THE-JOURNALOF...... kL 0 1988 13A, NUMBER1 SURGERY N

AMERICAN VOLUME journal SOCIETY FOR SURGERY OF THE HAND

ORIGINAL COMMUNICATIONS Relative motion of selected carpal : [cGrouther A kinematic analysis of the normal al The relative motion of selected and the was studied using five cadaver specimens labeled with metal markersto precisely quantitate their motions. Data was obtained by meansof a combinationof orthoradiography, sonic digitization, and computeranalysis. We concludethat the wrist functions as two carpal rows wiith the distal row bonesrelatively tightly airman: boundto one another and the proximal row bones less so but still movingtogether. Therefore, we theorize that the proximalrow functions as a variable geometryintercalated segmentbetween the distal row and the radius-triangular fibrocartilage. (J HANoSURG 1988;13A:1-10.)

L. K. Ruby, MD, W. P. Cooney III, MD, K. N. An, PhD, R. L. Linscheid, MD, and E. Y. S. Chao, PhD, Boston, Mass., and Rochester, Minn.

The study of wrist motion, both normal pathologic, has interested investigators since the of the 19th century. 1-3 Before 1895, investiga- consisted of direct visualization of the carpus, indirect methods were not available. In 1896, reported the first radiologic study of a col- i:.:~li! lea’gue’s hand, and Johnson,5 Fisk6 and others, 7’3 stud- ~i[’!i~iiied wrist motion with x-ray examination. Recently, ¯ ~icomputer analysis has been used to increase the ac- :ii~!ii.~!iicuracy and-precision of measurements of wrist ! i~/ik motion. ~" 2o :":~/i Although some of the recent authors’" have studied

Fig. 1. Three dimensional carpal motion is measured the Section of HandSurgery, Departmentof OrthopedicSur- from a fixed reference of orthogonal radiographs and defined gery, Tufts UniversitySchool of Medicine,Boston, Mass. and the as x,y,z axis systembased on the distal radius. Orthopedic BiomeehanicsLaboratory, MayoClinic/Mayo Foun-. ~ clarion, Rochester,Minn. Receivedfor publicationFeb. 9, 1987;accepted in revised formJune individual° carpal motions, none except Delange et al) 10, 1987.,. -. have reported individual carpal bone motion with re- in~nyform have been receivedor will be receivedfrom spect to another carpal using computer analysis. We a commercialparty related directly or indirectly to the subjectof undertook this study to test some of the currently pop- this article. ular theories of wrist function and directly measure Reprint requests: LeonardK. Ruby,MD, Tufts’New England Medical Center, 750 WashingtonSt., Boston, MA02111-1854. intracarpal motion.

THEJOURNAL OF HANDSURGERY 1 2 Ruby et al. TheJournal of HAND

Fig. 2. Customdesigned tendon loading device and plexiglass biplanar x-raygrid. Theradius andulnar are rigidly mounted to the frame. Tendonforces to movethe wrist is actuated throughcalibrated springs.

