Alterations in wrist mechanics because of a functional loss of the scapholunate linkage usually progress to degenerative wrist arthritis. With loss of functional integrity of the scapholunate ligament, the scaphoid flexes and becomes incongruous with the elliptical fossa of the distal radius, leading to scapholunate advanced collapse (SLAC) (1). Similarly, a chronic scaphoid nonunion will lead to comparable radiographic and clinical findings. Classically, degenerative changes begin at the tip of the radial styloid (SLAC stage I) and progress to the obliteration of the entire radioscaphoid joint (stage II). Further collapse results in lunate extension and proximal capitate migration, leading to a dorsal intercalated segment instability (DISI) pattern. Finally, as the capitate migrates proximally, degenerative changes develop at the capitolunate articulation (stage III). The radiolunate articulation is nearly always spared (1).

SLAC wrist reconstruction is a salvage procedure designed to preserve wrist motion. It is indicated in symptomatic individuals who have failed nonsurgical treatment. The best indication is a stage III SLAC wrist where the capitolunate joint is destroyed. The radiolunate cartilage must be intact without carpal subluxation. Patients with avascular necrosis of the scaphoid (Preiser disease) or post-traumatic arthritis from distal radius fractures involving the radioscaphoid articulation are additional candidates for four-corner arthrodesis. Nondegenerative indications include chronic dynamic carpal instability, chronic perilunar instability, and nondissociative carpal instability (2).

The absolute contraindications include radiographic evidence of radiolunate arthritis, Kienböck disease, avascular necrosis of the capitate, and ulnar or volar carpal subluxation on the radius. Relative contraindications include inflammatory arthropathy (with the increased risk of ligament laxity
and carpal subluxation), a wrist arc of motion of less than 50 degrees in flexion and extension, and low demand patients.

Obtain a thorough history of the affected wrist along with performing a focused and detailed physical examination. Patients commonly complain of dorsal wrist pain and dorsal-radial swelling with limited use of the affected extremity for work or activities requiring loading the wrist in extension. A wide range of physiologic conditions converge on the final common pathway of degeneration found in SLAC wrist; thus, the clinical history is quite varied. Many patients have undergone previous surgery. Patients with scapholunate ligament dissociation may have undergone a ligamentous reconstruction, whereas patients with scaphoid nonunion have had attempts at internal fixation, often with concomitant bone grafting procedures.

Most patients with SLAC wrist have remarkably similar physical findings (Fig. 25-1). There is dorsal-radial swelling and tenderness, especially with resisted wrist extension. Range of motion is often severely restricted in flexion–extension and decreased in radial and ulnar deviation. The Watson scaphoid shift test (passive radial deviation of the wrist with dorsal pressure on the scaphoid tuberosity) is often painful and may produce a palpable clunk. Document preoperative grip and pinch strength along with performing a thorough neurologic examination, including evaluation for carpal tunnel syndrome.

Standard posteroanterior (PA) and lateral wrist radiographs are mandatory (Fig. 25-2), and dedicated scaphoid views may be obtained if necessary. Occasionally, a computed tomography (CT) scan or magnetic resonance imaging (MRI) may be of benefit to evaluate the extent of degenerative changes.