Fig. 1

a Anatomical position (left hand). After removing the palmar muscles and aponeurosis of the hand, the representation of the FDMB and the potential location of FDML or accessory FDMB were identified. b supine position (left hand). The red dots depict potential origins (hook of hamate bone, FDMB), while the blue dots illustrate potential insertions (fifth proximal, middle, distal phalanges, fifth metacarpal bone, FDMB, pisiform bone) for FDML or accessory FDMB in accordance with the literature. c Anatomical position (right hand). The red dots, representing potential origins (including the tendon of flexor carpi radialis, antebrachial fascia, tendon of palmaris longus, flexor retinaculum, tendon of flexor digitorum superficialis, tendon of flexor carpi ulnaris, intercompartmental septum, ODM), are indicative, whereas the blue dots illustrate potential insertion points (comprising ADM, FDMB, proximal phalanx of the fifth digit, palmar aponeurosis, tendon of flexor digitorum profundus, flexor retinaculum, ODM) for FDML or accessory FDMB, in accordance with the literature. ADM Abductor Digiti Minimi, ODM Opponens Digiti Minimi