Fig. 3. Biplanar radiographsdemonstrate "U"-shaped metal Materials and methods staples embeddedinto each carpal bone(scaphoid, lunate, Froma group of 12 fresh-frozen humanforearm spec- triquetrum, capitate, and hamate)to serve as markersfor imens, five were chosen for study that were free of tracing carpal bonemotion. A, xy or anteroposteriorview. disease and traumatic changes. The age range of the B, xz or lateral view. five specimens was from 23 to 55 years. There were four males and one female. By meansof the techniques surface of the radius. The dorsal wrist capsule was described below, in four the radius, scaphoid, lunate, triquetmm, and capitate were labeled; in the opened, preserving major dorsal carpal ligaments. markers were placed into the appropriate carpal bones fifth wrist, the radius, trapezoid, capitate, hamate,and triquetrum were labeled. The was not labeled and the dorsal capsule was closed. Each specimen was in any wrist. then rigidly mountedin a holding device with the radius and fixed by two Steinmanpins (Fig: 2). To apply The motions of the selected carpal bones were de- active force across the wrist and to movethe wrist under termined using biplanar orthoradiographs (two radio- gramspositioned at 90° to one another and fixed relative active tendon loading, each musculotendinousunit that to the x-ray source) (Fig. 1). The selected bones were crossed the wrist was loaded by attaching heavy (25 pound test) to each tendon group. The degree labeled with heavy duty "U"-shaped staples (Crafts- load was based on muscle cross-sectional area man, Sears RobuckCo., Chicago, Ill.) embeddedinto each carpal bone. Four identifiable positions on each studies. The tension was delivered by calibrated springs staple served as reference points to record carpal bone attached to the .holding device. Thus, active tendon motion. A separate T marker was placed on the dorsal loading was simulated to determine wrist motion and carpal bone alignment under phys!ologic conditions. oumalof ;,.- /ol. 13A,No. 1 Relative motion of selected carpal bones3 JRGERY: January1988

Fig. 4. Screwdisplacement axis defines individual carpal bonemotion along rotation andtranslation axis systems,in- dividualcarpal bones rotate andtranslate similarto the threads of a screw.

The loaded specimen was brought to the x-ray room where a fixed distance orthogonal x-ray system was available. Biplanar radiographs were taken in five po- s .!ons for each specimen:neutral, flexion, extension, r~.dial deviation, and ulnar deviation. Thesewrist po- sitions were obtained by using the spring loaded tendons 1~ ¯ to simulate physiologic motion and force. The load Fig. 5. Wrist motiondefined by x,y,z, axis system. Xaxis on each tendon group was measured in each position. alignedparallelwith the shaft of radius, positiveend proximal: This averaged 10.6 kg total load for each of the five y axis alignedtransversely across the carpusat 90° to the x specimens, axis, ppsitiveend radial. Z axis aligned90 ° to boththe x and Multidirectional wrist positions were measuredfrom y axis. ~edmetal ~:,~. biplanar films (Fig. 3, Aand B) taken througha custom lunate, designedplexiglass x-ray grid that providedlocalization xkers for and:three_dimensionalorientation of the carpal bones. ior view. Relative motions betweentwo selected carpal bones._ 2"he data points from the U markers and T marker were or between an individual carpal bone and the radius then digiti2ed with the sonic digitizer (Graf/PenScience during wrist motion were described using the concept Accessories Corp., Southport, Conn.) and the Apple of screw displacementaxis.Z~’ zz The screwaxis concept ;ule was IIe computer(USI International, Brisane, Calif.). The implies that each carpal boneboth rotates and translates digitized two-dimensionalcoordinates for each of the nts. The along its ownaxis system, whichis not fixed but moves al bones four identifiable "points" of each U marker and four up and down, similar to the threads of a screw aaen was I "points" of the T markersin both anteriorposterior (x,y) (Fig. 4). In this study, carpal bones were shownto both ae radius and lateral (x,z) planes were then used to reconstruct rotate and translate along an individual "screwaxis" as the corresponding three-dimensional coordinates in ro apply the ,wrist movedfrom flexion to extensionor from radial ist under space. Since the markerswere rigidly fixed to the bones, to ulnar deviation although the predominantmotion was unit that ,~ilithei definedlocationby andmarkers orientation alongthe of specific each labeledaxissystem bone ~see was rotatory. :avy line To ensure that these observations were accurate and egree of below). These data were analyzed by PDP11/34 (Dig- reproducible, repeat testing was performed. The exact ~nal area ital Equipment Corp., Maynard, MA.) computer pro- alignment of carpal bones was described by an. x,y,z t springs gramsfor calculation of the relative three-dimensional axis system (Fig. 5). This system was based on the motionof individual carpal bones in space and applied : tendon bone structure of the distal radius. The x axis was de- tion and to carpal bone kinematics during maximumwrist fined as that axis that lies along the shah of the radius aditions. motion. 4 Ruby et al. The Journal HAND SURG

