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Friday, October 8, 2010, 15:20-16:00Session B14: Hip ResurfacingIntroductionCorrelation Between Edge Loading and Wear in Hip Implants*Azad Hussain - Smith & Nephew Orthopaedics Ltd - Leamington Spa, UKKatrina Packer - Smith & Nephew Orthopaedics Ltd - Leamington Spa, UKChenxi Li - Smith & Nephew Orthopaedics Ltd - Leamington Spa, EnglandAmir Kamali - Smith & Nephew - Leamington Spa, England*Email: azad.hussain@smith-nephew.comAll hip replacements depend upon good orientation and positioning to ensure that implantsfunction well in vivo. Mal-orientated devices can lead to poor patient gait, poor range ofmotion, impingement, edge loading and high wear, which in turn may result in the prematurefailure of the implants.AimTo investigate the correlation between edge loading and wear on retrieved implants throughlinear wear analysis and radiographic examination of implants in vivo.Materials & Methods55 BHR retrieved acetabular cups with known times in vivo were examined. Linear wearanalysis was conducted using a Taylor-Hobson Talyrond 290 roundness machine. Edge loadedcups were classified as cups which showed the wear area crossing over the edge of the cup.Non-edge loaded devices were devices with the wear area within the articulating sphere of thecup, Figure 1. The maximum deviation of the profile from an ideal circle was taken as themaximum linear wear. The implant orientation angles for one edge loaded acetabularcomponent was determined by superimposing BHR models, generated by ProEngineer Wildfire4 with ISDX II extension software, onto frontal x-ray images, Figure. 2.ResultsIn this study 32 cups were classed as edge loaded and 23 classed as non-edge loaded. Non-edgeloaded cups had a linear wear rate of 1.48±1.01 µm/year. Edge loaded cups generated asignificantly higher linear wear rate of 24.02±22.72 µm/year than non-edge loaded devices. Forthe device analysed radiographically, the inclination was 62° and version angle was 16°. Theinclination angle of this device is outside the recommended inclination angle for the BHR andwould be considered as mal-orientated. The linear wear result showed that the device was edgeloaded with a wear rate of 22.25 µm/year.Discussion/ConclusionThis study aimed to find a correlation between edge loading and high wear of retrieved devices.The results in this study show that edge loaded bearings generate significantly higher linearfile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]