2025 ISAKOS Biennial Congress ePoster
Fractures In Oxford Unicompartmental Knee Arthroplasty Are Associated With A Decreased Medial Keel Cortex Distance Of The Tibial Implant – A Combined Clinical And Biomechanical Study
Julius Watrinet, MD, Dr. med. GERMANY
Sabrina Sandriesser, PhD, Murnau GERMANY
Rolf Schipp, MD, Garmisch-Partenkirchen GERMANY
Wolfgang Reng, MD, Garmisch-Partenkirchen GERMANY
BG Trauma Center Murnau, Murnau, GERMANY
FDA Status Cleared
Summary
Periprosthetic fractures in Oxford Unicompartmental Knee Arthroplasty are strongly associated with a decreased medial keel-cortex distance and the use of smaller tibial implant sizes, highlighting the importance of careful implant sizing and positioning to minimize fracture risk.
ePosters will be available shortly before Congress
Abstract
a. Introduction
This retrospective single-center study aimed to investigate factors influencing tibial periprosthetic fractures in Oxford Unicompartmental Knee Arthroplasty (UKA), with a specific focus on the association between tibial component sizing and positioning and the occurrence of fractures.
b. Methods
A total of 2063 cases of medial UKA using the Oxford® mobile partial knee implant were analyzed between July 2014 and September 2022. Various preoperative and postoperative radiographic parameters determining initial alignment and implant positioning as well as patient demographics were assessed. A synthetic bone model of the proximal tibia was manufactured and tibial component were implanted according to manufactures guidelines. Load was applied through an artificial medial femur condyle type Oxford on the medial tibia plateau trough a fitting mobile bearing and maximum load to failure [N] was documented. Mann-Whitney U tests was conducted to identify significant differences between groups.
c. Results
Of the 1853 cases included in the study, 19 patients experienced fractures. The fracture group presented with a significantly shorter relative mediolateral and posteroanterior distance between the keel and cortex (mediolateral: fracture: 23.9% ± 2.1%; no-fracture 27.0% ± 2.1%, p < 0.001, posteroanterior). Furthermore, the use of smaller-sized implants (AA) was associated with higher fracture rates (p < 0.001). Maximum load to failure was significantly lower in tibial implant size AA (Median 1035N (Q1 970N – Q3 1100N)) compared to tibial implant size A (Median 1165N (Q1 970N – 1100N), p = 0.031).
d. Conclusion
This study reveals that tibial periprosthetic fractures in Oxford UKA are significantly associated with shorter mediolateral keel-cortex distances and the use of smaller implant sizes, particularly size AA. The biomechanical testing corroborated the clinical findings, showing that smaller tibial component sizes, specifically size AA, have a reduced load to failure compared to larger sizes.