L5 Pedicle Subtraction Osteotomy Offers Maximal Correction for Sagittal Malalignment: A Cadaveric Study, Systematic Review, and Meta-Analysis of Real-World Patients.

Introduction: The relationship between pelvic incidence (PI) and lumbar lordosis (LL) is crucial for restoring proper spinal alignment. While various surgical options exist for addressing severe sagittal malalignment, lower segment (L4–S1) lordosis is essential for overall correction. L5 osteotomies are infrequently discussed in the literature, despite their importance in treating fixed sagittal deformities.

Methods: Twelve freshly thawed cadaveric lumbopelvic specimens were utilized to evaluate the technique of L5 pedicle subtraction osteotomy (PSO). A stepwise approach was employed to ensure reproducibility in clinical practice. Radiographic sagittal lumbopelvic parameters were measured pre-and post-osteotomy, and range of motion (flexion, extension, and lateral bending) was assessed.
A systematic review of biomechanical studies and real-world patient outcomes was also performed to investigate the radiographic and clinical efficacy of L5 PSO.

Results: A PRISMA identified 11 studies on L5 PSO, including 226 patients. The cadaveric study demonstrated a significant increase in the mean lordotic angle from L4 to S1 after the osteotomy. The intact specimens had a mean angle of 30.12°±7.56°, which increased to 46.81°±7.75° post-operatively in L2-S1 instrumented specimens. Adding S1 alar screw fixation showed a similar mean angle of 46.76°±7.63°, indicating no significant difference in the degree of correction with or without pelvic instrumentation.
A meta-analysis of real-world patient data confirmed that PSO at any level improved lumbar lordosis, global tilt, pelvic tilt, sacral slope, and the PI-LL mismatch. A significantly greater improvement for L5-PSO was observed in global tilt (MD: 5.77; 95% CI: 1.46-10.09; P < 0.01) and L4-S1 lordosis (MD: 13.56; 95% CI: 5.87-21.24). Range of motion (ROM) testing revealed no differences between groups with or without L5-PSO. Notably, one L2-S1 instrumented specimen sustained a type III sacral fracture during ROM testing.

Conclusion : L5 PSO offers substantial correction of sagittal imbalance, significantly improving lumbar lordosis and global tilt, as real- world data confirms. Despite achieving similar lordotic angles with or without pelvic fixation, supplemental instrumentation enhances post-osteotomy stability. While biomechanical stability is achievable, the procedure carries a high complication risk, emphasizing the need for careful patient selection. Nevertheless, patient satisfaction is high when optimal sagittal alignment is restored.