Posterior Intradiscal Osteotomy With Posterior Approach Anterior Column Release at L5-S1 for Rigid Flat Back Deformity: A Single-Approach Alternative to ALIF or PSO for Sagittal Balance Restoration

BACKGROUND AND IMPORTANCE: Restoring distal lumbar lordosis at a fused L5-S1 junction is challenging in adult spinal deformity surgery, particularly in revision cases with limited anterior access. Posterior intradiscal osteotomy (IDO) with posterior approach anterior column release (P-ACR) provides a single-posterior approach for mobilizing the anterior column and restoring distal lumbar lordosis without the risks of retroperitoneal exposure. This report details the operative nuances and technical sequence for L5-S1 IDO with P-ACR and summarizes early outcomes from complex revision cases. CLINICAL PRESENTATION: Four patients with rigid sagittal imbalance, prior multilevel lumbar surgery, and near-complete L5-S1 autofusion underwent L5-S1 IDO with P-ACR. Three patients were nonambulatory preoperatively. In each case, the fused disc space was mobilized through controlled P-ACR, permitting insertion of an anteriorly positioned expandable cage at L5-S1. The mean lumbar lordosis improved from −28.6° preoperatively to −46.9° postoperatively (mean gain 18.3°). Sagittal vertical axis improved from 107.9 mm to 65.4 mm (mean reduction 42.6 mm, 39.4%). These radiographical gains were accompanied by reductions in pelvic tilt (−13.1°) and improvements in functional status and pain scores. CONCLUSION: L5-S1 IDO with P-ACR offers a posterior-only solution for restoring distal lumbar lordosis in patients with rigid lumbosacral deformity. By enabling anterior cage placement from a posterior corridor, this approach avoids the exposure-related risks of anterior lumbar interbody fusion and the morbidity of pedicle subtraction osteotomy while providing effective correction in heavily scarred revision fields. The stepwise description and illustrative cases may assist spine surgeons in incorporating this technique into practice.