Before discussing the effect that ASCs have in creating value for patients, their short yet complex history must be examined because the growth and development of ASCs have shaped the function of the US healthcare system. Originally, the ASC concept was completely novel, and early innovators had to overcome practical hurdles to realize and promote the spread and standardization of ASCs. Reimbursement, licensing, and regulation needed to be formalized with commercial and governmental payers. Regulatory progress followed, but was slower, and ultimately defined the role of the ASC in the US healthcare environment.

The concept of ambulatory surgery finds roots in the work of Robert Campbell and Andrew Fullerton, surgical pioneers at the Royal Victoria Hospital in Belfast, Northern Ireland, who first described outpatient surgery for an inguinal hernia in the British Medical Journal in 1899⁵ and Lancet in 1904.⁶ This change in the early 1900s was spurred by the development of short-acting anesthetic agents that allowed the possibility of rapid recovery from surgery. Pioneers skirted around the idea of ambulatory surgery until the early 1960s, when health care professionals and legislators called for an improvement in accessibility, safety, and affordability of surgery.¹

The ASC made its US debut in 1966 and 1967 in California and Washington, DC, respectively, following several years of discussion and physician development. These first two entities were associated with hospitals, but Wallace Reed, MD, and John Ford, MD, began to lobby for a stand-alone facility, which ultimately was realized on February 12, 1968 as a “Surgicenter.” Although initial reports were promising and patient satisfaction was high, insurance companies refused reimbursement because the relevant policy at the time required admission to the hospital for 18 hours postoperatively. Payer hesitation to approve ambulatory surgery was rooted in concern for safety, but ultimately stunted the growth of ASCs.

In the early 1970s, with new American Society of Anesthesiologists guidelines for safety, the number of ASCs began to rapidly expand (Figure 1). At the national and state level, legislation allowed expansion and financial stability as malpractice lawsuits decreased and proof of safety increased. By 1979, more than 100 ASC facilities were operating in the United States. In the 1980s, the number of facilities continued to increase, with Medicare developing and updating Current Procedural Terminology codes and payment rates, ultimately still in current use. With the Centers for Medicare & Medicaid Services (CMS) on board with ASC utilization and payments, expansion continued in the 1990 and 2000s, reaching 5,400 ASCs in 2015.¹

Currently, ASCs are subject to regulatory standards at the state and federal levels, with independent accreditation. Federally, ASCs must be certified under Medicare Conditions for Coverage and demonstrate compliance with state law. Medicare also restricts the scope of procedures at ASCs while it requires reporting of quality measures and maintenance of emergency preparedness plans.³,⁷ The regulation of scope of practice lies in the Medicare CMS inpatient-only procedure list and ASC approval list. This significantly restricted ASCs, but in 2018, total knee arthroplasty (TKA) was removed from the inpatient-only procedure list, but still had to be performed in a hospital. Total hip arthroplasty (THA) was removed in 2020 and TKA was added to the ASC covered list. By January 1, 2021, Medicarefunded musculoskeletal procedures were permitted to be performed at an ASC, eventually extending to all procedures.

At the state level, 43 states require licensure to operate an ASC and the remaining seven require some form of accreditation similar to Medicare certification.
Independent bodies that accredit ASCs include Accreditation Association for Ambulatory Health Care, the American Association for the Accreditation of Ambulatory Surgery Facilities, the American Osteopathic Association, and The Joint Commission. There are 18 states that do not require ASC accreditation at this time.⁷ Although this timeline illustrates how regulatory policy has lagged behind the advancement of outpatient surgery, it is encouraging to see legislation catch up to ASC innovation and advancement of outpatient care.

With the explosive growth of ASCs and the need to demonstrate and standardize system processes for outpatient surgery, various centers developed criteria and protocols. Driven by the foundational pursuit of increased efficiency, decreased cost to patients and the healthcare system, and preservation of the safety of patients, the protocols focused primarily on maintaining the quality of outcomes as well as the ability to safely ambulate, successfully manage pain with oral medications, spontaneously void, and to tolerate a diet prior to same-day discharge. In 2009, Berger et al⁸ demonstrated the implementation of a regimented perioperative protocol for outpatient surgery sufficient for outpatient TKA or unicompartmental knee arthroplasty with few readmissions, emergency room visits, or complications. Another published protocol for optimization of patients as candidates for same-day discharge preoperatively was from Moore et al⁹ where patients underwent preoperative laboratory, telephone screening questionnaire, and physical examination to stratify patients into one of three categories. Each category placed a patient on an assessment schedule with preoperative anesthesia evaluation for optimization of modifiable risk factors for surgery. These protocols, among many others, highlighted relevant factors such as older age, later surgery end time, greater number of patient reported allergies, risk assessment and prediction tool score, and STOP-BANG sleep apnea score that affected the likelihood of a patient being discharged on the day of surgery.⁹ Additionally, protocols such as these illustrated the importance of preoperative evaluation and contributed to the value of outpatient surgery through improvement of perioperative efficiency, safety, pain management, and well-defined postoperative management. It is important to acknowledge that the widespread implementation of outpatient surgical care pathways not only delivered consistent patient outcomes in the ASC, but the downstream effect led to quality improvement in the hospital setting as well; this occurred as a result of both competition and transfer of lessons learned in the ASC setting. In standardizing perioperative optimization, patient education begins early, and expectations are set creating the opportunity to achieve higher postoperative patient satisfaction and better patient-reported outcomes. This strategy allows the perioperative team to fine-tune daily workflow knowing that patients meet a specific set of criteria and that the objectives for each patient are largely the same.¹⁰ Optimization of perioperative evaluation, patient education, expectations, and workflow improvement act in concert to improve the overall value of the orthopaedic procedure in question.

