Relationship between global muscle atrophy and sagittal imbalance in patients with degenerative lumbar scoliosis: a study based on three-dimensional reconstruction.

Objective: To explore the three-dimensional (3D) characteristics of the paraspinal muscle (PSM) and the risk factors associated with sagittal imbalance (SI) in degenerative lumbar scoliosis (DLS) patients.

Methods: 168 patients with DLS were included in this study. We evaluated radiographic parameters, including spinopelvic parameters, apical intervertebral height, mean osteophyte formation score, apical vertebral rotation, mean facet degeneration, vertebral bone quality, mean intervertebral disc degeneration, mean modic changes, and relative muscle volume (rMV) of the PSM, including the paraspinal extensor muscle (PEM) and psoas major (PS), and fat infiltration (FI) of the PSM.

Results: Significant differences were found in the rMV of PEM, PS, and FI of PEM between the concave and convex sides of the spine (p < 0.001). Seventy-two patients comprised the SI group, and 96 comprised the sagittal balance (SB) group. All the rMV of the PSM of the patients with SI were smaller than those of those with SB (p < 0.05). The patients with SI were older than those with SB (p = 0.001). Additionally, in comparison to those with SB, the patients with SI had less LL and SS (p < 0.05), as well as an increased SVA and PT (p < 0.05). Furthermore, logistic regression revealed that age, LL, and the rMV of PS on the concave side influenced sagittal imbalance.

Conclusions: This study revealed that the degeneration of the PSM on both sides was asymmetric and that aging, loss of LL, and global atrophy of the PSM, especially the concave side of PS, were significantly correlated with SI in patients with DLS.