Failed mechanisms of ultra high molecular weight polyethylene for tibial malresection in unicompartmental knee arthroplasty

The advanced development of knee prostheses has nearly become the final and major treatment for degenerative arthritis. However, previous clinical studies of unicompartmental knee arthroplasty (UKA) have found that complications caused by the wear of polyethylene (PE) tibial components remain a problem. Therefore, the prevention and reduction of PE tibial component damage is the focus of this study. Tibial plateau malresection is the most common problem in performing UKA and it often causes malposition of the tibial implant. Malposition is most likely the main reason of accelerating the wear and dislocation of PE tibial components. Therefore, this study employed in vitro simulation to investigate the stress changes of PE tibial components in malposition and to further understand damage to PE tibial components. From the study results of in vitro simulation analysis, unicompartmental knee prostheses (UKP) had the best performance in tibial posterior slope at 5°. In varus/valgus malresection, varus was not affected by changes of angle. Anatomical UKP had better performance. Anatomical UKP should avoid malresection of valgus angle exceeding 5° while symmetrical UKP should avoid malresection of valgus angle exceeding 10°, otherwise it would accelerate the wear of PE tibial components and shorten UKP lifespan.