During the 1970s, when total joint arthroplasty (TJA) became popularized for inflammatory arthritis, the average length of stay was 3 weeks,¹ and this gradually decreased to 5 days by the 2000s.² As the techniques, implants, and perioperative care models have continued to evolve since then, the length of stay has progressively shortened, and as of 2019, approximately 3% of hip and knee arthroplasties in the United States³ were being performed on an outpatient basis, either in a hospital or at an ambulatory surgical center (ASC). As more literature is published indicating that outpatient arthroplasty can be performed safely, this trend is likely to continue.

Multiple pressures have pushed arthroplasty surgeons to adopt outpatient programs. These include economic pressures, such as decreasing reimbursements by commercial and government payers, as well as the Centers for Medicare and Medicaid Services (CMS) removing total knee arthroplasty and total hip arthroplasty (THA) surgery from the CMS Inpatient Only List on January 1, 2018, and January 1, 2020, respectively. Increasingly, patients themselves have also become advocates of same-day discharges, and perceptions among the arthroplasty patient population are changing.^4,5,6

Hip replacement has outpaced knee replacement in outpatient TJA, likely because of less pain and more rapid recovery.^7,8,9,10,11 The direct anterior approach (DAA) for THA has been the most popular approach for outpatient THA,^{12,13,14,15,16} which may be for similar reasons. The early function and pain outcomes associated with DAA THA lend themselves to rapid recovery programs,^14,17 which have quickly evolved into outpatient programs.

The clinical setting for outpatient THA may be either a hospital or an ASC. The same goals of a safe and successful surgery followed by rapid evaluation and treatment by rehabilitation services and subsequent discharge home must be met at either location. Each has its benefits and drawbacks.

Designing a successful outpatient THA program requires institutional buy-in and multidisciplinary cooperation in whichever surgical setting it is performed. Therefore, performing outpatient total hip replacement at a hospital where arthroplasty has been performed on a strictly inpatient basis can be a challenge. Culture change can be difficult to achieve, which makes ambulatory centers, where the baseline culture focuses on ensuring that all patients go home the same day of surgery, an attractive option. Concerns for TJA in an ASC model are the lack of equipment and specialists immediately available in case of an untoward complication, as well as the possibility that the patient may require an overnight stay due to failure to progress as expected postoperatively. Still, previous reports suggest that outpatient joint replacement has a track record of being safe in either clinical setting.^18,19,20

Outpatient joint replacements were arguably first pioneered and innovated by Dr. Richard Berger dating back to 2001. By 2019, Dr. Berger had reported a 70% same-day discharge rate for his primary arthroplasty population, and these numbers are in line with the senior author’s (RID) experience in 2020.²¹ Dr. Berger credits his minimization of soft tissue trauma during surgery, which allowed his patients to consume fewer analgesics, leading to an easier rehabilitation for patients and earlier discharge. Another pioneer of outpatient joint replacement was Dr. Keith Berend, who credits the DAA as an important catalyst for outpatient THA feasibility at his institution. This surgical approach has allowed for successful outcomes for many of his patients.²²

Substantial advances have been made in arthroplasty to minimize surgical trauma and maximize perioperative pain control, which have enabled patients to regain mobility within hours of surgical intervention and be safely discharged to home the same day. The recent literature suggests that surgeons should understand the indications and contraindications for the safe performance of outpatient arthroplasty in a hospital and ASC setting as well as know how to optimize, medically manage, prepare, and rehabilitate patients. To undertake outpatient arthroplasty, surgeons must be knowledgeable in multimodal anesthesia techniques, effective venous thromboembolism prophylaxis, blood management, and wound management. In addition, surgeons must learn the subtle nuances of specialized surgical techniques that lend themselves to outpatient arthroplasty, such as the DAA in THA.²³

To develop a successful, safe, outpatient arthroplasty practice, surgeons must have the support of a multidisciplinary team, which includes an orthopaedic surgeon, an anesthesiologist, nurses, physical therapists, and a discharge planner. An Instructional Course Lecture article in 2016 by Berger et al²⁴ recommended that surgeons start with healthier, motivated patients and focus on THA and unicompartmental knee replacements in the learning curve phase of the transition to outpatient TJA.

THA has been successfully performed on an inpatient basis for decades. In recent years, there has been a convergence of pressures from multiple directions to push a greater percentage of these cases toward the outpatient model. Some of these are economic, with hospital systems as well as payers (both commercial and government) looking for cost containment. Other pressures are being exerted by the patients themselves, many of whom prefer to recover at home instead of in a hospital or rehabilitation center. Most recently, in 2020, the desire for patients to avoid hospital admission in order to help minimize their risk for coronavirus disease 2019 (COVID-19) exposure has become another driver in the demand for same-day discharge to home after TJA. Finally, there may be patient safety issues, such as the aim to optimize patients and thereby minimize infection risk, that may influence all stakeholders’ (patients, surgeon, hospital systems, and payers) decision to shift toward outpatient arthroplasty.

