Practice Essentials
Gamekeeper's thumb was originally described by Campbell in 1955 when he reported chronic laxity of the ulnar collateral ligament (UCL) of the thumb in 24 Scottish gamekeepers. The injury occurred as gamekeepers sacrificed wounded rabbits and other small game by breaking their necks between the ground and their thumbs and index fingers. Injury is caused by a fall onto the outstretched hand, causing a forced abduction and extension of the thumb. Today, this injury is more a result of delayed treatment of an acute injury. The alternative term, skier's thumb, was popularized by Gerber et al and has become more synonymous with an acute injury. A significant proportion of these injuries are a result of a fall or blows to the thumbs. One of the common mechanisms is a skier landing against the ski pole or ground while the thumb is abducted, causing a valgus force on the thumb. [1, 2, 3]
Gamekeeper's thumb, or skier’s thumb, may constitute up to 50% of hand injuries in skiers. It may also be seen in patients with rheumatoid arthritis, those who have been in a motor vehicle accident, and athletes of other sports with injuries resulting from a fall onto an outstretched hand with an abducted thumb. MRI can establish the integrity of the ulnar collateral ligament. MRI can also distinguish between a Stener lesion and a nondisplaced or minimally retracted tear. Ultrasonography is also considered safe and accurate. [4] Stener lesion was first described by Bertil Stener, in 1962, who described the anatomy and treatment of displacement of the ulnar collateral ligament (UCL) of the metacarpophalangeal (MCP) joint. A Stener lesion occurs when there is forceful abduction of the thumb, leading to avulsion of the distal UCL from its insertion at the base of the proximal phalanx of the thumb. The severed end of the tendon then becomes entangled in the adductor aponeurosis. [2, 3]
Symptoms
Patients may complain of pain, swelling, and/or ecchymosis of the MCP joint after a fall or blow to the thumb, forcing it into a combination of hyperextension and radial (lateral) deviation. This commonly occurs while participating in sports but has been noted in patients who fall on outstretched hands and in motor vehicle accidents. The most common mechanism is a fall while holding onto a ski pole. This injury can also be seen in a football player forcibly abducting and hyperextending a thumb while holding back a rushing opponent.
Patients may also complain of weakness or worsening pain when pinching the thumb against the index finger when no acute injury is reported.
Testing
Standard radiographs should be obtained before lateral stress examination, because stress testing may cause further displacement of an avulsion fracture that was originally minimally displaced. Valgus (lateral) stress testing can determine the integrity of the UCL. For the emergency physician, carrying out highly specific tests may not be practical. Standard radiographs and adequate physical examination should be enough to determine those cases that necessitate surgical repair. Stability of the opposite thumb should be tested as well for comparison. Administration of local anesthetic may be necessary to facilitate optimal examination.
Treatment
The emergency medicine physician should immobilize all suspected injuries in a thumb spica splint and have the patient follow up within 1 week.
Complete UCL tears require surgical intervention. Gamekeeper's fractures are usually treated conservatively, but those involving more than 30% of the joint surface and those that are malrotated or displaced should not be manipulated. Those fractures are indications for surgical intervention. [4]
Injuries that are not fixed surgically require application of a well-molded functional brace (short arm thumb spica or a smaller, glove-type thumb spica) for 4-6 weeks, with the MCP joint typically flexed to about 20-30°.
An orthopedic or hand surgeon should be notified if the injury requires operative management to ensure timely repair.
Pathophysiology
The metacarpophalangeal (MCP) joint is a diarthrodial joint with the metacarpal head stabilized by ligamentous and musculotendinous attachments. The thumb MCP joint is capable of motion predominately in flexion and extension with a limited degree of rotation. The ulnar collateral ligament provides static stabilization of the thumb MCP joint. The UCL consists of both a proper ligament and an accessory ligament. The proper is taut in flexion, while the accessory is taut in extension.
The dynamic stabilizers are the intrinsic and extrinsic muscles of the thumb or most notably the adductor pollicis muscle. Dorsally, this muscle expands to form the adductor aponeurosis lying superficial to the UCL.
Chronic laxity of the UCL results from repetitive lateral stress applied to the abducted MCP joint—in particular, the stabilizing ligaments on the ulnar side of the thumb MCP joint. Subsequent instability of the first MCP joint can result from the chronic laxity of the UCL and, moreover, lead to functional disability such as weakness of pincer grasp and arthritis.
An acute injury results from a sudden forced abduction stress at the MCP, particularly a fall against a ski pole or the ground. The distal attachment on the proximal phalanx is the most frequent site of rupture. The UCL may even avulse a small portion of the proximal phalanx at its insertion site. The rate of associated fractures in the skeletally mature varies from 23-50% of patients treated operatively.
A Stener lesion occurs when the ruptured end of the UCL retracts and becomes abnormally displaced proximal to the adductor aponeurosis and may be palpated clinically on the ulnar side of the MCP joint. Proper anatomical alignment and healing becomes impeded because the adductor aponeurosis becomes interposed between the sites of insertion on the proximal phalanx with the ruptured end. This lesion can also be associated with a fracture as well.
In the pediatric population, epiphyseal fusion of the proximal phalanx occurs in those aged 16-18 years. Ulnar collateral ligament ruptures of the thumb MCP joint in children are usually associated with epiphyseal fractures (Salter-Harris III) of the proximal phalanx.
Epidemiology
The incidence is increased in skiers. This common injury can also be sustained while playing football or rugby. Some instances of skier's thumb injuries are reported in sports with direct ball-to-thumb impact, such as volleyball. Gripped object sports cannot be implicated as the lone risk factor, since thumb injuries are not common in sports such as lacrosse, hockey, or tennis. Ulnar collateral injuries have been reported in cases of people falling on outstretched hands with the thumb without reports of gripping any handle.
Skier's thumb is the most common upper extremity injury in skiing and is second only to medial collateral ligament (MCL) injury of the knee. Reported injury rates in downhill skiing vary between 2.3 and 4.4 per 1000 skiing days. Of these, between 7% and 9.5% are injuries to the UCL.
The incidence of Stener lesion–diagnosed definitively during surgery—was first noted in 64% of patients with clinical UCL injuries. Subsequent studies report between 14% and 87% of patients.
Disruption of the UCL leads to instability of the first MCP joint. This results in poor pincer grasp and opposition and can ultimately lead to degenerative arthritic changes and difficulty carrying on the activities of daily living secondary to chronic pain.
If the diagnosis is missed or the injury is not treated properly, enduring pain, weak pincer grasp, or arthritis may result.
Prognosis
Most authors agree that early diagnosis is the most important factor that determines the functional outcome.
Nonsurgical conservative management usually yields thumbs with normal range of motion.
Early referral/consultation is indicated, especially if some degree of uncertainty exists about whether a complete UCL tear is present.
The failure rate is about 50% using conservative treatment with functional bracing and early motion exercises.
Early surgical intervention—within 3 weeks of injury—has led to good results in the treatment of gamekeeper's/skier's thumb injury. The prognosis may be worse if surgical intervention has been delayed. The anatomy may be too distorted by 6 weeks to permit direct repair; however, studies have reported good results obtainable with late repair or reconstruction.
-
Lateral radiograph displaying a gamekeeper's fracture.
