eMedicine Specialties > Emergency Medicine > Trauma & Orthopedics

Gamekeeper Thumb

Author: Michael A Secko IV, MD, Clinical Assistant Instructor, Staff Physician, Clinical Assistant Instructor, Department of Emergency Medicine, Kings County Hospital, State University of New York Downstate Medical Center
Coauthor(s): Mark A Silverberg, MD, FACEP, MMB, Assistant Professor, Assistant Residency Director, Department of Emergency Medicine, State University of New York Downstate College of Medicine; Consulting Staff, Department of Emergency Medicine, Staten Island University Hospital, Kings County Hospital, University Hospital, State University of New York Downstate at Brooklyn; Joseph Kim, MD, Chairman, Department of Emergency Medicine, Western Medical Center; Clinical Instructor, University of California at Irvine
Contributor Information and Disclosures

Updated: Apr 9, 2008

Introduction

Background

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.

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 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.

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.

Frequency

United States

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.

Mortality/Morbidity

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.

Clinical

History

• 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.

Physical

• The injured thumb should be evaluated for pain, point tenderness, ecchymosis, and/or swelling, specifically on the ulnar aspect of the MCP joint.
• A palpable mass on the ulnar aspect of the MCP joint may be obvious and may represent the ruptured UCL that is abnormally displaced proximally and dorsally relative to the adductor aponeurosis.
• 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. Stability of the opposite thumb should be tested as well for comparison.
  • Stress examination is performed while stabilizing the thumb metacarpal with one hand to prevent rotation. The thumb should be placed in 30° flexion, and a lateral (radial) stress should be applied on the joint.
  • A displaced avulsion fracture is a contraindication to stress testing but a nondisplaced fracture is not.
  • Administration of local anesthetic may be necessary to facilitate optimal examination. This can be accomplished by either a local injection of 1% lidocaine into the MCP joint or by blocking the sensory branches of the radial and median nerves at the wrist.
  • Laxity (angulation) of more than 35° or laxity 15° more than the uninjured side suggests a complete rupture of the proper collateral ligament. Laxity (angulation) less than 35° or comparative laxity less than 15° probably denotes an incomplete rupture.
  • The accessory collateral ligament may remain intact, and gross instability may not be present. Therefore, examination in extension should be performed. Reports have demonstrated that laxity of the MCP joint in extension when stressed, consistently indicates tears of the proper and accessory collateral ligaments and is more commonly associated with a Stener lesion. Laxity of more than 35° or laxity of 15° more than the uninjured side may suggest rupture of the accessory collateral ligament.
  • If lateral (valgus) laxity of the MCP joint exists for both the flexed and extended positions, then complete rupture of the UCL should be suspected, and greater possibility of a Stener lesion exists.

Causes

Fall onto outstretched hand causing a forced abduction and extension of the thumb

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