Quantitative MRI and X-ray analysis of disc degeneration and paraspinal muscle changes in degenerative spondylolisthesis.

Background And Objective: The intervertebral disc degeneration changes and paraspinal muscles changes are believed to be risk factors for lumbar degenerative spondylolisthesis (LDS). But there is limited quantitative information about this progression. This study is to reveal their changes the in the progression of LDS.

Methods: Data were gathered from 149 middle-aged degenerative spondylolisthesis patients and same amount of age- and sex-matched control group with both lumber spine MRI and X-ray. Narrowed disc space were measured in percent as anterior inferior disc height (DHIA)/anterior superior disc height (DHSA), inferior disc height (DHI)/superior disc height (DHS), and posterior inferior disc height (DHIP)/posterior superior disc height (DHSP). Signal intensity ratio of multifidus muscle (RM) and erector spinae (RES) to psoas muscle, muscle atrophy ratio of lean CSA (LCSA) to gross CSA (GCSA) of paraspinal muscles were calculated.

Results: In the case group the most common slipped vertebra was L4 (75.84%). Disc height (DHIA/DHSA, DHI/DHS) and multifidus muscle atrophy ratio (M-LCSA/M-GCSA) tended to be lower than those in the control group, whereas the disc degeneration degree and T2 signal intensity ratio (RM,RES) of the paraspinal muscles and erector spinae muscle atrophy ratio were higher than control group. The difference between the two groups was statistically significant (P< 0.05). Using multivariate logistic regression analysis, it was confirmed that ES-LCSA/ES-GCSA, especially RM are independent predisposing factors to lumbar spondylolisthesis (OR > 1, P< 0.05) while DHIA/DHSA, M-LCSA/M-GCSA are independent protective factors (OR < 1, P< 0.05).

Conclusions: Decreased anterior disc height and multifidus muscle atrophy are found in the LDS patients and thy could be the cause of LDS. The presence of erector spinae hypertrophy could be a compensatory mechanism to compensate for the instability.