An extensor digitorum brevis manus coexisting with the typical extensor indicis muscle: a rare dissection finding.

The forearm extensor muscle and hand extensor tendons are composed of several structures with unique anatomy identified with high morphological variability. During a routine dissection of a 74-year-old donated male cadaver, the right hand was isolated for educational purposes. After carefully dissecting the structures, an accessory muscle was identified. The accessory muscle corresponded to the extensor digitorum brevis manus (EDBM) inserted into the extensor indicis (EI) tendon, which was typically identified. According to the current literature, this occurrence corresponds to a rare variant, with 0.36-0.38% prevalence between the cadaveric studies. Knowledge of the hand extensor musculature is essential for orthopedics and plastic surgeons operating in the region to avoid iatrogenic injury.