Enhanced cost utility in adult deformity corrections can be achieved by application of contemporary age-adjusted realignment criteria

BACKGROUND CONTEXT: Studies have evaluated outcomes for sagittal age-adjusted alignment score (SAAS) in adult spinal deformity (ASD) corrective surgery, yet no study to date evaluated its cost-utility. PURPOSE: Our study aims to evaluate the cost-utility and cost-effectiveness of age-adjusted alignment targets. STUDY DESIGN/SETTING: Retrospective cohort study. PATIENT SAMPLE: Adult Spinal Deformity. OUTCOME MEASURES: Cost-utility. METHODS: We included ASD patients undergoing primary surgery fused from at least L1 and proximal, to the sacrum, with a minimum of 5-year follow-up. Published methods to determine costs were utilized based on CMS.gov definitions and the average DRG reimbursement rates. Utility was calculated using quality-adjusted life years (QALY) utilizing the Oswestry Disability Index (ODI) converted to Short-Form Six-Dimension (SF-6D), with a 3% discount applied for its decline with life expectancy. Cost-utility (CU) was determined by dividing the cost by the utility gained five years postoperatively. The cost-effectiveness (CE) threshold of $150,000 was used. Patients were categorized based on whether they met SAAS (M) [SAAS score of -1 to 1], were under-corrected (U) [<-1], or over-corrected (O) [>1]. Baseline variances amongst SAAS groups and meeting CE were adjusted using ANCOVA and controlled using multivariable logistic regression. RESULTS: A total of 231 patients were included (Age 64.5, 68% F, 27.9 kg/m2, CCI 1.05, Frailty 3.3). Major and minor complication rates were 11% and 47% respectively, with 26% undergoing reoperation by 5Y. The mean cost associated with surgery was $98,000, with a utility gained at 5Y of 0.52. The cost per QALY at 5Y was $248,300 at 5Y, with 39% meeting CE. The mean SAAS score preoperatively was -2.0±4.6, and postoperatively was 1.5±3.8. Postoperative SAAS categories: 29.2% M, 23.6% U, 47.2% O. O cohort was older and had lower BMI, with no difference in frailty, CCI, osteoporosis rates, and baseline HRQLs. Furthermore, O had lower baseline deformity in PT, PI-LL, SVA, TPA, and PI (all p<.05). SAAS under-corrected patients had higher rates of reoperation due to x-ray imbalance (21% U, 3% M, 6% O, p<.05), while overcorrected had higher rates of implant failure (p>.05). U had worse patient-reported outcomes at the last follow-up (ODI: 31 U, M 20, O 22, p=.1). Univariate and multivariable analysis depicted no difference in CU and CE for SAAS categories, even when extrapolating utility to life expectancy. SAAS score of >5 was found to be significant for CU and CE, with CU being 30% higher in those overcorrected at that score (p<.05). Comparative analysis for each incremental decrease in SAAS score found those with a score of <-4 having 20% higher CU (p=.04). In those overcorrected, lower age (OR: 0.910 [0.845-0.981], p=0.013) and baseline deformity in TPA was predictive of achieving CE (OR: 0.905 [0.822-0.996], p=0.04). While in those under-corrected, lower frailty (OR: 0.555 [0.344-0.894], p=0.016) and baseline deformity in PT (OR: 0.390 [0.183-0.831], p=0.015) was predictive. CONCLUSIONS: ASD corrective surgery improves patient outcomes and has favorable cost-utility in most patients. However, patients were significantly less likely to achieve cost-effectiveness and have a higher cost utility if the age-adjusted alignment was under-corrected by 1 SD and overcorrected by 1.5 SD. FDA Device/Drug Status: This abstract does not discuss or include any applicable devices or drugs.

Duke Scholars

Author Peter Passias Orthopaedic Surgery