An Evaluation of Retrieved UHMWPE Hip Joint Cups

Abstract

In this study it is demonstrated that the combined chemical and mechanical influences of the implant situation cause property changes of ultra-high-molecular-weight polyethylene (UHMWPE) hip joint cups. Nearly 250 loosened hip cups, retrieved 3 weeks to 14 years after implantation, were investigated. The clinical long-term behavior of various shaped polyethylene hip sockets are statistically analyzed. The main damage features were defined and described. Density measurements show a density increase with implantation time and a dependence of these changes from implant position and loading conditions. The rate of extractable constituents also increases with course of time. An increased in vivo conditioned oxidation of the UHMWPE can be demonstrated by infrared (IR) spectrometry. The density increase can be explained by post-crystallization, which is the result of oxidative chain scission. This leads to a reduction of the average molecular weight of the PE and to an increased extractability of constituents. Since these changes have been recognized as the reasons for aging and failing of UHMWPE, the methods of material characterization used in this study for retrieved implants will help to develop suitable in vitro testing and simulating methods. Characteristic damage features of hip cups allow direct relationships with construction characteristics and their improvement.

Endosomal damage and TLR2 mediated inflammasome activation by alkane particles in the generation of aseptic osteolysis

“…Even though UHMWPE oxidation has been described by several groups [3,4,9,12] we originally reported that the oxidize alkane polymers, within 10 to 16 carbon atoms are by far more immunogenic in TLR1/2 stimulation that the non oxidize counterpart [5]. Herein we complement the previous data with further experiments indicating that TLR1/2 engagement induces a pro-inflammatory transcription program mediated by NFkB signaling pathways, inducing the expression of pro-IL-1β and pro-IL-18.…”

In Vivo Oxidation of UHMWPE

“…Researchers began to investigate in vivo degradation of polyethylene in the 1980s but were not able to relate the changes they observed with clinical performance [8][9][10]. Researchers began to investigate in vivo degradation of polyethylene in the 1980s but were not able to relate the changes they observed with clinical performance [8][9][10].…”

Precoating of ultrahigh molecular weight polyethylene with polymethylmethacrylate: Interfacial strength

“…3,34,38,39 Therefore, the metal-backed cup, which is designed to reduce the stresses in the bone-bone cement the bone cement. 15,16,18,32,47 In the study by Wroblewski et al, 16 the emphasis of a need for secure adhesion between interface, would be ineffective. Furthermore, studies on metal-back cups revealed that preservation of some elasticthe surface of the UHMWPE and PMMA bone cement was stressed for the improvement of prosthesis fixation in the ity lost from hard metal shell liners is necessary for longterm success.…”

“…6,7 This showed that what is believed to be a weak mechanical property of bone cement is not a cause for the acetabular cup due to unnecessary introductions of stress concentrators. 47 For long-term efficacy of the THR, it is eventual failure in acetabular components but rather from an imperfect interface in the fixed sites. In cemented THR, necessary and perhaps essential that other effective means of fixation be developed.…”