Unilateral Right-Sided Progressive Flexor Digitorum Superficialis Brevis to the Little Finger: A Case Report With Review of Literature

The flexor digitorum superficialis (FDS), an intermediate flexor of the forearm, can present with variations in the musculature or tendons. Here, we report a very rare anomaly of the FDS-V tendon replaced by a muscle belly in the palm, which was a progressive variation. This variation was found in a 60-year-old female cadaver on the right hand. The anomalous belly took its origin from the center of the volar aspect of the flexor retinaculum and was inserted into the A2 pulley of the middle interphalangeal joint to the little finger. The anomalous muscle was innervated by a branch of the median nerve. Knowledge of such variations will be useful for hand surgeons for meticulous planning of surgeries of the palm. The occurrences of such variations might interfere with the biomechanics of the FDS tendons.