Multilevel Schwab grade II osteotomies for sagittal plane correction in the management of adult spinal deformity

Abstract

Background context: Prior reports have compared posterior column osteotomies with pedicle subtraction osteotomies in terms of utility for correcting fixed sagittal imbalance in adolescent patients with deformity. No prior reports have described the use of multilevel Smith-Petersen Osteotomies (SPOs) alone for surgical correction in the adult spinal deformity (ASD) population.

Purpose: The study aimed to determine the utility of multilevel SPOs in the management of global sagittal imbalance in ASD patients.

Study design/setting: This is a retrospective observational study at a single academic center.

Patient sample: The sample included 85 ASD patients.

Outcome measures: This is a radiographic outcomes cohort study.

Methods: The radiographs of 85 ASD patients were retrospectively evaluated before and after long-segment (>5 spinal levels) fusion and multilevel SPO (≥3 levels) for sagittal imbalance correction. The number of osteotomies, correction in regional lumbar lordosis (LL), and correction per osteotomy was evaluated. Independent predictors of correction per SPO were evaluated with a hierarchical linear regression analysis.

Results: Eighty-five patients (mean age: 67.5±11 years) were identified with ASD (372 SPOs). The mean preoperative sagittal vertical axis (SVA) and T1 pelvic angle (TPA) were 8.16±6.75 cm and 25°±13.23°, respectively. The mean postoperative central sacral vertical line (CSVL) and SVA were 0.67±0.70 cm and 1.29±5.41 cm, respectively. The mean improvement in SVA was 6.29 cm achieved with a correction of approximately 5.05° per SPO. The mean LL restoration was 20.3°±13.9°, and 33(39%) patients achieved a final pelvic incidence minus lumbar lordosis (PI-LL) ≤10°. Fifty-four (64%) achieved a postoperative PI-LL ≤15°, 75 (88%) with a PI-LL ≤20°, and 85 (100%) achieved a PI-LL ≤25°. Correction per SPO was similar regardless of prior fusion (4.87° vs. 5.72° for revisions, p=.192). In a subgroup analysis of SVA greater than 10 cm, there was no significant difference in the final LL, thoracic kyphosis, PI-LL, SVA, CSVL, and TPA, as compared with SVA <10 cm. The LL was the only independent predictor of osteotomy correction per level (LL: β coefficient=-0.108, confidence interval: -0.141 to 0.071, p<.0001).

Conclusions: Multilevel SPOs are feasible for restoration of LL as well as sagittal and coronal alignment in the ASD population with or without prior instrumented fusion.

Keywords: Adult spinal deformity; Osteotomy; Pedicle subtraction; Ponte; Sagittal; Schwab osteotomy classification; Scoliosis; Smith-Petersen.