THUMB UCL INJURIES

Question 1

Mechanism of injury for thumb UCL injuries

Answer 1

• Hyperabduction injuries
• Cause valgus instability
• Affects pinch grip

Question 2

Gamekeeper’s thumb

Answer 2

Chronic attenuation/ attritional injury

Question 3

Skier’s thumb

Answer 3

Acute traumatic injury

UCL comes off base of proximal phalanx in 90% cases

Question 4

Stener lesion

Answer 4

Bony or soft-tissue avulsion of UCL from base of P1 with interposition of adductor aponeurosis between avulsed ligament and its insertion = prevents ligament from healing
Stener lesion will not occur if:
1. Bony avulsion < 2mm displaced
2. UCL injury partial

Question 5

Stabilisers of thumb MCP joint

Answer 5

Bony vs. soft-tissue or static vs. dynamic
Static stabilisers:
1. Bony anatomy = MC head is
- less spherical
- wider
- does not extend as far dorsally
2. Capsuloligamenous structures
3. Sesamoids
- lie in lateral margins of volar plate
- adductor pollicis attaches to ulnar sesamoid
- FPB attaches to radial sesamoid
4. Aponeurotic insertions = greater into ulnar aspect of joint
Dynamic stabilisers = tendons crossing joint
1. Extrinsic tendons = EPL, EPB and FPL
2. Intrinsic tendons = AP, FPB and APB

Question 6

Anatomy of thumb UCL

Answer 6

1. Proper UCL
   - origin = dorsal aspect of head of MC
   - insertion = volar aspect of base of P1
   - taut in 30deg flexion
2. Accessory UCL
   - origin = MC head volar to proper UCL
   - insertion = volar plate
   - taut in extension
3. Volar plate
   - secondary stabiliser in extension
   - resists hyperextension

Question 7

Partial vs. complete thumb UCL rupture

Answer 7

1. Partial injury = only proper UCL
   - > 30deg opening at 30deg flexion
   - < 30deg opening in extension
   - Stener lesion not possible
2. Complete injury
   - > 30deg opening at 30deg flexion
   - > 30deg opening in extension
   - Stener lesion possible
   - also look for volar subluxation of joint = disruption of dorsal capsule +/- extensor tendon

Question 8

3 factors to consider in management of thumb UCL injuries

Answer 8

1. Acuity = repair vs. reconstruction
2. Degree = partial vs. complete vs. Stener
3. Arthritis

Question 9

3 main indications for surgical management of thumb UCL injuries

Answer 9

1. Failure of nonoperative measures = persistent pain or pinch instability
2. Complete tears
3. Stener lesions

Question 10

4 main surgical options with thumb UCL injuries

Answer 10

1. UCL repair
   - suture anchor below mid-axial line of P1
   - tension in 45deg flexion to avoid overtightening
2. UCL reconstruction
3. Adductor advancement
4. Arthrodesis
   - not arthroplasty as joint is unstable

Question 11

Position of arthrodesis of thumb MCPJ

Answer 11

Thumb pinch grip position
20-20-20
1. Flexion 20deg
2. Abduction 20deg 
3. Pronation 20deg