Congenital absence of flexor digitorum superficialis: implications for assessment of little finger lacerations.

Absence of flexor digitorum superficialis function in the little finger is a relatively common congenital anomaly that can complicate assessment of little finger injuries. We reviewed the prevalence of unilateral and bilateral absence of superficialis function in the published literature. In appropriate studies identified (1352 people), the anomaly was unilateral in 92 individuals (6.8%) and bilateral in 81 (6.0%). If superficialis function is absent in one little finger, the probability of absence in the opposite hand is 0.64. If superficialis function is present, the probability of absence in the other little finger is 0.02 (1 in 50). Absence of little finger superficialis function in one hand is therefore not a reliable indicator of this function in the opposite hand.