Keywords
total knee replacement - national survey - surgical technique - cementation technique
Introduction
Total knee replacement (TKR), one of the most frequent orthopedic surgeries in the
world, improves the quality of life of patients with advanced-stage gonarthrosis.[1]
[2] In Chile, the prepandemic TKR rate (2019) was of 28.2 per 100 thousand inhabitants,
corresponding to more than 5 thousand procedures per year.[3] The current waiting list for TKR in Chile is the second largest in the country according
to the Chilean Ministry of Health,[3] suggesting that both the TKR rate and the absolute number of procedures must increase
in the short term.
Some countries have national registries or information regarding the technique used
for TKR (such as Australia, New Zealand, Norway, Sweden, the United States, and the
United Kingdom).[4]
[5]
[6]
[7]
[8]
[9] However, in Latin American countries, there are no national registries to help us
understand our local reality. The only published record is from the Latin American
Society of Arthroscopy, Joint Reconstruction, and Sports Trauma (Sociedad Latinoamericana
de Artroscopía, Reconstrucción Articular y Trauma Deportivo, SLARD, in Spanish), which
encompasses several countries on the continent.[10]
The present study aimed to determine current TKR trends in Chile by analyzing different
technical aspects among knee surgeons performing this procedure and comparing them
with registries published by other countries.
Materials and Methods
We conducted a national survey concerning TKR for specialized surgeons working in
Chile to know their experiences and preferences. The survey was composed of multiple-choice
questions, and respondents had to choose only one alternative in each question. These
questions were mainly based on four aspects: general features, preoperative study,
surgical technique, and cementation technique ([Annex 1]). Surveys not answered in full were excluded.
We located the surgeons using the membership record of the Chilean Committee of Arthroscopic
Surgery and Knee Joint Replacement. We sent the survey via cell phone or email using
the Google Forms platform. The responses were recorded on the same platform and then
transferred to a Microsoft Excel (Microsoft Corp., Redmond, WA, United States) spreadsheet
for subgroup analysis and stratification according to years of experience (YOEs),
always preserving the anonymity of the participants.
Lastly, we compared the data obtained with those published in national registries
from the countries that have said registries, and with those obtained from the survey
carried out among SLARD members.
Results
We obtained 87 complete surveys from 192 participants at the time of completion (45%
of respondents). [Annex 1] shows the individual results of each answer to the multiple-choice questions.
Regarding General Features
Most respondents performed 25 to 50 TKRs per year (44%), with only 16% performing
more than 75 cases annually.
Only 20% used the outpatient modality; however, among them, almost half reported doing
so with a low frequency (less than 20% of their cases). In total 43% of the respondents
believed TKRs must always be performed in a hospital setting. This opinion was more
frequent among surgeons with more YOEs (< 10 YOEs: 33%; > 20 YOEs: 62%). Overall,
37% stated that they do not do that because of the lack of appropriate infrastructure.
Most respondents (81.6%) used a posterior cruciate ligament-sacrificing (posterior-stabilized,
PS) system. The posterior cruciate-retaining (CR) system was used more often when
associated with a robotic system (ROSA [Zimmer Biomet Robotics, Montpellier, France]
and CORI [Smith & Nephew, London, United Kingdom]).
The use of robotic systems reached a rate of 18%, with a higher frequency among surgeons
with more YOEs (< 10 YOEs: 13%; > 20 YOEs: 35%). The most used systems were the ROSA
and CORI (by 85% of surgeons who use robotic systems).
Concerning the Chilean Explicit Health Guarantees (Garantías Explícitas en Salud, GES, in Spanish) program, 90% of the respondents believe it must incorporate TKR,
with no differences in terms of YOEs.
Regarding the Preoperative Study
Most respondents (56%) performed the radiographic study in the anteroposterior, lateral,
axial and Rosenberg views, as well as teleradiography. A total of 14% and 31% of the
participants did not report the routine use of teleradiography and the Rosenberg view
respectively.
The use of the mechanical axis in preoperative planning was reported by 93%; 69% defined
the cutting angle in the distal femur according to the difference between the mechanical
and anatomical axes, while 11.5% always used the same angle degrees, regardless of
axis differences.
