Gamekeeper Thumb

Gamekeeper thumb is chronic attenuation or insufficiency of the ulnar collateral ligament of the thumb metacarpophalangeal joint from repeated radial stress, or an untreated acute rupture (skier thumb) that never healed. The original description was in gamekeepers who broke the necks of rabbits between the thumb and index finger.

• Causes today: repeated forced radial deviation in racquet sports, golf, skiing, bowling, handball, goalkeeping, wrestling, and manual work (chronic stress from pinching or gripping, a missed acute injury, or a partial tear that stretched).
• The ligament becomes lax and scarred, the joint is unstable on pinch, and over years the joint develops arthritis. The adductor aponeurosis may be interposed between the torn ligament end and its bone attachment in chronic complete tears, which prevents healing.
• It is more common in men and in those with repetitive pinch loading. Early diagnosis prevents progression.

• Chronic, activity related ulnar thumb pain at the base, weak and painful pinch (key pinch and tip pinch), difficulty with fine tasks (turning keys, opening jars, writing, holding a cup), an unstable thumb that "gives way", ulnar swelling or a palpable lump, and sometimes stiffness. Symptoms last for more than 6 weeks after an injury.
• Examination: tenderness along the ulnar side of the metacarpophalangeal joint, radial stress laxity in full extension and in 30 degrees of flexion compared with the other thumb (laxity above 30 to 35 degrees or 15 degrees more than the other side, with a soft or absent end point), reduced pinch strength on dynamometer, and joint prominence from subluxation (the proximal phalanx drifts radially and volarly).
• Differential diagnosis: carpometacarpal osteoarthritis, metacarpophalangeal osteoarthritis, radial collateral ligament injury, volar plate injury, trigger thumb, de Quervain tenosynovitis, scaphoid and other carpal injury, sesamoid pathology, rheumatoid arthritis and gout.
• Red flags: acute new injury on a chronic problem, fever, a locked joint, numbness and rapid swelling.
• Complications: progressive instability, osteoarthritis, loss of pinch, chronic pain, stiffness and disability.

• Clinical, with stress testing in extension and 30 degrees of flexion, comparison with the opposite thumb, and measurement of pinch strength (a loss of 30% or more is significant).
• X-rays of the thumb (anteroposterior, lateral, and stress views) show radial deviation and volar subluxation of the proximal phalanx, an old avulsion fragment, joint space narrowing and osteophytes.
• Ultrasound or MRI (with arthrography when needed) shows a torn, thickened or retracted ligament, interposition of the aponeurosis, and cartilage damage. MRI helps to plan surgery.

• Early chronic or partial instability (a firm end point, no arthritis): conservative treatment for 4 to 6 weeks:
  • A thumb spica splint or custom thermoplastic splint that stabilises the metacarpophalangeal joint (the interphalangeal joint free), worn full time for 4 to 6 weeks, then for activity.
  • Paracetamol 1 g orally 6 hourly, ibuprofen 400 mg 8 hourly with food for 1 to 2 weeks, or topical diclofenac 1% gel 2 to 4 g 3 to 4 times daily.
  • Hand therapy: progressive strengthening of the thenar and first dorsal interosseous muscles, pinch strengthening, activity modification and taping for sport.
  • A corticosteroid injection into the joint (triamcinolone 10 mg with lidocaine 1% 0.5 mL) is used only for arthritic pain, not for ligament laxity, and repeated injection weakens the ligament.
• Surgery for symptomatic instability that persists after conservative care, or for complete tears:
  • Direct ligament repair or reattachment with suture anchors, if there is enough good tissue (usually within 3 to 6 weeks of injury).
  • Reconstruction with a free tendon graft (palmaris longus or a strip of another tendon) through bone tunnels for chronic laxity with poor ligament tissue, and advancement of the adductor aponeurosis.
  • Arthrodesis of the metacarpophalangeal joint (in 15 to 20 degrees of flexion) for painful arthritis, or a failed reconstruction, with about 90% good results but loss of joint motion.
  • Prophylaxis: cefazolin 2 g IV once. Immobilise in a thumb spica for 4 to 6 weeks, then therapy. Return to full activity takes 3 to 4 months. Complications include nerve injury, stiffness, residual laxity and infection.
• Special groups:
  • Athletes and manual workers: graded return, tape or brace for sport, and review of technique and tool grips.
  • Elderly: assess for arthritis, accept less aggressive options, and consider fusion for low demand patients.
  • Rheumatoid arthritis: treat the disease, and prefer fusion in unstable joints.
  • Pregnancy: splint and paracetamol. Avoid NSAIDs after 20 weeks.
  • Anticoagulation: plan surgery with the prescriber.
• Follow up: review at 4 to 6 weeks of splinting and again at 3 months. Refer to hand surgery for persistent instability, weak pinch, complete tears, or arthritis.