Experience with an Outpatient Total Knee Arthroplasty Program in Chile: Evaluating Safety and Feasibility

Abstract

Introduction

Total knee arthroplasty (TKA) has evolved into a successful and safe procedure for treating severe osteoarthritis of the knee with a projected increase in incidence. Outpatient TKA has emerged as an efficient alternative, supported by technological advancements, rehabilitation protocols, and anesthetic techniques.

Objective

To describe the safety and short-term costs of outpatient and inpatient TKA at a hospital and analyze associated complications and reinterventions.

Materials and Methods

An observational retrospective study was conducted on patients who underwent primary TKA in 2022 at a single hospital. Patients with unicompartmental or revision arthroplasty were excluded. Patients were classified into two groups: outpatient (group 1) and inpatient (group 2). Demographic data was collected, and safety (emergency consultations in the first postoperative week), postoperative complications, reinterventions, mortality, and associated costs were evaluated.

Results

A total of 347 primary TKA procedures were registered, of which 267 (77%) were outpatient and 80 (23%) were inpatient, with a mean follow-up of 21 months (17–28). Nine early consultations (3.3%) were reported in the outpatient group and five (6.2%) in the inpatient group during the first 7 postoperative days. There were 18 reoperations in the outpatient group (6.7%) and nine (11.2%) in the inpatient group. No deaths were reported. Individual savings were USD 1,034, with total savings of USD 276,130.

Conclusion

Outpatient total knee arthroplasty is a safe procedure with complication rates similar to those in the inpatient setting and offers significant cost savings for both patients and the healthcare system.

Keywords

outpatient - total knee arthroplasty - postoperative complications - cost analysis

Introduction

Total knee arthroplasty (TKA) is a successful and safe procedure for the treatment of severe gonarthrosis. Its incidence is estimated to increase by 143% between 2012 and 2050.[1] Since its introduction, the technology, implants, and techniques have evolved, including earlier and more aggressive rehabilitation protocols, prioritizing movement, and early resumption of walking. Multidisciplinary management, advances in anesthetic techniques such as peripheral nerve blocks and multimodal anesthesia, along with the use of tranexamic acid, have reduced pain, perioperative bleeding, and the need for transfusions, shortening hospital stays and reducing costs for the healthcare system.[2] [3] [4]

Therefore, outpatient TKA is emerging as an innovative trend to enhance the efficiency of the surgical process and increase the number of procedures, without implying additional costs for the system or greater risks for the patient.

Authors like Lovald et al,[5] show that performing TKA on an outpatient basis would save up to USD 8,527 per case over two years, compared to a hospital stay of 3 to 4 days.

Worldwide, many hospitals and clinics perform this procedure on a completely outpatient basis.[6] In 2020, 5% of TKAs were outpatients,[7] a rate that increased during the COVID-19 pandemic. This increase, which in countries like Canada rose from 14% in 2019 to 34% in 2020, appears to be driven by the urgency of reducing non-respiratory hospitalizations and lowering the risk of infection in hospital settings.[8]

Several studies report on the safety of outpatient TKA, without increasing the rate of readmission or complications.[8] [9] However, according to a meta-analysis, there would be a slight increase in the rate of complications without increasing the rate of readmission.[10] Careful selection appears crucial to avoid complications. Currently, the incidence of patients under 60 years of age requiring TKA is increasing, making this group especially suitable for outpatient surgery due to fewer comorbidities and perioperative risks.[11]

In Chile, before the COVID-19 pandemic, the TKA rate was 28.23 per 100,000 inhabitants, making it the surgery with the second longest waiting list, with 15,132 pending cases. In 2020, because of the pandemic, there was a 64% drop in the incidence of TKA, and it is estimated that USD 250,000 - 506,000 per month is needed to recover missed surgeries.[12]

In our country, there is little information regarding outpatient prosthesis programs; there is only one study on outpatient hip prosthesis surgery, which shows it to be a safe procedure in selected patients.[13] We do not have any studies to date that include experience in knee prosthetic surgery; we only know that currently, no more than 20% of surgeons consider using this modality.[14]

Considering outpatient TKA as a possible solution to waiting lists, this study aims to describe the outcomes of outpatient (defined as hospitalization lasting less than 24 hours) and inpatient total knee arthroplasty in patients treated at a center in Chile, with a particular focus on safety, postoperative complications, and short-term costs, without attempting a direct comparison between the two approaches.

Materials and methods

Type of Study

A retrospective, observational study was conducted in which the results of patients undergoing total knee arthroplasty on an outpatient and inpatient basis in the same hospital center were described.