Y axis Global 1

Y axis Y axis $caphotd-Lunate 24*

Fig. 6. A, Pronation-supinationof carpal bone(s) occursabout thex axis longitudinal.B, Flexion-extensionof carpal bone(s) occursabout the y axis (transverse).C, Radial-ulnardeviation Fig. 7. A, Wrist-flexion-extensionis 112° and occursabout.:’ of carpal bone(s)occurs about the z axis (or vertical axis). the y axis. B, Scapholunatemotion is (24°) and occurs madlyabout the y axis. C, Lunotriquetral motionis andoccurs primadly about the y axis (flexion-extensionaxis). with the positive end pointing in the proximaldirection. The y axis was defined as that axis that lies perpendic- ular to the x axis with the positive end pointing in the ulnar rotation (Fig. 6, C). Wrist motionof the capitate radial direction in the right hand. Thez axis is that axis with respect to the distal radius is called global motion.’ formedby the "right hand rule" of free body analysis; Motionbetween the proximal and distal carpal rows that is, perpendicular to both x and y axes, with the referred to as intercarpal motion. Individual. positive end pointing in the palmardirection in the right tion (e.g., motion betweenthe scaphoid and the hand. In clinical terms of wrist motion, the x axis rep- within the proximal carpal row) is called resents the axis of longitudinal rotation (or pronation- bone motion. The results of relative motion of carpal supination axis) (Fig. 6, A). The y axis is transverse bones were described based on the defined coordinate and represents the flexion-extension axis (Fig. 6, B). axis system .and can be described by three components Thez axis is vertical and represents the axis of radial- along the x, y, and z coordinates. 13A, No. 1 Relative motion of selected carpal bones January 1988

I. Relative carpal bone motion with respect to radius (n = 4)

l Orientationofscrew~ Carpaltranslation Moving Reference Rotation (°) (mm) Wrist motion carpal bone Icarpal bone Radius 0.09 -0.93 -0.07 111.5 ± 15.8 -0.8 ± 0.7 Flexionto extension Capitate 1.9 ---1.3 Radius 0.09 - 0.94 - 0.05 80.3--- 7.9 Scaphoid -0,6 -- 1.7 Radius 0.24 -0.91 -0.14 58.6 +-- 15.1 Lunate -0.7 --- 1.8 Triquetrurn Radius 0.13 - 0.94 - 0.12 70~9 ± 17.2 - 0.91 - 0.14 25.4 2 25.8 -1:28 ± 9.8 Neutral(0 °) to extension Lunate Radius 0.24 - 0.91 - 0.14 35.0 ± 12.8 0.73 ± 0.6 Neutral(0 °) to flexion Lunate Radius 0.24 Radius 0.27 0.24 0.88 36.0 ± 6.8 -3.3 -- 2.3 deviationto ulnar Capitate 1.6 ± 1.0 Scaphoid Radius 0.20 - 0.66 0.42 51.4 +- 20.2 deviation -2.0 --- 0.5 Lunate Radius 0.12 - 0.72 0.49 35.1 ± 16.3 28.6-+ 10.0 -0.5 - 1.5 Triquetrum Radius 0.15 -0.04 0.65

*Cecrdinates defined on radius. x Ax~s, + pronation, - supination; y axis, + flexion, - extension; z axis, + ulnar deviation, - radial deviation.

Table II. Proximal row intracarpal motion (n = 4) Orientation ofscrewaxis* Rotation Carpaltranslation Moving . Reference y z (°) (ram) wrist motion carpal bone carpal bone 0.03 --- 0.77 Scaphoid Lunate 0.01 -0.92 0.19 24.60+-- 15.40 Flexionto extension 0.09 ± 0.87 Triquetrum Lunate -0.21 -0.89 0.08 18.00--- 2.20 ~ -0.55 9.97 ± 2.60 -0.27 ± 0.55 Radialdeviation to ulnar Scaphoid Lunate 0.07 0.50 0.16 14.00 ± 6.20 0.07 - 0.28 deviation Triquetrum Lunate 0.15 0.79

