Orthopedics

Review Article 

Evaluation, Management, and Outcomes of Lunate and Perilunate Dislocations

Avi D. Goodman, MD; Andrew P. Harris, MD; Joseph A. Gil, MD; Joseph Park, BS; Jeremy Raducha, MD; Christopher J. Got, MD

Abstract

Lunate and perilunate dislocations are potentially devastating injuries that are often unrecognized at initial evaluation. Prompt recognition and treatment is necessary to prevent adverse sequelae, including median nerve dysfunction, carpal instability, posttraumatic arthritis, reduced functionality, and avascular necrosis. In patients who are surgical candidates, operative intervention is warranted to restore carpal kinematics and provide optimal outcomes. [Orthopedics. 201x; xx(x):xx–xx.]

Abstract

Lunate and perilunate dislocations are potentially devastating injuries that are often unrecognized at initial evaluation. Prompt recognition and treatment is necessary to prevent adverse sequelae, including median nerve dysfunction, carpal instability, posttraumatic arthritis, reduced functionality, and avascular necrosis. In patients who are surgical candidates, operative intervention is warranted to restore carpal kinematics and provide optimal outcomes. [Orthopedics. 201x; xx(x):xx–xx.]

Perilunate dislocations are severe pan-carpal injuries that can present in the setting of high-energy trauma, and they involve the dissociation of 1 or more of the lunate articulations. If a complete dislocation occurs, this injury is termed a lunate dislocation. Given the severity of confounding injuries, delayed presentation, difficult radiographic interpretation, and occasional spontaneous reduction, up to 25% of perilunate dislocations are diagnosed weeks to years after the initial injury.1 Although most of these injuries have radiographic evidence of posttraumatic arthritis regardless of treatment, a delay in recognition and treatment of perilunate dislocations worsens already tenuous outcomes, including median nerve dysfunction, carpal instability, reduced functionality, and avascular necrosis.2,3 Therefore, the proper initial evaluation, management, and understanding of perilunate and lunate dislocations are essential.

Mechanism of Injury

Perilunate and lunate dislocations typically result from an axial load causing hyperextension, intercarpal supination, and ulnar deviation of the wrist.4,5 In 1980, Mayfield et al6 originally described this method by forcing 32 wrists into hyperextension by applying force to the thenar eminence and recording the injury pattern. Most perilunate injuries are associated with high-energy trauma—most commonly falls from height, followed by motor vehicle collisions.7,8 This axial force results in a predictable pattern of injury. Beginning from the radial aspect of the carpus, the force advances through the midcarpal region, toward the ulnar aspect. The 4 stages (Table 1) of injury progression were originally described by Mayfield et al (Figure 1), with the translunate/interlunate arc more recently described.1,6,9–11 However, some variability in injury patterns results from differences in force vectors and transmission paths.

Progression of Perilunate Injuries (Mayfield Classification)

Table 1:

Progression of Perilunate Injuries (Mayfield Classification)

Sequential pattern of perilunate injury progressing to lunate dislocation. The 4 stages of perilunate injury progress from I to IV in a clockwise fashion: (I) disruption of the radioscaphocapitate ligament (orange line) and scapholunate ligament (blue line), or fracture through the scaphoid; (II) disruption of the lunocapitate articulation (yellow line) or fracture through the capitate; (III) lunotriquetral ligament (red line) or fracture through the triquetrum; and (IV) radiolunate ligament (green line).

Figure 1:

Sequential pattern of perilunate injury progressing to lunate dislocation. The 4 stages of perilunate injury progress from I to IV in a clockwise fashion: (I) disruption of the radioscaphocapitate ligament (orange line) and scapholunate ligament (blue line), or fracture through the scaphoid; (II) disruption of the lunocapitate articulation (yellow line) or fracture through the capitate; (III) lunotriquetral ligament (red line) or fracture through the triquetrum; and (IV) radiolunate ligament (green line).

