Quantitative analysis of back muscle degeneration in the patients with the degenerative lumbar flat back using a digital image analysis - Comparison with the normal controls

Study Design. The degree of back muscle degeneration was quantified in patients with a degenerative lumbar flat back and a normal control group by magnetic resonance ( MR) imaging and a digital image analysis technique. Objective. To compare the degree of degeneration of the paravertebral back muscles of patients with that of a normal control group. Summary of Background Data. Extensive degeneration of the back muscle is well noted in patients with a degenerative lumbar flat back. Even though the problems of back muscles in the spinal column have been suggested to be one of the causes of spinal deformity, no study has quantified the extent of back muscle degeneration in spinal deformities such as a degenerative lumbar flat back. This study applied a method using MR imaging, which was originally developed to quantify the degree of the leg muscle degeneration in muscular dystrophy patients, to assess the degree of muscle degeneration of the spine in patients with a degenerative lumbar flat back. Methods. The digital images of the paravertebral back muscles in 21 female patients ( 11 patients with degenerative lumbar flat back deformity and 10 normal volunteers) using T2-weighted axial images and Picture Archiving and Communication System viewing software were analyzed and compared. The signal intensity, relative cross-sectional area ( CSA) ( the CSA of the paravertebral back muscle divided by that of the vertebral body in the same image), and the degree of the fat infiltration in the patients with degenerative flat back deformity and normal volunteers were measured and compared. Results. There was significantly higher signal intensity ( 295.9 +/- 57.1) and a larger area of fat infiltration ( 41.3% +/- 8.2%) of the back muscle of the patients group than that of the control ( 179.1 +/- 26.5 and 15.9% +/- 3.2%, respectively). The relative CSA of the back muscle compartment was constantly smaller in the patient group but significant differences were only found at the L4 - L5 level. These changes in the patient group were more significant in the lower lumbar levels than in the upper lumbar levels. Conclusion. T2 weighted MR Image analysis of the paravertebral back muscles in patients with degenerative lumbar flat back showed significant fat infiltration compared with those in the normal control using digital image analysis. Digital image analysis of the paravertebral back muscles is a useful tool for measuring the degree of paravertebral back muscle degeneration.