Lightning Podiums: Adult Spinal Deformity - Room 801A

Presented by: D. Ge

Author(s):

P. Zhou(1), J. Moon(1), B. Beaubrun(1), J. Tishelman(1), D. Vasquez-Montes(1), C. Varlotta(1), D. Ge(1), T. Errico(1), P. Passias(1), T. Protopsaltis(1), A. Buckland(1)

(1) New York University Langone Orthopedic Hospital, Division of Spinal Surgery, New York, NY, United States

Abstract

Introduction: Preoperative planning using dedicated computer software has been advocated to improve the accuracy in achieving desired operative alignment goals. Pre-contoured rods, manufactured to a specified preoperative plan, are a recent addition to remove surgeon error in rod contouring. However, the effect of pre-contouring rods on postoperative alignment has yet to be assessed in adult spinal deformity. The purpose of this study is to examine differences between sagittal alignment outcomes with the use of preoperative planning and the use of pre-contoured spinal rods in patients undergoing fusion for adult spinal deformity (ASD).

Methods: We performed a retrospective radiographic review patients undergoing 5 or more level fusions for ASD with the lower instrumented vertebra below L3 at a single institution between 2011 and 2015. Patients were designated into 3 groups according to the presence (PLAN) or absence (NOPLAN) of preoperative computer planning, and additionally if pre-contoured rods (PRECON) were utilized during surgery. Preoperative and postoperative alignments were measured on standing 90 cm radiographs in all patients. Radiographic alignment parameters obtained included sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), lumbar lordosis (LL) and PI-LL mismatch (PI-LL). Patients were also categorized by the SRS-Schwab modifiers for ASD. Alignment parameters and SRS-Schwab modifiers were assessed with and without controlling for preoperative PI-LL via propensity score matching. The alignment between each group was compared with a 1-way ANOVA. The proportion of patients in each group according to SRS-Schwab modifiers (0, 1+ and 2+ for SVA, PT and PI-LL) were compared using a Chi-squared test.

Results: 160 patients were included in this study: 43 NOPLAN, 62 PLAN, and 55 PRECON. Age, gender, and BMI did not differ significantly across all three groups. Preoperative alignment was significantly different across all groups (PI-LL and PT) with the PLAN group having more severe baseline deformity (Table 1). Postoperative alignment was not significantly different across the three groups. When assessing postoperative SRS-Schwab modifiers for the most severe deformity, the proportion of patients with SVA>90 mm was found to be significantly different between the Pre-contoured group (lowest proportion) and the other two groups (PLAN & PRECON) (Table 2). No other modifiers were found to be significantly different between groups. After propensity score matching, 38 patients remained in each group. There was no significant difference between preoperative and postoperative alignment parameters across all three groups (Table 3), although the post-hoc analysis for postoperative PI-LL difference between the NOPLAN and PLAN group approached significance (p=0.066). There was no significant preoperative difference observed between groups when categorized by SRS-Schwab modifiers. Postoperatively, there was significant difference detected between groups in terms of PT>30°, with the NOPLAN group having greater rate of postoperative deformity (Figure 1).

Conclusion: Pre-contoured spinal rods significantly reduce the frequency of severe malalignment by SVA in ASD correction. In addition, preoperative planning reduces the frequency of severe malalignment by PT in ASD correction.