Population and Data Collection

The total number of primary TKAs in patients operated on during 2022 (January 1 to December 31) was recorded. Unicompartmental or revision arthroplasties and patients without complete electronic medical records were excluded. Patients were divided into two groups: outpatient (Group 1) and inpatient (Group 2). Demographic data were recorded, and procedural safety was assessed in each group, measuring emergency department visits during the first postoperative week, postoperative complications, reoperations, mortality, and associated costs in each group.

Of all patients selected for TKA, those with ASA I or ASA II were included for outpatient surgery. ASA III patients, or those with any contraindications to an outpatient surgery program (medical or social), were operated on and hospitalized. The exclusion criteria for outpatient prosthetic surgery used at our hospital are attached. ([Figure 1])

Fig. 1 Exclusion criteria for primary total knee arthroplasty.

Finally, a cost analysis was performed for both groups with the data obtained by the institution's finance department, according to the local occupied bed days (OBD) value, considering 2 days of hospitalization.

Care and Surgery Protocol

Before surgery, a prophylactic dose of intravenous antibiotics and tranexamic acid are administered. Spinal anesthesia is used whenever possible. During surgery, an ischemia cuff is placed on the thigh from the start, which is deflated after the cement sets. This is applied using the vacuum cementation technique and gun pressurization. At the end of the operation, the anesthesiologist performs a peripheral adductor canal block, primarily aimed at blocking the saphenous nerve. Subsequently, if no complications arise that would modify outpatient management, a follow-up x-ray is requested. Once the anesthesia wears off and the patient can stand and walk with the support of a walker or cane, a physical therapist visits the patient and, if everything is in order, the patient can be discharged home.

In the outpatient management protocol, patients are assigned seven physical therapy and rehabilitation sessions with the physical therapist scheduled every other day. In addition, nurses assess and apply dressings as needed, while physicians intervene if an emergency referral or early medical follow-up is required.

Regarding medical follow-up, the first check-up with the surgeon takes place 7 days after surgery, and a second check-up is scheduled between days 14 and 21, during which any necessary staples or stitches are removed.

Results

During 2022, a total of 347 primary TKAs were recorded.

The average age was 68 years, with 73% being women. The main comorbidities included high blood pressure, diabetes, and dyslipidemia. A similar demographic distribution was observed between the two groups.

In the outpatient group, 267 primary TKAs were performed, with an average follow-up of 21 months. A total of 10 emergency department visits were observed within the first 7 postoperative days, with the main causes being pain and bleeding ([Table 1]). Additionally, 18 reinterventions were recorded (12 arthrofibroses, 3 infections, 2 periprosthetic fractures, and 1 arthroscopic cement removal).

Table 1

Reason for consultation	Ambulatory	Hospitalized
Bloody bandages	1	2
Other bleeding	3	1
COVID-19	1	0
Pain	2	1
Other cause, not related to arthroplasty	3	1

In the hospitalized group, 80 primary TKAs were performed, with the same follow-up and an average hospital stay of 48 hours. Five emergency department visits were recorded within the first 7 postoperative days. Regarding reinterventions, there were 9 cases (8 arthrofibroses and 1 case of patellar clunk).

No deaths were reported in either group.

In economic terms, the outpatient group had an average savings of USD 1,034 per patient, accumulating a total savings of USD 276,130 during the study period.

Discussion

This study is positioned as a pioneer in Chile in examining the safety and economic benefits associated with outpatient total knee replacements. Among the most notable findings is a comparable and even favorable safety rate compared to outpatient procedures, with no increase in postoperative complications. Furthermore, significant cost savings are observed for both users and the healthcare system.

Effectiveness and Safety of Ambulatory TKA

TKA is a successful and safe procedure, constantly seeking to evolve its technology, implants, and techniques, including faster and more aggressive rehabilitation protocols.

The study results indicate that both outpatient and inpatient total knee arthroplasty are viable options within their respective patient groups. In the outpatient group, a low number of emergency department visits and a moderate reoperation rate were observed, suggesting that this approach is safe in carefully selected patients. On the other hand, the inpatient group also showed favorable results, although with higher associated costs due to the hospital stay.

