Evaluation of Total Ankle Arthroplasty Using Highly Crosslinked Ultrahigh-Molecular-Weight Polyethylene Subjected to Physiological Loading.

Background: Highly crosslinked polyethylene (HXLPE) was developed for its superior wear properties in comparison to conventional polyethylene (CPE). Concern over fatigue resistance has prevented widespread adoption of HXLPE for use in total ankle arthroplasty (TAA). The aim of this study was to determine whether HXLPE has sufficient fatigue strength for total ankle arthroplasty under simulated physiologically relevant motion profiles and loading in the ankle.
Methods: Physiologic load and motion profiles representative of walking gait were incorporated into a computational model of a semiconstrained, fixed-bearing TAA to determine the loading state with highest stresses in the HXLPE bearing. Subsequent fatigue testing to 10 million cycles (Mc) at 5600 N was performed to assess bearing strength.
Results: Peak stresses in the bearing were predicted at peak axial load and peak dorsiflexion during gait, occurring near heel off. All samples withstood 10 Mc of fatigue loading at that orientation without polyethylene bearing fracture.
Conclusion: HXLPE had sufficient fatigue strength to withstand 10 Mc of loading at more than 5 times body weight at the point of peak stresses during simulated gait in total ankle arthroplasty.
Clinical Relevance: HXLPE may be mechanically strong enough to withstand the in vivo demands of the ankle. Improvements in wear afforded by HXLPE can be obtained without compromising sufficient polyethylene strength properties in total ankle arthroplasty.