An Accessory Flexor of the Thumb

Abstract

The presence of accessory muscles, nerves and other tissues/organs in the upper limb and other parts of the body of some individuals have been previously reported. We report the case of a cadaver with an accessory flexor muscle of the left thumb. This muscle is located on the volar aspect of the left forearm. It originates from the lower fibres of flexor digitorum superficialis (sublimis) and inserts into the tendon of flexor pollicis longus. It is supplied by the median nerve and produced flexion of the thumb at the interphalangeal joint. It therefore facilitated flexion of the thumb and the grasp mechanism of the individual. We have named it “Flexor Pollicis Accessorius”. Awareness of this is important to Anatomists and surgeons especially plastic/hand surgeons.