Evaluation

Although perilunate dislocations may occur in isolation, when they occur during high-energy trauma, Advanced Trauma Life Support protocols should be followed for evaluation and resuscitation. Additional injuries should be addressed as they are discovered, with particular attention paid to the ipsilateral upper extremity.

Acute perilunate dislocations typically present with pain and swelling over the dorsal and/or volar aspect of the carpus, often with dorsal wrist tenderness over the scapholunate ligament, limited range of motion, and frank deformity.7 However, low-impact injuries may result in minimal deformity with or without any associated nerve or tendon damage. The lunate may dislocate into the carpal tunnel or self-reduce entirely, depending on the kinetic profile and mechanism of injury. Given the spectrum of possible clinical presentations, a thorough neurovascular assessment and orthogonal radiographs are necessary to obtain a better understanding of the extent of injury.9 If median (or other) nerve compromise exists (eg, acute paresthesias or abnormal 2-point discrimination in the median nerve distribution), this adds urgency to the treatment algorithm and must be documented.

Radiographic Findings and Classification

Anteroposterior, lateral, and oblique radiographs of the wrist must be obtained during initial evaluation. Lateral radiographs with normal findings should reveal a collinear axis of the radius, lunate, and capitate (Figure 2).9 This longitudinal axis may be interrupted by displacement of the capitate in relation to the radius, indicating a perilunate dislocation of the same direction.8 Posteroanterior radiographs should also be assessed for any patterns of instability. The 3 arcs of Gilula's lines, smooth and continuous carpal lines on the anteroposterior/posteroanterior radiograph, consist of the borders of the radiocarpal row, the midcarpal row, and the proximal surface of the distal carpal row (Figure 3).12 Any disruption of these arcs suggests a lunate, perilunate, and carpal dislocation or fracture, respectively.7,12 Advanced imaging is rarely indicated in the initial evaluation of ligamentous perilunate dislocations; however, a computed tomography scan may aid the diagnosis of and better define some carpal bone fractures.

Lateral radiograph with normal findings revealing a collinear axis of the radius (red), lunate (yellow), and capitate (green).

Figure 2:

Lateral radiograph with normal findings revealing a collinear axis of the radius (red), lunate (yellow), and capitate (green).

Anteroposterior radiograph of the right wrist with normal findings showing Gilula's 3 carpal arcs.

Figure 3:

Anteroposterior radiograph of the right wrist with normal findings showing Gilula's 3 carpal arcs.

Perilunate injuries are most commonly classified using the system of Mayfield et al6 (Figure 1, Table 1). In a stage I injury (disruption of the scapholunate ligament or transscaphoid fracture), radiographs may reveal a widening of the scapholunate space. The images should also be carefully inspected for a scaphoid or other carpal bone fracture.

A stage II injury (lunocapitate articulation disruption) often presents with the capitate dislocated dorsally, in addition to stage I findings. A posteroanterior view of a perilunate dislocation may reveal an overlap of the distal and proximal carpal rows with possible scaphoid fracture and subluxation.7 An overlap of the triquetrum on the lunate suggests a stage III perilunate injury (disruption of the lunotriquetral interosseous ligaments), and an associated volar fracture of the triquetrum may be exhibited.7

With a stage IV injury, a lunate dislocation, rotation of the lunate in the volar direction presents as a triangular appearance known as the “piece of pie” sign (Figure 4) on a posteroanterior view. This rotation in the lateral view yields the “spilled teacup” sign, in which the lunate resembles a teacup tipped in the volar direction.7

A stage IV lunate dislocation. Note the “piece of pie” sign on the anteroposterior (A) and oblique (B) radiographs and the “spilled teacup” sign on the lateral (C) radiograph.

Figure 4:

A stage IV lunate dislocation. Note the “piece of pie” sign on the anteroposterior (A) and oblique (B) radiographs and the “spilled teacup” sign on the lateral (C) radiograph.

