Epidemiology and Risk Factors for Revision Total Knee Arthroplasty in Chinese Patients: A Retrospective Study in Changchun, Jilin Province, China

Introduction

Total knee arthroplasty (TKA) has become the most effective treatment for patients with end-stage knee osteoarthritis, either primary or secondary, and rheumatoid arthritis with severe pain and disabilities [1,2]. While the indications of TKA have been broadened to include younger and more active patients in the past decade, the demand for this procedure is projected to increase substantially [3,4], as is the need for revision TKA in the future [5,6]. As the salvage procedure when TKA fails, revision TKA, although reported to be reliable and cost-effective, generally remains a substantial clinical challenge for orthopedic surgeons and their patients, with inferior outcomes and higher cost than primary TKA [7,8]. Therefore, illumination of the causes of revision TKA is essential for improving surgical performance and minimizing the risk of failure [3,9].

Although multiple epidemiological studies and national registration data are demonstrating that the primary reasons for revision TKA in Western countries are infection, aseptic loosening, instability, wear, and pains [10–12], only a few studies have clarified the causes of failure after TKA in Asian patients, with heterogeneous results from different areas. Kasahara et al reported that the most common cumulative reason for TKA failure in Japan was loosening (40%), followed by infection (24%), wear (9%), and instability (9%) [3]. Koh et al reported that the major reason for the failure of TKA in Korea was infection (38%), followed by loosening (33%), wear (13%), and instability (7%) [5]. Prince et al reported that infection (74%), loosening (13%), periprosthetic fracture (6%), and instability (4%) were the most common failure mechanisms in India [13]. The observed differences in results can be attributed to variations in patient demographics and lifestyles [3,14].

Although the use of TKA in China has increased substantially over the past decades [15,16], owing to the lack of a joint registry, limited data were reported from China regarding the cause of TKA failure. Moreover, as the demographic trends have diverged from those of Western countries, the modes of TKA failures in China can also be different. We therefore aimed to (1) investigate the etiology of TKA failures in a cohort of Chinese patients and (2) determine the related demographic and anthropometric risk factors, such as body mass index (BMI), smoking history, age, and sex in Jilin, China, to examine the actual situation.

Material and Methods

ETHICS APPROVAL:

Approval was obtained from the Institutional Review Board of the Second Hospital of Jilin University (No.20200710). All methods were conducted in accordance with the relevant guidelines and regulations. Written informed consent and consent for publication were obtained from all participants.

STUDY DESIGN AND POPULATION:

We conducted a retrospective analysis of all primary TKAs and revisions performed at the Provincial Orthopedic Center (Orthopedic Medical Center of the Second Hospital of Jilin University) in Changchun, Jilin Province, China, between April 1, 2014, and May 31, 2022. During this period, 1927 (1437 patients) primary TKAs and 109 (107 patients) revision TKAs were performed. All the patients provided informed consent for surgery and data collection. Each orthopedic surgeon at the institution was board-certified and had over 15 years of experience in TKA.

DATA COLLECTION:

The study collected patient demographics, such as age and sex, anthropometric measures, such as BMI, and important clinical information, such as smoking history. We also obtained the interval from the primary TKA to the revision procedures, as well as whether the primary TKA was performed at our institution or referred from elsewhere.

The mechanisms for primary TKA failure were discussed and determined by 2 experienced surgeons based on the review of an entire history, radiographic investigations, clinical examination, intraoperative findings, inspection of the explanted components, and the results of blood examination and tissue cultures, referring to the standardized definitions of TKA revision reasons (Table 1). Patients who underwent revision TKA were then assigned to groups according to the reason for revision, classified in the following 7 categories: infection, aseptic loosening, stiffness, periprosthetic fracture, instability, extensor mechanism insufficiency, and malposition. For patients with more than one reason for the revision, we used the primary surgeon’s determination of the main failure mechanism. For patients who underwent revision TKA more than once, the first-time revision reason was used for analysis. All revision TKA patients were categorized into early and late failure groups based on the time interval between primary TKA and revision procedure, using 2 years as the cut-off point [17].