Regarding patient selection for the outpatient procedure, systematic reviews highlight that education, exclusion of patients with comorbidities, multimodal anesthesia, and social support are key factors for the success of an outpatient procedure.[15]

There is a consensus that careful patient selection is critical for the safety of outpatient TKA, with the ideal patient being relatively young and healthy, with strong social support. However, given the lack of objective criteria and agreement to determine which patients can safely undergo outpatient TKA, risk assessment scales have been developed, such as the Outpatient Arthroplasty Risk Assessment (OARA) by Ziembra-Davis et al. This tool stratifies patients into nine areas of comorbidity to generate a risk category ([Figure 2]). Its applicability and clinical correlation have been evaluated, and it has been compared with other scoring systems. One example is a study in which 2,051 primary TKAs were analyzed. An OARA score of up to 79 was found to have a positive predictive value of 98.8%, a specificity of 99.3%, and a false-positive rate of 0.7% in identifying patients who can safely undergo outpatient TKA, providing a more standardized system for patient selection.[16] Our initial approach did not use a scoring scale to determine candidate patients; instead, selection was based on the aforementioned exclusion criteria. However, upon retrospective analysis of the data, we observed that all patients who underwent outpatient TKA had OARA scores below 79 points, suggesting that this tool could be useful in the future to standardize patient selection.

Fig. 2 Outpatient Arthroplasty Risk Assessment score (OARA).

Among other improvements, advances in multimodal anesthetic procedures, such as peripheral nerve blocks, have been successful in reducing pain and opioid-related complications.[17] In our case series, all patients underwent multimodal anesthesia, including peripheral nerve blocks, thus avoiding the use of general anesthesia and facilitating an outpatient procedure.

Early readmissions or consultations in the emergency department are a critical consideration in outpatient total knee arthroplasty, as patient safety and proper recovery must be the primary focus. One study conducted a review of the US registry using the American College of Surgeons' National Surgical Quality Improvement Program (NSQIP). A complication rate of 8% was reported in outpatient TKAs. This study highlighted that there was no increase in readmission or reintervention rates in outpatient procedures, suggesting that these factors do not constitute an increased risk for postoperative complications.[18]

A review of 439 outpatient TKAs performed at a specialized center for this type of procedure found a low rate of complications (1.4%) and hospital readmissions (0.7%), with an average length of stay of 500 minutes, with an operative time of 136 minutes and 201 minutes until ambulation. It is also notable that almost a third of the study patients were ASA III.[19] Upon reviewing this center's practice, we found a multimodal and coordinated approach, supported by the previously discussed concepts regarding patient selection, anesthetic advances, and multidisciplinary support.

Compared to our caseload, we had a higher complication and reintervention rate of 3.7% and 5.9%, respectively, despite our multidisciplinary and multimodal management practices. This leads us to believe that strengthening systems and promoting specialization within the clinical center is important, but strengthening education, patient preparation, and proper selection are essential to reduce the complication rate.

It is noteworthy that within our study population, the outpatient group had a lower rate of early consultation in the emergency department (3.7% vs. 6.2%) and a lower rate of reoperation (5.9% vs. 8.7%) than the hospitalized group. This difference can be inferred from the pre-selection of patients for each group based on comorbidities, prior functionality, and ability to cooperate to be a candidate for the outpatient procedure.

Economic Impact of Outpatient TKA

Evaluating the economic impact and actual savings of performing outpatient TKA is a complex task, as it involves considering multiple factors. These include inherent differences between regions and municipalities, healthcare systems, population characteristics, insurance type and reimbursement rates, as well as individual patient preferences. All of these elements must be taken into account when analyzing the cost and feasibility of outpatient arthroplasty.

Bertin et al. highlighted the savings of performing outpatient arthroplasty (hip replacement surgery in this case) by comparing 10 outpatients with 10 inpatients, observing that the average bill was USD 4,000 lower for the outpatient group.[20] On the other hand, Aynardi et al. compared 119 patients who underwent outpatient arthroplasties with 78 inpatients, finding that the average final cost for outpatients was almost $7,000 lower than for inpatients.[21] A meta-analysis by Bemelmans et al. shows a decrease in costs in favor of the outpatient procedure, with variations between different centers in the U.S. The average cost was approximately USD 6,800, with a range from USD 2,500 to $21,000, indicating that comparisons between centers and countries are difficult, especially with long-term follow-up. Even so, the outpatient option remains the one with the lowest associated cost, both for the patient and the institution.[22]

Lovald et al. presented a study on the length of hospital stay in patients with TKA, classified into four categories: outpatient (less than 24 hours), 1 to 2 days, 3 to 4 days, and more than 5 days. Outpatients and those with a stay of 1 to 2 days generated savings of USD 8,527 and USD 1,927, respectively, compared to patients with a stay of 3 to 4 days.[5]

Our case series is aligned with the literature, estimating savings of USD 1,034 per patient. Although this amount is consistent with what has been described in other studies, it is lower due to the base costs of the Chilean healthcare system compared to other systems. In local currency (CLP), the total savings recorded during the study period in 2022 was approximately $262,000,000. This amount could be redirected to other needs of the hospital. Furthermore, the 267 outpatient cases contributed to bed availability throughout the year, allowing their use for other patients. These factors translate into significant savings for both the hospital and the healthcare system.

