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Comparison of metal-on-metal hip simulator wear measured by gravimetric, CMM and optical profiling methods

Comparison of metal-on-metal hip simulator wear measured by gravimetric, CMM and optical profiling methods
Comparison of metal-on-metal hip simulator wear measured by gravimetric, CMM and optical profiling methods
Simulation of wear in artificial joint implants is critical for evaluating implant designs and materials. Traditional protocols employ the gravimetric method to determine the loss of material by measuring the weight of the implant components before and after various test intervals and after the completed test. However, the gravimetric method cannot identify the location, area coverage or maximum depth of the wear and it has difficulties with proportionally small weight changes in relatively heavy implants. In this study, we compare the gravimetric method with two geometric surface methods; an optical light method (RedLux) and a coordinate measuring method (CMM). We tested ten Adept hips in a simulator for 2 million cycles (MC). Gravimetric and optical methods were performed at 0.33, 0.66, 1.00, 1.33 and 2 MC. CMM measurements were done before and after the test. A high correlation was found between the gravimetric and optical methods for both heads (R 2  =  0.997) and for cups (R 2  =  0.96). Both geometric methods (optical and CMM) measured more volume loss than the gravimetric method (for the heads, p  =  0.004 (optical) and p  =  0.08 (CMM); for the cups p  =  0.01 (optical) and p  =  0.003 (CMM)). Two cups recorded negative wear at 2 MC by the gravimetric method but none did by either the optical method or by CMM. The geometric methods were prone to confounding factors such as surface deformation and the gravimetric method could be confounded by protein absorption and backside wear. Both of the geometric methods were able to show the location, area covered and depth of the wear on the bearing surfaces, and track their changes during the test run; providing significant advantages to solely using the gravimetric method.
Alberts, L. Russell
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Martinez-nogues, Vanesa
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Baker Cook, Richard
b87155e8-2dcb-4c3f-a4de-52fcf36b5f95
Maul, Christian
c19cb80b-1d13-451d-83df-36f244f9d9db
Bills, Paul
153d69fc-ebf6-4ddf-9596-6a9691b35ec8
Racasan, R.
e10356fa-9034-4737-aed1-2d7dce67aa99
Stolz, Martin
7bfa1d59-511d-471b-96ce-679b343b5d1d
Wood, Robert J.K.
d9523d31-41a8-459a-8831-70e29ffe8a73
Alberts, L. Russell
f43781a6-3262-401c-8436-843340f6afa1
Martinez-nogues, Vanesa
5f44b806-932c-4752-b675-8e1121092fd4
Baker Cook, Richard
b87155e8-2dcb-4c3f-a4de-52fcf36b5f95
Maul, Christian
c19cb80b-1d13-451d-83df-36f244f9d9db
Bills, Paul
153d69fc-ebf6-4ddf-9596-6a9691b35ec8
Racasan, R.
e10356fa-9034-4737-aed1-2d7dce67aa99
Stolz, Martin
7bfa1d59-511d-471b-96ce-679b343b5d1d
Wood, Robert J.K.
d9523d31-41a8-459a-8831-70e29ffe8a73

Alberts, L. Russell, Martinez-nogues, Vanesa, Baker Cook, Richard, Maul, Christian, Bills, Paul, Racasan, R., Stolz, Martin and Wood, Robert J.K. (2018) Comparison of metal-on-metal hip simulator wear measured by gravimetric, CMM and optical profiling methods. Surface Topography: Metrology and Properties, 6 (1), [014002]. (doi:10.1088/2051-672X/aaa518).

Record type: Article

Abstract

Simulation of wear in artificial joint implants is critical for evaluating implant designs and materials. Traditional protocols employ the gravimetric method to determine the loss of material by measuring the weight of the implant components before and after various test intervals and after the completed test. However, the gravimetric method cannot identify the location, area coverage or maximum depth of the wear and it has difficulties with proportionally small weight changes in relatively heavy implants. In this study, we compare the gravimetric method with two geometric surface methods; an optical light method (RedLux) and a coordinate measuring method (CMM). We tested ten Adept hips in a simulator for 2 million cycles (MC). Gravimetric and optical methods were performed at 0.33, 0.66, 1.00, 1.33 and 2 MC. CMM measurements were done before and after the test. A high correlation was found between the gravimetric and optical methods for both heads (R 2  =  0.997) and for cups (R 2  =  0.96). Both geometric methods (optical and CMM) measured more volume loss than the gravimetric method (for the heads, p  =  0.004 (optical) and p  =  0.08 (CMM); for the cups p  =  0.01 (optical) and p  =  0.003 (CMM)). Two cups recorded negative wear at 2 MC by the gravimetric method but none did by either the optical method or by CMM. The geometric methods were prone to confounding factors such as surface deformation and the gravimetric method could be confounded by protein absorption and backside wear. Both of the geometric methods were able to show the location, area covered and depth of the wear on the bearing surfaces, and track their changes during the test run; providing significant advantages to solely using the gravimetric method.

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More information

Accepted/In Press date: 4 January 2018
e-pub ahead of print date: 4 January 2018
Published date: 29 January 2018

Identifiers

Local EPrints ID: 421116
URI: http://eprints.soton.ac.uk/id/eprint/421116
PURE UUID: e0c44908-3aae-4733-a3dd-8bcd0de248c1
ORCID for Martin Stolz: ORCID iD orcid.org/0000-0002-0732-0811
ORCID for Robert J.K. Wood: ORCID iD orcid.org/0000-0003-0681-9239

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Date deposited: 22 May 2018 16:30
Last modified: 20 Jul 2019 01:19

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Contributors

Author: L. Russell Alberts
Author: Vanesa Martinez-nogues
Author: Richard Baker Cook
Author: Christian Maul
Author: Paul Bills
Author: R. Racasan
Author: Martin Stolz ORCID iD

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