Anatomic Motor Point Localization of the Biceps Brachii and Brachialis Muscles

Injection of the neurolytic agents into motor points of the biceps brachii or brachialis muscles is an effective treatment of spasticity of the elbow flexors in many stroke survivors. Accurate localization of the motor points of each muscle is necessary for enhancing the efficacy of motor point blocks. To identify the precise locations of the motor points (terminal nerve endings) of the biceps brachii and brachialis muscles in relation to anatomic surface landmarks for motor point blocks, we dissected 23 limbs from 12 cadavers. A reference line was defined as a line connecting the coracoid process with the lateral epicondyle of the humerus. The location of the motor points of the biceps brachii and brachialis muscles was identified in reference to the reference line. The motor point of the biceps brachii muscle was found to be approximately half of the reference line. In the brachialis muscle, the location of the motor point was 70% of the reference line from the coracoid process and 2 cm medial to the line. The results are expected to facilitate effective localization of the motor point block of these muscles in selective motor nerve block.