192. The effects of global alignment and proportionality scores on postoperative outcomes following adult spinal deformity correction

Abstract

<h3>BACKGROUND CONTEXT</h3> Restoring sagittal alignment in adult spinal deformity (ASD) surgery is a common goal to improve patient clinical outcomes and minimize long-term complications. Recent enthusiasm has suggested that achievement of global alignment and proportionality alignment may influence mechanical failures and as such may potentially influence ultimate outcomes. <h3>PURPOSE</h3> To investigate which components of the GAP score are most associated with patient-reported and clinical outcomes. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study of prospective, multicenter ASD database. <h3>PATIENT SAMPLE</h3> This study included 227 ASD patients. <h3>OUTCOME MEASURES</h3> Complications; health-related quality of life (HRQL): ODI, SRS-22r, SF-36. <h3>METHODS</h3> Operative ASD patients (scoliosis >20°, SVA>5cm, PT>25°, or TK>60 °,) with a fusion at L1 or higher with available baseline and 2-year radiographic and HRQL data were included. Multivariate analysis (MVA) was used to find an association between the global alignment and proportionality (GAP) score higher risk individual categories: moderately disproportioned (MD) - (GAP >2 and <7) and severely disproportioned (SD) - (GAP >7). Severe sagittal deformity was defined by a ++ in SRS-Schwab for SVA, or PI-LL. Mechanical complications excluded PJK. <h3>RESULTS</h3> A total of 227 ASD patients met the inclusion criteria (59.9yrs±14.0, 79%F, BMI: 27.7 kg/m2 ±6.0, ASD-FI: 3.3±1.6, CCI: 1.8 ±1.7). Surgically, patients had mean levels fused of 11.1±4.4, length of stay (LOS) of 7.9 days±4.4, estimated blood loss (EBL) of 1577 mL, operative time of 377 min, with 63% undergoing an osteotomy. In the full cohort, controlling for age, and CCI, MVA showed no association of GAP MD or SD patients with PJF, or mechanical complications, (p>0.05) but MD patients showed a positive correlation with development of PJK [OR: 2, 95% CI: 1-3.7, p<0.05]. In a cohort of patients with severe sagittal deformity, GAP MD (4.2[1.3-13.4]) and GAP SD (3.3[1.06-10]) criteria was predictive of PJK by 2 years, and in a cohort of patients 65 and older, GAP MD (5[1.4-18], p=.014) and GAP SD (3.6[1-12], p=.04) were also predictive of 2-year PJK development. There was no association with PJF or mechanical complications. In a cohort of patients with a history of prior fusion, or in patients less than 65 years of age, there was no correlation of GAP MD/GAP SD with PJK, PJF, or mechanical complications. The continuous 6W GAP score, as well as the GAP categories, did not show significant correlations with patient reported outcomes at 2 years. <h3>CONCLUSIONS</h3> Since the introduction of the global alignment and proportionality (GAP), literature has been inconclusive on the utility of the GAP score in clinical practice. Our study shows that the GAP score had strong predictive potential for proximal junctional kyphosis (PJK), specifically, in patients with severe baseline sagittal malalignment and/or those 65 and older, and, may have less utility in younger patients, or those with a previous fusion. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.