Perilunate Fracture Dislocations

Updated: Jul 05, 2016
  • Author: Peter M Murray, MD; Chief Editor: Harris Gellman, MD  more...
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Overview

Background

Perilunate dislocation and perilunate fracture dislocation are injuries that involve traumatic rupture of the radioscaphocapitate (RSC) ligament, the scapholunate interosseous ligament, and the lunotriquetral interosseous ligament. [1] Fractures of the radial styloid, the scaphoid, the trapezium, the capitate, and the triquetrum also may be associated with the dorsal or the volar perilunate dislocation. The result of perilunate dislocation and of perilunate fracture dislocation is an extremely unstable wrist, potentially producing devastating complications. [2]

Perilunate dislocations and perilunate fracture dislocations are the most devastating closed injuries of the wrist. [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13] They often are missed on initial evaluation, leading to devastating complications. These injuries occur as the final stage of a spectrum of injuries progressing around the wrist in a radial-to-ulnar direction.

Before the advent of radiography, fractures of the distal radius, carpal instability, and carpal dislocations were at best difficult to distinguish. In 1855, Malgaine was the first to publish a description of perilunate fracture dislocations. Later, Cousins, Destot, and de Quervain reported on this injury. Tavernier reported the first true series in 1906. Destot contributed greatly to the general understanding of wrist instability in the work Injuries of the Wrist: A Radiographic Study (1918). [14]

Subsequently, enthusiasm for the study of wrist instability was lost until 1968, when Fisk presented the Royal College of Surgeons Hunterian Lecture on the concept of the intercalated segment, referring to the kinematics of the proximal carpal row. In 1972, Linscheid et al further modified this concept by introducing the terms volar intercalated segment instability (VISI) and dorsal intercalated segment instability (DISI). [15]  In 1980, Mayfield et al illustrated the mechanism of perilunar wrist instability as a series of four stages resulting in perilunate dislocations or lunate dislocations. [16]

In the setting of a high-energy wrist injury, radiographs must be scrutinized carefully for perilunate dislocation or one of its variants. Prompt open reduction with ligamentous repair or reconstruction is necessary to achieve favorable results. Posttraumatic arthrosis may result after these injuries irrespective of treatment, requiring a late salvage operation.

For patient education resources, see Wrist Injury.

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Anatomy

The carpus is composed of two rows of bones, as follows [17] :

  • Proximal carpal row (scaphoid, lunate, and triquetrum)
  • Distal carpal row (trapezium, trapezoid, capitate, and hamate)

The wrist joint is composed of the following two types of ligaments:

  • Intrinsic - These ligaments are short, stout ligaments that stabilize adjacent carpal bones
  • Extrinsic - These ligaments span the proximal carpal row and the distal carpal row

Within the proximal carpal row, the scapholunate interosseous ligament binds the scaphoid to the lunate. [18] This ligament has the following three portions:

  • Proximal
  • Distal
  • Volar

The dorsal portion of the ligament supplies the majority of stabilizing strength to the scapholunate articulation. The lunotriquetral interosseous ligament secures the articulation of the lunate and the triquetrum. Although stout, the interosseous ligaments of the proximal carpal row allow relative motion between the scaphoid and lunate and between the lunate and the triquetrum.

The distal carpal row is also stabilized by intrinsic ligaments, such as the capitohamate ligament, which is composed of dorsal, deep, palmar, and longitudinal components.

The scaphotrapeziotrapezoidal (STT) joints are stabilized by a ligamentous complex that is intrinsic and extrinsic in nature and includes the following:

  • Scaphotrapezial ligament
  • Scaphocapitate capsular ligament
  • Dorsal and palmar STT capsular ligaments

The extrinsic carpal ligaments provide the structural integrity for the articulations of the proximal and distal carpal rows. The RSC ligament originates from the radial styloid, crosses the waist of the scaphoid, and inserts on the volar waist region of the capitate.

Immediately ulnar to the RSC ligament is the radiolunotriquetral ligament, which originates from the radial styloid, sends an attachment to the volar aspect of the lunate, and then terminates on the triquetrum. The short radiolunate originates from the most ulnar aspect of the distal radial articular surface and inserts on the proximal volar aspect of the lunate.