*Coordinate defined on radius. ,x Axis, + pronation, - supination; y axis, + flexion, - extension; z axis, + ulnar deviation, ’- radial deviation.

the scaphoid rotates 51.4 ° and° the triquetrum 28.6 ,,o,* ,," ~’(~;~"~)Motion of the wrist is a complex interaction of seven (Table I). This proximal carpal row rotation occurs pri- : i~ ~.:carpal bones, each with a separate axis of motion yet marily about the y axis (flexion-extension), but there . :!~/interde~endent on the position of adjacent carpal corn- also a significant amount of motion about the z axis : N!ponents and the alignment of the carpus with the distal (radial-ulnar deviation). The scaphoid, lunate, and tri- .i~i radius. The number of possible combinations of relative quetrum move from a flexed position in radial deviation s about i’.~icarpal position is so large that only the most clinically through neutral to an extended position in ulnar devia- tion. The majority of this flexion-extension movement ars pri-~.ii: ~iirelevant ~wer~ examined and are reported in this study. ° occurs f~omthe neutral wrist position to’ulnar deviation, is) (18 Global wrist motion is defined as movement of the n axis). : !;~capitate with respect to the distal radius (Table I). Dur- rather than from radial deviation to neutral. Flexion- extension, radial-ulnar angulation, and carpal transla- : ~iing simulated full flexion-extension of 111.5° (motion tion are present as the proximal row moves on the distal : i:~i!about the y axis), the capitate rotates about the y axis respect to the distal radius. The scaphoid rotates radius in both flexion-extension and radial-ulnar devia- the lunate 58.6°, and the triquetrum 70.1 °. In tion. The amount of carpal bone translation, however, is extremely small (range from 0.5 to 3.3 mm) (Ta- ?OWS model of dynamically loaded fresh cadaver wrist ~al carpal motion is undoubtedly less than in ble II). measurements of wrist motion that are a com- Intracarpal bone motion occurs between both the acarpal of radiocarpal, midcarpal, and carpalmetacarpal proximal row bones and distal row bones during wrist carpal movement. Intracarpal proximal row motion (Table II) is measured with the lunate as the reference body. Note rdinate During global wrist motion from full radial deviation ~onents °) that as the .wrist moves from flexion to extension full ulnar deviation (motion about the z axis, 36.0 ° 35.1° with respect to the distal radius, (Fig. 7, A) the scaphoid extends 24.6 with respect to Rubyet al. TheJournal HAND SURGERy

¥ axis Y axis Z ax|s Global 36o

axis Soaphold-Lunateo 10 ig. 9. Aand B, In wrist flexion-extensionof 112°, capito- ~ lunate motionis 56° (about the y axis). C and D, In ~st radiouln~deviation, capito-lunate motionis 40°, primarily about the flexion-extensionaxis (y axis), with only Fig. 8. A, Wristradioulnar deviation is 36° andoccurs about componentsof radioulnar motion(z axis) and the z axis. B, Scapholunatemotion is 10° aboutthe y axis supination(x axis). and C, 10° about° the z axis. D, Triquetrolunatemotion is 14 and occurs predominantlyabout the y axis during wrist ra- °, dioulnardeviation (Table II). the capitate 8.9 whiletrapezoid capitate motionis only r!~il 6.8°. In radial to ulnar deviation, the hamate 3.9° on the capitate, and capito-trapezoidal motion °. the lunate (Fig. 7, B). During the same motion, the 5.1 triquetrum extends 18.0° (Fig. 7, C) with respect The last important carpal motion that was measured the lunate, indicating overall greater scapholunatethan is that which occurs betweenthe proximal and distal;~ lun0triquetral motion. Duringradial to ulnar deviation carpal rows (intercarpal motion) (Table IV). (Fig. 8) scapholunate intracarpal motion is present itate represents the distal rowand the lunate the °) imal row. In wrist flexion-extension (global motion about the z axis (10.0 and the y axis (10°). That is, °) ° the scaphoid ulnar deviates and extends (Fig. 8, B and 112 (Fig. 9, A) there is 56.0 of lunocapitate motion C). Lunotriquetral motion (14.0°) occurs primarily in (Fig. 9, B). Fromfull flexion to neutral accounts 34.8° (62%) and from neutral to full extension, 26.8 flexion-extension (Fig. 8, D). (38%) of lunocapitate motion. During radioulnar In the distal row, intracarpal motionis less than in ° the proximal row for both flexion-extension and ra- viation (global motionof 36.00) there is 40.7 of dioulnar deviation motions (Table III). As the wrist ocapitate motionprimarily in the flexion-extensionaxis, movesfrom flexion to extension, the hamate rotates on with a smaller degree of motion about the radioulnar axis (Fig. 9, C and D). Capitate scaphoid motion .e Journal of Vol. 13A, No. 1 SURGERY January 1988 Relative motion of selected carpal bones 7

