Thumb Ulnar Collateral Ligament Injury
What is it: The ulnar collateral ligament (UCL) stabilizes the ulnar side of the first metacarpal phalangeal joint.
How does it present: The injury is usually caused by a forced abduction and/or hyperextension to the thumb, and is often called gamekeeper’s thumb or skier’s thumb. Patients will complain of pain along the ulnar side of the base of the thumb, they may also have swelling or bruising. Movement in abduction or extension often worsens pain.
Common exam findings: There may be swelling and tenderness along the ulnar side of the base of the thumb. X-rays should always be examined to evaluate for an avulsion fracture prior to stressing the ulnar collateral ligament. Potentially a non-displaced avulsion fracture may become displaced if the ligament is stressed before knowing of it presence. If no avulsion fracture is noted, the ligament may be stressed. Generally greater than 20 degrees of instability compared to the non-injured side indicates a probably full thickness tear. If there is no instability, and only tenderness over the UCL ligament, a sprain or partial tear is likely. Injuries to the UCL of the thumb can cause decreased pinch strength.
Tests and treatment: As stated above, x-rays should be done prior to exam to determine if an avulsion fracture is present. If a displaced avulsion fracture is present, then referral should be made to orthopedics. If a full thickness tear of the UCL is a concern, referral is also indicated to consider surgical repair. In full thickness tears, the ligament can be kept out of place by the adductor aponeurosis that prevents full healing and results in chronic instability, called a Stener lesion. Treatment of partial tears of the UCL involve immobilizing in a thumb spica splint or cast for four to six weeks.