Trans-Scaphoid Transcapitate Perilunate Fracture-Dislocation

Discussion

The exact biomechanism of TSTC-PLFD is unclear. Impaction of the wrist in extension seems to be the most important predictor of this injury.^5,7,9-11 According to Stein and Siegel,¹⁰ scaphoid fractures first allow hyperextension of the wrist; the lunate and the capitate rotate dorsally, and the dorsal surface of the capitate impacts the dorsal edge of the distal radius, causing a fracture of the neck of the capitate. If the wrist continues to rotate into further hyperextension, the unsupported, proximal part of the capitate rotates 90° around itself.^9,10 When the carpus returns to neutral position, the bone fragment of the capitate rotates further, reaching a position of 180°, with its proximal articular surface facing distally. In this type of injury, the axis of rotation is transverse (radioulnar), in contrast to the perpendicular (anteroposterior) axis of rotation suggested by the initial report by Fenton.⁵ The scaphoid is fractured by impaction of the radial styloid process. Monahan and Galasko¹¹ reported a case of capitate fracture with palmar displacement and 90° rotation of the proximal bone fragment; the fragmented surface was facing dorsally. A transverse axis of rotation, as in our patient’s case, could explain this type of displacement supporting the mechanism of injury proposed by Stein and Siegel.¹⁰ Vance and colleagues⁷ described various patterns of scaphocapitate fractures and concluded that no single mechanism of injury accounts for these types of injuries. Other authors have considered scaphocapitate syndrome as a specific type of TSTC-PLFD, one that reduces either spontaneously or with manipulation.^1,3,12 Detailed evaluation of standard anteroposterior and lateral wrist radiographs can provide enough evidence for the diagnosis of this injury. Computed tomography may define further the type and extent of injury.⁷ In our patient’s case, wrist impaction caused the scaphoid and capitate fractures and the avulsion of the capsule attachment to the triquetrum. The distal fragment of the capitate subluxated dorsally in relation to the lunate. The lateral radiograph of the wrist showed its position in the lunate fossa. According to the classification of Herzberg and colleagues¹² and Mayfield and colleagues,¹³ this represents a dorsal PLFD of the greater carpal bones arc.

Conservative treatment is not recommended for PLFD because closed reduction usually is not possible, and poor functional outcomes are common. Instead, optimal treatment is open reduction, anatomical alignment, and ligamentous and osseous stabilization.^7,12,14,15 Dorsal, palmar, and combined approaches have been used in surgery for perilunate injuries. A dorsal approach through a radius-based capsular flap allows excellent exposure of the dorsal wrist and facilitates reduction of fractures.⁹ Capitate reduction should precede scaphoid reduction because scaphoid reduction cannot be easily maintained, especially when the fracture interface is comminuted.⁷ In addition, scaphoid reduction may be guided from the radial surface of the capitate. Moreover, when the scaphoid is fixated first, reduction of the rotated head of the capitate usually is difficult. In our patient’s case, traction applied through the external fixator facilitated reduction and K-wire fixation of the capitate fracture. After scaphoid fixation, the K-wires were advanced through the capitate to the lunate to stabilize the capitolunate joint. The wrist must be immobilized for 6 to 8 weeks after surgical repair of PLFD. A cast can be used, but, as with our patient, an external fixator facilitates fracture reduction and wrist stability during osteosynthesis. During immobilization, the wrist should be maintained in neutral position to avoid stretching the dorsal and palmar wrist capsule and ligaments.¹⁶The most important complications of scaphoid and capitate fractures and PLFD are osteonecrosis and nonunion.^17-20 Similar to scaphoid fractures, capitate fractures proximal to the waist of the capitate are associated with increased risk of osteonecrosis. Therefore, anatomical reduction and stabilization favor revascularization of the proximal bone fragment. Moreover, any osteonecrosis that occurs in the proximal part of the capitate is not an indication for further surgery as long as wrist height is maintained. Nonunion is not common after open reduction and internal fixation of PLFD (eg, our patient’s fractures healed completely).¹⁷ Radiographically, nonunion is characterized by bone absorption and sclerosis of the ends of the bone. Treatment of capitate nonunion depends on symptom severity, bone fragment size, and radiographic evidence of arthritic changes.^3,7,21-23 Treatment options include resection of sclerotic edges, bone grafting, and stabilization²¹ and removal of the proximal capitate fragment and limited arthrodesis,²² as arthritic changes likely are inevitable.^22,23TSTC-PLFD is a rare wrist injury. Careful radiographic evaluation of the carpal bones and their relationships on both anteroposterior and lateral views is mandatory in making the correct diagnosis. Open reduction (preferably with use of an external fixator) and internal fixation are recommended for optimal healing and functional outcomes.

Am J Orthop. 2017;46(4):E230-E234. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.