The lumbar multifidus muscle and patterns of pain

This paper describes the patterns of pain induced by injecting hypertonic saline into the lumbar multifidus muscle opposite the L5 spinous process in 15 healthy adult volunteers. All subjects experienced local pain while referred pain was reported by 13 subjects in one of two regions of the thigh; anterior (n=5n=5) or posterior (n=8n=8). These results confirm that the multifidus muscle may be a source of local and referred pain. Comparison of these maps with pain maps following stimulation of the L4 medial dorsal rami and L4-5 interspinous ligaments shows that pain arising from the band of multifidus innervated by the L4 dorsal ramus has a segmental distribution. In addition patterns of pain arising from multifidus clearly overlap those reported for other lumbar structures. These findings highlight the difficulty of using pain distribution to accurately identify specific lumbar structures as the source of pain.