Surgical sequence in anterior column realignment with posterior osteotomy is important for degree of adult spinal deformity correction: advantages and indications for posterior to anterior sequence

Background We hypothesized that posterior osteotomy prior to ACR (Anterior column realignment) through P-A-P surgical sequence would permit a greater correction for deformity corrective surgery than the traditional A-P sequence without posterior osteotomy. This study aimed to determine the impact of the P-A-P sequence on the restoration of lumbar lordosis (LL) compared to the A-P sequence in deformity corrective surgery for adult spinal deformity (ASD) patients and to identify the characteristics of patients who require this sequence. Methods Between 2017 and 2019, 260 ASD patients who had undergone combined corrective surgery were reviewed retrospectively. This study included 178 patients who underwent posterior osteotomy before the ACR (P-A group) and 82 patients who underwent the A-P sequence (A-P group). Sagittal spinopelvic parameters were determined from pre- and postoperative whole-spine radiographs and compared between the groups. To find better indications for the P-A-P sequence, we conducted additional analysis on postoperative outcomes of patients in the A-P group. Results The P-A group showed a significantly higher change in LL (53.7 degrees vs. 44.3 degrees, p < 0.001), C7 sagittal vertical axis (C7 SVA: 197.4 mm vs. 146.1 mm, p = 0.021), segmental lordosis (SL) L2/3 (16.2 degrees vs. 14.4 degrees, p = 0.043), SL L3/4 (16.2 degrees vs. 13.8 degrees, p = 0.004), and SL L4/5 (15.1 degrees vs. 11.3 degrees, p = 0.001) compared to the A-P group. At the final follow-up, pelvic incidence (PI) minus LL mismatch (PI - LL mismatch) was significantly higher in the A-P group (13.4 degrees vs. 2.9 degrees, p < 0.001). Stepwise logistic regression analysis showed that age >= 75 years (odds ratio [OR] = 2.151; 95% confidence interval [CI], 1.414-3.272; p < 0.001), severe osteoporosis (OR = 2.824; 95% CI, 1.481-5.381; p = 0.002), rigid lumbar curve with dynamic changes in LL < 10 degrees (OR = 5.150; 95% CI, 2.296-11.548; p < 0.001), and severe facet joint osteoarthritis (OR = 4.513; 95% CI, 1.958-10.402; p < 0.001) were independent risk factors for PI - LL mismatch >= 10 degrees after A-P surgery. Conclusion P-A-P sequence for deformity corrective surgery in ASD offers greater LL correction than the A-P sequence. Indications for the procedure include patients aged >= 75 years, severe osteoporosis, rigid lumbar curve with dynamic change in LL < 10 degrees, or more than four facet joints of Pathria grade 3 in the lumbar region.