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Updated: Jul 9, 2026

Intramuscular Injections Along the Motor End Plates: A Minimally Invasive Approach to Shuttle Tracers Directly into Motor Neurons
Published on: July 13, 2015
Anatomical localization of motor endplate bands in the human biceps brachii
Asif Amirali1, Liancai Mu, Jean-Michel Gracies
1Department of Otolaryngology, Mount Sinai School of Medicine, New York, New York, USA.
Objectives:
: Botulinum neurotoxin (BoNT) reduces disabling muscle contraction in numerous disorders with muscle overactivity. While motor endplates are the primary site of action for BoNT, their location is unknown in most human muscles. This study localized the motor endplate bands (MEB) within human biceps brachii (BB) muscles in relation to external landmarks.
Methods:
: Five human BB muscles were obtained from autopsy. Three muscles were processed for Sihler's stain, a nerve staining technique, and 2 were processed by whole-mount acetylcholinesterase stain.
Results:
: The major MEB in BB is an inverted V-shaped band, 1 cm in width, located 7 cm superior to the olecranon laterally, 11 cm superior to the olecranon in the middle, and 8 cm above the olecranon medially. The ratio of MEB location to total olecranon-acromion length is 0.25 at the lateral edge, 0.39 in the midline, and 0.28 at the medial edge.
Conclusions:
: This study localized MEB in human BB in reference to external landmarks. This data should improve the feasibility of endplate targeting when injecting BoNT in BB, which might enhance the clinical efficacy of these injections.
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