A torn ligament in a thumb
A torn ligament in the thumb usually affects the ulnar collateral ligament, which is used for pinching and grasping. The ulnar collateral ligament also stabilizes the thumb so that it does not bend too much. A tear in the ulnar collateral ligament is often called a skier’s thumb or a forester’s thumb; a skier’s thumb describes an acute injury and a forester’s thumb describes a chronic injury, but the terms are often used interchangeably.
Injuries to the collateral ligaments of the anterior ear are usually the result of a sudden force, called a valgus force, that bends the thumb back away from the hand. The sudden force on the thumb tears the ligament partially or completely. An acute injury, such as an extended thumb drop or repetitive motion injury due to overuse, can tear the ligament.
Pain occurs at the time of injury. Afterward, the thumb is unstable; it is difficult to grasp objects tightly between the thumb and forefinger. Bruising and swelling may develop at the base of the thumb. If the ligament has completely detached from one of the bones, the end may bend downward and form a lump that can be felt at the base of the thumb. This lump is called a Stener’s lesion.
The doctor may evaluate the extent of the injury using a stress test, which involves bending the thumb and measuring how far away you can get from the hand, compared to the uninjured thumb. The 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 from the uninjured thumb, the diagnosis is likely to be a complete tear. X-rays are done to check for fractures; sometimes a small piece of thumb bone is removed at the time of injury. This type of injury is called an avulsion fracture.
If the ligament is not completely torn, a cast may be used for about six weeks to stabilize the joint and allow the ligament to heal. Ice packs help reduce pain and swelling. If the ligament is completely torn, surgery is needed to repair it. A cast is usually used for six to eight weeks after surgery to repair a torn ligament in the thumb.
Even with surgery, complications can occur. The nerves of the thumb may be damaged, causing numbness. Stiffness, tenderness, and discomfort persist after surgery, but are usually reversible with physical therapy and usually disappear within a year.