Regarding the Surgical Technique
Regarding the surgical approach, 96.6% used the medial parapatellar approach, and
2.3% (2 surgeons) chose the approach depending on the case.
To determine the rotation of the femoral component, 78% of the surgeons used more
than one reference. Most surgeons who used a single reference chose the epicondylar
axis (16.3%).
The responses regarding patellar replacement presented a high variation, with no marked
trend toward any option; the frequency of the six alternatives ranged from 15% to
27%. In total, 41% of the surgeons tended to replace the patella (in 80% to 100% of
their operated cases), while 42.5% tended not to do so (in 0% to 20% of their operated
cases). The remaining respondents (16.1%) answered “sometimes” (in 50% of their cases).
There were no relevant differences when comparing the responses according to YOEs.
The extramedullary guide was used by 82% to address the tibia, and 80% used the gaps
system to check stability in flexion-extension before placing the definitive components,
with no differences per YOEs.
Regarding tourniquets, 34.5% of the surgeons did not use them, and 12% turned the
device on only during cementation. The remaining surgeons (about 50%) used it during
most of the procedures. Among them, most used the device until the components were
set (31% of all respondents). There were no differences regarding YOEs.
Most surgeons began implant placement from the tibia (74.8%), while 12.6% started
with the femur, and 12.6%, with the patella. The most frequent sequence was tibia-femur-patella
(72.4%).
A total of 81% of the surgeons waited until the cementation set before checking the
stability of the knee, while 12% did not wait to evaluate it.
Regarding the Cementation Technique
Vacuum systems for cementation were used by 31%, especially those surgeons with fewer
YOEs (< 10 YOEs: 36%; > 20 YOEs: 20%), as shown in [Image 1]. Most surgeons (95.4%) used cement in the components and the bone before its final
placement, and the remaining 4.6% placed the cement only in the implant, with no differences
in terms of YOEs.
Image 1 Use of vacuum cementation per years of experience.
There was a marked trend to place cement on the keel, with only 15% of the respondents
not doing so. Most respondents placed the cement with their finger (56.1%) or a spatula
(18.3%); only 22% of surgeons used a gun for placement. Most surgeons (95.3%) performed
cementation in 1 stage, and only 3.5%, in 2 stages.
Most aspects evaluated presented important differences in the comparison with the
national registries from other countries and more similarities with the SLARD registry
(especially regarding the surgical technique).
Discussion
The main strength of the present study was the development, as far as we know, of
the first record concerning TKR performance in Chile. This procedure is performed
with increasing frequency; in Chile, the rate per 100 thousand inhabitants constantly
increased in the last decade, going from 6.4 in 2010 to 28.2 in 2019.[3] This increase only stopped because of the coronavirus disease 2019 (COVID-19) pandemic,
but rates are once again rising at a fast pace. Despite this, we still do not have
a Chilean registry to help us objectify and better understand fundamental aspects
of surgery and how we are performing TKRs. The presented study achieved a rate of
45% of responses within the target population (the Chilean Committee of Arthroscopic
Surgery and Knee Joint Replacement). This may seem like a low number, but it is critical
to consider that many Chilean knee specialists do not have much experience with prosthetic
surgery. As a result, we expected a high loss when carrying out the survey. This fact
explains why it is reasonable to infer that the response rate among surgeons dedicated
to prosthetic knee surgery was much higher.
