Ella Tan | On 23, Dec 2014
Replacement materials – metal, polyethylene (PE), ceramic, cement
The materials used for Hip and knee joints processing are usually made from titanium and cobalt chrome. The difference is mainly in the bearing materials i.e. the materials of the moving parts:
1. PE/polyethylene – In Singapore only high-grade newer PE is sold. Untested newer products include the triple annealed PE +/- with Vit E. Their track records come from lab studies. Hip and knee implants undergo very different kinds of stresses and thus yield varied results, hence different assessments are needed.
2. Ceramic bearing surfaces – Oxinium and delta ceramics have come a long way from traditional manufacturing and boast of being ultra smooth. However, as yet there are no long term studies to justify the cost difference. As ceramics have very different properties from bone (using Young’s modulus of elasticity), they stretch and contract NOT in tandem with bone …thus, there might be loosening.
3. Cement of press-fit – PMMA cement will always have its place as long as osteoporosis exists! Press fit implants rely heavily on design, material and manufacturing process. The best in the market is trabecular metal technology from Zimmer.