Acute Dislocations of the Distal Radioulnar Joint and Distal Ulna Fractures
Total Page：16
File Type：pdf, Size：1020Kb
Acute Dislocations of the Distal Radioulnar Joint and Distal Ulna Fractures Brian T. Carlsen, MDa,b, David G. Dennison, MDb, Steven L. Moran, MDa,b,* KEYWORDS Distal radioulnar joint Dislocation Ulna fractures Wrist trauma ANATOMY AND BIOMECHANICS colleagues10 defined the shape of the sigmoid OF THE DISTAL RADIOULNAR JOINT notch in the transverse plane in 4 different config- urations: flat face (42% incidence), ski slope The ulna is the fixed unit of the forearm joint, with 1 (14%), C-type (30%), and S-type (14%). Although the hand, carpus, and radius rotating around it. the study did not include biomechanical evaluation Rotational forearm motion occurs at the distal ra- of the different joint configurations, the investiga- dioulnar joint (DRUJ) and proximal radioulnar joint tors proposed that this may have important impli- (PRUJ) at the elbow. DRUJ motion is primarily cations in the bony contribution to joint stability.10 rotational, but there are components of axial and The primary stabilizer of the DRUJ is the TFCC, translational motion that occur during loading originally described by Palmer and Werner.11 The and rotation. Axial motion is due to the crossing TFCC is composed of several structures, including relationship of the radius to the ulna in pronation. the triangular fibrocartilage (TFC), the ulnocarpal This axial motion can produce changes in the ulnar meniscus (meniscus homolog), the ulnar collateral variance that may be as great as 2 mm with full 2–5 ligament, the dorsal radioulnar ligament, the forearm rotation. Dorsal and palmar transla- palmar radioulnar ligament, and the subsheath of tional motion of the radius about the fixed ulnar the extensor carpi ulnaris (ECU).11 These struc- head also occurs with supination and pronation, 6–8 tures are not readily distinguishable on anatomic respectively. dissection and together are referred to as the Joint stability at the DRUJ is provided through TFCC. The central portion of the TFC makes up a combination of bony architecture and soft tissue the articular disk. This disk forms the ulnocarpal constraints, which include the ligaments found in articulation and effectively cushions the ulnar the triangular fibrocartilage complex (TFCC), the head. In contrast to the peripheral TFCC, the artic- pronator quadratus, and the interosseous ular disk is relatively avascular and therefore is membrane (IOM). The bony architecture of the presumed to be incapable of significant healing DRUJ accounts for only 20% of the joint’s 12 9 capabilities. stability ; thus most of the stability is provided by The dorsal and palmar radioulnar ligaments are the soft tissue attachments. In addition, individual thought to be responsible for most of the stability variation in the bony configuration of the DRUJ at the DRUJ.9,13 Significant research has been per- may also affect its stability. A study by Tolat and formed to determine which component of the a Division of Plastic Surgery, Department of Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA b Division of Hand Surgery, Department of Orthopaedic Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA * Corresponding author. Division of Hand Surgery, Department of Orthopaedic Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail address: [email protected] Hand Clin 26 (2010) 503–516 doi:10.1016/j.hcl.2010.05.009 0749-0712/10/$ – see front matter ª 2010 Elsevier Inc. All rights reserved. hand.theclinics.com 504 Carlsen et al radioulnar ligament complex (palmar or dorsal) is the radius that dislocates away from its original more critical for joint stability.14–16 Hagert,13 in anatomic position. However, the clinical and radio- 1994, helped answer this question and recognized graphic appearance of DRUJ dislocation is one of that palmar and dorsal components of the radioul- ulnar dislocation relative to the radius, which has nar ligaments were necessary for DRUJ stability. resulted in the historic description of such injuries Hagert described the existence of superficial and in terms of the ulna’s relationship to the radius. In deep portions of the the dorsal and palmar radioul- this article, the authors use this technically incor- nar ligaments. The superficial fibers attach to the rect but widely accepted description. They refer base of the ulnar styloid and thus are susceptible to a dorsal dislocation as occurring when the to injury in cases of peripheral TFCC tears. The ulna resides dorsal to the radius and volar disloca- deep fibers, sometimes referred to as the ligamen- tion as occurring when the ulna resides volar to the tum subcruentum, attach to the fovea and are thus radius. susceptible to injury in cases of basilar ulnar styloid Isolated acute dislocation of the DRUJ (with or fractures. In pronation, the dorsal superficial fibers without ulnar styloid fracture) is less common tighten together with the palmar deep fibers. than dislocation