Regarding general features, we found that 67% of surgeons in Chile performed fewer
than 50 TKRs per year. This result is consistent with those of registries from countries
such as New Zealand and the United Kingdom, but not with the SLARD registry. In New
Zealand, 33% of the surgeons reported performing more than 40 TKRs per year. In the
United Kingdom, 34% performed fewer than 25 TKRs per year, and only 12% performed
more than 100 TKRs per year. In Latin America, the SLARD study reported that 54% of
surgeons performed fewer than 30 TKRs per year, which seems to be a lower number compared
with those of our study, since only 24.1% of the participants reported operating fewer
than 25 TKRs annually.[10]
The present study shows that the number of surgeons performing TKR on an outpatient
basis remains low, with only 12% of them doing it frequently. In fact, there still
seems to be some apprehension about it, since almost half of the participants believe
this option deserves no consideration. The national registries published do not report
the percentage of outpatient TKRs, so we cannot make an objective comparison. However,
some studies have reported a dramatic increase in outpatient TKR performance, from
0.2% of cases in 2017 to 36.4% in 2019 in the United States.[11] In any case, we can infer that the trend in Chile may change over time, since younger
surgeons are the ones who consider this option most frequently. In addition, in countries
like the United States, Medicare and Medicaid eliminated TKR reimbursement only for
hospitalized patients in 2018, and already cover the procedure for patients undergoing
outpatient surgery.[12]
The use of robotic systems has increased in Chile in recent years, which can be observed
by the rate of 18% of respondents who reported using some technological system. This
does not mean that 18% of TKRs are robotic, so we cannot compare it with data from
other registries. For instance, the Australian registry showed that 60% of TKRs in
2021 were performed with some kind of assistance, such as navigation, robotic systems,
or image-derived instrumentation (IDI), and the American registry[8] reported 14.7% of imaging-assisted TKRs in 2022 ([Image 2]). We can say that Chile has a higher number of surgeons using these systems compared
to Latin America per the SLARD registry (5%). We can also state that, in Chile, robotic
systems are used more frequently by more experienced surgeons (35% versus 13%), which
is probably related to the greater access to these systems in the private sector,
which has a higher percentage of surgeons with more than 20 YOEs.
Image 2 Imaging-assisted surgery.
Most Chilean surgeons use the PS system (81.6%) in TKRs, contrasting with Sweden (CR:
96%; PS: 4%), Australia (CR: 76%; PS: 15%; medial pivot: 9%), and New Zealand (CR:
78%; PS: 18%)[4]
[5]
[7] ([Image 3]). The Australia and New Zealand registries mentioned using the CR system to a greater
extent due to a slightly lower revision rate compared with that of the PS. In Chile,
we do not have published studies comparing the CR and PS systems, only reports of
non-comparative cohorts.[13]
[14] As a result, the choice still relies on personal experience. Although there was
an association regarding CR component use with the ROSA robotic system, this occurred
because one of the groups using a robotic system (per the survey) previously used
CR-type prostheses.
Image 3 Prosthesis per stability system.
Regarding the surgical technique, most surgeons use a medial parapatellar approach
(96.6%), which is consistent with international registries.
The decision to perform patellar replacement has always been controversial, with countries
like the United States and Australia showing high replacement rates, ranging from
92% to 94% and 76% respectively. However, other countries record very low rates, including
New Zealand (35%), Norway (7%), and Sweden (4%). The present study showed that 41%
of the surgeons tend to replace the patella in most cases, which is more in line with
the data from the SLARD study (approximately 50%).[10] The decision remains surgeon-dependent, based on local experience, as demonstrated
by the Australian registry, which showed a slightly higher revision rate in patients
operated on without patellar replacement, which motivated their surgeons to change
their conduct around 2010.[4]
Regarding tourniquets, approximately 65% of the respondents used them at some point
during surgery. This trend was consistent with the SLARD study and it was also very
similar to the Norwegian registry, which reported a 61% usage rate in 2020. However,
worldwide, the records are very variable; for instance, in the United States,[6] a study reported a 100% usage rate in 2010,[15] while Sweden recorded a 28% rate in 2021.[7]
Finally, regarding the cementation technique, we observed that only 31% of the surgeons
use vacuum systems; however, this frequency is higher among younger surgeons. Although
there are not many publications about this issue, a survey answered in 2022 by 903
knee surgeons in the United States showed that 80% used vacuum systems during TKR.[16] The literature is somewhat contradictory regarding the benefit of using vacuum systems,
since some studies showed more cement penetration into the bone,[17] while others did not observe many differences.[18] As such, we still do not have clear guidelines regarding which technique to use,
which is why the use of vacuum systems is not yet popular in many countries (including
Chile).
Conclusion
There is high variability in the performance of knee arthroplasties in Chile, with
some trends similar and others very different from registries from other countries
and greater consistency with the Latin American SLARD registry. In general terms,
regarding different YOEs, there are no major differences in the surgical technique,
although there are differences in the cementation technique and use of robotic systems.
