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Numerical study of stress shielding evaluation of hip implant stems coated with composite (carbon/PEEK) and polymeric (PEEK) coating materials.

Ayham Darwich, Hasan Nazha, William Abbas

The forces applied to the prosthesis during human activity produce dynamic stresses varying in time and may causing stress shielding in prosthesis-bone system. Therefore, it is important to reduce stress shielding effect. This study aimed to investigates, using finite element analysis, how a PEEK and carbon/ PEEK composite coating materials on a titanium alloy hip implant stem could reduce stress shielding effect corresponding to different human activities: standing up, normal walking and climbing stairs under dynamic loadings to find out which of all these models have a better performance. A 3D finite element model of femur, hip implants, coating layers with composite (carbon/PEEK) and polymeric (PEEK) coating materials were constructed for finite element analysis. A time-dependent cycling load was applied on the prosthesis head. The maximum increase in load transfer to the bone was 207% for the prosthesis coated with carbon/PEEK configuration I (fibers orientated with 0, +45, -45, and 90 degrees) in average compared to uncoated one. Numerical result showed that the carbon/PEEK composite material (configuration I) seems to be a good solution to distribute the applied load and transfer it to the bone, thus to reduce stress shielding problems and to prolong lifetime of the prosthesisbone system. It will prevent aseptic loosening and enhance the stability of the system