In this study, we found that the most frequent reason for the revision was infection (38.6%), followed by aseptic loosening (28.1%) and instability (10.1%). Infection (56.1%) and aseptic loosening (49.4%) were the most frequent reasons for early and late revisions. The reasons for revision TKA have changed over the last decade, and the numbers of infections have decreased combined with the increase of aseptic loosening.
With a growing number of TKA, the number of revisions increases. The revision risk at 10 years in the major Arthroplasty registries is reported to be about 5%: the Australian Joint Replacement Report stated a 5.5% revision rate after 10 years[9]; for the UK[14], the reported revision rates are below 5% and slightly more than 5.5% for Sweden[10]. The revision causes, however, are different from those listed in the published data, see Table. 2.
In 2002, Sharkey did a retrospective review for reasons of revision TKA. They found that the most common reason for failure among the patients was polyethylene wear, followed by aseptic loosening, instability, and infection[2]. In 2010, using the Nationwide Inpatient Sample database, Bozic found that the most common causes of revision TKA were infection (25.2%), followed by implant loosening (16.1%)[15]. However, over the last decade, failure mechanisms have changed and polyethylene wear as a revision cause decreased combined with the increase of infection. In 2014, 12 years after their first article, Sharkey et al. found a dramatic decrease in the rate of polyethylene wear as the cause of revision. Infection and aseptic loosening were still the most common reasons of revision TKA[6]. In the latest article, Geary reported a 30-year experience of revision TKA and found that the leading cause for failure was infection (38.5%), followed by aseptic loosening (20.9%) and instability (14.2%)[16]. Our result showed that the reasons for revision TKA in China were comparable to those in this study.
In this study we found that reasons for early and late revisions were different. In early revisions, the most frequent reason for the revision was infection followed by instability and Patellar complications. As for late revisions, the most frequent reason for the revision was aseptic loosening, followed by infection and instability. Several studies had reported the difference between early and late revision. Infection and aseptic loosening were the leading reasons for early and late revisions. Infection was the most common reason for revision TKA. The American registry even tops this number by 63% infections accounting for early failures (<3 months from the primary procedure)[17]. Aseptic loosening is the second most common reason for revisions, and unlike infection, it occurred frequently throughout follow-up. Many risk factors contributed to aseptic loosening, and most of them need a long time to come into play[18]. Moreover, some patients had a higher tolerance for this symptom, which prolonged the diagnostic time.
Over the last decade, with the development of surgical technique and advancement in prosthesis design, failure mechanisms have changed. In this study, we found that the numbers of infections have decreased combined with the increase of aseptic loosening. Several studies reported the increasing of aseptic loosening and decreasing of instability[6]. We compiled literature from a 20-year period and found that the revision rate of aseptic loosening before 2010 was low combined with a high proportion of instability. (See table 2) After 2010, the proportion changed. Such improvements in stability following TKA may be attributable to advancements in the operative technique, the development and increased utilization of posterior stabilized prostheses may also be responsible. Loosening of the prosthesis is related to TKA component fixation methodology. There is still a debate concerning optimal fixation, which includes the cement technique and the use of cementless components. Although perioperative prophylactic antibiotics and other anti-infection modalities have been widely utilized in primary TKA, infection is still one of the most common major complications, the most difficult to treat, and the most expensive complication related to joint replacement surgery.
In our center, 7 patients received revision TKA because of the diagnosis of pain. The rate of pain in published articles was low and some articles did not include this diagnosis. However, in the registries of New Zealand, Norway, England, Wales, Northern Ireland, and the Isle of Man, high rates of revision due to unexplained pain have been reported, with an incidence as high as 29.4% observed in New Zealand knee revisions[19]. However, the registries system may not have detailed information about revisions. Patients who suffered from instability, patellar complications or even low-grade infection might be misdiagnosed with pain. Some authors agree with the common sense that revision operations should only be performed if the cause(s) of the complaints described have been identified and fit the clinical picture, as revision surgery for unexplained pain has consistently been shown to result in poor outcomes[20, 21].
We acknowledge the strengths and limitations of this study. Firstly, it is one of the first studies to determine the cause of revisions in China, as there is no registry system in China. Our single-center study filled the gap for the lack of research in this area in China. Secondly, we garnered detailed information about all previous revisions, which made our diagnosis more accurate. We believe that our data are representative of tertiary care centers.
However, most patients were referred to our department and we did not have complete baseline information on the primary TKA. Furthermore, we collected the operation time which was not always the precise time to failure. Time to failure is usually less than the operation time, which may lead to bias to the group study. We were not able to get detailed information about all previous revisions in all cases. Thus, we could not account for the potential effect of other patient characteristics that might be strongly associated with TKA failures, such as patient comorbidities, preoperative deformities, functional status, activity level, socioeconomic status, and education level. In some cases, more than one reasons lead to revision and we categorized the patients into the leading revision cause. Our study was a single-center study, which may lead to selection bias in patients, a case that is unlikely to occur for multi-center or joint replacement registry studies. However, there are no joint registry systems in China, and studies focused on this field in China were limited. Further multi-center or registry system studies with detailed information focused on the revision TKA are still needed in China.