The Incidence of Denervation of the Sacrospinales Muscles Following Spinal Surgery

The posterior paravertebral muscles of the lumbar spine are supplied segmentally by the posterior primary rami of the lumbar and sacral nerves. Electromyographic examination of these muscles is used to seek evidence of specific lumbar and sacral nerve root compromise. An anatomic study of the posterior rami and their branches has demonstrated that these nerves are very liable to be damaged during a routine posterior surgical approach to the lumbar spine. In a clinical and electromyographic study of 113 patients, all of whom underwent posterior lumbar spinal surgery, it was shown that some measure of denervation of the paravertebral muscles occurred in 96% of cases. Denervation was shown to persist for many years following surgery, and reservation was only partial. It was concluded that diagnostic electromyography of the paraspinal muscles in a postsurgical patient is of no value.