Through their development over decades, ASCs have undergone a rigorous vetting process to demonstrate equal, if not better, outcomes when compared with the traditional inpatient setting. Quality comparisons include the rate of readmission, complications, and adverse events. In expanding ASC breadth, efficacy in the hospital outpatient department was established first. An American College of Surgeons—National Surgical Quality Improvement Program analysis evaluated hospital stays and categorized patients into outpatient (less than one midnight) versus inpatient (more than one midnight). Using a propensity score matching and multivariate analysis, adverse events and readmissions were evaluated and it was found that the only increased risk for outpatient joint arthroplasty procedures was for a blood transfusion when compared with inpatient procedures. Otherwise, there were no increases in minor (pneumonia, wound dehiscence, urinary tract infection, or renal insufficiency) or serious (return to operating room, wound-related infection, thromboembolic event, renal failure, heart attack, cardiac event, stroke, or unplanned intubation, sepsis, or death) adverse events. This study, among many others, demonstrated that arthroplasty procedures could be performed safely in the outpatient setting.⁹ Another study prospectively evaluated inpatient (more than 24 hours, admitted as inpatient status) versus outpatient (in this study, this includes both patients who are discharged the same day of surgery and those who are placed in an observation status and discharged the following day) TKA and found equivalent Knee Society scores, functional scores, and ranges of motion between cohorts at a mean of 24 months postoperatively. Outpatient TKA was also found to have similar quality of recovery.¹¹

Within the realm of outcomes, and given a significant part of the burgeoning performance improvement movement in arthroplasty, patient-reported outcome measures (PROMs) have been used to further evaluate patient outcomes associated with inpatient, outpatient, and ASC procedures. Prospectively, a single surgeon evaluated 43 TKA inpatients and outpatients with a diary, complications, emergency department visits, and PROM results. Patient reports showed that quality of recovery was similar between groups and no outcome scores had statistically significant differences. There were no statistical differences between groups in complications or return to the emergency department.¹² A study of Medicare patients evaluated TKA patients who spent 3 to 4 nights in a hospital with patients who had shortened or extended-stay outpatient procedures. At 2 years, the outpatient and 1- to 2-day- stay groups reported less pain and stiffness.¹³

Notwithstanding PROM evaluation, overall patient satisfaction is also equivalent if not superior in outpatient surgery. A prospective study of 43 inpatient and 43 outpatient TKA patients evaluated 12-Item Short Form Health Survey scores, Hospital Consumer Assessment of Healthcare Providers and Systems, custom tools, and the National Health Service Friends and Family Test. Outpatients had superior quality of recovery postoperative day 1 measured by the Quality of Recovery-9 tool, had overall lower opioid requirement, and better reported pain levels. There was a correlation between well-controlled pain and satisfaction score. Ultimately, outpatient TKA resulted in no difference in PROM and satisfaction
when compared with inpatient TKA.¹² ASC outcomes, whether clinical or patient reported, indicate that outpatient surgery via ASCs is a positively driving force in adding/improving value in orthopaedic surgery.

Implementation and development of ASCs demanded rationalization for the capitalization of new infrastructure, drawing off staff from other health care settings, and specialization of staff for a smaller variety of procedures. To make the change justifiable, there must be a large volume of patients who undergo the procedure and it must be reimbursed at a reasonable and sustainable rate. It is thoroughly documented that there is projected to be an increased volume of orthopaedic procedures, especially THA and TKA, and this trend is projected to continue as the population ages. This provides a significant amount of demand that, when combined with increased accessibility and lower price, makes the procedure readily available to more of the population, thus mobilizing latent demand. Because ASCs do not require the same infrastructure and services as a fully equipped hospital, fixed institutional costs are lower.