RESUMEN
This study examined retrieved UHMWPE tibial bearings made from a remelted highly crosslinked (HXL) UHMWPE to determine whether the material is chemically stable in vivo. Retrieved tibial components were measured for changes in ketone oxidation and crosslink density. Oxidation increased with in vivo duration, and a significant decrease in crosslink density with increased mean ketone oxidation index was observed. These results suggest that in vivo oxidation is causing material degradation. Furthermore, a subsurface whitened damage region was found below the articular surface of one bearing, indicating the possibility of a clinically relevant decrease in mechanical properties of this component. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 39-45, 2017.
Asunto(s)
Polietilenos , Tibia , Animales , Oxidación-Reducción , Polietilenos/química , Polietilenos/farmacocinética , Polietilenos/farmacología , Tibia/lesiones , Tibia/metabolismo , Tibia/patología , Soporte de PesoRESUMEN
This study seeks to identify important factors related to backside wear of tibial inserts in vivo and determine an appropriate wear model for backside wear. An IRB approved database was queried for tibial inserts of a single design from one manufacturer that exhibited evidence of rotatory motion on the backside of the polyethylene. These devices were measured for volumetric wear using a previously established protocol. Features including the change in locking lip width and measurement of micro-motion marks were used to describe the motion pattern. Volumetric wear and implant characteristics were compared using linear regressions by modeling wear theories suggested by Archard and Wang to determine the most appropriate model for backside wear. The Wang model showed that duration, adjusted sliding distance, and cross-shear index accounted for approximately 58% of the volumetric wear variation while adjusted sliding distance and duration in vivo accounted for approximately 35% of the volumetric wear variation in the Archard model. Patient weight (p = 0.750), patient BMI (p = 0.680), and backside area (p = 0.784) of the tibial insert were all found to be non-significant in the Wang model. Similarly, patient weight (p = 0.233), patient BMI (p = 0.162), and backside area (p = 0.796) were found to be non-significant in the Archard model. Multidirectional micro-motion appears to contribute significantly to the wear of these components, supporting the Wang theory of cross-shear for polyethylene wear. Cross-shear of polymers on an unpolished titanium tray can lead to an increase in wear debris in the body. Care should be taken when designing locking mechanisms and tray designs. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1933-1940, 2016.