Conjoined flexor and extensor pollicis longus tendons in the hypoplastic thumb.

A congenital anomalous band between the flexor pollicis longus and extensor pollicis longus tendons is, according to the literature, a rare condition. This anomalous junctura was recognized in three children with congenital thumb hypoplasia. Improved thumb function was noted after surgical release of the band in all cases. In the assessment of a child with a hypoplastic thumb and apparent absent extrinsic muscle function, one should consider the possibility of conjoined flexor and extensor tendons.