Nicholas Todd, DO¹; Jacob Roe, DO¹; Jeffrey Dulik, DO²; Dean Marshall, DO²; Frederick Korpi, DO^3
1Department of Orthopedic Surgery, Aultman Hospital
²Spectrum Orthopedics, Ohio Specialty Surgical Suites
³Department of Orthopedic Surgery, Aultman Hospital; Spectrum Orthopedics, Ohio Specialty Surgical Suites

Abstract

Background
Total hip arthroplasty (THA) was removed from the “inpatient only” list for Medicare Beneficiaries in January of 2020. As a result, outpatient THA’s have been performed at ambulatory surgery centers (ASC) more frequently. This study aims to evaluate outcomes of Medicare patients who underwent outpatient THA at an ASC.

Methods
We conducted a review of Medicare patients who underwent THA at an ASC between January 1st, 2021 and June 30th, 2021 performed by four orthopedic surgeons. 

Results
Twenty-nine patients were identified who underwent primary THA. There was a mean age of 72.2 +/- 5.9 and body mass index of 29.2 +/- 4.8.  The mean preoperative PROMIS scores were 43.7 +/- 5.3 for the physical domain and 53.1 +/- 7.6 for the mental domain with postoperative PROMIS scores of 49.0 +/- 6.1 (p < 0.01) and 53.4 +/- 9.5 (p = 0.79) respectively at six weeks, and 51.6 +/- 7.8 (p < 0.01) and 53.4 +/- 7.9 (p = 0.67) respectively at six months. The mean preoperative PROM-HOOS score was 51.0 +/- 13.4 compared with postoperative scores of 78.4 +/- 10.1 (p < 0.01) and 80.9 +/- 16.6 (p < 0.01) at six weeks and six months respectively. There were a total of seven minor complications and two major complications in a total of eight patients. Minor complications included one superficial wound treated with local wound care, two lateral femoral cutaneous nerve palsies, two quarter-inch leg length discrepancies, one case of heterotopic ossification and, one greater trochanter fracture. Major complications included one superficial wound infection resulting in superficial irrigation and debridement with retention of hardware, and one pulmonary embolism. Total recovery time and time within the ASC were on average 225.0 +/- 76.1 minutes and 411.2 +/- 74.0 minutes respectively.

Conclusion
Our findings demonstrate that outpatient surgery at an ASC resulted in significant improvements of  post-operative PROMIS and HOOS scores with low major complication rates when performing total hip arthroplasty in the Medicare population. In order to optimize patient outcomes, close collaboration with the surgeon, anesthesia team, and patient is recommended to achieve these results.

Keywords: Total hip arthroplasty, Complications, Outpatient, Ambulatory surgery center, Medicare

Level of Evidence: IV

Introduction
Total hip arthroplasty (THA) is amongst one of the most common orthopedic procedures performed, with a reported 370,000 performed in 2014 (1,2). This number is only expected to increase with the aging population with predictions of 171% increase by 2030 and 330% by 2060 (1). The Centers of Medicare and Medicaid (CMS) have removed total hip arthroplasty (THA) from the inpatient-only surgical list in January 2020 (3). Furthermore, beginning in January of 2021, THA was added to the ambulatory surgery center covered procedure list (4). Several studies have documented that THA with institutional care pathways can be safely performed as an outpatient procedure as well as same-day discharge with equivalent or better short-term outcomes than traditional inpatient THA (5). These studies have largely been hospital-based with patients commonly having to undergo short hospital stays with a single overnight stay. This is not only a safe procedure to be performed outpatient but can also provide substantial savings to the healthcare system (6). Despite the increasing evidence in the safety and efficacy of the procedure there are a plethora of concerns about discharging a patient prematurely after undergoing a THA (7,8). Some studies have concluded that increased length of stay is associated with increased complication and readmission after Total Joint Arthroplasty (TJA) for patients with a hospital stay of 3 days or more (9). The safety of major surgeries at ambulatory surgery centers remains a question throughout the orthopedic community. We have previously reported 6-month outcomes on Medicare patients who had outpatient total knee arthroplasty at our ASC without increased complications (10). The surgery center has been performing outpatient THAs since 2014. Six hundred thirty-six THA have been performed on privately insured patients. The objective of this research study is to report the six-month patient-reported outcomes and complications of Medicare patients following outpatient total hip arthroplasty in an ambulatory surgery center. 