STATISTICAL ANALYSIS:

To statistically evaluate the influence of patient demographic features on the causes of revision TKA, we randomly selected 107 patients from 1437 primary TKA patients as the control group to match the 107 patients with revision TKA, as conducted before [3]. Then bivariable and multivariable analyses were performed to compare demographic and anthropometric variables between primary and revision TKA patients. Chi-square tests were used to compare categorical variables, and unpaired t tests were used to compare continuous variables. Multivariate logistic regression was used to account for potentially confounding variables. Age, sex, BMI, and smoking history were considered as explanatory variables in the model. All statistical analyses were performed by the authors (Y.S., J.L., and J.W.) using SPSS 26.0 (IBM Corp, Armonk, NY, USA).

Results

In 107 revision TKA patients, primary TKAs were performed in only 19 patients (17.8%) at our center; 88 patients (82.2%) were referred to our center for revision; 27 knees were revised more than 1 time, and 80 patients had just 1 surgery. Among the revisions, the average interval from primary to failure was 2.0 years (14 days to 17 years); most patients (77/107, 72.0%) had revision TKA procedures within 2 years after the primary TKA, with an average interval to revision of 0.7 years (14 days to 1.8 years); 30/107 (28.0%) revision TKAs were performed beyond 2 years after the primary TKA, with an average interval to revision of 5.1 years (2–17 years). Although the proportion of male patients was higher (23.4%) in the revision TKA group than in the primary TKA group (20.6%), there was no statistically significant difference between the 2 groups (P=0.62). The average age of the revision group was 63.8±9.2 years which was similar to that of the primary TKA group (66.7±11.7 years, P=0.07). The average BMI of the revision TKA group was 25.7±3.7 kg/m2, which was not significantly different from that of the primary TKA group (25.4±3.87 kg/m2, P=0.39). The observed proportion of patients who smoked in the revision group was significantly higher than that in the primary TKA group (17/90 vs 7/100, P=0.03) (Table 2).

The leading failure mechanism in the overall revision group was infection (53.3%), followed by aseptic loosening (21.5%), stiffness (15.0%), instability (3.7%), malposition (2.8%), periprosthetic fractures (2.8%), and extensor mechanism disruption (0.9%). In the early revision group, the leading cause of revision was infection (59.7%), followed by stiffness (18.2%) and aseptic loosening (13.0%). In the late revision group, aseptic loosening (43.3%), infection (36.7%), and stiffness (6.7%) were the main reasons for TKA failures. Infection was the most common reason for failure in the early revision TKA group (59.7%), whereas in the late revision TKA group, it was the second most prevalent cause (36.7%). Although stiffness was the second most common reason for early revision (18.2%), it was the third most common reason for late revision TKA (6.7%) (Figures 1, 2).

Considering the demographic differences between the primary TKA group and each subgroup within the revision TKA group, there was a significantly higher (P=0.04) percentage of male patients in the infection subgroup (20/57, 35.1%) than in the primary TKA group (22/107, 20.6%). In addition, infection was more frequently seen in the patients who smoked (11/46, P=0.01) (Table 3). Multivariate logistic regression revealed an increased risk of revision TKA for infection in male patients (OR=4.87; 95% CI, 1.67–14.21; P=0.04). Although there was no significant difference, patients with high BMI appeared to have a slightly increased risk of TKA revision for periprosthetic fracture (OR=1.55; 95% CI, 0.99–2.43; P=0.06) (Table 4).

Discussion

While the incidence and modes of TKA failure have been well described in Western countries and some other Asian countries [3,5,18], the etiology and causes of revision TKA in China were seldom reported. This study demonstrated that the revision TKA incidence in a provincial orthopedic center in China was 1.3% (19/1437) in the last 8 years, with infection (53.3%), aseptic loosening (21.5%), and stiffness (15.0%) as the most common TKA failure mechanisms in this area, which could be affected by patient demographic features such as sex and smoking.

