High early failure rate for a new unicondylar knee system

This single-center retrospective study evaluated early failure rates for an unicompartmental knee arthroplasty (UKA) system with an anti-allergic surface.

We studied 87 consecutive joints received an UKA at a single center between 2017 and 2020. All patients received a fully cemented anti-allergic Univation-Aesculap partial knee replacement implant with a corundum blasting surface. All joints had precise indication of unicompartmental arthroplasty according to the current criteria of this procedure. The current series was restricted to patients undergoing medial cemented UKA. Medial compartment osteoarthritis was the main indication.

We found early failure (aseptic loosening) was documented in 20 of the 87 joints (23%). The time to failure ranged from 7 weeks to 3 years, for an estimated 33% (15-46%) cumulative hazard rate for implant loosening over three years. No cases of periprosthetic joint infection were found. On average, the patients began complaining about first symptoms during the third month after surgery. In most cases (66.66%), the cement remained fixed to the bone.

Based on these early results, the manufacturer of this implant stopped all further distribution. Continued efforts should be made to understand the clinical and radiographic outcomes of alternative and anti-allergic surface coatings in knee arthroplasty.