row intracarpal motion (n = 1)

Orientation of screw axis* Moving Reference Rotation Carpal translation (mm) Wrist motion carpal bone carpal bone z (°)

Flexionto extension Hamate Capitate - 0.34 0.80 0.50 8.92 - 0.48 Trapezoid Capitate 0.16 0.59 0.79 6.00 - 1.07 ’ Trapezoid Hamate 0.71 -0.70 0.10 5.40 0.19 Radialdeviation to ulnar Hamate Capitate -0.67 -0.19 -0.71 3.90 -0.10 deviation Trapezoid Capitate ¯ -0.10 0.70 0.71 5.10 0.26 Trapezoid Hamate 0.26 0.53 0.81 7.99 0.71

*Coordinate defined on radius. x Axis, + pronation, - supination; y axis, + flexion, - extension; z axis, + ulnar deviation, - radial deviation.

%~ble IV. Relative intercarpal bone motion of capitate with respect to proximal row (n = 4)

Moving Reference l Orientation of screw axis* Carpal translation Wrist motion carpal bone carpal bone ~ y z RotatiOn(o) (mm)

Flexionto extension Capitate Scaphoid 0.01 -0.92 -0.07 32.9 -+ 8.7 1.20 --- 1.60 Capitate Lunate -0.01 -0.93 0.07 56.0 ± 14.3 0.54 +- 0.60 Capitate Triquetrum 0.04 0.93 0.05 42.3 ± 13.4 0.69 -+ 9.81 Neutral(0 °) to extension Capitate Lunate -0.01 -0.93 0.07 26.8 +-- 12.1 0.50 --- 0.24 Neutral(0 °) to flexion Capitate Lunate -0.01 -0.93 0.07 34.8--- 12.1.. 0.48 - 0.25 Radialdeviation to ulnar Capitate Scaphoid 0.29 0.81 0.44 37.3 --- 20.0 -0.10 --- 0.30 deviation Capitate Lunate 0.33 0.85 0.25 40.7 +- 18.3 1.00 +- 0.30 Capitate Triquetrum 0.42 0.78 0.26 30.2 ~ 14.8 0.60 ± 1.01

*Coordinate defined on radius; x Axis, + pronation, - supination; y axis, + flexion, - extension; z axis, + ulnar deviation, - radial deviation.