Materials and Methods
We conducted a retrospective cohort review study by manually reviewing and extracting electronic medical records on Medicare patients who underwent total hip arthroplasty between January 1, 2021 and June 30, 2021. A total of forty patients underwent THA who met operative indications between January 1st, 2021 to June 30th, 2021. Surgeries were performed by four surgeons at a single ambulatory surgical center. Inclusion criteria were Medicare patients who underwent primary THA during the first six months of the year 2021 and had six months of post-operative follow-up to allow us to identify the majority of acute post-operative complications which occur in the first days to weeks after THA. Twenty-nine patients met the inclusion criteria. All patients who underwent THA at the ASC were reviewed and, those who did not have Medicare insurance or a full six month follow-up were excluded from the study. Eleven of the forty patients were excluded due to incomplete post operative patient-reported outcome measures within the first 6 months. All patients had pre-operative medical evaluations and were screened by the anesthesia providers prior to scheduled surgery date. Eligibility for THA at the ASC was determined by the attending surgeon in conjunction with the anesthesia team. Absolute contraindications for surgery to be performed at the ASC were as follows: unstable ASA III or IV, morbid obesity with complications, acute intoxication, known malignant hyperthermia or malignant hyperthermia susceptible, infectious communicable disease, and inadequate home support available. The surgery center has been performing outpatient THA’s since 2014 and, 636 THA were successfully performed in privately insured patients. All patients who met preoperative requirements to have surgery performed at the ASC were allowed to proceed.

All surgeries were completed using a Direct Anterior Approach (DAA) using the surgeon’s preferred instrumentation and implants. All patients were managed with a surgeon-specific rehabilitation protocol both pre and post-operatively. Data including demographics, laterality, ASA class, complications within the first 6 months, readmission rates, total and recovery time in the ambulatory surgical center, and need for assistive devices post-operatively was collected. At the preoperative visit, all patients were entered into both a physical and mental Patient Reported Outcome Measurement and Information System (PROMIS) and Patient reported outcomes via Hip Disability and Osteoarthritis Outcome Score (HOOS). Both systems are validated scoring systems for patients undergoing THA (11, 12). Post-operatively, all patients received online PROMIS and HOOS questionnaires at 6 weeks and 6 months. 

Results
Twenty-nine patients met the inclusion criteria for this study. All patients were diagnosed with end-stage osteoarthritis, had failed nonoperative treatment, underwent primary THA, and were enrolled in a qualified Medicare insurance program at the time of surgery. 

Complete demographic data is presented in Table 1. Patients had a mean age of 72.2 +/- 5.9 years and, body mass index of 29.2 +/- 4.8.  Twelve patients were male (41%) and seventeen were female (59%). Preoperative physical and mental PROMIS scores were 43.7 +/- 5.3 and 53.1 +/- 7.6 respectively. Six weeks postoperative PROMIS scores averaged 49.0 +/- 6.1 (p < 0.01) for the physical domain and 53.4 +/- 9.5 (p = 0.79) for the mental domain. Six-month postoperative PROMIS scores were 51.6 +/- 7.8 (p < 0.01) for the physical domain and 53.4 +/- 7.9 (p = 0.67) for the mental domain. Preoperative HOOS scores averaged 51.0 +/- 13.4. HOOS scores were 78.4 +/- 10.1 (p < 0.01) and 80.9 +/- 16.6 (p < 0.01) at six weeks and six months respectively. Statistical data is summarized in Table 2. 

Table 1.

Table 2.

All twenty-nine patients underwent a direct anterior approach. Total time spent in recovery was 225.0 +/- 76.1 minutes and, overall length of stay was 411.2 +/- 74.0 minutes on average. Seventeen patients were classified as ASA II (59%) and, twelve were ASA III (41%). Overall, eight patients received spinal anesthesia (28%) and twenty-one underwent general anesthesia (72%). All patients received supplementary periarticular injections for post operative pain control tailored to the specific primary surgeon’s preferences. Surgical data is summarized in Table 3.

Table 3.

