Scapholunat

Scapholunat, more commonly written as scapholunate, refers to the joint between the scaphoid and lunate bones in the proximal row of the wrist. This articulation is stabilized by a set of ligaments, most notably the scapholunate interosseous ligament, along with dorsal and volar components of the scapholunate ligaments and the surrounding joint capsule. The scaphoid is located laterally (thumb side) and the lunate lies medially, and together they contribute to the complex movements of the wrist.

The scapholunate joint plays a central role in coordinating motion between the proximal carpal rows and in maintaining carpal alignment during flexion, extension, and radial deviation. The scapholunate interosseous ligament is the primary stabilizer, with the dorsal portion providing most of the stability and the volar portion supporting resistance to angular gapping.

Injuries to the scapholunate region are common after falls on an outstretched hand (FOOSH) and can range from sprains to complete dissociation. Acute injuries may present with dorsoradial wrist pain, swelling, and instability. Diagnosis often involves radiographs showing scapholunate dissociation, with signs such as an increased scapholunate gap (the Terry Thomas sign) or a widened scapholunate interval. Chronic instability can lead to degenerative changes in the wrist, known as SLAC (scapholunate advanced collapse) deformity.

Treatment depends on severity and chronicity. Minor sprains may respond to immobilization, while complete tears often require surgical repair or reconstruction to restore stability. Chronic cases may necessitate salvage procedures such as partial wrist arthrodesis (four-corner fusion) or proximal row carpectomy. Early recognition and management are important to prevent progressive arthritis and functional loss.