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.
