Effect of paraspinal muscle morphometry in degenerative and isthmic spondylolisthesis: an MRI study

The aim of this study is to investigate the role of the cross-sectional area (CSA) of the lumbar paraspinal muscles in the development of degenerative and isthmic spondylolisthesis and its effect on the percentage of slip (PoS).

This retrospective single-center study included 171 patients, 100 of whom were isthmic and 71 patients with degenerative lumbar spondylolisthesis. First, CSAs of bilateral psoas major (PM), erector spinae (ES), and multifidus (MF) muscles were measured using MRI, and then the ratio of muscle areas to L5 vertebral body (VB) area was calculated. PoS was found by dividing the displacement distance of the superior vertebra to the corpus AP diameter of the inferior vertebra on sagittal T2-weighted images. Group comparisons were performed for muscle CSAs, VB ratios, PoS, disc height, and Modic changes, with additional analyses adjusted for age using ANCOVA.

The PoS rate of the degenerative group cases was found to be statistically significantly lower than the isthmic group cases (p = 0.002). The CSA of bilateral PM, bilateral MF, and right ES muscles of the patients with degenerative spondylolisthesis was found to be statistically significantly lower than the group with isthmic spondylolisthesis (p < 0.05). The MF/VB ratio was found to be significantly lower in the degenerative group (p < 0.01). After age adjustment, only the MF CSA difference persisted.

MF atrophy in degenerative spondylolisthesis appears to be associated with the underlying pathology rather than aging alone. These findings support incorporating targeted multifidus-strengthening and paraspinal muscle-preserving strategies into rehabilitation programs for spondylolisthesis.