The decision to operate on a child with congenital thumb hypoplasia must be carefully considered. Key factors to consider are:
- the ability of the child to undertake prehensile grasp
- adaptation to the deficit
- the severity of associated anomalies eg first webspace contracture
- cosmetic appearance
Essentially, there are a range of procedures that can be utilised to improve function and which are are applied according to the deficit. Ideally, all procedures are carried out in one go. However, the Blauth classification is a useful way of predicting the likely surgical approach:
- type I: no surgical treatment required usually
- type II: likely to need:
- opposition transfer to address intrinsic muscle absence
- first web space release to address narrowing
- ulnar collateral ligament reconstruction to address UCL laxity
- type IIIa: as II but also improvement of flexion and extension at the interphalangeal joint due to extrinsic muscle hypoplasia
- type IIIb:
- the main controversy due to instability of the CMCJ
- some authorities will attempt reconstruction but most will opt for pollicisation
- some families will find the ablation of the digit and need for pollicisation as difficult to understand given the small but relatively normal appearance of the thumb
- type IV and V: pollicisation
Techniques available in the surgical armamentarium include:
- ulnar collateral ligament reconstruction
- web space release
- opposition transfer
- skeletal lengthening
- pollicisation
- reconstruction of extrinsic flexor and extensor function