Scaphoid nonunion: correction of deformity with bone graft and internal fixation

Abstract

The scaphoid is the most commonly fractured bone in the carpus. Although greater than 90% of scaphoid fractures unite with cast immobilization, failure to heal remains a clinical reality, particularly when the fracture is displaced or associated with intracarpal instability [1–3]. Dabezies [4] reported a 55% incidence of nonunion and a 50% rate of proximal pole avascular necrosis (AVN) in scaphoid fractures with greater than 1 mm of displacement. Cooney and colleagues [2] noted a nonunion rate of 46% for 13 displaced scaphoid fractures. Scaphoid nonunion has been associated with progressive symptomatic radiocarpal and midcarpal arthrosis [5–7]. This arthrosis is the sequela of altered wrist kinematics [3,8,9]. The alteration of wrist kinematics reflects not only motion through the nonunion site, but also the apex-dorsal malalignment of the scaphoid (the so-called humpback deformity) with associated dorsal angulation of the lunate and alteration in carpal height [10,11]. Although scaphoid deformity and its adverse effects on kinematics were recognized early on by Fisk [12], for many years the standard treatment of symptomatic scaphoid nonunion was based on gaining union without an attempt to correct the deformity of the scaphoid. It has been recognized, however, that some patients with residual bony deformity of the healed scaphoid may continue to have pain and functional limitations [13–15]. As a result of a greater appreciation of carpal kinematics, many authors now believe that the approach to a scaphoid nonunion should consist of realigning the scaphoid anatomy and gaining union. Scaphoid deformity Posttraumatic scaphoid deformity is complex but predictable. Displaced scaphoid fragments lie in a so-called humpback configuration with flexion of the distal fragment. The dorsal intercalary pattern of carpal instability (DISI) follows [16]. With the use of three-dimensional reconstructions of computed tomography images, the three-dimensional orientation of a fractured scaphoid has been represented more clearly. Belsole and coworkers [17] looked at a series of scaphoid nonunions and performed a detailed three-dimensional CT evaluation comparing the fractured and contralateral scaphoids. They found that the proximal scaphoid fracture component is extended, radially deviated, and supinated in relation to the distal fracture component. They also identified that the volume and configuration of missing bone is consistent. The amount of the scaphoid bone that was lost varied from 6% to 15% of bone volume. The bony defect is prismatic with a quadrilateral base facing palmarly.