Highest Achievable Outcomes for Adult Spinal Deformity Corrective Surgery

Study Design. Retrospective single-center study. Objective. To assess the influence of frailty on optimal outcome following ASD corrective surgery. Summary of Background Data. Frailty is a determining factor in outcomes after ASD surgery and may exert a ceiling effect on the best possible outcome. Methods. ASD patients with frailty measures, baseline, and 2-year ODI included. Frailty was classified as Not Frail (NF), Frail (F) and Severely Frail (SF) based on the modified Frailty Index, then stratified into quartiles based on two-year ODI improvement (most improved designated “Highest”). Logistic regression analyzed relationships between frailty and ODI score and improvement, maintenance, or deterioration. A Kaplan-Meier survival curve was used to analyze differences in time to complication or reoperation. Results. A total of 393 ASD patients were isolated (55.2% NF, 31.0% F, and 13.7% SF), then classified as 12.5% NF-Highest, 17.8% F-Highest, and 3.1% SF-Highest. The SF group had the highest rate of deterioration (16.7%, P =0.025) in the second postoperative year, but the groups were similar in improvement (NF: 10.1%, F: 11.5%, SF: 9.3%, P =0.886). Improvement of SF patients was greatest at six months (ΔODI of −22.6±18.0, P <0.001), but NF and F patients reached maximal ODI at 2 years (ΔODI of −15.7±17.9 and −20.5±18.4, respectively). SF patients initially showed the greatest improvement in ODI (NF: −4.8±19.0, F: −12.4±19.3, SF: −22.6±18.0 at six months, P <0.001). A Kaplan-Meier survival curve showed a trend of less time to major complication or reoperation by 2 years with increasing frailty (NF: 7.5±0.381 yr, F: 6.7±0.511 yr, SF: 5.8±0.757 yr; P =0.113). Conclusions. Increasing frailty had a negative effect on maximal improvement, where severely frail patients exhibited a parabolic effect with greater initial improvement due to higher baseline disability, but reached a ceiling effect with less overall maximal improvement. Severe frailty may exert a ceiling effect on improvement and impair maintenance of improvement following surgery. Level of Evidence. Level III.