Refining Risk-Adjustment of 90-Day Costs Following Surgical Fixation of Ankle Fractures: An Analysis of Medicare Beneficiaries

Abstract

As the current healthcare model transitions from fee-for-service to value-based payments, identifying cost-drivers of 90-day payments following surgical procedures will be a key factor in risk-adjusting prospective bundled payments and ensuring success of these alternative payment models. The 5% Medicare Standard Analytical Files data set for 2005–2014 was used to identify patients undergoing open reduction and internal fixation (ORIF) for isolated unimalleolar, bimalleolar, and trimalleolar ankle fractures. All acute care and post–acute care payments starting from day 0 of surgery to day 90 postoperatively were used to calculate 90-day costs. Patients with missing data were excluded. Multivariate linear regression modeling was used to derive marginal cost impact of patient-level (age, sex, and comorbidities), procedure-level (fracture type, morphology, location of surgery, concurrent ankle arthroscopy, and syndesmotic fixation), and state-level factors on 90-day costs after surgery. A total of 6499 patients were included in the study. The risk-adjusted 90-day cost for a female patient, aged 65 to 69 years, undergoing outpatient ORIF for a closed unimalleolar ankle fracture in Michigan was $6949 ± $1060. Individuals aged <65 or ≥70 years had significantly higher costs. Procedure-level factors associated with significant marginal cost increases were inpatient surgery (+$5577), trimalleolar fracture (+$1082), and syndesmotic fixation (+$2822). The top 5 comorbidities with the largest marginal cost increases were chronic kidney disease (+$8897), malnutrition (+$7908), obesity (+$5362), cerebrovascular disease/stroke (+$4159), and anemia (+$3087). Higher costs were seen in Nevada (+$6371), Massachusetts (+$4497), Oklahoma (+$4002), New Jersey (+$3802), and Maryland (+$3043) compared with Michigan. With the use of a national administrative claims database, the study identifies numerous patient-level, procedure-level, and state-level factors that significantly contribute to the cost variation seen in 90-day payments after ORIF for ankle fracture. Risk adjustment of 90-day costs will become a necessity as bundled-payment models begin to take over the current fee-for-service model in patients with fractures.