From the base of the ulnar styloid, two ligaments—the ulnocapitate and the ulnotriquetral—originate. A portion of the ulnotriquetral ligament continues across the midcarpal joint to insert on the waist of the capitate and join the RSC ligament, forming an inverted V. This ligament is known as the ulnocapitate ligament, and the inverted-V confluence is known as the arcuate ligament. Just proximal to the base of the V is a soft spot, the space of Poirier.

Found between the short radiolunate ligament and the radiolunotriquetral ligament is the radioscapholunate ligament, which is also known as the ligament of Testut. The designation of this structure as a ligament is actually a misnomer: Histologic studies have shown that it is a vascular structure devoid of any true collagen fibers and that it lacks structural integrity.

Within the dorsal capsule of the wrist are two ligaments of particular importance:

  • Dorsal intercarpal ligament
  • Dorsal radiocarpal ligament

The former courses transversely from the waist of the scaphoid across the carpus, inserting onto the dorsal aspect of the triquetrum; the latter spans a distance from its origin on the radial styloid to its place of insertion on the dorsal aspect of the triquetrum. Together, these two ligaments form a V, with the base of the V on the triquetrum. Between the limbs of the V is the less substantial dorsal wrist capsule.

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Pathophysiology

Pure ligamentous perilunar injuries of the wrist are classified as lesser arc injuries, whereas the transosseous variants are regarded as greater arc injuries. The mechanism of perilunate dislocations has been described as a four-stage process, as follows:

  • First stage - The RSC ligament and the scapholunate interosseous ligament rupture
  • Second stage - Dislocation of the capitolunate joint occurs as the injury progresses through the space of Poirier
  • Third stage - The lunotriquetral interosseous ligament ruptures.
  • Fourth stage - The lunate becomes dislocated

This mechanism has been reproduced in a cadaver model by applying pronation and ulnar deviation on a hyperextended cadaver wrist.

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Etiology

Perilunate dislocations and perilunate fracture dislocations typically occur in young adults who are exposed to high-energy trauma, such as a fall from a height. In these injuries, the fall generally results in the wrist being axially loaded by the body, trapping the hand in the hyperextended and ulnarly deviated position. The angle of hyperextension determines the extent of injury. If sufficient loads are applied, the ulnarly deviated wrist, hyperextended beyond 100º, produces a perilunate dislocation or one of the fracture dislocation variants.

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Epidemiology

Little is known about the true incidence of perilunate dislocations and perilunate fracture dislocations. Because the subtlety of wrist injuries often is not fully appreciated, many believe that perilunate injuries in general are underdiagnosed. Perilunate dislocation, lunate dislocation, and perilunate fracture dislocation variants have been estimated to account for fewer than 10% of all wrist injuries. In a study reviewing perilunate dislocations, 61% were of the transscaphoid perilunate type.

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Prognosis

The outcomes of perilunate dislocations and perilunate fracture dislocations are best when emergency reduction of the carpus is performed, followed by accurate open reduction and internal fixation (ORIF). The incidence of carpal instability and subsequent posttraumatic arthritis is believed to be reduced with ORIF, including accurate repair or reconstruction of the scapholunate interosseous ligament.

The combination of dorsal and volar approaches to the wrist in the treatment of perilunate dislocations has been studied; however, the prognosis of these injuries remains guarded because of the significant incidence of posttraumatic arthritis, which can occur irrespective of treatment. [6]  Capo et al reported reasonable and functional clinical results after treatment of perilunate fracture dislocations with a combined volar-dorsal approach. [19]

Krief et al retrospectively studied 30 patients with perilunate dislocation (n=14) and perilunate fracture dislocation (n=16) to evaluate clinical, functional, and radiologic outcomes at a mean follow-up of 18 years (range, 15-24 years). [20]  Relative to the contralateral side, the mean flexion-extension arc was 68%, the radial-ulnar abduction arc 67%, the pronation-supination arc 80%, and the mean grip strength 70%. The mean Mayo wrist score was 70, the mean Quick Disabilities of the Arm Shoulder and Hand score 20, and the Patient-Rated Wrist Evaluation score 21. Five patients underwent a secondary procedure,a and six had a complex regional pain syndrome type 1.

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