Dorsal view left hand

Volar view left hand

Thumb Metacarpal-phalangeal joint injury usually result from thumb hyperextended with a forced abduction force, commonly during a skiing injury. Chronic over distension may also occur as with an occupational hazard, as classically described as Gamekeepers thumb injury.

Thumb MCP joint extended with hyperabduction

Injury Mechanism:

• Direct force to thumb metacarpal-phalangeal (MCP) joint with thumb in extension with forced abduction
• Associated injuries include: Intra-articular thumb basal fractures of proximal phalanx and Steiner lesion (the Ulnar collateral ligament is displaced dorsally over adductor aponeurosis)
• Chronic laxity may result from overstretching of the Ulnar collateral ligament (UCL) as classically describe with Gamekeepers in Britain. The occupational overstraining of the MCP results in overstretching and associated instability of the MCP joint.

Causes:

• Acute injury as seen with skiing
• Overuse injury in occupations requiring twisting abduction thumb movements as in the historic Gamekeepers injured thumb

Presentation:

• Pain in thumb at MCP joint area at the side of UCL
• Deformity

Clinically:

• Tenderness at UCL area of the MCP joint
• Deformity
• Palpable mass (UCL retracted)
• Valgus stress testing of UCL demonstrating instability

Stress testing MC-P1 joint:

> 15° compared to the contralateral uninjured side indicates instability

Radiology:

X-ray

• Robert view: Thumb AP (true AP of thumb: forearm in maximum probation with thumb dorsum against cassette) and lateral views (hand pronated 30° with radiographic beam angled 15° distally)

CT

• Ideal to view intraarticular fractures and surgical planning

Non operative

Indications:

• Acute, nondisplaced grade Ⅰ/Ⅱ can me managed in thumb spica
  Bracing/cast immobilization until union
• Union 4-6 weeks

Surgery

Indications:

• Open fractures
• Acute unstable grade Ⅲ (> 35° MCP joint angulation or >15° compared to contralateral side on stress testing)
• Steiner lesion (usually associated with grade Ⅲ tears
• Displaced avulsion tears
• >25% articular fracture

Surgical fixation options:

• Open fractures
• Acute tear: repair ± anchors
• Chronic tears: UCL reconstruction

Thumb spica POP

Dorsoulnar approach:

Incision:  1cm proximal to MCP joint extended in a palmar direction around the ulnar aspect of the joint.

Overlying the ulnar collateral ligament include adductor pollicis aponeurosis & dorsal sensory branch of Radial nerve. Retract nerve & divide adductor pollicis aponeurosis overlying the UCL.

Repair UCL with anchor. Alternatively pass suture fixation to ligament through drill holes of P1 and tie on opposite bone end.

Active wrist ROM after 2 weeks

Finger adduction strengthening

Finger abduction strengthening

Hand grip strengthening