Introduction: The Roussouly classification analyses sagittal pelvic parameter-based lumbar morphology. The impact of iatrogenic Roussouly type changes on postoperative outcomes in adult spine deformity (ASD) patients have not been extensively investigated
Methods: ASD patients with clinical and radiographic data from baseline (BL) to 2 years (2Y) were stratified by Roussouly (R) type (sacral-slope based and theoretical pelvic-incidence based). Means comparisons tests (ANOVA and Chi-square) were used to assess differences between both groups. Backstep logistic regression analyses were used to analyze associations between R changes and patient outcomes, including the minimum clinically important differences (MCID) in functional metrics.
Results: 525 patients were included (Age: 60.8 ± 14.1 years, BMI: 27.2 ± 5.5 kg/m2, CCI: 1.72 ± 1.68). 79% of patients were female. By R type, 8.3% were type 1, 53.6% type 2, 26.3% type 3 & 11.9% type 4. Post-op, 39% of patients changed R shape, 95% type 1, 17.6% type 2, 24.7% type 3 and 32% type 4 (p < 0.001). 39% of patients matched theoretical R type post-op (39.5% type 1, 29.4% type 2, 40.1% type 3 and 79% of type 4, p< 0.001). When controlling for baseline clinical and radiographic differences, R shape switches associated with higher risk of proximal junctional kyphosis/failure (PJK/F) development were: type 1-to-2 (OR 2.5, 95% CI 1.1-5.6, p=0.024), 2-to-4 (OR 2.8, 1.1-7.7, p=0.039), 3-to-4 (OR 2.3, 1.1-4.9, p=0.033). R 4-to-3 switches had the highest mechanical complication risks (OR 3.4, 1.2-9.4, p=0.016). R 1-to-2 had the highest rates of achieving ODI MCID at 6 weeks (23.5%,
Conclusion : While a significant portion of patients match postop theoretical Roussouly type, many of those matched at baseline are prone to becoming unmatched postop. Postoperative Roussouly shape changes influence patient outcomes and should be accounted for when planning ASD surgery.
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