ABSTRACT
STUDY DESIGN: Retrospective evaluation. OBJECTIVES: To determine the relationship between lumbar disc degeneration and back muscle degeneration. SUMMARY OF LITERATURE REVIEW: In the degenerative cascade of the spine described by Kirkaldy-Willis, degeneration of the disc and of the facet joint co-occur with aging. However, the muscles of the back are not included in this model. Several studies have reported significant correlations between back muscle degeneration and facet joint arthritis. The purpose of our study was to evaluate relationships between lumbar disc degeneration and fatty degeneration of the back muscles. MATERIALS AND METHODS: In this study, 65 patients over the age of 50 years who had undergone lumbar spine MRI in our orthopaedic clinic were recruited. Fatty degeneration of the back muscles was qualitatively graded from I to III by the degree of the fat signal in the muscle layer, including both the multifidus and erector spinae. Lumbar disc degeneration was graded from I to V according to the Pfirrmann grade. Correlations between the back muscle degeneration grade and radiological parameters were analyzed. RESULTS: The degeneration grade of the multifidus correlated positively with age and the grade of disc degeneration. Correlations with other radiologic parameters were not significant. The degeneration grade of the erector spinae correlated positively with age. Other radiologic parameters were not significant. CONCLUSIONS: There was a significant correlation between lumbar disc degeneration and multifidus degeneration. Erector spinae degeneration was correlated with age, but not with lumbar disc degeneration. The degenerative cascade of the spine was accompanied by fatty changes of the multifidus with aging.