Localization of the Motor Nerve Branches and Motor Points of the Hamstring Muscles and Triceps Surae Muscle

ABSTRACT

OBJECTIVE: To identify the precise locations of the motor branches and motor points of hamstring and triceps surae muscles to the bony landmarks. METHOD: Twenty-eight limbs of 14 adult cadavers were anatomically dissected. The adult cadavers were selected randomly without regard to gender and age. The cadravers which were unable to obtain a neutral position or which received a trauma to the posterior thighs or the lower legs were excluded from the study. The number and location of the motor branches and motor points from sciatic nerve to each hamstirng muscles and from tibial nerve to each triceps surae muscles were identified related to the bony landmarks. Bony landmarks were ischial tuberosity, medial and lateral epicondyles of femur, and medial and lateral malleolli of tibia. The length of femur was defined as the distance from the ischial tuberosity to the intercondylar line of femur and the length of lower leg was defined as the distance from the intercondylar line of femur to the intermalleolar line of tibia. The locations of the muscular branches and the motor points were expressed as the percentage of the length of femur and lower leg. RESULTS: One muscular branch from the sciatic nerve to the semimembranosus muscle and from the posterior tibial nerve to the soleus muscle, and one or two muscular branches to the biceps femoris, semitendinosus, and semimembranosus, medial gastrocnemius, lateral gastrocnemius and soleus muscle were located at 23.0+/-5.7%, 21.0+/-10.5%, 25.0+/-10.3% of the femur from the ischial tuberosity and 2.0+/-6.2%, 4.0+/-3.3% and 10.0+/-3.3% of the lower leg from the intercondylar line of femur. There were one to four motor points in the hamstring and triceps surae muscles. The motor points of biceps femoris, semitendinosus and semimembranosus were located at 33.0+/-7.8%, 28.0+/-14.5% and 48.0+/-19.0% of the femur. The motor points of the medial gastrocnemius, lateral gastrocnemius and soleus were located in 5.0+/-0.6%, 10.0+/-3.0% and 18.0+/-4.3% of the lower leg below the intercondylar line of femur. CONCLUSION: The identification of the locations of muscular branches and motor points related to the bony landmarks from this study would increase the accuracy of the motor branch blocks or motor point blocks to the hamstrings and triceps surae muscles.