Document Type : RESEARCH PAPER
Authors
1
Department of Orthopedic Surgery, Imam Hossein Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
2
Associate Professor of Neurosurgery, Department of Neurosurgery, School of Medicine, Imam Hossein Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran
3
Department of Radiology Imam Hossein Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
4
Orthopedic Surgeon, Department of Spine Surgery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
5
Research Assistant, Arak University of Medical Sciences, Arak, Iran.
6
Research Assistant, Neurology Department, Arak University of Medical Sciences, Arak, Iran.
10.22038/abjs.2026.87894.3981
Abstract
Objectives: To examine the association between lumbar sagittal alignment and intervertebral disc degeneration severity, accounting for anthropometric indices and exploring sex-specific effects.
Methods: In this cross-sectional study we analyzed 102 adults referred for low back pain who underwent standing lateral lumbar radiography and lumbar MRI (505 disc-level observations, L1–L2 to L5–S1). Segmental lordosis and sacral slope (SS) were measured on radiographs; disc degeneration was graded by Pfirrmann classification on MRI. Anthropometrics (BMI, waist-to-hip ratio, waist-to-height ratio, wrist circumference) and demographics were recorded. Primary inference used multilevel (subject random intercept) ordinal logistic regression adjusting for age, sex, disc level and SS; each anthropometric measure was added separately. Sensitivity analyses included sex-restricted models and a male-only Bayesian multilevel ordinal model.
Results: Mean age was 50.0 (SD 13.2) years; 78 (76%) participants were female. Disc level and age were the strongest predictors of degeneration: lower lumbar segments had markedly higher odds of advanced Pfirrmann grade (L4–L5 adjusted OR 5.65, 95% CI 3.37–9.45; L5–S1 adjusted OR 6.72, 95% CI 3.05–14.81). After accounting for level, greater segmental lordosis was independently associated with lower odds of more severe degeneration (adjusted OR 0.94 per 1° increase, 95% CI 0.90–0.98; p=0.007). SS was not independently associated with Pfirrmann grade (p=0.109). Among anthropometrics, only wrist circumference showed a modest association (adjusted OR 1.19 per 1 cm, 95% CI 1.00–1.40; p=0.048). The male-only Bayesian model produced concordant results (posterior OR 0.93 per 1°; 95% CrI 0.88–0.98).
Conclusions: Disc level and age dominate determinants of lumbar disc degeneration. Controlling for level, greater segmental lordosis is independently protective, while SS and common anthropometric indices (except a modest wrist circumference effect) are not. These results highlight the importance of level-specific modelling in sagittal alignment research.
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