Anatomical Localization of Motor Points of the Abductor Hallucis Muscle: A Cadaveric Study

OBJECTIVE To identify the anatomical motor points of the abductor hallucis muscle in cadavers. METHODS Motor nerve branches to the abductor hallucis muscles were examined in eight Korean cadaver feet. The motor point was defined as the site where the intramuscular nerve penetrates the muscle belly. The reference line connects the metatarsal base of the hallux (H) to the medial tubercle of the calcaneus (C). The x coordinate was the horizontal distance from the motor point to the point where the perpendicular line from the navicular tuberosity crossed the reference line. The y coordinate was the perpendicular distance from the motor point to the navicular tuberosity. RESULTS Most of the medial plantar nerves to the abductor hallucis muscles divide into multiple branches before entering the muscles. One, two, and three motor branches were observed in 37.5%, 37.5%, and 25% of the feet, respectively. The ratios of the main motor point from the H with respect to the H-C line were: main motor point, 68.79%±5.69%; second motor point, 73.45%±3.25%. The mean x coordinate value from the main motor point was 0.65±0.49 cm. The mean value of the y coordinate was 1.43±0.35 cm. All of the motor points of the abductor hallucis were consistently found inferior and posterior to the navicular tuberosity. CONCLUSION This study identified accurate locations of anatomical motor points of the abductor hallucis muscle by means of cadaveric dissection, which can be helpful for electrophysiological studies in order to correctly diagnose the various neuropathies associated with tibial nerve components.