The most common way to injure the ulnar collateral ligament of the thumb is to fall on the hand with the thumb stretched out. The skier's thumb, is also known as the gamekeeper's thumb. Both similar conditions and both involve insufficiency of the ulnar collateral ligament (ULC) of the thumb (Figure 1).
Skier's Thumb is an acute condition that is acquired after a fall or similar abduction injury to the MCP joint of the thumb.Gamekeeper's Thumb is a chronic condition that develops as a result of repeated episodes of hyperabduction.
When the injury occurs, a tear or possible avulsion of the ligament may occur at the site of insertion into the proximal phalanx of the thumb (Figure 2).
Stener Lesion is considered a surgical situation, the torn ligament or the avulsion fracture may become entrapped by the aponeurosis of the adductor pollicis muscle (Figure 3). The ruptured ligament or avulsed fragment is less likely to heal without surgical treatment. The Stener lesion is present in about 80% of complete ruptures involving the ulnar collateral ligament of the thumb.
Injury to the ulnar collateral ligament is characterized by painful swelling and weakness when grasping with the thumb. Bruise-like discolorations may be present on the skin around the joint.
Diagnosis is usually done by clinical exam and stress views.
Stress Views Examination
Local anesthesia should be given when doing the stress views. Ulnar collateral ligament stress test in full extension is best to test the accessory collateral portion of the UCL (Figure 4). The ulnar collateral ligament stress test in a flexed position is used to isolate the proper portion of the ligament (Figure 5). The proper portion of the UCL will usually tear first, followed by the accessory portion of the ligament. If the joint is unstable when testing in full extension, then both portions of the ligament are torn.
Significance of Angulation in Stress Views
The angle between the first metacarpal and the proximal phalanx is assessed (Figure 6). Stress test in extension with abduction of the thumb more than 40° will indicate a complete injury. When compared to the other side of the thumb, a difference of 15° is positive for complete injury.
Treatment of UCL Injuries
When the ligament is partially torn, a thumb spica splint is usually used and the ligaments will usually heal without surgery. A complete tear of the ligament may need surgery, especially if it is associated with a Stener lesion.
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