Scapholunate Ligament Injury

Wilfredor · Wikimedia Commons · CC BY-SA 3.0

The scapholunate (SL) ligament links the scaphoid and lunate bones at the center of the wrist and is the most important stabilizer of the proximal carpal row. A partial or complete tear disrupts the kinematic relationship between these bones, eventually leading to a predictable pattern of wrist arthritis called SLAC (scapholunate advanced collapse) wrist if left untreated.

SL injuries usually occur from a fall on an outstretched hand. Symptoms are dorsal wrist pain between the radius and the third metacarpal, weak grip, and pain with weight-bearing through the wrist.

The Watson test (scaphoid shift maneuver) is the classic provocative exam. X-rays may show widening between the scaphoid and lunate (Terry-Thomas sign) or a ring sign (foreshortened scaphoid in AP view). MRI arthrography is the most sensitive non-invasive test; wrist arthroscopy remains the gold standard and allows simultaneous treatment.

Complete SL tears with dynamic or static instability require surgical repair or reconstruction. The longer the delay, the less likely a primary repair can succeed.

External patient-education references and related OSI pages for additional background:

• Britannica — Ligament
• Britannica — Hand (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language