Contact Stress and Wear Analysis of Zirconia Against Alumina for Normal and Physically Demanding Loads in Hip Prosthesis

Abstract

Risky gait activities lead to severe wear in orthopaedic implants during postoperative periods. The aim of the present study is to predict the linear and volumetric wear of zirconia (ZrO2) vs alumina (Al2O3) hip implants subject to risky and normal gait activities. Initially, the gait loads pertaining to risky gait activities were converted to equivalent normal loads. Then using the computed normal loads, friction and wear coefficients of ZrO2 ball against Al2O3 disc were calculated from Pin-on-Disc (POD) tribometer under dry and lubricating conditions. Saline solution, a bio-lubricant was utilized for lubrication purpose to mimic synovial fluid properties. Nineteen gait activities stair ascending or descending, carrying load, lifting load and ladder up or down etc., grouped as A, B, C and D were used to determine friction and wear coefficients. Finite Element Method (FEM) was employed to predict the wear of the bearing couple. The developed contact pressure for these gait activities was then utilized to compute linear and volumetric wear for 2 million cycles. Our findings suggests that, patients regularly involved in group C and D type gait activities were likely to cause more wear which may accelerate early implant failure.