Archives of Orthopaedic and Trauma Surgery - 2026-03-04 - Journal Article
Data from the Swiss National Arthroplasty Registry SIRIS suggest that unicompartmental knee arthroplasty is associated with a lower risk of periprosthetic joint infection than total knee arthroplasty.
Wahl P, Brand C, Christen B
Topics
Key Takeaway
UKA carries half the PJI revision risk of TKA (HR 0.53, p<0.001), but implant-retaining revision for PJI fails in approximately one-third of cases for both implant types.
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Summary
Using SIRIS registry data, this study compared PJI revision rates and implant-retaining revision failure rates between primary UKA and TKA. UKA had a significantly lower PJI revision rate (HR 0.53, p<0.001) despite a higher overall revision rate (HR 1.29, p<0.001). Implant-retaining revision (debridement with isolated inlay exchange) failed in 34.8% of UKA and 32.1% of TKA cases, with a non-significant trend toward faster failure in UKA (HR 1.56, p=0.099).
Key Limitation
The registry does not capture PJI diagnostic criteria, infecting organism, antibiotic regimen, or timing of infection onset, preventing any analysis of whether outcome differences reflect patient selection, microbiology, or surgical factors.
Original Abstract
INTRODUCTION
Periprosthetic joint infection (PJI) remains a severe complication in arthroplasty. Unicompartmental knee arthroplasty (UKA) may have lower PJI rates than total knee arthroplasty (TKA) because of smaller implants and less extensive surgical exposure. However, PJI treatment after UKA is challenging due to restricted debridement and limited options for local antibiotic delivery. This study compared the revision rate for PJI and the failure rate of implant-retaining revision for PJI between UKA and TKA in the Swiss national joint registry (SIRIS).
METHODS
A retrospective analysis was conducted using SIRIS data from 2012 to 2024, examining the first revision after primary UKA or TKA and the re-revision rate after debridement with isolated inlay exchange for PJI. Both analyses assessed revisions for any cause and specifically for PJI. Kaplan-Meier survival curves and hazard ratios (HR) were calculated.
RESULTS
Among 35’286 primary UKA and 188’952 primary TKA, 149 and 1’546 were revised for PJI, respectively. Revision rates for any cause were higher for UKA than TKA (HR 1.29, p < 0.001), whereas PJI-related revisions were about half as frequent (HR 0.53, p < 0.001). Following implant-retaining revision for PJI, repeat revision rates increased more rapidly for UKA than TKA, reaching 34.8% and 32.1%, respectively (HR 1.56, p = 0.099). The statistical precision for UKA was limited by small numbers.
CONCLUSIONS
In SIRIS, the revision rate for PJI after primary UKA was about half that after primary TKA, while the revision rate for any cause was higher. These findings support the hypothesis that smaller implants and less extensive surgery may be associated with lower infection risk. Despite limited debridement options, implant-retaining revision for PJI after UKA was as successful as after TKA. Nonetheless, failure rates for such procedures remain high in Switzerland, at roughly one-third.
SUPPLEMENTARY INFORMATION
The online version contains supplementary material available at 10.1007/s00402-025-06156-5.