Clinical Relevance of the SRS-Schwab Classification for Degenerative Lumbar Scoliosis

Study Design. Retrospective cohort study. Objective. The aim of this study was to evaluate the clinical relevance of the SRS-Schwab classification for degenerative lumbar scoliosis (DLS). Summary of Background Data. The SRS-Schwab classification has been presented and validated as a useful tool for adult spinal deformity (ASD). This classification includes various types of ASD (degenerative de novo scoliosis or adult form of idiopathic scoliosis). However, DLS has different clinical characteristics and pathophysiology compared with other forms of ASD. Methods. In this retrospective cohort study, 216 (146 conservatively treated and 70 surgically treated) DLS patients were enrolled. The average patient age was 72.1 ± 7.4 years. Clinical parameters for disability were measured using Oswestry disability index (ODI) and back and leg pain numerical rating scale. Radiographic parameters included SRS-Schwab sagittal modifiers (pelvic tilt [PT]; sagittal vertical axis [SVA];pelvic incidence-lumbar lordosis [PI-LL]), T1 pelvic angle, and coronal parameters (Cobb's angle [CA]; coronal imbalance [CI]; coronal deviation distance [CDD]; tilting angle [TA]). Correlations between clinical parameters and radiographic parameters were assessed and surgical rates along the SRS-Schwab sagittal modifiers were evaluated. Results. Only PI-LL as a sagittal radiographic parameter showed a weak correlation with clinical parameters (r = 0.137–0.176) (P < 0.05). Coronal parameters such as CA, CI, CDD, and TA also showed weak correlation with clinical parameters (r = 0.137–0.202) (P < 0.05). Multiple regression analysis identified CA, CI, CDD, and PI-LL to be correlated with clinical parameters. On analysis for clinical outcomes (surgical rates and patient self-reported disability) along the grades of the SRS-Schwab sagittal modifiers, PT and SVA were not related to higher surgical rates or disability. Conclusion. Even though some radiological parameters showed statistically significant results, correlation between radiological and clinical parameters was weak. Not only deformity but also other clinical factors should be considered when evaluating DLS. Level of Evidence: 4

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