12°, capito- D, In wrist also measured. As the wrist extends from the flexed tutes, without obvious longitudinal axes or prominent o, primarily ° easily identifiable landmarks. In addition, their motion only small position, the scaphoid moves 32.9 with respect to the is primarily rotational and often in more than one pronation- capitate. In radial to ulnar deviation of the wrist, the scaphoid moves 37.3 °, primarily about the flexion- axis. This type of motion is notoriously difficult to extension axis, with some rotation about the z axis measure on radiographs. It is also difficult to detect (radioulnardeviation) (Table IV). foliation if only a small portion of the bone is vis-- tion is only The serew axis concept is important since it allows ib].e, as is the case during dissection or surgical ex- :ate moves measurement of individual carpal bone motion in three posure. Further, most relative motion is quite small, motion is axes rather than exclusively in flexion-extension or ra- which increases the error of observation. For these rea- !iii": dioulnar deviation. For example, during wrist exten- sons, recent investigators have labeled the carpal bones measured:,°, I~!gl sion, the capitate is observed to flex and extend 56.0 and used sophisticated, accurate, and minimally inva- and distal ’I~!~i but this is associated with a small degree of axial ro- sire techniques to measure three-dimensional motion, ¯ The cap- (x .--.0.18) and radial angulation (z = 0.3). such as light emitting diodes and sonic pulsation ; the prox- During radial to ulnar deviation, the lunate not only markers.V,.15. 17-19 motion of flexes and extends on the capitate (y = 0.88), the pri- On the basis of principles established in measuring z~’ ~: ate motion mary movement, but also rotates (x = 0.35)¯ the motion of other upper extremity , we have :counts for elected to use a technique to directly measure carpal Discussion sion, motion by means of metal staples attached to each bone. oulnar Despite over one hundred years of clinical and an- Orthogonal biplanar films allow visualization of the lo- ~’ .7° of lun- atomic investigation into carpal kinematics z~z8 the cation of each marker. These markers were measured asion axis, subject of carpal bone motion has remained an enigma. with the sonic digitizer, and computer analysis was used radioulnar The reasons for this are both anatomic and-functional. to generate an accurate quantitative analysis of indi- lotion was The carpal bones are small, irregularly shaped struc- vidual carpal motion. Furthermore, to provide a de- The Journal of 8 Ruby etal. HAND SURGERY

