Fetal anatomy of the abductor pollicis brevis and its clinical importance

Objectives: The abductor pollicis brevis exhibits a variant course in newborns with radial polydactyly or syndactyly; however, its morphology in human fetuses has not been previously studied. This study aims to document the dimensions and attachment points of abductor pollicis brevis in human fetuses. Methods: The study consisted of 27 (15 females and 12 males) fetuses with a mean gestational age of 24.08±4.18 weeks. The attachment points (its insertion and origin) of abductor pollicis brevis were determined. The width, length and area of the muscle were measured with ImageJ software. The insertion and origin points were classified according to the literature. Results: The mean width, length and area of abductor pollicis brevis were 3.52±1.33 mm, 9.19±2.73 mm and 30.84±20.39 mm2, respectively. The muscle most commonly originated from the flexor retinaculum and the tubercle of the scaphoid bone (Type 1) and inserted at the lateral side of the first metacarpophalangeal joint (Type A). Conclusion: This study is the first to classify the origin and insertion of the abductor pollicis brevis in human fetuses. These findings could be valuable for hand surgeons performing surgical interventions in this region in newborns. Additionally, the growth patterns identified in our study may be used to estimate the size of the abductor pollicis brevis in fetuses.