The predictive power of the Roussouly classification on mechanical complications after surgery for adult spinal deformity: systematic review and meta-analysis

Background With the increasing prevalence of adult spinal deformity (ASD) in the aging population, the need for corrective surgery has surged, highlighting the importance of preventing mechanical complications (MC) such as junctional kyphosis/failure and rod breakage. The Roussouly classification, which categorizes natural variations in spinal posture, may hold predictive value in assessing the risk of these complications, as it guides the restoration of sagittal alignment based on a patient's preoperative spinal shape. Methods PubMed, Cochrane, and Google Scholar (pages 1-20) were searched through August 2024 to find articles comparing the incidence of mechanical complications between patients who were matched and mismatched to their ideal Roussouly shape after surgery for ASD. Extracted data consisted of the risk of mechanical complications, and the risk of reoperations. Results 10 retrospective studies were included in this meta-analysis, with 1454 patients divided into 2 groups, the first group matching Roussouly classification (716 patients, 49%) and the second unmatched (738 patients, 51%). A 5-times lower rate of mechanical complication (Odds-Ratio = 0.22; 95% CI: 0.12-0.41, p < 0.001) was found in the matched group at an average follow-up of 3.6 years. Furthermore, when examining specific mechanical complications, there were higher rates of both PJK (Odds-Ratio = 1.59; 95% CI: 1.07-2.38, p = 0.02) and rod breakages (Odds-Ratio = 1.75; 95% CI: 1.15-2.66, p = 0.01) in the unmatched group. However, no difference in the rate of reoperations was observed between the two groups (Odds-Ratio = 0.48; 95% CI: 0.18-1.28, p = 0.14). Conclusion Matching patients to their ideal Roussouly type in adult spinal deformity surgery significantly reduces mechanical complications making it a secure and efficient method. Future studies should compare the Roussouly classification to other alignment models to determine optimal alignment for ASD correction surgery. Level of evidenceIII.