Foraminoplastic inferior pedicle subtraction osteotomy: a novel pedicle subtraction osteotomy technique for adult spinal deformity with radiographic outcomes and complications

OBJECTIVE The objective of this study was to introduce and evaluate foraminoplastic inferior pedicle subtraction osteotomy (FiPSO), a novel technique that involves downward resection of the pedicle and vertebral body, aimed at addressing rigid lower lumbar kyphosis. METHODS The clinical records were reviewed of the patients who underwent corrective surgery from January 2012 through December 2021 for adult spinal deformity using a combination of procedures: pedicle subtraction osteotomy (PSO) at the lumbar level and spinopelvic fixation. Inclusion criteria included patients older than 40 years with sagittal imbalance symptoms and significant radiographic findings: sagittal vertical axis (SVA) > 50 mm, pelvic tilt (PT) > 25°, or pelvic incidence (PI) minus lumbar lordosis (LL) > 10°. Patients were categorized into three groups: L1–3 PSO, L4–S1 PSO, and FiPSO. The authors assessed thoracic kyphosis, LL, lower LL (LLL), PI, PT, sacral slope, SVA, global tilt (GT), and Global Alignment and Proportion (GAP) score preoperatively, postoperatively, and at the last follow-up. Complications were also analyzed. RESULTS A total of 65 patients were included in the final analysis: 25 in the L1–3 PSO group, 29 in the L4–S1 PSO group, and 11 in the FiPSO group. The FiPSO group showed significantly larger postoperative LLL (39.2° ± 7.7° vs 29.7° ± 10.7°, p < 0.05) and smaller PI-LL mismatch (9.6° ± 10.3° vs 24.6° ± 13.4°, p < 0.01) compared to the L4–S1 PSO groups. At the last follow-up, the FiPSO group maintained larger LLL (38.3° ± 8.9° vs 27.1° ± 10.0°, p < 0.05), lower PT (23.1° ± 9.9° vs 33.3° ± 10.7°, p < 0.05), and good global sagittal alignment (SVA, 64.0 ± 43.8 mm vs 106.8 ± 55.7 mm, p < 0.05; GT, 28.7° ± 13.9° vs 43.5° ± 15.5°, p < 0.05) compared to the L4–S1 PSO group. The FiPSO group had higher nerve deficits (45%) but lower proximal junctional kyphosis (18%) and revision surgery rates (9.1%) than the L1–3 or L4–S1 PSO groups. However, the differences were not statistically significant. CONCLUSIONS FiPSO provides effective lower lumbar correction and long-term sagittal alignment with comparable complication rates, offering a valuable option for overcoming the challenges associated with PSO in the lower lumbar spine.