Selective changes in multifidus dimensions in patients with chronic low back pain.

This study of 52 patients (27 men) with recent (< 18 months) or chronic (> 18 months) low back and unilateral radicular pain symptoms was undertaken to investigate whether wasting of the paraspinal muscle components is generalised or selective. During the patients' routine computed tomographic lumbar spinal scans a standardised transaxial view was obtained along the upper end-plate of the L4 vertebra, and the cross-sectional areas of the paraspinal muscles and their components, multifidus and erector spinae, estimated. Irrespective of whether the symptoms were recent or chronic, multifidus dimensions were significantly greater on the side ipsilateral to the radicular pain symptoms. The results indicate selective changes of multifidus in these patients and possibly reflect an adaptive response by this muscle, such as to an increased role in stabilising the lumbar spine in the face of overall paraspinal muscle atrophy.