Minor complications were defined as any reported postoperative outcome that deviated from normal recovery, but did not require reoperation, hospitalization, or those that required either nominal therapy or no treatment. There were seven minor complications reported. There was one superficial wound complication which consisted of blistering under the dressing at first post-op visit. This was treated with local wound care without antibiotics. Two lateral femoral cutaneous nerve palsies were reported. Both resolved with observation. Two leg length discrepancies were reported. Each was treated with ¼” heel lifts. One case of asymptomatic heterotopic ossification was noted radiographically. There was no treatment administered. There were two major complications. One patient presented with a superficial wound infection refractory to oral antibiotic therapy and underwent superficial irrigation and debridement with subsequent antibiotic therapy without the need for hardware removal or exchange. Additionally, one patient was diagnosed with a pulmonary embolism six weeks post-operatively. The patient was placed on long-term anticoagulant therapy. This patient was also found to have a small iatrogenic greater trochanter fracture which was treated with a walker and limitation in active hip abduction for six weeks. This fracture healed uneventfully without need for further intervention. Complications are summarized in Table 4.

Table 4.

Patients were free of all assistive devices at 8.0 +/- 4.9 weeks excluding one patient who continued using a cane for management of spinal stenosis symptoms. 

Discussion
There are numerous studies that demonstrate outpatient total hip arthroplasty can be considered in appropriately selected patients.^13-15 The safety of total joint arthroplasty performed at an ASC has been questioned and subsequently studied. Outpatient total joint arthroplasty has been performed in the past in hospital-based settings with good results when compared to inpatient arthroplasty procedures.¹⁶ Additionally, newer perioperative anesthesia and rapid rehabilitation protocols have allowed patients to meet discharge criteria on day of surgery.¹⁷ While outpatient THA have been performed for several years, Medicare has only recently removed it from the inpatient only list resulting in limited studies examining the outcomes of Medicare patients undergoing outpatient THA. The primary aim of this study was to demonstrate the safety of outpatient THA in Medicare patients at an ambulatory surgery center.

We were able to characterize postoperative complications that occurred within six months in our Medicare patients that underwent elective THA at the ambulatory surgery center. Of the 29 patients included there were a total of two major complications. There was one case (3.4%) of superficial wound infection requiring a return to the operating room for a superficial irrigation and debridement and, one additional case (3.4%) with wound problems that healed with local wound care. These findings correlate with data described in the literature, which report an 11.5% wound complication rate and 1.9% reoperation rate due to wound complications in a series of 651 DAA THA.¹⁸ Additionally, there was one case of pulmonary embolism (3.4%) which is a known compilation after THA with a reported incidence of 0.3 – 0.46%.^19,20 While our reported outcomes showed a higher incidence of PE, this was found in only one patient in our sample size of 29. Our minor postoperative complications included LFCN palsy (6.9%), LLD (6.9%), HO (3.4%) and, fracture of the greater trochanter (3.4%). The incidence of these minor complications found in our series of patients is equal to, or less than what is currently reported. LFCN has been reported to have an incidence of anywhere between 14.8% to 81% in patients undergoing a DAA.^21-23 LLD of at least 15mm has been reported to be present in 18% of patients undergoing DAA THA.²⁴ Heterotopic ossification was found to be present in 26.7% of patients undergoing DAA THA within 35 weeks, and fractures of the greater trochanter were present in 3% of patients.^25,26 These findings are reassuring and supportive of the safety of THA in Medicare patients at an ambulatory surgery center with comparable complication rates in the historical literature.

The current study has limitations. The sample size of our patients was relatively small so it may not be representative of a larger cohort. The data was collected over the first six months after THA was removed from the Medicare inpatient-only list. Additionally, follow-up was limited to six months. This allowed us to identify the vast majority of postoperative complications which generally occur within days to weeks postoperatively. We do recognize however that that a small percentage of complications may have been missed if they occurred after the six-month time frame.

Conclusion
Our findings demonstrate that outpatient surgery at an ASC resulted in significant improvements of post-operative PROMIS and HOOS scores with low major complication rates when performing total hip arthroplasty in the Medicare population. In order to optimize patient outcomes, close collaboration with the surgeon, anesthesia team, and patient is recommended to achieve these results.

Ethical and Transparency Statements
Institutional review board exemption was granted for this study. Written informed consent was obtained from all participants for publication of this study. All participants were informed of the study and were given the opportunity to opt out at any time. 

Conflicts of interest
The authors declare that they have no known competing financial interest or personal relationships that could have appeared to influence the work reported in the paper. 

Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

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