Accurate segmental motor innervation of human lower-extremity skeletal muscles.

Background: There is limited knowledge about accurate segmental motor innervation of the human lower extremity skeletal muscles. The aim of the present study was to explore the truth of segmental motor innervation of the lower extremity.

Methods: Included in this study were 20 patients with unilateral fracture of the sacrum and sacral nerve injury, who underwent internal fixation and decompression of the sacral nerve in our hospital between June 2009 and January 2014. L4-S4 nerve roots of the uninjured side were stimulated during operation. Motor innervation was determined by stimulating the spinal nerves with supramaximal intensity.

Results: We found the gluteus medius and the gluteus maximus were both mainly innervated by L5 and S1. In addition, the nerve fibres that innervated the extensor digitorum brevis, the abductor hallucis and the flexor digitorum brevis were mainly from S2 to S3.

Conclusions: Our study provides the electrophysiological mapping of the segmental anatomy of the human lower extremity muscles, which should be clinically useful in helping the diagnosis and treatment of nerve injury and neuropathies.