Influence of Young's Modulus of Loaded Implants on Bone Remodelling

Materials and Methods: 16 Saanen goats, each receiving 1 Ti implant (Young's mod. 110 GPa) and 1 high-density polyethylene (PE) implant (Young's mod. 1 GPa) in one femoral condyle were selected. A 100 nm Ti coating was applied on both types of implants. The implants protruded in the knee joint space and were directly weight bearing. The first group of 8 goats was sacrificed after 6 and the second group after 6 months of loading. Histological sectioning and 3D trabecular bone parameters were calculated on the micro-CT images for the neck, middle and apex areas. A linear mixed-model, together with multiple testing corrections by Tukey procedure for pairwise differences were used and α was set at 5%.

Results: For the 3D-bone parameters, the difference between the Ti and PE implants was not significantly different (p>0.05) between the zones (neck, middle and apex) for both groups of goats. The implants could therefore be considered in their entirety. The PE implants showed significantly more bone-to-implant contact (p=0.04) after 6 months of loading compared to the Ti implants. After 6 weeks of loading, the PE implant presented lower connectivity and smaller marrow spaces in the 0-500 µm ROI. In the 500-1500 µm ROI more bone volume was present for the PE implant. After 6 months, the PE implants showed more bone volume and thicker trabeculae than the Ti implants for the entire length of the implant. This effect was already present in the 0-500 µm ROI.

Conclusion: The experimental results suggest that implant stiffness affects the peri-implant tissue response, which may be related to differences in peri-implant strains.

Support by Fund for Scientific Research, Flanders N° 101/8 & 1.5.118.02.