Asymmetry of muscle changes is most pronounced at the apex of degenerative lumbar scoliosis: a retrospective cross-sectional analysis of older adults.

Authors

Lukas Schönnagel, Nathalie Pfeiffer, Thilo Khakzad, Maximilian Muellner, Hendrik Schmidt, Matthias Pumberger, Friederike Schömig

Published in

Spine deformity. Jun 15, 2026. Epub Jun 15, 2026.

Abstract

Even though adult degenerative scoliosis (ADS) is an increasingly relevant pathology in the aging spine, its pathophysiology has yet to be fully understood. As some previous studies have shown degeneration of the paraspinal muscles to be associated with ADS, this study aimed to examine side-specific degeneration of the erector spinae (ES), multifidus (MF), and psoas (PS) along the concave and convex aspects of the curvature.
This retrospective study included patients with adult degenerative scoliosis (Cobb > 10°) and a defined apex at L3 who underwent spinal fusion surgery of at least 2 levels at a tertiary academic center. Paraspinal muscle morphology was assessed on preoperative axial T2-weighted MRIs, including fatty infiltration (FI) and height-adjusted functional cross-sectional area (fCSA). Measurements were performed bilaterally from L1/2 to L5/S1 using standardized segmentation and Otsu thresholding. Spinopelvic parameters, including Cobb angle, sagittal vertical axis (SVA), lumbar lordosis (LL), and sacral slope (SS), were measured on standing radiographs. Differences between the concave and convex sides were assessed using Wilcoxon signed-rank tests. Associations with spinopelvic alignment were analyzed using multivariable linear regression adjusted for age, sex, and BMI.
A total of 51 patients with median age of 82 (IQR 72 - 85) and 70.6% posterior-only surgery were included. Marked asymmetries in paraspinal muscle composition were observed, particularly at and around the apex. The mean Cobb angle was 18.4° (15.1° - 24.3°). FI was higher and fCSA lower on the concave side, with the strongest differences in the MF at L2/3 and L3/4 (15.53, IQR 4.71-26.65, p < 0.001). Greater asymmetry in MF FI (β: 0.22, 95% CI: - 0.40- - 0.05, p = 0.014, η² = 0.147) and ES FI (β: 0.45, 95% CI: - 0.69- - 0.21, p < 0.001, η² = 0.268) was significantly associated with an increased Cobb angle. In contrast, increased erector spinae fCSA on both sides was significantly associated with greater SVA (β: 11.52, 95% CI: 3.28-19.77, p = 0.008, η² = 0.193).
Our results show a significant asymmetry in muscle degeneration with more pronounced changes on the concave curve side, as well as an association of increased asymmetry with an increasing Cobb angle. In contrast, greater sagittal imbalance was linked to increased muscle mass, indicating a potential hypertrophic adaptation rather than muscle atrophy as the principal contributor to sagittal decompensation. Although our cohort is predominantly geriatric and limited to patients with moderate Cobb angles, our results should be taken into consideration for further research and when developing novel treatment strategies for these patients.

PMID:
42298282
Bibliographic data and abstract were imported from PubMed on 16 Jun 2026.

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