Background: Demand for total hip arthroplasty (THA) in ambulatory surgery centers (ASCs) is rapidly increasing. Increased efficiency is crucial in ASCs to manage this rising demand, particularly considering different surgical approaches and their varying time requirements. Optimizing efficiency can help meet the demand while ensuring safe and timely same-day discharge (SDD). This study examined the time spent in each care phase for THA patients in an outpatient ASC, the success rate and delays of SDD, and operative outcomes including estimated blood loss, 90-day complication rates, and 1-year patient-reported outcomes., Methods: A retrospective review was performed between January 1, 2019 and January 1, 2021 for all primary THA patients in a single free-standing ASC. Demographics, baseline functions, phase of care times, perioperative outcomes, 90 day complications, and patient-reported outcomes were recorded and compared stratified by surgical approach. Comparison was done using two-tailed t-tests and Fisher's exact tests. Multivariate both-direction stepwise regression analyses were performed to control for differences in group demographic factors such as age, sex, body mass index (BMI), preoperative assistive device use, attendance at preoperative class, American Society of Anesthesiologists (ASA) score, Charlson Comorbidity Index, and preoperative diagnosis., Results: Our groups differed in age, BMI, assistive device use, preoperative class attendance, and preoperative Veterans Rand 12 Item Health Survey (VR-12) physical component score (PCS). The direct anterior approach (DAA) and posterior approach (PA) cohorts varied significantly in minutes spent in each phase of care except for Spinal Time and Total physical therapy (PT) Time in Post-Anesthesia Care Unit (PACU). Direct Anterior Approach was faster that PA in Spinal State to Incision Time (26.8 ± 10.9 versus 35.0 ± 10.1; P < 0.001), Set-up/Take-down Time (20.5 ± 5.8 versus 30.2 ± 8.2; P < 0.001), Operative Time (37.5 ± 14.5 versus 50.4 ± 6.7; P < 0.001), Total operating room (OR) Time (57.8 ± 17.4 versus 80.5 ± 11.4; P < 0.001), and Arrival to Discharge Time (383.8 ± 71.2 versus 418.4 ± 60.8; P < 0.001). The PA was faster than DAA in Time to Initiation of PT (46.3 ± 25.1 versus 71.4 ± 34.7; P < 0.001), PACU Arrival to PT Cleared Time (124.9 ± 42.3 versus 144.3 ± 47.8; P < 0.001), and Total PACU Time (127.8 ± 47.4 versus 143.4 ± 47.8; P < 0.001). Surgical approach, age, BMI, and preoperative use of an assistive device were the most common predictive factors for phase of care time differences. Excessive spinal was the most common reason to delay physical therapy. The 90 day complications were not associated with surgical approach and patient-reported outcomes at 12, 26, or 52 weeks showed no significant differences., Conclusion: Direct anterior surgical approach showed shorter arrival to discharge time, and total OR time compared to PA with similar patient-reported outcomes (PROs) and complications. Both approaches were equally effective at achieving SDD. Operative time and set-up/take-down time were the main drivers of improved efficiency in the DAA group. Time to initiation of PT was prolonged in the DAA group, due to a standard spinal block time with a shorter OR time., (Copyright © 2024 Elsevier Inc. All rights reserved.)