Introduction: Numerous schemas ASD assessment schemas have been developed predominantly with open surgical techniques in practice. The potential applications in minimally-invasive surgery (MIS) have not been extensively investigated.
Methods: Realignment schematics assessed included: SRS-Schwab, Global Alignment & Proportion (GAP) score, Sagittal Age-Adjusted Score (SAAS), and Roussouly type. Means comparisons tests analysed differences between groups. Logistic regressions analyzed associations between realignment schemas and postoperative outcomes.
Results: 704 patients included (Age 64.4 +/- 9.2, 80% female, BMI 27.7 +/- 5.2, CCI: 1.90 +/- 1.64, ODI 45.8 +/- 17.1). 572 were open (81.3%) and 132 were MIS cases. MIS patients were older (69 vs 59 years, p< 0.001), more comorbid (CCI 2.46 vs 1.62, p=0.001) and more frail (8.83 vs 6.35, p< 0.001) at baseline (BL), but there were no differences in deformity (PI-LL, SVA & T1PA, all p>0.05). Both groups did not differ in BL GAP scores and SAAS, and were considered severely disproportioned as per GAP score. The open group had more levels fused surgically (mean levels fused 11.5 vs 4.6, p< 0.001). Post-operative GAP and SAAS proportionality matching similarly did not differ immediately postoperatively. The open group demonstrated higher rates of mechanical complications (18.2% vs 7.6%, p=0.003), proximal junctional kyphosis/failure (PJK/PJF) {28.5% vs 9.8%, p< 0.001, and higher rates of reoperation for PJK/PJF (5.8% vs 1.5%, p=0.043). MIS patients were less likely to experience mechanical complications (MC) at 2 years (OR 0.37, 95% CI: 0.19-0.73, p=0.004). In patients who were GAP and SAAS matched post-op, but demonstrated PJK/F at 2 years, MIS patients had higher risk of developing MCs (MIS: OR 8.4, 1.99-35.18, p=0.004 vs Open: OR 1.58, 1.01-2.47, p=0.046). However, when controlling for age, BMI, levels fused and PJK/F occurrence at 2 years, there were no significant differences in likelihood for developing MCs.
Conclusion : The GAP and SAAS schemas appear to perform similarly in open and MIS cases. However, there remains a gap in the literature for validated MIS-specific realignment schemas.
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