associated with a fracture of the Conversely, in supination, the palmar superficial radius or distal ulna.27 The first report of an iso- fibers together with the dorsal deep fibers are taut lated dislocation of the DRUJ without fracture and effectively constrain DRUJ motion.13 Other was by Desault in 1777.28,29 Since then, there studies have confirmed the reciprocal relationship have been numerous case reports and small series between the superficial and deep portions of the ra- describing such injuries.6,19,30–35 The direction of dioulnar ligament, further emphasizing that the dislocation can be either volar or dorsal, although deep palmar and dorsal ligaments attach to the dorsal dislocation is probably more common. fovea and prevent dorsal and palmar subluxation Dorsal dislocations are believed to result from with forearm rotation, respectively. The superficial a hyperpronation force, and volar dislocations palmar and dorsal ligaments attach to the ulnar from a hypersupination force.19–21 Although an styloid and act as rotational restraints to supination acute dislocation must result in an injury to the and pronation, respectively.17,18 Work by Stuart TFCC, the amount and degree of injury required and colleagues9 and other investigators have for dislocation of the DRUJ is not entirely clear shown that dorsal displacement of the distal ulna and DRUJ dislocation may not require complete relative to the radius is most likely because of failure disruption of the TFCC.19,32,36,37 One premise for of the palmar radioulnar ligament, whereas palmar this observation is that, in many cases, the DRUJ displacement of the ulna relative to the radius is is notably stable after reduction of the disloca- because of failure of the dorsal radioulnar tion.6,32 Hagert13,38 has described injury of the ligament.19–21 volar radioulnar ligament and dorsal joint capsule An additional secondary constraint to palmar with dorsal dislocation. The reverse mechanism displacement and dislocation includes the also occurs with rupture of the dorsal radioulnar IOM.16,22–24 The IOM contains several ligamentous ligament and volar joint capsule in a volar components along its length. The central band is dislocation.36 a stout ligament that runs obliquely from proximal In a dorsal dislocation, there is typically a history on the radius to distal on the ulna, fanning out of hyperpronation force, usually as a result of a fall towards its insertion on the ulna.25 The central on the outstretched hand. In this situation, the band is thought to play an important role in the hand is typically fixed by gravity to the ground, longitudinal stabilization of the forearm.25,26 The and the body, together with the ulna, rotates distal oblique bundle is a thick band of tissue in around the hand, wrist, and radius unit. The patient the distal one-sixth of the membrane. It originates presents with the hand fixed in pronation, with the proximally on the ulnar shaft, in the same location inability to supinate and a dorsal prominence of as the proximal pronator quadratus muscle, and the ulnar head. attaches distally to the capsule of the DRUJ. The In cases of volar dislocation, there is a history of bundle may contribute some fibers to the volar hypersupination and the patient is unable to and dorsal radioulnar ligaments.23 Although this pronate. The ulnar head is usually not visibly prom- structure is consistently present, its thickness inent on the volar wrist because of the overlying may vary from patient to patient.22,23 soft tissues. However, there can be a hollow dorsally where the ulnar head is usually visible in the uninjured wrist. The wrist can appear narrow Acute Isolated DRUJ Dislocation because of the now compressive pull of the As previously mentioned, the ulna is the fixed pronator quadratus muscle, resulting in a dimin- structure of the forearm, and anatomically it is ished transverse dimension.29,36 In either direction DRUJ Dislocations and Distal Ulna Fractures 505 of dislocation, the examination findings can be be necessary to achieve closed reduction. obscured by ecchymosis and swelling. Because of the vascularity and healing potential Plain 2-view radiographs that include the wrist, of the peripheral TFCC,12 closed treatment is forearm, and elbow are critical for the evaluation frequently successful in the restoration of a stable of suspected DRUJ dislocation. The anteroposte- construct. rior (AP) view in a dorsal dislocation typically So-called complex dislocations occur when shows a widened DRUJ with divergence of the there is interposed soft tissue that blocks closed radius and ulna when compared with the contra- reduction. These dislocations typically occur in lateral normal DRUJ, whereas a volar dislocation conjunction with a Galeazzi fracture and are dis- demonstrates an overlap of the radius and ulna cussed later; however, nonreducible simple dislo- at the DRUJ because of the convergent pull of cations without soft tissue interposition can also the pronator quadratus.