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Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_11 | Pages 142 - 142
1 Jul 2014
Mohaddes M Malchau H Herberts P Johansson P Kärrholm J
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Summary Statement

We analysed impaction bone grafting used together with cemented or uncemented fixation in acetabular revision surgery. The overall risk for re-revision did not differ between the cemented and uncemented group. However, aseptic loosening was more common in the cemented group.

Background

Several surgical techniques address bone defects in cup revision surgery. Bone impaction grafting, introduced more than thirty years ago, is a biologically and mechanically appealing method. The primary aim of this study was to evaluate the effect of bone impaction grafting when used with uncemented and cemented fixation in cup revision surgery. Uncemented cups resting on more than 50% host bone were used as controls.


Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_11 | Pages 201 - 201
1 Jul 2014
Rowell S Reyes C Malchau H Muratoglu O
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Summary

Four highly cross-linked UHWMPEs except vitamin E-stabilised explants

Introduction

The development of both first and second generation highly cross-linked material focused on stabilizing radiation-induced free radicals as the sole precursor to oxidative degradation; however, secondary in vivo oxidation mechanisms have been identified in both conventional and highly cross-linked UHMWPE, induced by absorbed lipids and cyclic mechanical load. Retrieval studies are reporting in vivo oxidation highly cross-linked retrievals with up to ten year in vivo durations. Preclinical aging tests did not predict these in vivo material changes. With only a decade of these materials in clinical use, retrieval studies are limited to mid-term follow-up. In vitro studies face a challenge in effectively replicating the precise in vivo conditions that lead to this loss of oxidation resistance. In this study, we bypass replicating these in vivo variables by examining surgically-retrieved components, thereby testing material that has been affectively “pre-conditioned” by their in vivo service. After a preliminary post-operative analysis, we subjected retrievals to accelerated aging tests in order to predict the extent to which their oxidative stability had been uniquely compromised in vivo.


Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_11 | Pages 202 - 202
1 Jul 2014
Rowell S Estok D Kreuzer S Malchau H Muratoglu O
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Summary

Sequentially irradiated and annealed UHMWPE hip and knee retrievals showed subsurface in vivo oxidation in both the articular surface and unloaded surfaces, while three of four never-implanted shelf stored liners had oxidation in the bulk.

Introduction

Highly cross-linked polyethylene was developed to improve the wear resistance of UHMWPE bearing surfaces in total hip arthroplasty. First generation irradiated and annealed polyethylene showed high oxidation in vivo, largely attributed to only the partial-quenching of free radicals, along with additional radicals generated during terminal gamma sterilization. A second generation, three-step sequential irradiation and annealing method was advanced with the promise of better oxidative stability and improved mechanical properties. We hypothesised that without the complete elimination of free radicals combined with gas plasma sterilization requiring oxygen-permeable packaging, that this second generation material would be prone to shelf-oxidation in addition to in vivo oxidation.