Joyce TJ

Langton DJ

Nargol AVF

Newcastle University E-Prints

Newcastle University e-prints  Date deposited:  11th June 2010 Version of file:  Author final [Conference Proceeding] Peer Review Status:  Peer-reviewed  Citation for published item: Joyce TJ, Langton DJ, Nargol AVF. A Study of the Wear of Explanted Metal-on-Metal Resurfacing Hip Prostheses. In: European Conference on Tribology (EcoTrib).2009,Pisa, Italy Further information on publisher website:  Publishers copyright statement: This paper was originally presented as a paper at the European Conference on Tribology, Pisa, 2009. Use Policy: The full-text may be used and/or reproduced and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not for profit purposes provided that: • A full bibliographic reference is made to the original source • A link is made to the metadata record in Newcastle E-prints • The full text is not changed in any way. The full-text must not be sold in any format or medium without the formal permission of the copyright holders.    Robinson Library, University of Newcastle upon Tyne,  Newcastle upon Tyne. NE1 7RU.  Tel. 0191 222 6000  A STUDY OF THE WEAR OF EXPLANTED METAL-ON-METAL RESURFACING HIP PROSTHESES Thomas J Joyce1, David J. Langton2, Antoni V F Nargol2 1 School of Mechanical and Systems Engineering, Newcastle University, UK +44 191 222 6214, E-mail: t.j.joyce@ncl.ac.uk  2 Joint Replacement Unit, University Hospital of North Tees, Stockton-on-Tees, UK ABSTRACT One of the most recent and controversial designs of hip replacement is the metal-on-metal resurfacing prosthesis.  These devices are said to be aimed at younger more active patients who would quickly wear out a traditional total hip replacement.  Due to the relatively recent introduction of hip resurfacing devices there are few studies of failed and explanted devices of this type.  However, from a large, independent, single-surgeon cohort a number of hip resurfacing prostheses which had failed were obtained.  The majority were associated with groin pain in patients and a minority with fracture of the femur.  Acetabular cup and femoral head components were analyzed using a roundness meauring machine and a co-ordinate measuring machine.  Components associated with fracture of the femur showed minimal out of roundness changes compared with typical production values.  In contrast, components associated with groin pain in patients showed much greater out of roundness values, which were taken to be indicative of wear.  All of this data was augmented by co-ordinate measuring machine data.  Therefore it is likely that the groin pain of patients was associated with an adverse reaction to excessive metal wear debris.   Keywords: metal-on-metal, cobalt chrome, hip resurfacing, explant analysis INTRODUCTION Although the majority of total hip replacement operations are very successful procedures there is a constant need to improve these devices for the long-term benefit of patients suffering from common musculo-skeletal diseases.  One of the latest group of implants are known as hip resurfacings, and they consist of a rel tiv ly large diameter femoral head articulating within a thin acetabular cup.  Both components are manufactured from cobalt chrome.  Various designs of such metal-on-metal hip resurfacing prostheses are offered by several orthopedic engineering companies and many of these devices show good short to medium term clinical results [1].  However there ar concerns over such implants including the higher ion levels in the blood of patients fitted with them [2].  Much valuable data can be learnt from explanted prostheses which have ‘failed’ and then been removed from patients.  As hip resurfacing prostheses have only recently been introduced, there are relatively few such retrieval studies [3].    METHODS AND MATERIALS Twelve femoral and acetabular components from metal-on-metal hip resurfacing prostheses were obtained at revision operations.  The majority were revised due to the patient suffering groin pain.  In these cases, at revision operation an effusion was always seen from the joint capsule.  A minority of components were obtained following revision after the patient’s femur had fractured.  Each component was examined using a Zeiss TSK Rondcom60A roundness measuring machine and a Mitutoyo LEGEX co-ordinate m asuring machine.  Out of roundness measurements were taken on three planes for each acetabular and femoral component.  The co-ordinate measuring machine was used to obtain 12 traces at 30° intervals for each acetabular and femoral component.  Both machines allowed areas of localized wear to be identified and the maximum wear depth to be quantified.   RESULTS The maximum out of roundness values for the twelve components are given in table 1.  As can be seen, those components associated with fracture of the femur all showed the lowest out of roundness values.  Where pain and effusion were associated with the reason for revision, the out of roundness values were much greater, up to a maximum of 91.8µm.  For the cups associated with pain and effusion, the out of roundness traces indicated that wear took place towards the edge of the cup and a typical trace is shown in figure 1.  A similar range of values and results were obtained from the co-ordinate measuring machine and a typical trace is given in figure 2.    Component Patient Head/Cup Max out of roundness (µm) Reason for revision 1 A Head 91.8 Pain, effusion 2 A Cup 64.0 Pain, effusion 3 B Head 38.0 Pain, effusion 4 B Cup 28.8 Pain, effusion 5 C Head 17.7 Pain, effusion 6 C Cup 14.8 Pain, effusion 7 D Head 31.3 Pain, effusion 8 E Head 2.7 Fracture of femur 9 F Head 38.8 Pain, effusion 10 G Head 24.7 Pain, effusion 11 H Head 3.1 Fracture of femur 12 I Head 2.0 Fracture of femur Table 1: Maximum out of roundness values of the 12 xplanted components.   Fig. 1: Roundness trace from cup component 6 showing localized edge wear.   Fig.2: Typical co-ordinate measuring machine trace from the head of an explanted component showing localised wear and a maximum local wear depth of 68µm  DISCUSSION Both the out of roundness measurements and those frm the co-ordinate measuring machine provided information about the wear of the implants.  For a new component, a typical out of roundness value would be of the order of less than 5µm.  Therefore, from table 1, it can be seen that components 8, 11 and 12 (all from patients whose femurs had fractured) showed minimal distortion or wear after removal.  Such data lso helps to verify the accuracy of the measuring technique.  To the authors’ best knowledge, the dichotomy between low wear components associated with femoral fracture and high wear explants associated with groin pain and effusion has not previously been reported.  For the three paired components, the out of roundness data suggested that wear was greater on the femoral components than on the acetabular components.  Typical co-ordinate measuring machine scans, such as that in figure 2, helped to identify localized areas of wear and maxi um wear depths.  Values in the range of <2µm to 164µm have been reported previously [3] and show good agreement with the findings of this study.   REFERENCES [1] Shimmin A., Beaule P.E. and Campbell P., Metal-on-Metal Hip Resurfacing Arthroplasty, J. Bone Joint Surg., 90 (2008) 637-654. [2] Keegan G.M., Learmonth I.D. and Case C.P., Orthopaedic metals and their potential toxicity in the arthroplasty patient: a review of current knowledge and future strategies, J. Bone Joint Surg., 89-B (2007), 567-573. [3] Campbell P., Beaule P., Ebramzadeh E., Le Duff M., De Smet K., Lu Z. and Amstutz H., A study of implant failure in metal-on-metal surface arthroplasties. Clin. Ortho. Rel. Res., 453 (2006) 35-46.   

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A Study of the Wear of Explanted Metal-on-Metal Resurfacing Hip Prostheses

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A Study of the Wear of Explanted Metal-on-Metal Resurfacing Hip Prostheses

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