Alternatively, perilunate dissociation injuries may be described using the arc methodology: the loading mechanism results in fracture through the greater arc, ligamentous disruption through the lesser arc, and/or fracture through the translunate/interlunate arc13 (Figure 5). Greater arc injury results in fracture of the respective carpal bone or radial styloid, whereas lesser arc injury is associated with ligamentous disruption.6 Mayfield et al6 showed that higher velocity axial loads result in purely ligamentous injury of the lesser arc, whereas lower velocity axial loads tend to result in fractures within the greater arc. As described by Mayfield et al,6 the greater arc begins at the scaphoid, traverses the capitate, and ends at the triquetrum (Figure 5). Perilunate or lunate dislocations that only involve greater arc fractures are described by the fractures involved.1,6 For example, an associated scaphoid fracture is described as a transscaphoid perilunate dislocation, a scaphoid fracture with a capitate fracture is termed a transscaphoid, transcapitate perilunate dislocation, and so on. Each of these fracture fragments is associated with its respective ligament of the lesser arc. The intact scapholunate and lunotriquetral ligaments remain in continuity to the scaphoid, capitate, and triquetral fracture fragments.1,2,6

Anteroposterior radiograph of a left wrist showing the greater arc (A), lesser arc (B), and translunate arc (C). Injury to the greater arc results in transscaphoid, transcapitate, and/or transtriquetral fracture. The lesser arc injuries result in scapholunate, lunocapitate, and/or lunotriquetral ligament injury. Injury to the translunate arc results in lunate fracture. All injury arc patterns may occur in isolation or in combination.

Figure 5:

Anteroposterior radiograph of a left wrist showing the greater arc (A), lesser arc (B), and translunate arc (C). Injury to the greater arc results in transscaphoid, transcapitate, and/or transtriquetral fracture. The lesser arc injuries result in scapholunate, lunocapitate, and/or lunotriquetral ligament injury. Injury to the translunate arc results in lunate fracture. All injury arc patterns may occur in isolation or in combination.

The lesser arc represents the ligamentous injuries that may occur.6 As with greater arc injuries, the force pattern progresses from radial to ulnar. The lesser arc begins at the scapholunate ligament, traverses the lunocapitate joint and lunotriquetral ligament, and ends at the short radiolunate ligament (Figure 5).6 The fourth stage (short radiolunate ligament disruption) results in a lunate dislocation.2

In 2008, the translunate arc concept was described by Bain et al11 (Figure 5). Approximately 34 cases have been reported in the literature since 1976.10 This arc may be more easily understood as fracture of the lunate associated with ligament disruption on the opposite end of the greater arc.10 All injuries can occur in isolation or in combination with another type (Figure 6).

Anteroposterior (A), oblique (B), and lateral (C) radiographs of a left wrist showing a transscaphoid, transtriquetral perilunate fracture-dislocation associated with a distal radius fracture.

Figure 6:

Anteroposterior (A), oblique (B), and lateral (C) radiographs of a left wrist showing a transscaphoid, transtriquetral perilunate fracture-dislocation associated with a distal radius fracture.

Approximately 60% of perilunate injuries present with transscaphoid fractures, 72% of which are transverse fractures through the middle third.14 In a retrospective multicenter study of 166 perilunate dislocations, perilunate fracture-dislocations were more common than ligamentous perilunate dislocations, occurring at a ratio of 2 to 1.3 In the same series, dorsal transscaphoid perilunate fracture-dislocations accounted for 96% of perilunate fracture dislocations and 61% of the entire series.3 The direction of displacement was predominantly dorsal (97%) compared with volar (3%).3

Management

Closed Reduction and Immobilization

Carpal dislocations require urgent hand surgery consultation. Studies comparing nonsurgical with surgical intervention have consistently shown better outcomes for the latter.9 Because of the disruption of structurally crucial ligaments, closed reduction and immobilization alone is inadequate to provide necessary architectural support.

Closed reduction and splinting is more effective with perilunate dislocations and less so with lunate dislocations because of the extent of ligamentous damage.7 Initial management of lunate dislocations involves a closed reduction and immobilization using a sugar-tong splint.9 Patients are discouraged from applying any axial load to the injured wrist.

