Factors Associated with the Maintenance of Cost-Effectiveness at 5 Years in Adult Spinal Deformity Corrective Surgery

Study Design. Retrospective cohort. Objective. To evaluate factors associated with the long-term durability of cost-effectiveness (CE) in ASD patients. Background. A substantial increase in costs associated with the surgical treatment for adult spinal deformity (ASD) has given precedence to scrutinize the value and utility it provides. Methods. We included 327 operative ASD patients with five-year (5 yr) follow-up. Published methods were used to determine costs based on CMS. gov definitions and were based on the average DRG reimbursement rates. The 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 in life expectancy. The CE threshold of 150, 000 was used for primary analysis. Results. Major and minor complication rates were 11% and 47%, respectively, with 26% undergoing reoperation by five years. The mean cost associated with surgery was 91, 095±47, 003, with a utility gain of 0. 091±0. 086 at one years, QALY gained at 2 years of 0. 171±0. 183, and at five years of 0. 42±0. 43. The cost per QALY at two years was 414, 885, which decreased to 142, 058 at five years. With the threshold of 150, 000 for CE, 19% met CE at two years and 56% at five years. In those in which revision was avoided, 87% met cumulative CE till life expectancy. Controlling analysis depicted higher baseline CCI and pelvic tilt (PT) to be the strongest predictors for not maintaining durable CE to five years CCI OR: 1. 821 (1. 159–2. 862), P =0. 009 PT OR: 1. 079 (1. 007–1. 155), P =0. 030. Conclusions. Most patients achieved cost-effectiveness after four years postoperatively, with 56% meeting at five years postoperatively. When revision was avoided, 87% of patients met cumulative cost-effectiveness till life expectancy. Mechanical complications were predictive of failure to achieve cost-effectiveness at two years, while comorbidity burden and medical complications were at five years.