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Condition

Scapholunate Ligament Injury

A tear of the key ligament between two small bones of the wrist. Often missed at first because the x-rays look normal, but untreated it can lead to progressive wrist arthritis.

What is the scapholunate ligament?

The wrist is made up of eight small bones held together by a web of ligaments. The two most important bones in the front row are the scaphoid and the lunate. They are connected by the scapholunate (SL) ligament, which keeps the two bones moving together as a unit. When this ligament tears, the scaphoid and lunate start to drift apart and rotate differently, and the normal mechanics of the wrist break down.

The most common mechanism is a fall on an outstretched hand. A scapholunate tear can happen alone or with a distal radius fracture or scaphoid fracture.

Common symptoms

  • Pain on the back of the wrist, especially just past the end of the radius, after a fall or a wrench
  • Swelling on top of the wrist
  • A clicking, popping, or clunking sensation with wrist motion
  • Weakness of grip, particularly when pushing up from a chair or doing pushups
  • Pain that worsens with loading the wrist in extension

Scapholunate tears are frequently misdiagnosed as a "wrist sprain" in the emergency department when x-rays are read as normal. Pain that persists beyond 4 to 6 weeks after a fall should prompt further evaluation.

Stages of injury

Scapholunate injuries exist on a spectrum, and the right treatment depends on where the injury is on that spectrum:

  • Partial tear. The ligament is stretched or partially torn. The scaphoid and lunate still move together normally. X-rays look normal; the injury may only be seen on MRI or wrist arthroscopy.
  • Complete tear (dynamic instability). The ligament is fully torn but the bones only separate when the wrist is stressed in a certain position. Standard x-rays may look normal; special stress x-rays or arthroscopy are needed to see it.
  • Complete tear with static instability. The bones have drifted apart and can be seen out of position on a standard x-ray — a gap between the scaphoid and lunate (sometimes called the "Terry Thomas sign") and a tipped-back lunate (DISI pattern).
  • SLAC wrist (scapholunate advanced collapse). A long-standing, untreated tear eventually wears through the cartilage and produces a specific, progressive pattern of arthritis in the wrist.

How it is diagnosed

  • Exam. Dr. Barrera will check for tenderness directly over the scapholunate interval and perform specific stress tests (such as the Watson scaphoid shift test) to feel for abnormal movement between the scaphoid and lunate.
  • X-rays. Including specific stress views (clenched-fist PA) that can reveal a dynamic tear not visible on a plain x-ray.
  • MRI. Can confirm a ligament tear and assess the surrounding cartilage.
  • Wrist arthroscopy. A small camera placed inside the wrist is still the most accurate way to grade a scapholunate tear and see the cartilage directly. It can be both diagnostic and therapeutic in the same setting.

Treatment options

Non-surgical treatment

  • Splinting, activity modification, and hand therapy. Partial tears and some stable complete tears can settle down with a period of immobilization followed by a specific wrist-stabilizing exercise program.
  • Corticosteroid injection. Sometimes used to calm inflammation inside the wrist joint, particularly in partial tears.

Surgical treatment

The right operation depends on how long ago the injury happened, how much the bones have drifted, and whether the cartilage is still healthy.

  • Arthroscopic debridement and pinning. For partial or recent complete tears with healthy cartilage, an arthroscopic operation can clean up the torn ligament and temporarily pin the bones back together while they heal.
  • Primary repair. When the injury is less than a few months old and the ligament is good quality, the torn ligament can be reattached directly to the bone with small suture anchors, often with an internal brace for support.
  • Ligament reconstruction. For chronic tears where the original ligament is no longer repairable, a new ligament can be rebuilt using a tendon graft (several different techniques exist). These reconstructions require a period of cast or pin immobilization followed by a structured therapy program.
  • Salvage procedures for SLAC arthritis. When the tear has been untreated long enough that the cartilage has worn out, the scaphoid and lunate cannot be saved. Options include proximal row carpectomy (removing the damaged bones) or a four-corner fusion with scaphoid excision. Both are reliable pain-relieving operations that preserve useful, if reduced, wrist motion.

What to expect at your visit

Dr. Barrera will ask about the mechanism of injury and the time course, examine the wrist, and review x-rays. Additional imaging (stress x-rays, MRI) or a diagnostic arthroscopy may be recommended depending on exam findings. Because the right operation is entirely different for a fresh tear versus a chronic one, the evaluation is focused on determining exactly where the injury sits on the spectrum above.

Dr. Barrera's approach

The scapholunate ligament is one of the most commonly missed injuries in the wrist, and timing is everything. A tear caught within the first few weeks can often be repaired directly with a very good result. The same tear, five years later, requires a reconstruction or sometimes a salvage operation. Dr. Barrera has fellowship training in wrist arthroscopy and in the full range of scapholunate repair and reconstruction techniques, and will tailor the operation to the stage of injury.

When to call the office sooner

Call us if wrist pain and swelling are getting worse rather than better, if your wrist becomes locked in one position or you cannot move it, if you have new numbness in the fingers, or if you develop redness, warmth, and fever around the wrist.

Related

Scaphoid fracture · Distal radius fracture · Wrist arthritis

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