scription of carpal bone motionin a loaded wrist, we; as a unit with very little intracarpal motion. The have activated the wrist motors based on physiologic imal row also moves as a unit, although cross-sectional area studies. motion betweenthe scaphoid and lunate and lunate This technique of carpal bone marking (which has triquetrumoccurs with all wrist movement.’3’,4, ,8 been used by the authors previously) has specific lim- radial to ulnar deviation (approximately35 ° to 45°), the itations. First, it can only be used in vitro. It requires scaphoid and lunate rotate primarily about the flexion- exposure of the carpals and the implantation of metal extension axis in the same direction. In addition, markers. This has the potential for disturbing normal radial to ulnar deviation, the capitate translates intercarpal motionby injuring normalstructures, such inantly in the dorsal-palmaraxis, e.g., the capitate dis- as the dorsal capsular ligaments. Althoughan attempt places palmarlyin radial deviation and dorsally in ulnar was madeto reproduce in vivo wrist loading with cal- deviation. These findings correlate well with previous! ibrated tension placed on the tendons, we cannot rea- observationsZ4.25 and indicate that carpal bone motions sonably expect to have duplicated all of the normal are interdependent on each other, with the bones of the forces that act on the wrist. Further, because of limi- proximal carpal row having more individual rotation tations of the techniqueand material available for study, than those of the distal carpal row. This proximal only five specimensand four positions of carpal motion intracarpal motion creates a variable geometry from neutral were examined. Specimenvariation and calated segmentso that no matter which position the constantly changing loading patterns mayimpose limits wrist assumes, the proximal carpal row fits itself to on the clinical application of such data. Comparedwith both the distal row and the radius and triangular fibro- previous carpal motionstudies, however,this technique cartilage. The small amountof distal row intracarpal has more precision than physiologically recorded dis- motionand triangular fibrocartilage flexibility placementof light emitting diodes or three-dimensional further adaptation of the. articular surfaces to one an- sonic digitization. The disadvantages of these latter other. This mechanismprobably serves to maximize’ methods are that the transducers (spark gap and LED contact area and prevent incongruity. Also, since markers) project out from the carpus, which mayin- the center of wrist motion is in the head of the capi- terfere with ligament and tendon function, and are tate,’7’ ~8 capitate displacementmay allow changein the heavy, possibly disturbing carpal motion. Further, they momentarms of the wrist motors increasing their ef- are based on empirically loaded tendon forces and use ficiency. In summary,we believe that a proximal row- passive wrist positioning in determining wrist motion. distal row modelfits the kinematic data better than. a Berger’s study,’9 for example,relates carpal bone mo- column theory of wrist motion. tion to rotation magnituderatios (RMR)rather than rSomeauthors’2’ 23 have found extension to be greate direct comparison of carpal bone movementbased on at the radiocarpal than midcarpal joints, while othe~, individualz° screw displacement axes. DeLangeet al. such as Volz28 and Wagner29 found radiocarpal and mid- published a more accurate study involving assessment carpal motionto be equally divided. In the experiments of three-dimensional carpal bone motion with x-ray reported here, carpal motion of flexion to extension st.ereophotogrammetric analysis. Here, rigid body mo- through a meantotal arc of 112° seemedto be equally tion of carpal bones demonstratedresults similar to our divided between the radiocarpal (56°) and midcarpal ownin that flexion-extension motion was equally di- joints (56°). However,each contributed a different vided betweenthe radiocarpal and midcarpal joints and percentageof the total arc of wrist motion.For that the scaphoidhad the largest rotation and the lunate as the wrist movesfrom neutral to flexion, capitolunate the smallest rotation of bones in the proximal row. motion is 38° and radiolunate motion is 35°. Fromneu- Although we agree with the conclusions of DeLange tral to extension, however, there was 27° of midcarpal and associates2° they reported their results as relative motion and 25° at the radiocarpal joint (Tables I and to the radius as a reference body. To the best of our IV). Wecould not confirm the theory-proposed knowledge, our study is unique in reporting accurate MacConailP° that the approximation of the proximal intercarpal and intracarpal motion. carpal~ row in extension acts like a vise to trap the ~ If one accepts that capitate motionis a goodindicator capitate: betweenthe scaphoid and .tfiquetrum, forcing of total wrist motion,then total wrist motionfrom flex- the capitate into full extension. ion to extension and radial deviation to ulnar deviation In consideringmotion from radial to ulnar deviation, i is similar to those described by previous authors.’l, ,z we found that moremotion occurs at the midcarpal than The distal row (trapezoid, capitate, and hamate) moves the radiocarpal joint by about 25%. The capitategen-- 13A, No. 1 Relative motionof ~elected carpal bones9 January1988

