Gamekeeper's thumb, also known as skier's thumb or break-dancer's thumb is avulsion or rupture of the ulnar collateral ligament (UCL) of the first metacarpophalangeal joint.
Skier's thumb refers to acute injury due to trauma, from hyperabduction of the thumb as it is caught by the ski pole strap. Gamekeeper's thumb refers to chronic non-traumatic overuse injury (stress and repetitive trauma) that gradually injure the ulnar collateral ligamnt.
Repetitive injury of the ulnar collateral ligament of the thumb metacarpophalangeal joint caused when the gamekeeper broke the neck of game, using their thumb, index finger and the ground, leading to eventual tear of the ligament. Gamekeeping and poaching have largely fallen by the wayside as a recreational activity. This injury is now seen more frequently in skiers, and in the 80s, break dancers.
More chronic presentations will present will laxity. Typically (in skiers) an awkward fall with the pole in hand can forcibly hyperabduct the thumb during a fall.
The UCL may partially or completely rupture or may avulse off its bony attachments. The distal attachment site to the proximal phalangeal base is the most common site of avulsion.
The aim of imaging is to define any fracture, determine if there is instability (joint space widening), and identify a Stener lesion. A classification into six types has been proposed by Hintermann et al. in 1993 (see the classification of gamekeeper's thumb).
If a small avulsion fracture is present, then this could be seen at the ulnar corner of the base of the proximal phalanx or ulnar first metacarpal head. Stress radiographs are sensitive.
If the tear is in the mid-substance, with no associated fracture then the ulnar side of the joint may appear widened. If the diagnosis is suspected stress views were once upon a time recommended; however, the concern now exists that performing these views can displace the torn undisplaced end of the ligament dorsal to adductor pollicis muscle, thereby creating a Stener lesion .
Ultrasound is helpful in identifying not only the tear and any retraction but also whether or not a Stener lesion is present. Clearly, this requires a knowledge of local anatomy and the use of a high-frequency MSK probe. The adductor aponeurosis will not slide freely over the UCL on passive thumb interphalangeal joint flexion in a Stener injury.
MRI is increasingly used to assess x-ray occult injuries to the ulnar collateral or to attempt to identify a Stener lesion. Findings include:
- discontinuity of the ligament +/- joint capsule
- bone marrow edema and fracture
- Stener lesion
Treatment and prognosis
Treatment depends on classification but essentially surgical treatment is offered to patients with:
- joint instability
- a displaced avulsion fracture
- the presence of a Stener lesion (interposition of the adductor pollicis muscle and adductor aponeurosis between the torn end of the UCL and the base of the proximal phalanx) .
History and etymology
It was first described in, you guessed it, Scottish gamekeepers, by Campbell in 1955 who would manually sacrifice wounded rabbits . Clearly, gamekeepers who also ski are almost certain to incur this injury.