The ulnar collateral ligament (UCL) complex includes the ulnar proper collateral ligament and the ulnar accessory collateral ligament [1]. These ligaments are located deep to the adductor aponeurosis of the thumb and stabilize the first metacarpophalangeal (MCP) joint. Tears can occur if a valgus force is applied to an abducted first MCP joint [2]. A lesion of the UCL is commonly called skier’s thumb.

Acute injuries can occur when the strap on a ski pole forcibly abducts the thumb. In the United States, estimates for skiing injuries are 3 or 4 per 1000 skier-hours; thumb injuries account for about 10% of skiing injuries [3]. A study of downhill skiing found that thumb injuries accounted for 17% of skiing injuries, second only to knee injuries [4]. Three fourths of the thumb injuries were UCL sprains. UCL injury in football players may be related to falls or blocking. Other sports involving ball handling or equipment with repetitive abduction forces to the thumb, like basketball or lacrosse, can cause injury to the UCL.

UCL injuries may be accompanied by avulsion fractures. Complete tears can fold back proximally when they are ruptured distally and become interposed between the adductor aponeurosis [1]. This injury is known as the Stener lesion and has been described as a complication of complete UCL tears, with a frequency ranging from 33% to 80% [5].

Chronic ligamentous laxity is more common in occupational conditions associated with repetitive stresses to the thumb. The term gamekeeper’s thumb was coined in the mid-1950s to describe an occupational injury of Scottish gamekeepers [6]. The term is also used for acute injuries to the UCL.

Rupture of the thumb MCP joint UCL represents one of the most common ligamentous injuries of the hand. Failure to recognize these injuries or to treat them appropriately can lead to instability, pain, and weakness of the joint [7].

Symptoms

Patients report pain and instability of the thumb joint. In the acute injury setting, patients can often recall the instant of injury. If the UCL is ruptured, patients report swelling and hematoma formation; pain may be minimal with complete tears. When pain is present, it can cause thumb weakness and reduced function. Numbness and paresthesias are not typical findings.

Physical Examination

The physical examination begins with the uninvolved thumb, noting the individual’s normal range of motion and stability. Palpate to determine the point of maximal tenderness, assessing for distal tenderness; if the ligament is torn, it tears distally off the proximal phalanx. Initially, the examiner may be able to detect a knot at the site of ligament disruption. Laxity of the UCL is the key finding on examination. Ligament injuries are graded as follows: grade I sprains, local injury without loss of integrity; grade II sprains, local injury with partial loss of integrity, but end-feel is present; and grade III sprains, complete tear with loss of integrity and end-feel (Fig. 38.1). Passive abduction can be painful, especially in acute grade I and grade II sprains.

f38-01-9781455775774 — FIGURE 38.1 Skier’s thumb. The ulnar collateral ligament to the metacarpophalangeal joint is disrupted by an abduction force. (From Mellion MB. Office Sports Medicine, 2nd ed. Philadelphia, Hanley & Belfus, 1996.)

The UCL should be tested with the first MCP joint in extension and flexion to evaluate all bands. The excursion is compared with the uninjured side. Testing for disruption of the ulnar proper collateral ligament is done with the thumb flexed to 90 degrees [1]. With the thumb in extension, a false-negative finding may result. The stability of the joint will not be impaired even if the ulnar proper collateral ligament is torn because of the taut ulnar accessory ligament in extension.

To avoid a false interpretation, the examiner must prevent MCP rotation by grasping the thumb proximal to the joint. If there is more than 30 degrees of laxity (or 15 degrees more laxity than on the noninjured side), rupture of the proper collateral ligament is likely. The thumb is then positioned in extension for repeated valgus stress testing. If valgus laxity is less than 30 degrees (or 15 degrees less than on the noninjured side), the accessory collateral ligament is intact. If valgus laxity is greater than 30 degrees (or 15 degrees more than on the noninjured side), the accessory collateral ligament is also ruptured [8].

A displaced fracture is a contraindication to stress testing. The fracture is manifested with swelling or discoloration on the ulnar side of the first MCP joint and tenderness along the base of the proximal phalanx. Some authors recommend that conventional radiographs be obtained before stressing of the UCL to determine whether a large undisplaced fracture is present because stress testing could cause displacement [9]. More than 3 mm of volar subluxation of the proximal phalanx indicates gross instability. The patient may be unable to pinch. Pain may limit the complete examination and lead to underestimation of injury extent. Infiltration of local anesthetic around the injury site can reduce discomfort and improve the accuracy of the examination [10].

Avulsion fracture represents a special class of collateral ligament injury. It cannot be graded I to III because technically the ligament is not torn. However, it still deserves mention because fracture can compromise the bone-ligament-bone stabilization complex and lead to chronic symptoms [11].