with scleroderma have artic- The wrist is more often involved than the hand. Early in 13 ular symptoms. The radiographic findings appear to be the disease there is juxta-articular osteoporosis, soft-tissue limited primarily to the hands and secondarily to the wrist. In swelling secondary to synovitis, and a loss of complete wrist the wrist, the findings are resorption of soft tissue and amor- extension.74 With persistence of the disease process, there is phous subcutaneous calcification (Fig. 100). acceleration of growth maturation in the wrist, as seen by Dermatomyositis is most commonly associated with the increase in the number and size of the carpal bones. The radiographic abnormality of soft-tissue calcification. The cal- carpal bones become irregular in their contour secondary to cification is usually along the intermuscular fascial planes erosions occurring at a young age and repairing with growth. and may be seen within the subcutaneous tissues and about Nineteen percent of patients demonstrate ankylosis at the 13 joints. At times, transient osteoporosis may be seen. wrist with relative sparing of one of the three compartments. Most frequently the common carpometacarpal and midcar- Mixed Connective Tissue Disease pal compartments are ankylosed, with total sparing of the Mixed connective tissue disease (MCTD) is a disease that is radiocarpal compartment. Spontaneous intercarpal or radio- made up by a combination of collagen vascular diseases, such carpal fusion occurs more commonly in children with JRA as SLE, scleroderma, and/or rheumatoid arthritis. The radio- than in adults. graphic features of this combined disorder are an “overlap” of Secondary changes may occur in the distal radial epiphysis findings observed in each condition. To make the radio- consisting of wedging and fragmentation (Fig. 101). With graphic diagnosis, one should identify at least one feature of time, an ulnar deviation of the wrist and radial deviation of a specific arthritis and one feature of another type of arthritis. the digits appear.51,74 The wrist deformity is in contrast to the Some patients display a unique feature of preferential anky- usual pattern of radial deviation seen in adults. It may be losis of the capitate to the trapezoid.13 related in part to shortening of the ulna secondary to premature physeal arrest. This, in conjunction with attenuation of Juvenile Chronic Arthritis the volar wrist ligaments, results in ulnar and volar translo- Juvenile chronic arthritis (JCA) includes juvenile-onset anky- cation of the carpus, leading to a bayonet deformity.51 In- losing spondylitis, psoriatic arthritis of inflammatory bowel volvement of the basal joint of the thumb may lead to dorsal 288 R.A. Loredo, D.G. Sorge, and G. Garcia

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