Determinants of cost-effectiveness in minimally invasive surgery for adult spinal deformity correction

BACKGROUND CONTEXT: The substantial financial implications of minimally invasive surgery (MIS) for adult spinal deformity (ASD) necessitate a thorough assessment of its inherent value and efficacy. Previously, factors contributing to both short-term and protracted cost-effectiveness (CE) have not been systematically examined within the context of minimally invasive surgery for adult spinal deformity (MIS-ASD). Investigating these determinants can yield pivotal insight to optimize the efficacy of such surgical interventions while concurrently moderating associated expenditures. PURPOSE: To evaluate factors associated with achieving cost-effectiveness in MIS-ASD surgery. STUDY DESIGN/SETTING: Retrospective cohort study. PATIENT SAMPLE: MIS-ASD. OUTCOME MEASURES: Cost-utility. METHODS: We evaluated MIS-ASD patients undergoing fusion of >2 levels with LLIF or ALIF and 4-year follow-up. Published methods to determine costs were based on CMS.gov definitions and the average DRG reimbursement rates (453-455). 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 overall costs by the total utility gained. The CE threshold of $150,000 was used for primary analysis to evaluate factors associated with meeting 4-year (4Y) CE. Patients who met 4Y CE (CE4+) were assessed relative to those who did not (CE4-). RESULTS: A total of 86 patients were included. Revision surgery occurred in 27%. The overall mean cost was $74,000. Cost-utility (CU) at 4Y was $267,000, with 40% meeting CE4+. The mean cumulative QALY gained was 1.0±1.2. In patients who did not have revision surgery, 54% met CE at 4Y, while 76% met CE until life expectancy. There was no difference in length of stay (7.4 vs 8.5, p=0.1), ICU admission rates (17% vs 18%, p=0.8), or time in ICU (both with median of 1 day). While controlling for age, frailty, and the severity of preoperative deformity (SVA, PI, PI-LL, PT, and TPA), the postoperative correction did not vary amongst those who met cost-effectiveness compared to those who didn't at 4 years postoperatively. Those with greater baseline disability (OR: 1.11 [1.05-1.182], p<0.001) and frailty (OR: 1.79 [1.08-2.97], p=0.02) had a higher likelihood of achieving CE4+. Lower comorbidity burden was associated with increased odds of achieving CE4+ (CCI OR: 1.753 [1.11-2.76], p=0.02). Improved correction of PI-LL mismatch based on age-adjusted values was associated with achieving CE4+ (PI-LL OR: 3.80 [1.66-8.74], p=0.002). Major complications had 6x higher odds (OR: 6.029 [2.227-16.323], p<0.001) of failure to achieve CE4+, whereas reoperations had 12x odds (OR: 11.87 [3.54-39.78], p<0.001). CONCLUSIONS: Factors associated with achieving cost-effectiveness were age-adjusted PI-LL mismatch correction, lower comorbidity burden, higher disability and higher frailty. Reoperation and major complications were associated with failure to achieve cost-effectiveness. When revision surgery is avoided, over 50% of patients met cost-effectiveness criteria within four years and over 75% over lifetime after MIS-ASD surgery. FDA Device/Drug Status: This abstract does not discuss or include any applicable devices or drugs.

Duke Scholars

Author Peter Passias Orthopaedic Surgery