A torn ligament in the thumb usually affects the ulnar collateral ligament, which is used to pinch and grasp. The ulnar collateral ligament also stabilizes the thumb so it doesn’t bend too far. An ulnar collateral ligament tear is often called a skier’s thumb or a gamekeeper’s thumb; skier’s thumb describes an acute injury and gamekeeper’s thumb a chronic injury, but the terms are often used interchangeably.
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Ulnar collateral ligament injuries are usually the result of a sudden force, called a valgus force, bending the thumb backwards, away from the hand. The sudden force on the thumb tears the ligament either partially or completely. An acute injury such as a fall on the outstretched thumb or a repetitive motion injury from overuse can tear the ligament.
Pain occurs at the time of the injury. Afterward, the thumb is unstable; it’s difficult to grasp objects tightly between the thumb and index finger. Bruising and swelling may develop at the base of the thumb. If the ligament has completely torn away from one of the bones, the end may fold under and form a bump that can be felt at the base of the thumb. This bump is called a Stener lesion.
Your doctor may assess the degree of injury by stress testing, which involves bending the thumb and measuring how far it can be moved away from the hand, compared to the uninjured thumb. Ability to move the thumb less than 30 degrees, or 15 degrees more than the uninjured thumb, indicates a partial tear. If the thumb can move more than 30 degrees from the hand or more than 15 degrees than the uninjured thumb, diagnosis is likely to be a complete tear. X-rays are done to check for fractures; sometimes a small piece of bone is pulled away from the thumb at the time of injury. This type of injury is called an avulsion fracture.
If the ligament isn’t completely torn, a cast may be used for around six weeks to stabilize the joint and allow the ligament to heal. Ice packs help decrease pain and swelling. If the ligament is completely torn, surgery to repair the ligament is necessary. A cast is normally worn for six to eight weeks after surgery to repair a torn ligament in the thumb.
Even with surgery, complications can occur. Nerves in the thumb can be damaged, resulting in numbness. Stiffness, tenderness and discomfort persist after surgery, but are usually reversible with physical therapy and usually subside within a year.