Bifid Thumb-Plain Film

10 yr old child with history of injury , on X ray of the left hand shows an oblique   opacity in continuity with the 1^st Metacarpal with no separate epiphysis and suggestion of abnormal soft tisues in the region with stippled opacity at base of proximal phalanx. X ray of  the other hand shows  only soft tissue abnormality with no bony component. This possibly representative of Bifid Thumb (pre axial polydactyly) type of congenital hand anomalies.

Teaching points  by Dr MGK Murthy, Dr Sumer Sethi.

Duplication or polydactyly is common. Can be complete or partial

Bifid thumb occurs in  about 1 in 3000 births

Usually unilateral , but bilaterality is known. Cause is not known

Hand develops from Apical Ectodermal Ridge(AER)  around 3 to 8 weeks of gestation

Wassel classified the highly complex  hand anomalies as type I(Failure of formation),II(failure of differentiation),III(duplication), IV( overgrowth), Type V(undergrowth),type 6 (constriction band syndromes) and type 7(generalized anomalies and syndromes )

Can be 

·         just extra soft tissue not adherent to skeleton, devoid of bone, cartilage, joints or tendons (as in the non injured hand in our case )

·         digits may show duplication with components like bifid metacarpal (like our  case injured hand )or

·         there may be a complete digits formation with its own metacarpal.

Ellis van creveld syndrome is associated with bifid thumb

 Treatment is usually surgical and involves resection to avoid restriction of movements apart from cosmetic effect. Early surgery is defined as under 2 years and late is defined beyond that . Most surgeons prefer 2^nd year for surgery with good results