Avoiding an inpatient admission prevents many of the obvious direct costs associated with the overnight stay in the hospital, including inpatient nursing, staff, medications, bed costs, and dietary needs. A more complete picture looks at the full episode of care, from preoperative planning through to surgery as well as the complete spectrum of postoperative care. Although the postoperative care burden placed on the clinical staff may be higher in outpatients, an inpatient admission may cost more while in the hospital but can also cost less preoperatively by using fewer resources compared with the more intensive education and planning required for outpatient THA. Although many studies exist on the subject,^25,26,27 the exact cost differential will be different for each institution or clinical setting, and a variety of options in care exist that can tip the balance in favor of one or the other. With regard to costs associated with postdischarge rehabilitation, a variety of new methods such as web-based rehabilitation have been shown to further minimize such expenses.²⁸ Whether the entire episode of care is more sensible economically for outpatient joints has not been firmly established and is likely contingent on multiple factors. Certainly, the direct hospital costs are minimized in the outpatient care model.

A recent retrospective study sought to investigate the cost savings by comparing 119 outpatient with 78 inpatient DAA THAs performed by a single surgeon over 3 years.²⁵ They concluded that outpatient THA saved an average of $6798 ($24,529 vs $31,327; P = .0001). A similar study by Husted et al²⁷ concluded outpatient procedures were about two-thirds less costly than the costs associated with 2-day stays and provided no increase in complications or readmissions.

Having established that outpatient THA can effectively save money for the surgical episode of care, many commercial insurance companies have reduced compensation for outpatient THA relative to inpatient THA while at the same time have required stricter criteria to be met before approving the operation to be performed inpatient. Other commercial insurers have now decided that all patients undergoing elective THA will be designated and preauthorized as “outpatient” or “23-hour” stay by default, forcing surgeons and/or hospitals to appeal this in advance of surgery, adding a significant administrative burden if inpatient care is anticipated. In the past 2 years, these changes have forced many surgeons and health care systems to establish their own outpatient programs.

On January 1, 2020, the CMS removed THA from the Inpatient Only List,²⁹ allowing surgeons to perform THA on Medicare patients on an outpatient basis for the first time. Previously, a 3-night inpatient stay was required for Medicare patients who were being discharged to a skilled nursing facility, with some total joint programs having a 2-night waiver if participating in bundled payment programs.

The COVID-19 pandemic was a worldwide disruption on a scale never seen in modern history. This crisis has served to suddenly underscore the need to conserve precious hospital inpatient resources and beds. Many arthroplasties were initially canceled or postponed in the interest of saving both personal protective equipment and hospital capacity for patients with COVID-19. Outpatient THA has the advantages of providing this medically elective yet essentially necessary procedure without decreasing available hospital beds, keeping healthy arthroplasty patients away from ill patients on medical-surgical units, and decreasing overall exposure to health care personnel in a controlled manner. After the pandemic, the “phase 1” of recovery in many total joint centers was to perform TJA on patients under the age of 65 years who had minimal comorbid disease and who could be discharged following the surgery without needing hospital admission. Thus, the need to have outpatient THA protocols in place has never been more important than as seen following the COVID-19 pandemic, and the lessons learned from this process will likely influence arthroplasty programs for many years ahead.

THA was called “the operation of the century”³⁰ for its success in preserving mobility and quality of life to patients with hip pain that previously would be a
debilitating handicap. However, as demographics have shifted and the demand for hip arthroplasty increased in younger patients, payers began looking for cost containment. The US federal government spends an estimated $15 billion in health care costs on THAs annually.³¹ Therefore, the outpatient model of THA may be part of the evolving solution to help satisfy the ever-increasing societal demand and minimize the overall associated economic burden.

The DAA to THA has become a popular approach nationwide, and surgeons who perform DAA THA cite its excellent early functional outcomes and rapid recovery.^{7,12,32,33,34} This may give DAA an advantage over other approaches for outpatient THA; rapid pain control and function should help avoid failures of same-day discharges. Other advantages of the DAA include its ease of early rehabilitation due to many surgeons allowing DAA THA patients to be discharged with minimal, or even no, hip precautions.

Although a small number of THAs performed in the United States are performed using the DAA, the percentage of outpatient THAs performed via the DAA is believed to be much higher. Because outpatient THA can also be safely performed by nonanterior approaches,^18,35 this disparity may be due to confounders related to surgeon preference. The “early adopter” surgeons may be more likely to both perform the DAA and invest in an outpatient program. Patient perceptions may also be involved. If patients perceive that the DAA has a more rapid recovery, they may be more inclined to schedule a same-day THA with a surgeon offering the DAA. Whatever the patient perception or surgeon motivators involved, all of these have positioned the DAA THA as a major player in the outpatient arthroplasty space.