Our study indicated that the major causes for revision TKA in Jilin, China, were similar to those in other areas. In Korea, Koh et al reported that infection (38%), aseptic loosening (33%), and polyethylene wear (13%) were the most common reasons for revision TKA [5]. In the United Kingdom, Hossain et al analyzed 349 cases of revision TKA and found that infection (33%) and aseptic loosening (15%) were the main modes of failed TKA [19]. In Japan, Kasahara et al reported that the most common revision reasons were aseptic loosening (40%), infection (24%), osteolysis/wear (9%), and instability (9%) in a study of 140 patients who had revision TKA. The reason for the different results reported by Japan may be the different lifestyle of the patients. Japanese individuals frequently engage in squatting and kneeling postures, which are risk factors for knee osteoarthritis and mechanical loosening [3]. Although infection, aseptic loosening, and stiffness have been identified as common causes of revision TKA, the causes of TKA failure in specialized centers are likely to be different from population-based registries [20]. In the registries of the United Kingdom (28.2%) and Australia (24.5%), aseptic loosening is the most frequent reason for revision TKA, followed by infection (19.2% and 23.9%, respectively) [12,21]. The reason for the high frequency of periprosthetic joint infection (PJI) in single/multi-center studies might be that TKA revisions related to PJI are generally considered extremely complicated and expensive [22,23]. Meanwhile, revisions related to aseptic loosening and other mechanical drawbacks might be considered “simple” revisions and tend to be performed in local hospitals, whereas PJI-related revisions are more frequently referred to specialized orthopedic centers with experience and sufficient resources [20,24]. This also explains why the proportion of patients with PJI in the present study was higher than that reported in some other studies.

The predominant failure mechanisms of TKA in this study focused on infection, aseptic loosening, stiffness, instability, periprosthetic fracture, malposition, and extensor mechanism disruption, while they did not include patella resurfacing, malalignment, and periprosthetic wear as the causes of TKA failure. Our institute does not perform patella resurfacing routinely, as patellar resurfacing remains a controversial issue in primary TKA, and there was no superiority found of patellar resurfacing or non-resurfacing in terms of clinical or radiological outcomes [25–27]. Malalignment was not included in the present study, because the full-length weight-bearing radiographs of the whole lower extremity were not routinely taken after the primary TKA at our institute. Therefore, we could not clarify the changes in the femoral and tibial components’ alignment and thus were unable to clearly determine whether the components had a malalignment during the follow-up. It has been generally accepted that polyethylene wear activates osteolysis, results in a gradual loosening of the implant, and even becomes the most common etiology for TKA failure [28]. However, with the development of more resilient biomaterials, polyethylene wear is no longer one of the most common indications for revision TKA [17,28]. Noticeable polyethylene wear was identified in only 2 cases (2.8%) in the present study and was classified as aseptic loosening, following previous study principles [29].

The average interval from primary TKA to failure of the early revision TKA group was 0.7 years (14 days to 1.8 years) and 5.1 years (2–17 years) for the late revision group, similar to the results reported by other countries. In a single-center retrospective study of 781 revision TKAs performed in the United States, Sharkey et al found that the average time between primary and revision TKA was 0.8 years (1 day to 2.0 years) in the early failure group, and 6.9 years (2.0–30.4 years) in the late revision TKA group (≥2 years) [17]. Mulhall et al reported that the mean interval between the primary procedure and early failure was 0.9 years (±0.5 years) and 9.9 years (±5.3 years) for late failure (≥2 years) in a multicenter prospective study of 318 patients with failed TKAs [30]. The cause of TKA failure changes over time. Our study showed that infection was the most common cause of failure for patients who underwent revision TKA in less than 2 years and second to aseptic loosening in late failures. Stiffness was identified as the second most common failure mechanism in the early revision group, while it was rare in the late revision group, comparable with the findings reported in other countries [11,14]. Meanwhile, aseptic loosening accounted for 13.0% in the early revision group, while it increased to 43.3% in the late revision group.

