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Clinical fracture of cross-linked UHMWPE acetabular liners

Paper ID Volume ID Publish Year Pages File Format Full-Text
8925 610 2009 11 PDF Available
Title
Clinical fracture of cross-linked UHMWPE acetabular liners
Abstract

Highly cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is increasingly used as a bearing material in total hip replacements. Cross-linking of UHMWPE has been shown to increase wear resistance but decrease its fracture resistance. We analyzed the clinical fracture failure of four cross-linked UHMWPE total hip replacement components of four different designs via microscopic observation of the fracture surfaces, and found that in all cases fractures initiated at stress concentrations in an unsupported region of the component (termed the elevated rim). Finite element analyses (FEA) of each individual implant design were then conducted. Results from this analysis demonstrated that the predicted magnitude and orientation of maximum principal stress due to mechanical loading of the elevated rim was sufficient to propagate initiated fatigue cracks in each case. FEA also predicted that cracks may arrest after some amount of growth due to a steep stress gradient near the initiation site. Further, while anatomical positioning of the implant and material properties affect the risk of fracture, we examined whether these failures are strongly related to the notched elevated rim design feature that is common to the four failed cases presented here. We believe that cross-linked UHMWPE remains an excellent bearing material for total hip replacements but that designs employing this material should mitigate stress concentrations or other design features that increase the risk of fracture.

Keywords
Acetabular liner; UHMWPE; Notch fatigue; Fractography; Crosslinking; Fracture
First Page Preview
Clinical fracture of cross-linked UHMWPE acetabular liners
Publisher
Database: Elsevier - ScienceDirect
Journal: Biomaterials - Volume 30, Issue 29, October 2009, Pages 5572–5582
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering