Anatomical validation of needle placement for cervical paraspinal mapping of the multifidus.

Abstract

The paraspinal muscles are an important component of electrodiagnostic testing for radiculopathy. In the cervical region, a protocol for cervical paraspinal mapping assumes accurate placement of the electromyography (EMG) needle into the cervical multifidus. However, there is scant information regarding the accuracy of needle placement in that muscle. This study examines the accuracy of this protocol in sampling the intended multifidus muscle of cadavers. An experienced electromyographer directed needles to multifidus at C5, C7, and T2 spinous processes of 19 embalmed cadavers, and injected color dyes. Separately another examiner dissected the cadavers, noting whether the dye was in the correct location and whether its trajectory approached any "danger zones" of nerve, artery, or joint. The dye was in the multifidus muscle 100% of the time and hit the intended bony target in 79%, 73%, and 79% of C5, C7, and T2 insertions. No insertion was found in a danger zone. The results indicate modest accuracy for EMG needle placement as proposed in the clinical protocol. Clinical utility of this method requires more work including the establishment of norms, sensitivities, specificities, and clinical impact.