Risk Factors for Delayed Discharge and Adverse Outcomes Following Outpatient Billed Total Knee Arthroplasty

Background: The volume of outpatient total knee arthroplasty (TKA) has increased with advances in perioperative protocols, patient selection, and recent policy changes regarding insurance authorization. This study analyzed 30-day outcomes from a national database to better understand risk factors for delayed discharge (length of stay [LOS] >1), readmission, and reoperation after outpatient TKA. Methods: The National Surgical Quality Improvement Program (NSQIP) database was utilized to collect TKA (CPT 27447) billed as outpatient surgery performed from 2013 to 2018. Patient demographics, comorbidities, and short-term outcomes were collected and compared in LOS 0 versus LOS >1 cohorts. Subgroup analysis was completed for TKA performed in 2018, after the Center for Medicare Services removal of TKA from the inpatient-only list. Results: A total of 13,669 patients had outpatient TKA performed from 2013 to 2018. Most patients had LOS >1 day (77.1%). The LOS 0 cohort demonstrated a lower 30-day readmission rate (1.8%) compared to LOS >1 (2.8%), P > .01. Both groups demonstrated a low 30-day reoperation rate, LOS 0 (0.7%) and LOS >1 (1.1%), P =.05. Regression analysis demonstrated risk factors for LOS >1 day included COPD, ASA >3, age >75, and BMI >35 kg/m2. Regression analysis demonstrated male gender, age >75, ASA >3, and albumin <3.5 g/dL were risk factors for readmission. Hypertension was a risk factor for 30-day reoperation. Conclusion: Risk factors for LOS >1 day include age >75, ASA >3, BMI >35 kg/m2. In addition, BMI >35 kg/m2 was a risk factor for readmission and reoperation. These findings reinforce appropriate patient selection when considering outpatient TKA.

Automated summary

This study analyzed the outcomes of outpatient total knee arthroplasty (TKA) using a national database. The risk factors for delayed discharge, readmission, and reoperation were identified. It was found that risk factors for delayed discharge include COPD, ASA >3, age >75, and BMI >35 kg/m2. Risk factors for readmission and reoperation were male gender, age >75, ASA >3, and albumin <3.5 g/dL. These findings highlight the importance of appropriate patient selection in outpatient TKA.