Polydactyly

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