10 yr old child with history of injury , on X ray of the left hand shows an oblique opacity in continuity with the 1st 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 2nd year for surgery with good results
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