Patient demographic features seem associated with the cause of revision TKA in Jilin, China. The percentage of patients who smoked in the infection subgroup was higher than that in the primary TKA group (P=0.01) in the present study. This finding agreed with the results reported by Huttunen et al, who demonstrated that smokers were at increased risk of surgical infection [31]. Moreover, male sex was identified as a risk factor for TKA-related infection (P=0.04), and the percentage of male patients in the infection group was higher than that in other subgroups (OR=4.87; 95% CI, 1.67–14.21; P=0.04), as determined by multiple logistic regression analysis. This is consistent with the study conducted by Kasahara et al in Japan, which indicated that male patients were more susceptible to infection than female patients, as the smoking rate is significantly higher among Japanese men than women [3]. Similarly, the smoking rate of male patients (20.1%) in the present study was higher than that of female patients (5.3%). However, there was no significant difference in BMI between the revision TKA group and primary TKA group, although some studies reported obesity (BMI >30 kg/m2) could be a risk factor for TKA failure [32]. This conflict might be the differences in the degree of obesity of the population in different countries. In this study, the proportion of patients who were obese was only 14.0%, like the study performed in Japan, with the percentage of obese patients relatively small, suggesting BMI may not affect the revision TKA burden in Asian countries [3]. Alarmingly, even before any failure occurs, higher BMI and smoking have been reported to be associated with improvement in postoperative poor quality of life following primary TKAs [33].

It is important to note some limitations of this study. First, due to this being a single-center retrospective study, our analysis was limited to patients who had undergone primary and revision TKA within this institute. In other words, the study’s sample size is insufficient for making a comprehensive evaluation to determine the etiology and risk factors of TKA failures in China. However, although there were only 1927 primary TKA and 109 revision TKA procedures, we did include all cases performed in the only provincial and major orthopedic center in Jilin Province, China, over a long period (8 years) between April 1, 2014, and May 31, 2022, and there were no missing data for all patients. Moreover, considering the data of the multi-center study is provided from many different surgeons who might have different judgement for categorizing the revision causes [6,12,20], our study, with the possibility to review the patients’ records, gave a more clear and detailed picture of the failure causes with less diagnostic suspicion bias, especially in the situation for patients with more than 1 reason for TKA revision, in which the primary failure mechanism should be determined. It is essential to note that this study provided a reference and original data for relevant multi-center studies, which are being performed by the authors and should be critical for investigating the actual situation in China. Second, we did not consider the influence of the primary implant used in the revision TKA group. In this study, 88 revision TKA patients (82.2% of our cohort) were referred from external institutions. As different implants were used by surgeons with various experience and surgical skills, it would have been difficult to assess and compare the impact of the different types of implants [3]. Third, although this study did not include malalignment as one of the TKA failures, it is necessary to note that implant alignment outliers are extremely common following TKA, even among highly experienced high-volume fellowship-trained arthroplasty surgeons at high-volume academic centers [34,35]. In a study by Kazarian et al, 31.0% of 1570 primary TKAs had at least 1 outlier measurement (femoral coronal angle, tibial coronal angle, tibial sagittal angle, distant femoral angle, proximal tibial angle, or posterior tibial slope angle) [34]. As implant alignment outliers have a statistically significant impact on implant survival, risk of TKA failure, and patient satisfaction [36,37], future studies should focus more on the malalignment measurements to analyze TKA failure mechanisms. Finally, a power analysis was not performed before the study was initiated, thus the number of patients may need to be improved to assess instability, periprosthetic fracture, malposition, and other causes of failure properly; that is, there was a risk of a type II error.

Conclusions

This study demonstrated that infection, aseptic loosening, and stiffness were the most common etiologies of primary TKA failure over 8 years for patients who underwent revision TKA at our institute, a provincial orthopedic center in China. Infection was the leading mechanism of early failure and second to aseptic loosening in patients revised longer than 2 years before. Male sex and smoking history were associated with the incidence of TKA-related infection. Although there seemed an increased risk of periprosthetic fracture in patients with high BMI, BMI was not a contributing factor to the failure of TKA in this retrospective study. We provided a look at the TKA failure mechanisms and etiology in China; however, considering the substantial increase in TKA use in the past decades, multi-center studies and population-based registry data would help draw a clearer picture of the current situation.