The significance of fat and muscle areas in the lumbar paraspinal space : a CT study

The object of this study was to determine the significance of fat deposition and muscle dimensions on CT in the unoperated lumbar paraspinal space. Fifty patients were prospectively studied. Paraspinal fat (PSF) and muscle (PSM) areas were correlated with various demographic and anatomical variables in patients with and without low back pain. The fat and muscle areas were derived from a standard CT image using a thresholding technique. Regression equations indicated that the total amount of PSF increases with age and subcutaneous fat area. The PSM area decreases with age. There was no correlation with the other variables examined. We conclude that PSF deposition and PSM dimensions on CT are related to patient age and the amount of subcutaneous fat. Paraspinal fat deposition is not a sign of muscle atrophy, and neither parameter is related to low back pain symptoms. Therefore, in patients who have not undergone spinal surgery, PSF and PSM areas are not of clinical or functional significance.