Total Hip Arthroplasty and the Medicare Inpatient-Only List: An Analysis of Complications in Medicare-Aged Patients Undergoing Outpatient Surgery

The Centers for Medicare and Medicaid Services has solicited public comments for the 2019 Proposed Rule to remove total hip arthroplasty (THA) from the inpatient-only list. Concerns exist regarding the safety of discharging higher risk Medicare patients as an outpatient and whether hospitals may still be reimbursed for an inpatient procedure. The purpose of this study is to determine whether Medicare-aged patients undergoing outpatient THA have higher complication rates than patients who underwent inpatient THA. We also sought to identify characteristics of Medicare-aged patients that are associated with increased risk of complications or longer stay following short-stay THA.

We queried the American College of Surgeons National Surgical Quality Improvement Program database for patients over age 65 who underwent primary THA between 2015 and 2016. We compared demographics, comorbidities, and 30-day complication, reoperation, and readmission rates among outpatient, short-stay, and inpatient groups. A multivariate regression analysis identified patients who are at an increased risk for complications and a longer inpatient stay following short-stay THA.

Of the 34,416 Medicare-aged patients who underwent THA, 310 (1%) were discharged on postoperative day 0, 5698 (16.5%) on postoperative day 1, and 28,408 (82.5%) were inpatients. The outpatient and short-stay patients had lower 30-day complication and readmission rates than the inpatient group. Independent risk factors for developing a complication or requiring an inpatient stay included general anesthesia, body mass index >35 kg/m ², diabetes, chronic obstructive pulmonary disease, congestive heart failure, hypertension, malnutrition, female gender, age >75 years, minority ethnicity, and an American Society of Anesthesiologists score of 4 (all P < .05).

Outpatient and short-stay THA appears to be safe in a small subset of Medicare-aged patients. Centers for Medicare and Medicaid Services should allow surgeons flexibility in determining admission status based on each patient’s risk profile.