Outpatient vs. inpatient hip arthroplasty: a matched case-control study on a 90-day complication rate and 2-year patient-reported outcomes

BACKGROUND: The transition to outpatient-based surgery is a major development occurring in recent years in the field of total hip arthroplasty (THA). The effect of this transition on patient-reported outcomes (PROs) is still not well established. The purpose of the current study was to compare patients undergoing inpatient THA (iTHA) to patients undergoing outpatient THA (oTHA) regarding (1) perioperative variables including surgical time, blood loss, and length of stay (2) 90-day complication rates and unplanned emergency room or office visits (3) 2-year PROs including modified Harris hip score (mHHS), Harris hip score (HHS), forgotten joint score (FJS), pain, and satisfaction, as well as the quality of live measures. METHODS: The American Hip Institute registry was analyzed for patients undergoing THA between July 2014 and April 2016. The first 100 patients undergoing oTHA were selected and matched to 100 patients undergoing iTHA via propensity matching based on the following variables: age, sex, body mass index (BMI), Charlson comorbidity index (CCI), and smoking status. The primary outcomes were PROs at 2 years post-operatively. The secondary outcomes were perioperative surgical variables, 90-day complication rates, and unplanned emergency and clinic visits. RESULTS: After exclusions, 91 patients remained in each group and were compared. The oTHA group showed improved 2-year PROs with regard to mHHS (91.5 vs. 86.2; P = 0.02), HHS (92.3 vs. 87.4; P = 0.02), and pain (1.0 vs. 1.5; P = 0.04). The oTHA group had an average length of stay of 6.8 h compared to 43.2 h for the iTHA group (P < 0.001). There were no significant differences between the groups regarding readmissions, emergency room visits, and unplanned clinic visits. Complications and revision rates were similar in both groups. CONCLUSION: In appropriately selected, younger patients, oTHA can achieve improved postoperative 2-year PROs compared to iTHA. We found no differences regarding postoperative short-term complications or 2-year revision rates, and no differences in unplanned office visits or readmissions. LEVEL OF EVIDENCE: Prognostic level 3.