Epidemiology
More common in African Americans
Aetiology
Sporadic and AD
VACTERL
Classification
Preaxial
Type 1: Thumb polydactyly
Type 2: Triphalangeal thumb
Type 3: Index polydactyly
Type 4: Polysyndactyly
Central
Duplication of the IF / MF / RF
- Rare
Postaxial
Type A Extra well formed ulnar digit articulating with a metatarsal
Type B Extra poorly formed ulnar digit / often a skin tag
Classification
I Soft tissue only
II Bone elements
III Own metacarpal
Management
Simple soft tissue
Tie string & autoamputates at birth
Complex
Operate at ~ 1 year in hand
- once old enough to be safe for operation
- general rule is to amputate outside extra digit
Thumb Polydactyly
Wassell Classification
Most common variety
- duplicated proximal phalanz with single metacarpal
- Type IV
Usually delete radial thumb
Issues
1. Smaller thumb
2. Unstable MCPJ with type IV
- important to rebalance residual digit with joint capsule & tendon insertions
- otherwise will end up with Z deformity
- ulna deviation at MCPJ, radial at IPJ
3. Angular deformity
- caused by supernumerary thumb and delay in surgery
- may need osteotomy