Introduction
Background
Gamekeeper's thumb is an insufficiency of the ulnar collateral ligament (UCL) of the metacarpophalangeal (MCP) joint of the thumb. Campbell originally coined the term in 1955 because the condition was most commonly associated with Scottish gamekeepers (especially rabbit keepers) as a work-related injury.1 The injury occurred as the gamekeepers sacrificed game such as rabbits by breaking the animals' necks between the thumb and index finger of the gamekeeper and the ground. As a result, a valgus force was placed onto the abducted metacarpophalangeal (MCP) joint, leading to a ruptured ulnar collateral ligament (UCL) injury and chronic attritional injury that resulted in instability, which was accompanied by pain and weakness of the pinch grasp. (See also the eMedicine article Gamekeeper Thumb.)
In the present day, this type of injury is typically more acute. The most common cause is a skier's hand landing on a ski pole, causing a valgus force on the thumb.2 The term "skier's thumb" represents the more acute nature of the injury. Because stability of the thumb is important for prehension, treatment is directed toward optimizing ligament healing to restore full function. (See also the eMedicine article Skier's Thumb.)
For excellent patient education resources, visit eMedicine's Hand, Wrist, Elbow, and Shoulder Center and Sports Injury Center. Also, see eMedicine's patient education article Skier's Thumb and Repetitive Motion Injuries.
Frequency
United States
Gamekeeper's thumb is a fairly common injury, with an increased incidence in skiers that does not depend on the type of ski pole used. No known sex predilection is associated with this condition.
International
No apparent difference exists in the international population with regard to the frequency or incidence of gamekeeper's thumb.
Functional Anatomy
The MCP joint is a diarthrodial joint that is primarily involved in flexion and extension. The static restraints and some dynamic stabilizers provide joint stability. The static restraints include the proper collateral ligament (mostly in flexion), the accessory collateral ligament (mostly in extension), the palmar plate (mostly in extension), and the dorsal capsule (limited, in flexion). The dynamic stabilizers include the thumb intrinsic and extrinsic muscles. The adductor mechanism is particularly important here, because it inserts onto the extensor expansion through its aponeurosis, which lies superficial to the UCL.The UCL is a 4- to 8-mm X 12- to 14-mm band that originates from the metacarpal head and inserts into the medial aspect and base of the proximal phalanx of the thumb. Occasionally, when the UCL is strained, it avulses the bone at its insertion and leads to a gamekeeper's fracture (see Images 1-2).
A Stener lesion occurs when the adductor aponeurosis becomes interposed between the ruptured UCL and its site of insertion at the base of the proximal phalanx. Thus, the distal portion of the ligament retracts and points superficially and proximally. A rupture of the proper and accessory collateral ligaments must occur for this injury to happen. The UCL no longer contacts its area of insertion and cannot heal. This lesion can also be associated with a gamekeeper's fracture,3 which can be subtle or obvious (see Images 1-2). However, a lump or mass over the ulnar aspect of the MCP joint of the thumb does not necessarily imply a fracture; it may be the result of the Stener lesion. (See also the eMedicine article Stener Lesion.)
Sport-Specific Biomechanics
Considerable variation may be observed in the range of flexion and extension of the thumb MCP joint. The variation of normal joints can include ranges of motion (ROMs) from 5-115° of flexion and extension. In full extension, valgus laxity averages 6° and increases to an average of 12° in 15° of flexion.
Clinical
History
The gamekeeper's thumb injury may be caused by a valgus stress of any kind to the thumb. The most common history is a fall onto an outstretched arm with an abducted thumb. This commonly occurs in skiers with a ski pole in the hand, which prevents adduction of the thumb when the skier falls.
Physical
- The contralateral, unaffected thumb should be evaluated first for ROM and valgus stability in both extension and 30° of flexion. Then, evaluate the injured thumb for swelling and pain at the ulnar aspect of the MCP joint. Ecchymosis is frequently seen.
- Proper collateral ligament rupture
- The accessory collateral ligament may remain intact, and gross instability may not be present.
- The thumb should be placed in 30° of flexion and tested for valgus instability in this position. This should only be done after radiographs have been obtained that rule out a gamekeeper's fracture. Although a gamekeeper's fracture is a contraindication to stress testing, a nondisplaced avulsion fracture is not. If the patient's pain is too severe, the joint may be anesthetized with a lidocaine injection before stress testing.
- Thirty degrees of laxity or one that is 15° more than that present on the uninjured side represents a ruptured proper collateral ligament in this position.4,5
- A supination deformity of the MCP joint, which may also be visualized, can be associated with volar subluxation of the MCP joint and suggests instability.
- Accessory collateral ligament rupture
- A palpable mass present on the ulnar aspect of the MCP joint may represent the retracted UCL stump, which is displaced proximally and dorsally to the adductor aponeurosis.
- A Stener lesion can only be present when both the proper and accessory collateral ligaments are ruptured. In more than 80% of complete ruptures of the UCL, a Stener lesion is present, whether it is palpable or not.
- Stress testing with the thumb in the extended position is the best test for determining the competence of the accessory collateral portion of the UCL. Again, valgus laxity of more than 30º or a laxity that is 15º more than that on the uninjured side suggests rupture of this portion of the ligament.4,5
- If valgus laxity of the thumb's MCP joint is present in both the flexed and extended positions, complete UCL rupture should be suspected.
Causes
- Skiing with poles
- Falling onto an outstretched arm with the thumb abducted
- Valgus-producing force on the thumb MCP joint
- Rheumatoid arthritis (See also Medscape's Rheumatoid Arthritis Resource Center and the eMedicine articles Rheumatoid Arthritis [in the Physical Medicine and Rehabilitation section] and Rheumatoid Arthritis [in the Rheumatology section].)
- Generalized ligamentous laxity
More on Gamekeeper's Thumb |
 Overview: Gamekeeper's Thumb |
| Differential Diagnoses & Workup: Gamekeeper's Thumb |
| Treatment & Medication: Gamekeeper's Thumb |
| Follow-up: Gamekeeper's Thumb |
| Multimedia: Gamekeeper's Thumb |
| References |
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References
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Sollerman C, Abrahamsson SO, Lundborg G, Adalbert K. Functional splinting versus plaster cast for ruptures of the ulnar collateral ligament of the thumb. A prospective randomized study of 63 cases. Acta Orthop Scand. Dec 1991;62(6):524-6. [Medline].
Maheshwari R, Sharma H, Duncan RD. Metacarpophalangeal joint dislocation of the thumb in children. J Bone Joint Surg Br. Feb 2007;89(2):227-9. [Medline].
Abrahamsson SO, Sollerman C, Lundborg G, Larsson J, Egund N. Diagnosis of displaced ulnar collateral ligament of the metacarpophalangeal joint of the thumb. J Hand Surg [Am]. May 1990;15(3):457-60. [Medline].
Gerber C, Senn E, Matter P. Skier's thumb. Surgical treatment of recent injuries to the ulnar collateral ligament of the thumb's metacarpophalangeal joint. Am J Sports Med. May-Jun 1981;9(3):171-7. [Medline].
Stener B. Displacement of the ruptured ulnar collateral ligament of the metacarpo-phalangeal joint of the thumb. J Bone Joint Surg [Br]. July 1962;44:869-79. [Full Text].
Further Reading
Keywords
instability of the thumb, skier's thumb, Stener lesion, ulnar collateral ligament tear, UCL tear, proper collateral ligament tear, thumb injury, thumb pain
