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

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.