Ulnar Collateral Ligament (UCL) Thumb Tear: MRI, Ultrasound, Repair, Splint, and Treatment

Ulnar Collateral Ligament (UCL) Thumb Tear:

• What is Ulnar Collateral Ligament (UCL) Thumb Tear?
• MRI
• Ultrasound
• Repair
• Splint
• Treatment

What is Ulnar Collateral Ligament (UCL) Thumb Tear?

An Ulnar Collateral Ligament (UCL) thumb tear is a common hand injury that affects the ligament located on the inner side of the thumb’s metacarpophalangeal (MCP) joint. This ligament provides stability during pinching and gripping actions. It’s often injured in athletes, especially skiers (hence the term “skier’s thumb”), or in individuals who experience a sudden force that pulls the thumb outward. A partial or complete tear of this ligament leads to pain, swelling, and instability of the thumb joint.

The condition can be either a partial tear, where the ligament is stretched but still intact, or a complete tear, where the ligament is fully detached, sometimes with a small bone fragment (avulsion fracture). Left untreated, a UCL tear can lead to chronic instability, weakness in grip or pinch, and early joint arthritis. Proper diagnosis and timely management are crucial for optimal recovery and to restore thumb function.

MRI

Magnetic Resonance Imaging (MRI) is the gold standard for diagnosing UCL injuries of the thumb. MRI provides a clear, detailed image of the soft tissues, allowing physicians to differentiate between partial and complete tears, as well as identify associated injuries like Stener lesions—where the torn ligament becomes trapped above the adductor aponeurosis, preventing natural healing.

MRI findings typically show discontinuity of the ligament fibers, surrounding soft tissue swelling, and sometimes bone marrow edema if an avulsion is present. A complete UCL tear on MRI may show the ligament retracted from its normal attachment. Radiologists use both coronal and sagittal views to accurately assess ligament integrity and guide treatment decisions.

Ultrasound

Ultrasound is another valuable diagnostic tool for evaluating UCL injuries, particularly when MRI is unavailable or contraindicated. It allows real-time visualization of the ligament, joint, and surrounding soft tissues. Dynamic ultrasound can demonstrate laxity by comparing the injured thumb with the contralateral (uninjured) side during valgus stress testing.

A high-frequency linear probe is used to assess the ligament’s continuity, thickness, and echogenicity. In cases of complete rupture, ultrasound may reveal a gap or irregularity where the ligament fibers should be, or displacement of the torn ligament (as seen in a Stener lesion). Ultrasound is quick, non-invasive, and cost-effective, making it an excellent first-line imaging tool in skilled hands.

Repair

Surgical repair is typically required for complete UCL tears, especially if a Stener lesion is present. The goal of surgery is to reattach the ligament to its normal anatomic position on the proximal phalanx and restore thumb stability. In acute cases, direct suture repair is often sufficient. For chronic tears or cases with poor tissue quality, tendon grafts or anchors may be used to reconstruct the ligament.

Surgery is usually performed under regional or general anesthesia. Postoperatively, the thumb is immobilized in a cast or splint for several weeks to allow healing. Early surgical intervention has a high success rate, with most patients regaining full strength and stability within a few months. Delayed treatment, however, may result in residual laxity or arthritis due to chronic instability.

Splint

Splinting is the mainstay of conservative management for partial UCL tears or postoperative immobilization following repair. The most commonly used device is a thumb spica splint or cast, which stabilizes the MCP joint while allowing motion at the interphalangeal joint. This positioning promotes healing of the ligament while maintaining partial thumb function.

The splint is typically worn for 4–6 weeks, depending on the severity of the injury and the healing progress. During this period, patients should avoid activities that stress the thumb. After immobilization, physiotherapy may be initiated to regain motion, strength, and stability. Proper splint fit and adherence to immobilization guidelines are essential to ensure full recovery and prevent chronic weakness or deformity.

Treatment

Treatment of a UCL thumb tear depends on the extent of injury. Partial tears are usually managed non-surgically with rest, immobilization, and gradual rehabilitation. Anti-inflammatory medications and cold therapy help reduce pain and swelling in the acute phase. Once the ligament has healed adequately, strengthening exercises are introduced to restore grip and pinch strength.

Complete tears or cases with a Stener lesion require surgical repair or reconstruction. Post-surgery, the patient undergoes immobilization followed by structured hand therapy. Long-term outcomes are generally excellent, with most individuals returning to normal activities within 8–12 weeks. However, failure to treat a severe UCL tear can lead to chronic instability and loss of thumb function, underscoring the importance of timely diagnosis and appropriate management.