Anatomic localization of motor points in gastrocnemius and soleus muscles

To identify the range of the terminal motor points of the triceps surae muscles in relation to bony landmarks.

Eight limbs of four male cadavers were anatomically dissected. The range of terminal motor points from the tibial nerve to each triceps surae muscle was identified related to the bony landmarks. Bony landmarks were medial and lateral epicondyles of the femur and medial and lateral malleoli of the tibia. The length of the lower leg was defined as the distance from the intercondylar line of the femur to the intermalleolar line of the tibia. The locations of the motor points were expressed as the percentage of the length of the lower leg.

The motor points of the medial gastrocnemius, lateral gastrocnemius, and soleus muscles were diffusely distributed along the muscle longitudinal bulk. The highest motor points of the medial gastrocnemius, lateral gastrocnemius, and soleus were located in 9.6% +/- 3.5%, 12.0% +/- 3.4%, and 20.5% +/- 3.9%, respectively, of the length of the lower leg. The lowest motor points were located in 37.5% +/- 5.5%, 37.9% +/- 2.3%, and 46.7% +/- 3.6%, respectively, of the length of the lower leg.

The present study defined the longitudinal distribution pattern of terminal motor points in the triceps surae muscles. This concept can be helpful for further studies evaluating the effectiveness of the botulinum toxin injection method.