Aseptic loosening and infection are the most common causes for revision THAs. Revision due to fracture and instability were much less common in our center. Studies from Finland, Sweden, and the United States [15,17-19] have reported aseptic loosening as the leading reason for revision. With improved tribology and surface coating techniques, the proportion of aseptic loosening in revision THAs is decreasing in western countries. Clohisy et al. [20] and Ulrich et al. [19] reported data from their respective centers in 2004 and 2008, respectively, where the proportion of aseptic loosening in revision THAs was 55% and 52%, respectively. In 2016, Haynes et al. [21] showed that aseptic loosening only accounted for 31.3% of hip revision cases. In our center, revisions due to aseptic loosening have increased over the last 20 years. Total hip arthroplasty was performed in the late 1990s in our country. Poor surgical techniques and improper implant selection were the main reasons for aseptic loosening. Clohisy et al. [22] reported that cemented prostheses had a higher rate of loosening than uncemented prostheses, indicating the importance of cementing surgical techniques and implant design [23-25]. For the bearing surface, the early design of non-crosslinked polyethylene had higher wear and revision rates [26,27]. Surgeons should attempt to increase the durability of primary arthroplasty by improving their surgical techniques and selecting a well-documented prosthesis for their patients.
Infection and instability are significant complications that lead to revision, mainly noted in the early postoperative period. The proportion of revisions for infection has decreased in 10 years, between 2009 and 2019, at other centers. Lachiewicz et al. [28] published a retrospective review of two cohorts of 100 consecutive revisions performed 10 years apart by one surgeon. For the early cohort, the indications for infection were 10% compared with 7% in the recent cohort. However, the proportion of infection-related revisions was 17.3% in the present study, which is higher than that seen in other studies [21]. There was a selection bias in our center, as doctors in rural areas may miss the treatment window for debridement and prosthesis retention when facing acute peri-prosthetic infection. Patients were referred to our hospital when infection was chronic with persistent pain or sinus formation. A two-stage revision was the treatment of choice for chronic infection. Peri-prosthetic infection was difficult to manage, with high chances of re-revision. This was demonstrated in our study by the observed high chances of infection in revision cases. Doctors should avoid delaying an acute infection until it becomes chronic by treating patients following the Musculoskeletal Infection Society guidelines [29]. We expect a decrease in infections due to improved prophylaxis for periprosthetic joint infection and delicate surgical manipulation [30].
We found that infection and aseptic loosening were the most common reasons for multiple revisions, indicating treatment difficulties in facing these types of failures. Jafari et al. [31] analyzed 1,366 revision THAs and reported that 256 of these revisions failed, mainly due to infection (30.2%), instability (25.1%), and aseptic loosening (19.4%), with an average time to failure of 16.6 months. Springer et al. [32] reported that the most common reasons for failure in 141 patients requiring a second revision were instability (35%), aseptic loosening (30%), and infection (12%). Interestingly, we had limited cases of revisions for instability. Surgical approach and surgeon experience may affect THA stability [33]. Our proportion of THA failure due to instability was lower than that in the reports from the United States. Bozic et al. [34] published a retrospective study using the Healthcare Cost and Utilization Project Nationwide Inpatient Sample database, which included 51,345 revision THA cases from October 2005 to December 2006. The results showed that the most common causes of revision were instability/dislocation (22.5%), mechanical loosening (19.7%), and infection (14.8%). Gwam et al. [35] used the National Inpatient Sample database to identify all revision THA procedures performed in the 5 years between January 2009 and December 2013. They also discovered that the most common indications for revision THA in the United States were dislocation (17.3%) and mechanical loosening (16.8%). However, there was a lower instability-induced revision incidence in the present study, which may be explained by the following two reasons: intraoperatively, when facing hip instabilities, surgeons tend to increase soft tissue tension by increasing leg length or offset, and postoperatively, stricter and longer posture protection contributes to reducing joint dislocation rate. These management techniques sacrifice the hip range of motion, thus helping reduce hip dislocation chances. However, when patients have less range of motion in the hip, they have to compensate by recruiting more spine motion for daily activities, leading to more lumbar pain [36]. The high proportion of hip revisions due to instability in the United States reminds surgeons to modify their practice to provide high-quality medical services, such as using a direct anterior approach for faster postoperative rehabilitation [37]. Furthermore, patients may benefit from the use of larger femoral head sizes, elevated or lipped liners, high-offset femoral stems, and dual mobility implants to improve hip stability and maintain an adequate range of motion.
As our hospital is located in a city center, transportation remains a challenge for patients with periprosthetic fractures; therefore, the number of patients with periprosthetic fractures is relatively low in the present study. Zheng et al. [38] reviewed patients with Vancouver type B peri-prosthetic fractures in two departments of a single, large hospital in China from 2008 to 2016. The results showed that all fractures healed in the surgical treatment group. Internal fixation for B2 and B3 fractures requires more prolonged healing and has relatively poorer mobility postoperatively than revision THA.
The present study revealed a higher rate of revisions due to infection among patients aged less than 60 years and higher proportions of aseptic loosening, periprosthetic fracture, and instability among those aged 60 years or more. The characteristics of each disease entity may explain this finding. Older patients experience more aseptic loosening, which is a long-term postoperative complication. Infection may occur at any time postoperatively, primarily in the early postoperative period. Cnudde et al. [13] reported that reoperation in the early postoperative period (90 days) was primarily due to infection or dislocation, according to SHAR.
Our study has several limitations. First, this was a retrospective study; therefore, we were limited to evaluating data that have already been collected. We were unable to identify the details of each failure mode, and the limited level of knowledge of the disease at the time of surgery may have caused misdiagnoses or underdiagnoses. We attempted to find all possible data to minimize this limitation. Furthermore, some revision surgery details were not compared due to the heterogeneity of revision surgeries, and the authors did not evaluate the survivorship of these revision surgeries. These theoretical assumptions should be proven in future clinical studies. Second, as this was a single-center study, we used the institutional database, which only included patients who were treated at our center. This may have caused a selection bias and may not represent revision THA prevalence in a wider area. A local or national database will be necessary for more precise information and to obtain a comprehensive understanding of the national situation regarding THA. Third, data on cases of infection did not provide a distinction between those that occurred in those with one-stage and two-stage surgery. Fourth, as many patients underwent primary THA in other institutions, we were unable to obtain all information regarding patients' index procedures. The establishment of a national arthroplasty registration database will help solve this problem. Further efforts are necessary to improve the details of each revision case to obtain more in-depth research results.