INTRODUCTION: Degenerative lumbar scoliosis (DLS) is a three‐dimensional deformity including asymmetric collapse and lateral rotator olisthesis, and caused the radiculopathy and low back pain due to spinal stenosis. Asymmetric degeneration of intervertebral disc, the facet joints and vertebral body wedging are thought to be the factor, however, the role of the paravertebral muscles (PVM) in the pathogenesis remains unclear. The purpose of this study was to investigate the muscle degeneration in patients with DLS and lumbar canal stenosis (LCS) without scoliosis, and to find out features of muscle degeneration in DLS.
METHODS: Fifty‐seven patients with DLS (DLS group) and 50 age and sex matched patients with LCS without scoliosis (LCS group) were retrospectively reviewed. Cross sectional area (CSA) of bilateral multifidus and longissimus muscles at each level was measured on the axial view of a magnetic resonance image by using computer software. The percentage of fat infiltrated area (%FIA) was measured using threshold technique. Muscle biopsy and histological evaluation were also performed in some patients.
RESULTS: In DLS group, the CSA of multifidus muscle was significantly smaller and %FIA of both muscles were significantly higher in concave side than in convex side. Histological evaluation showed reduction of the muscle fibers size and the number of nuclei in concave side. In LCS group, there was no significant difference in total CSA or %FIA area between left side and right side. However, in the patients with unilateral radiculopathy of LCS group, CSA of multifidus muscle was significantly smaller and %FIA of both muscles were significantly higher in the symptomatic side especially at one level below.
DISCUSSION: MR Image analysis of the paravertebral muscles in patients with DLS showed that muscle degeneration was more often seen in the concave side. Radiculopathy and weak lever‐arm may cause degeneration of paravertebral muscles.