II. Pathophysiology
- Ulnar collateral ligament rupture at thumb from forced abduction
- Historically named for gamekeepers who broke the neck of small mammals with their hands
- Occurs at first metacarpophalangeal joint (thumb base)
- Fall on Outstretched Hand (FOOSH)
- Skier falls with pole strap wrapped at wrist
- Pole strap levers thumb into abduction and extension
- Radial collateral ligament tear may also occur instead
- Not common
III. Anatomy: Ulnar collateral ligament
- Proper ulnar collateral ligament (UCL)
- Attaches dorsal First Metacarpal head to ulnar base of proximal phalanx
- Accessory ulnar collateral ligament (UCL)
- Attaches volar First Metacarpal head to ulnar base of proximal phalanx
IV. Signs
- Pain at medial base of thumb (ulnar aspect)
- Test active and passive thumb abduction
- Assess thumb metacarpophalangeal joint (MCP) laxity
- Laxity with 35 to 40 degrees of joint opening (or no clear endpoint) is considered abnormal
- Compare with uninjured side
- Apply valgus stress at MCP joint (radially deviating the thumb) in each of 2 positions
- Test proper UCL with thumb flexed to 30 degrees at MCP joint
- Test accessory UCL with thumb in extension at MCP joint
- Assess for Stener Lesion (associated with Grade III injuries)
- Displaced distal end of ruptured ligament
- Proximal UCL trapped outside adductor aponeurosis
- Presents as tender mass at UCL, and joint instability
- Requires surgery
V. Differential Diagnosis
- Bennet's Fracture
- Rolando fracture
- Scaphoid Fracture
VI. Grading: Compare to uninjured side
- Grade 1 sprain: No laxity
- Grade 2 sprain: Increased laxity >15 degrees, but firm endpoint
- Grade 3 sprain
- Increased laxity with no firm endpoint
- Joint opening usually >30 degrees
VII. Imaging
- Hand XRay (AP, Lateral and Oblique Views)
- Evaluate for Fracture
- Epiphyseal Fracture in children and teens may also occur in this region
- Sesamoid bone at the MCP is a normal finding and may obscure injury findings
- Proximal phalanx volar subluxation may be present
- Related to dorsal capsule or Volar Plate Injury
- Evaluate for Fracture
- UCL Ligament Ultrasound
- Test Sensitivity approaches 92%
- Hand MRI
- Indicated in unstable Grade III UCL Ruptures
VIII. Management
- Indications for Surgical Repair: Unstable thumb
- No endpoint in abduction of thumb
- Initial: Splinting for 6 weeks
- Molded plastic thumb lock immobilizer or
- Thumb Spica Cast or splint
- Later: Dynamic Splinting for additional 6 weeks
- Indicated for athletes - splint during sports only
- Use one of splints above or taping
- Dorsal Taping (0.5 inch tape)
- Apply anchor strips at wrist and over distal thumb
- Start tape at anchor strip at wrist
- Apply over web space between thumb and index
- Attach at distal anchor strip on thumb
- Build upwards with consecutive tapes
- Return to sports
- May participate if splinted and no pain or reinjury
IX. Management: Orthopedic Referral Indications
X. Complications
- Unstable MCP joint with weak pincher grasp
- Osteoarthritis
XI. References
- Dolbec (2019) Crit Dec Emerg Med 33(1): 17-25
- Broder (2023) Crit Dec Emerg Med 37(8): 20-1