Under intravenous sedation (either a benzodiazepine such as diazepam or sedatives such as propofol), the patient's arm is held in longitudinal traction prior to (or during) the reduction attempt. Hanging the hand in finger traps with weight hanging from the biceps may be a useful adjunct, as countertraction is mandatory to achieve sufficient distraction for reduction. The classic teaching at the authors' institution is 10-10-10: 10 mg of diazepam, hanging in 10 pounds of traction, for 10 minutes before attempting reduction. The precise reduction maneuver depends on the patient's injury; however, for the most common dorsal perilunate dislocations, the patient's wrist is held in longitudinal traction and the surgeon's thumb is placed on the volar aspect of the lunate and used to apply a dorsal-directed force while the wrist is slowly brought into flexion, guiding the lunate back into the radiolunate fossa and lunocapitate articulation.9,15 Described as the “paradox of reduction,” restoration of the scapholunate relation by means of radial deviation results in a widening of the torn palmar ligaments and the inability to restore scaphoid flexion, which would, conversely, require ulnar deviation for correction.6,9

Surgical Management

A variety of surgical options have been proposed for treatment: closed reduction with percutaneous pinning (Figure 7), open reduction and internal fixation, arthroscopic repair, external fixation, and acute proximal row carpectomy. Regardless of fixation method, patients should be managed acutely—within 6 weeks of injury—as late treatment may impact surgical outcomes because of fibrosis, soft tissue scarring, and avascular necrosis.9,16,17 Herzberg et al3 reported that perilunate dislocations/fracture dislocations treated 6 weeks after injury or those with open injuries had significantly worse clinical outcome scores (P<.05) than those treated within 6 weeks. Certain injury patterns are not amenable to early definitive open reduction and internal fixation. Associated comminuted distal radius fractures, severe soft tissue injuries, and severe ligament disruption may require spanning external fixation for additional stabilization and result in further complications.9 The use of external fixation with percutaneous K-wire fixation has shown acceptable return to work and satisfactory functional and radiographic outcomes in most patients at 3 years.18

Anteroposterior (A) and lateral (B) radiographs of the wrist following closed reduction and percutaneous pinning of a lesser arc perilunate dislocation.

Figure 7:

Anteroposterior (A) and lateral (B) radiographs of the wrist following closed reduction and percutaneous pinning of a lesser arc perilunate dislocation.

Open reduction and internal fixation and closed reduction with percutaneous pinning have been shown to have better long-term outcomes than closed reduction and casting.3,19,20 Open reduction can be performed through volar or dorsal surgical approaches or through a combination of the 2. The volar approach is favorable when the lunate has dislocated volarly, as beginning with the side of dislocation allows primary reduction of the lunate and provides easy access to release the transverse carpal ligament. The volar approach also allows for direct repair of the volar capsule's space of Poirier, between the volar radiocapitate and the volar radiotriquetral ligaments, through which the lunate typically dislocates. It also allows repair of the volar lunotriquetral ligament and removal of any osteochondral fragments.9

Alternatively, the dorsal approach provides direct access to the carpus, which is optimal for realignment. The scaphoid and other fractured carpal bones, as well as the scapholunate interosseous ligament, are accessible for direct repair. The volar lunotriquetral and dorsal scapholunate interosseous ligaments are the strongest portions of their respective ligaments. Proper exposure and restoration of the scapholunate interosseous ligament is believed to play a significant role in a successful long-term outcome.9 The combined dorsal–volar approach offers the advantages of both approaches and allows the surgeon complete visualization and dual access to all structures requiring repair.9 The complexity of the intercarpal relationship disruptions involved in lunate dislocations often requires the combined dorsal–volar approach.21

Other techniques have been described with mid-term outcomes comparable to those of open reduction and internal fixation. Kim et al22, showed that arthroscopic reduction and percutaneous fixation with K-wires and headless compression screws allows for minimal incisions and blood loss, with a lower rate of posttraumatic arthritis on radiographs at an average follow-up of 31 months. Muller et al23 reported that acute proximal row carpectomy can be used to manage perilunate dislocations, with outcomes similar to those of open reduction and internal fixation at approximately 3-year follow-up. The proximal row carpectomy group also benefited from a single surgical incision, a shorter operative time, and a shorter immobilization period.23

Neglected perilunate injuries may be managed using various salvage procedures, including proximal row carpectomy, wrist arthrodesis, and lunate excision. However, given that there is no consensus regarding the most appropriate salvage procedure or the appropriate time window, management remains controversial.9 Even with these options, inappropriate (or no) initial treatment risks poor outcomes.