As seen in previously cited international studies, in appropriately selected patients, the current literature highlights the potentially significant cost savings of arthroplasties performed on an outpatient basis. It will be crucial to conduct additional studies, especially those that compare costs in detail, breaking down all aspects of hospitalization, and using larger samples. It is estimated that by 2026, outpatient TKA will account for half of all arthroplasties in the United States, with a clear trend toward this approach in other countries.[23]

The transition from inpatient surgery to an outpatient procedure is a process that requires prior study and analysis. In the U.S., this transition has been implemented through the Centers for Medicare and Medicaid Services (CMS). The key to this transition lies in appropriate patient selection, considering their medical history, home environment, prior functional status, and personal motivation before surgery. This is just one of many aspects to consider, along with a multidisciplinary approach that includes physical therapy and home nursing services. Finally, an important aspect to consider is discharge time, as procedures performed in the afternoon are often preferred for inpatient care.[24]

Implementation of outpatient ATR in Chile

After analyzing the global literature and our results, which confirm that the procedure can be performed safely, providing benefits for both the patient and the healthcare system, the need arises to implement and promote it in various centers. In this context, the question arises: how can we carry out this task effectively?

Social factors and the home environment can significantly influence the success of outpatient surgery.[25] These factors should be assessed both before and after the procedure. One example is the recommendation to smokers to stop smoking before surgery, as smoking has been identified as a significant risk factor for same-day discharge and postoperative complications following outpatient arthroplasty.[26] [27] [28] Another key aspect is the availability of a responsible person at the time of discharge, who can help transport the patient, receive discharge documentation and collaborate in postoperative care.[29] [30] The health literacy level of the patient and their support network are also crucial, as low literacy has been associated with higher rates of early consultations and hospital readmissions after surgery.[31] [32]

These factors are of great importance when promoting the development of outpatient TKA, especially considering that the Chilean public health system primarily serves patients of moderate or low income, who sometimes lack social support and adequate health literacy. Although this is a gradual process, to promote the advancement of outpatient TKA, the focus must be on strict and appropriate patient selection, thorough pre- and post-surgical preparation, and a multidisciplinary team where all members collaborate smoothly and effectively. This team must be supported by a robust and well-trained home hospitalization program, ensuring the program's success and safety.

Limitations

One of the main limitations of this study is that the outpatient and inpatient groups are not directly comparable, which limits the possibility of drawing definitive conclusions about the superiority of one approach or the other. The primary objective of the study was to describe the outcomes within each group, and future studies with more robust designs are needed to make more precise comparisons. The retrospective observational design introduces the possibility of bias that could affect the results. This limits the validity of the conclusions, as patient assignment to the groups was not random, which may lead to an unrepresentative distribution of complications or reinterventions.

Furthermore, the study only included TKA cases, excluding unicompartmental arthroplasties, which could lead to incorrect generalization of the results when applying them to other types of arthroplasties. Although a cost analysis was conducted, the economic perspective presented may be limited, as indirect or long-term costs associated with outpatient TKA were not considered, potentially underestimating or overestimating the true economic impact of this approach. Finally, although costs associated with the procedure were recorded, these are specific to the Chilean context, which could limit the applicability of the findings to other health systems with different cost structures.

Future prospective studies, with more robust designs and randomized comparison groups, will allow a more precise evaluation of the safety, costs, and functional outcomes of ambulatory TKA in different settings.

Conclusion

This study provides a detailed description of the outcomes of TKA in both an outpatient and inpatient setting. Although the groups differed in their characteristics, the results suggest that both approaches were safe and effective within the selected groups, supported by substantial cost savings in the outpatient group. Future studies could focus on refining patient selection for each approach, which may be a valuable strategy for addressing waiting lists and optimizing resources in the Chilean healthcare system.

Conflicto de Interés

Los autores declaran no tener conflicto de intereses y nada que revelar.

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Publication History

Received: 20 December 2024

Accepted: 02 April 2025

Article published online:
20 May 2025