222. PI and age-optimal alignment within the fusion in ASD surgery improves outcomes and minimizes mechanical failures?

Abstract

BACKGROUND CONTEXT Age specific alignment targets have been shown to optimize outcomes and minimizing the risks of mechanical failure like proximal junctional kyphosis (PJK). Recently, PI has been shown to be an important determinant of spinal alignment but the role of PI and age-optimal alignment has not been analyzed simultaneously with respect to PJK and clinical outcomes. Previous PJK studies have used SVA to measure over- or undercorrection, however in patients with PJK, SVA underestimates the overcorrection because of patient compensation and the PJK itself increases the SVA. The T1 Pelvic Angle (TPA) has been proposed as useful perioperative planning parameter; using the component of TPA within the fusion (T10PA) allows for measuring spinopelvic alignment separate from that of the unfused thoracic spine and any PJK that may occur postoperatively. PURPOSE To identify age- and PI-optimal alignment targets using a component angle of TPA within the fusion to define over and under-correction and their relationship to PJK and clinical outcomes. STUDY DESIGN/SETTING Retrospective analysis of a prospective, multicenter database PATIENT SAMPLE Operative ASD patients OUTCOME MEASURES SF36-PCS, PJK METHODS A prospective database of operative ASD patients was analyzed. Patients with fusions to the pelvis and UIV above T11 were included in the PJK analysis. Alignment within the fusion was correlated with clinical outcomes and PI. SF36-PCS normative data were used to compute PI- and age-optimal alignment for each patient. Over-, under- and optimally-corrected groups were determined using intervals from optimal alignment within the fusion to define the group boundaries. The rate of severe PJK (change>20°) was determined for each group. RESULTS A total of 1052 patients met inclusion criteria. Alignment within the fusion correlated with SF36-PCS and PI. At 6 weeks, 40.7% were optimally-corrected vs 39.4% overcorrected vs 20.9% undercorrected. The overall rate of PJK was 13.6%. Overcorrected patients had the highest PJK rate (18.1%) compared with optimally (11.3%) and undercorrected (9.5%), p CONCLUSIONS A component angle of TPA within the fusion, separate from the PJK, was used to determine age and PI-optimal alignment. Correcting ASD patients to optimal alignment within the fusion produced clinical outcome improvements with the lowest rates of PJK. This age and PI-specific approach to spinal alignment within the fusion provides ASD correction targets for surgeons that can be used intraoperatively. Future studies are warranted to verify the reliability of such intraoperative spinopelvic measurements. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.