Determinants of Cost-Effectiveness in Minimally Invasive Surgery for Adult Spinal Deformity Correction: A Multicenter Analysis

Introduction: The substantial financial implications of minimally invasive surgery for adult spinal deformity necessitate a thorough assessment of its inherent value and efficacy. Factors contributing to protracted cost-effectiveness (CE) have not been examined in 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.

Methods: MIS-ASD patients fused >2 levels with LLIF or ALIF and 4-year (4Y) follow-up were included. Published methods determined costs based on CMS.gov definitions and average DRG reimbursement rates. Utility was calculated using quality-adjusted life years (QALY), with a 3% discount applied for decline with life expectancy. Cost-utility (CU) was determined by dividing costs by total utility gained. Those who met CE at 4Y (CE4+) were evaluated relative to those who did not (CE4-).

Results: 86 patients met inclusion. Revision surgery occurred in 27%. The overall mean cost was $74,000. CU at 4Y was $267,000, with 40% meeting CE4+ and a cumulative QALY gain of 1.01.2. In patients without revision, 54% met CE at 4Y, while 76% met CE until life expectancy. No difference in length of stay, ICU admission rates, or time in ICU. Those with greater baseline disability (OR: 1.1, p<.05) and frailty (OR: 1.8, p<.05) had a higher likelihood of achieving CE4+. Lower comorbidity burden was associated with increased odds of achieving CE4+ (CCI OR: 1.8, p<.05). Improved correction of PI-LL mismatch based on age-adjusted values was associated with achieving CE4+ (PI-LL OR: 3.8, p<.05). Major complications had 6x higher odds of failure to achieve CE4+, whereas reoperations had 12x odds (both p<.05).

Conclusion : 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.