Summary

Patients with rheumatic diseases do not carry an increased risk for revision surgery in total knee arthroplasty.

Abstract

Background

Rheumatic diseases and their treatments can be associated with an increased susceptibility to infections, reduced bone quality, and a higher rate of osteoarthritis. Due to the increased rate of osteoarthritis, patients with rheumatic diseases are more likely to need joint replacement surgery, such as total knee arthroplasty (TKA). However, whether these patients are also more likely to need revision surgery following TKA remains unknown.

Purpose

The aim of this study was to compare the risk of revision surgery in patients with rheumatic diseases with primary TKA with that of patients without rheumatic diseases.

Methods

Using data from the German Endoprosthesis Register (EPRD), 12,674 cases of primary unconstrained TKA in patients with rheumatic diseases (RAs) were compared with 399,578 cases of primary unconstrained TKA in patients without rheumatic diseases (Non-RAs) over an 8-year period.
Revisions were categorized based on the surgical and procedural codes (OPS) recorded in the registry into major revisions (replacement of any bony implant component) and minor revisions (no replacement of bony implant component), including secondary patellar replacement.
The cumulative risk for these procedures was analyzed overall, as well as separately for septic and aseptic revisions, using the Kaplan-Meier estimator. Differences in the revision rates between RAs and Non-RAs were tested for statistical significance using the Log-Rank test. Additionally, the rates of cases with patellar replacement at primary implantation in both groups were compared and tested for statistical significance using the Wilcoxon and Chi-square tests.

Results

The cumulative risk for major revisions in RAs with primary unconstrained TKA after 8 years was 2.9% ( 95% confidence interval [CI] 2.5–3.5) and 2.5% (CI 2.2–3.0) for minor revisions. In contrast, Non-RAs had a risk of 2.5% (CI 2.4–2.6, p = 0.05) for major revisions and 2.7% (CI 2.6–2.7; p = 0.3) for minor revisions.
The analysis, stratified by septic and aseptic revisions, showed no significant differences in the risk of revision surgeries for RAs in septic major (1.0% vs. 0.7%; p = 0.08) and minor (0.7% vs. 0.6%; p = 0.2) revisions, as well as aseptic major revisions (2.0% vs. 1.8%; p = 0.2). Aseptic minor revisions, including secondary patellar replacement, were the only cases where a small but statistically significant difference was found between RAs and Non-RAs, in favor of RAs (1.9% vs. 2.0%; p = 0.03).
RAs received significantly more patellar replacements during the primary implantation compared to Non-RAs (RA: 17%, Non-RA: 14%; p < 0.001).

Conclusion

Patients with rheumatic diseases do not carry an increased risk for revision surgery in total knee arthroplasty. However, the rate of primary patellar replacement is significantly higher among these patients compared to those without rheumatic diseases.