greater contribution by the midcarpal joints to flexion erally movessynchronously with respect to the lunate. than to extension. The sameis true of the radiocarpal But, as noted previously, when the wrist movesfrom joint, which contributes more to flexion than to ex- iial to ulnar deviation, the capitate translates from tension. palmarto dorsal and rotates about the dorsal-palmar(z) 2. Radial and ulnar deviation takes place moreat the axis. Thelunate and the rest of the proximalrow, how- midcarpalthan the radiocarpal joint, although both con- ;ver, movefrom flexion into extensionabout the y axis. tribute. : Weber~° has proposed an ingenious theory of carpal 3. Dulf.ng radial to ulnar deviation, the proximalrow Hestates that the triquetrohamateinterface con- movesfrom flexion to extension, and the distal row : trois the rotation of the proximalrow by virtue of the translates palmarto dorsal and rotates radial to ulnar. bony . Our data; which show displacement of 4. In flexion to extension, the proximalrow exhibits the distal row fromdorsal to palmar as the wrist moves increased intracarpal motion, especially the scaphoid. ulnar to radial deviation, is consistent with this 5. The: lunate is the least mobileof the proximalrow ther)ry, although does not prove it. carpals with respect to the radius during wrist flexion- ’~n general, this work confirms concepts popularized extension motion. Fisk,23 Linscheid and Dobyns,26 and Sarrafian1" that 6. The screw axis concept accurately reflects carpal that the proximalrow acts as an intercalated seg- bone motion as a complexmotion influenced by active betweenthe distal row and the radius. Since the wrist loading, position of adjacent carpal components, trapezoid, capitate, and hamatehave very little relative and alignment of the carpus with the distal radius. motion between them, the distal carpal row can be 7. On~the basis of these kinematicstudies, there is thought of as one functional unit. In radioulnar devia- little evidence to support a columnartheory of wrist allow tion, the scaphoid,lunate, and triquetrumexhibit little kinemat!ics, as the wrist movesin two functional units~ motion betweenthem and can be thought of as a func- le an- proximaland distal rows, with greater individual carpal dmize tic~:~.al unit. In flexion-extension,however, there is more bone motion occurring in the proximal row. since in:racarpal motion between the proximal row bones, the scaphoid. However,in all wrist motions, ; capi- there is always moremotion betweenthe proximal car- REFERENCES : in the row and the distal row and between the proximal eir ef- and the radius than there is within the proximal 1. GoodsirJ. Anatomicalmemoirs of John Goodsir. Edin- burgh, 1958. tl than ,ones. Moreover,all the carpal bones in each row 2. HenckeW. Die bewegungender Handwurzel.Z Rat Med in approximately the same direction no matter 18.’;9;7:27-41. what global wrist motion occurs. Thus, insofar as ki- 3. MeyerH. Einige worte uber beugung,streckung, supi- is concerned,it is justifiable to consider the nation und pronation. Arch Anat Physiol Wiss Med. Berlin: 1860;670-6. Die Statikund Mechanik des ~s divided into two functional units--distal row MenschlichenKnochengerustes (Engelmann, Leipzig, proximal row. "iments 1873). tension 4. BryceTH. Oncertain points in the anatomyand mech- ,~qualty anismof the wrist joint reviewedin the light of a series Fromthe:viewpoint of clinical application, it seems of roentgenray photographsof the living hand. J Anat obvious that the complex mechanismof carpal motion Physiol 1896;31:59-79. :amt~le,: !!ii~~I’ wouldnot readily adjust to alterations in the intracarpal, 5. J¢,hnsonHM. Varying positions of the carpal bonesin olu~ate ~ ilil ~ii~ midcarpalof radiocarpal relationships. Therecent en- the different movementsat the wrist. Part I: J AnatPhys- ,m neu- ii~il thusiasm for limited intracarpal arthro.desis mi.gi~ ~t iol 1907;41:109-22.Part II: J Anat Physiol 1907;41: dcarpal i’~i~! :be justified, f6finstance, considering the potenu - 280-92. Fick R. Ergebenisseeiner Untersuchungder Handbeue- s I and f:!ii~ iverse, long-term sequelae. Fusions across the midcarpal 6. :and gungenmit x-strahlen. Verh Anat Ges 15, Vers Bonn, ,sed by "i{i~i radiocarpal joints especially change normal carpal Erg H Anat Anz 1901;19:175-84. Handbuchder Ana- roximal i~i ii~i:i, kinematics. The kinematics of the rWe~tm~qt~t~2~ ...... before rational tr tomic und Mechanikde GelenkeIII, 2:1-3 Fisher, Jena be developed. In summary,the following conclu- 1911. 7. Cyriax EF. Onthe rotatory movementsof the wrist. Sions are drawn: J Anat1926;60:199-201. 1. Total flexion and extension motion is about 8. VonBonin G. Anote Onthe kinematicsof the wrist joint. ::~ equally divided between radiocarpal and midcarpal pal than joints, with a wide. variation of normal. There is a :I Anatd1919;63:259-62. 1re The Journal 10 Ruby et al. HAND

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JOURNAL EDITORSHIP

Theposition of Editor for this Journalwill become vacant in the spring of 1989. Anyoneinterested in servingas Editoris requestedto contactthe Chairman, Journal Committee:Dr. Lee W. Milford, 869 Madison Ave., Memphis, TN 38104.