The association of polyethylene insert thickness in primary medial unicondylar knee arthroplasty on survival, reason for revision and patient-reported outcomes measures. A Dutch arthroplasty register study
Approval date: February 13th 2026
WR Six, RCI van Geenen, SBT Bolder, I. Koenraadt - van Oost, A. Nijs, C Dijkman
Unicondylar knee arthroplasty (UKA) offers advantages over total knee arthroplasty (TKA), including better preservation of native biomechanics and superior patient-reported outcomes. However, concerns about higher revision rates persist. The main reason for revision in uncemented medial UKA include lateral osteoarthritis progression, tibial component loosening, periprosthetic fractures and instability. Insert thickness is determined by tibial resection depth and perioperative instability, thicker inserts may indicate excessive bone removal or soft tissue laxity, while too thin inserts can compromise stability. Despite the clinical significance, the impact of PE insert thickness on UKA outcomes remains poorly documented.
This study evaluates whether polyethylene (PE) insert thickness in UKA is associated with patient-reported outcomes, survival rates and reason for revision in patients with medial knee osteoarthritis. Our hypothesis is that favourable PE inserts (x±1 mm, x=desired insert thickness) will have a significantly lower revision rate compared to non-favourable/thick PE inserts (x≥+2mm, x=desired insert thickness) in UKA.
The study will analyse data from the LROI registry, including medial UKAs (both mobile and fixed bearing) performed for osteoarthritis from registry inception through 2024. Only prostheses with ODEP ratings of 5A or higher will be included to minimize device-specific confounding factors. Patients with prior high tibial osteotomy will be excluded.