Document Detail

An investigation into PEEK-on-PEEK as a bearing surface candidate for cervical total disc replacement.
MedLine Citation:
PMID:  22964013     Owner:  NLM     Status:  In-Data-Review    
BACKGROUND CONTEXT: Total disc replacement (TDR) is a relatively new reconstructive non-fusion technology for the spine that aims to overcome some of the limitations of fusion technology. The first generation artificial discs were mainly based on well-known material combinations from total hip replacement.
PURPOSE: To evaluate the feasibility of PEEK-on-PEEK as a bearing surface material for use in cervical TDR.
STUDY DESIGN: In vitro biotribological study including the assessment of different parameters, including the influence of radial clearance, axial load, and angular motion on the wear performance of a PEEK-on-PEEK bearing.
METHODS: PEEK-on-PEEK bearing couples with ball-and-socket articulation were prepared using standard production methods. Two groups of bearing couples, one with large radial clearances and the other with small radial clearances, were manufactured for testing. Wear tests were performed using a servo-hydraulic wear simulator that allowed controlled motions to be applied in three axes corresponding to flexion-extension, lateral bending, and axial rotation. In addition, a dynamic axial compressive load was applied to simulate the weight of the head. All tests were performed at 37°C (±2°C) in bovine calf serum with a 30 g/l protein concentration. In the first test series, the influence of the radial clearance on the wear behavior was evaluated using the load and motion parameters for cervical TDR as defined in the ISO standard 18192-1. Subsequent tests were performed to check if surface degradation was influenced by thermal effects. Finally, in a third series of tests, the effect of load and motion profiles on wear performance was investigated by applying increased loads and corresponding motion parameters for lumbar TDR as defined in the ISO standard 18192-1.
RESULTS: The measured wear rates for a PEEK-on-PEEK bearing under cervical test conditions were considerably larger than those of similar testing using UHMWPE-on-CoCr and seemed to depend on initial radial clearances. The PEEK bearing surfaces exhibited severe surface degradation for large and small clearances, but the group with smaller clearances seemed to have less severe damage. Thermal effects were not found to play a role in the surface degradation, as the temperature near the bearing surface was measured and found to vary only a few degrees during testing. A change of the wear test parameters to simulate lumbar loading resulted in a considerable wear rate reduction as well as in the preservation of the bearing surfaces.
CONCLUSIONS: It was found that a cervical TDR using a PEEK-on-PEEK bearing may be subjected to severe long-term degradation of the bearing surfaces. In this study, the use of PEEK as an articulation material for cervical TDR was found to be sensitive to loading conditions as well as to the initial clearance of the bearing surfaces. Despite the excellent properties of PEEK as an implant material, its use for articulating surfaces for cervical TDR must be critically reviewed.
Markus Kraft; David K Koch; Michael Bushelow
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The spine journal : official journal of the North American Spine Society     Volume:  12     ISSN:  1878-1632     ISO Abbreviation:  Spine J     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-09-11     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101130732     Medline TA:  Spine J     Country:  United States    
Other Details:
Languages:  eng     Pagination:  603-11     Citation Subset:  IM    
Copyright Information:
Copyright © 2012 Elsevier Inc. All rights reserved.
Synthes GmbH, Eimattstrasse 3, CH-4436 Oberdorf BL, Switzerland.
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