Complications

Despite predictable injury patterns, lunate and perilunate dislocations are often misdiagnosed, leading to serious complications and a poor clinical prognosis. For various reasons, up to 25% of perilunate dislocations are undiagnosed or misdiagnosed in the acute setting.7 Carpal injuries can often be overshadowed by more severe, life-threatening injuries sustained in the high-energy trauma. Furthermore, radiographic images may be inadequately assessed or what they reveal may go unrecognized by a physician unfamiliar with perilunate or lunate dislocations.21

Delayed treatment may result in reduced functionality and range of motion, carpal instability, pain, and carpal tunnel syndrome from the palmar lunate dislocating into the carpal tunnel and compressing the median nerve.7 Studies have reported that patients who underwent surgical treatment exhibited signs of permanent damage at only 2 months after initial injury, including progressive degenerative changes of the radiocapitate and midcarpal joints.24 Chronic carpal instability will ultimately progress to end-stage scapholunate advanced collapse deformity of the wrist.

Conclusion

Perilunate and lunate dislocations are severe injuries that warrant vigilance in patients with a concerning mechanism of injury. After a radiographic and clinical workup, the dislocation must be addressed with prompt reduction and splinting, often followed by surgery. All operative techniques have similar mid- to long-term-functional and radiographic outcomes, so the authors recommend that surgeons choose the method with which they are most comfortable and that is most suited for the particular injury pattern.3,18,20,22,23 However, even the most effective treatment usually falls short of restoring normal function in these severe injuries, but early treatment can reduce the rates of pain, instability, and nerve damage and improve functionality.

References

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  17. Charalambous CP, Mills SP, Hayton MJ. Gradual distraction using an external fixator followed by open reduction in the treatment of chronic lunate dislocation. Hand Surg. 2010;15(1):27–29. doi:10.1142/S0218810410004436 [CrossRef]
  18. Savvidou OD, Beltsios M, Sakellariou VI, Papagelopoulos PJ. Perilunate dislocations treated with external fixation and percutaneous pinning. J Wrist Surg. 2015;4(2):76–80. doi:10.1055/s-0035-1550159 [CrossRef]
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Progression of Perilunate Injuries (Mayfield Classification)

StageDescription
I—Scapholunate dissociationForce is initially transferred directly through the scaphoid, resulting in a transscaphoid fracture or tear through the scapholunate ligament, leading to a scapholunate dissociation
II—Perilunate dislocationThe injury travels as a series of ligament disruptions around the lunate, from radial to ulnar, starting with the disruption of the lunocapitate association
III—Triquetrum dislocationDisruption of the lunotriquetral interosseous ligament and lunotriquetral ligament separates the carpus from the lunate. The lunate dislocates dorsally, misaligning both the carpus and the lunate with the distal radius.
IV—Lunate dislocationDisruption of the dorsal radiolunate ligament causes a palmar lunate dislocation into the carpal tunnel. The remaining carpus often self-reduces.
Authors

The authors are from the Department of Orthopaedics (ADG, APH, JAG, JR, CJG), Warren Alpert Medical School, Brown University (JP), Providence, Rhode Island.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: Andrew P. Harris, MD, Department of Orthopaedics, Warren Alpert Medical School, Brown University, 593 Eddy St, Providence, RI 02903 ( Aharri26@gmail.com).

Received: November 12, 2017
Accepted: March 07, 2018

10.3928/01477447-20181102-05

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