Influence of implant location on the mechanical characteristics using the transcortical model

Mechanical evaluation of implants harvested following surgical implantation is often performed as part of the screening process for new materials or surface textures. The question of randomization with respect to implant placement often arises when attempting to design a study to evaluate several implant types, while minimizing the number of animals required to perform the investigation. The purpose of this study was to analyze the effects of implant placement within the canine femur on mechanical characteristics of the bone-implant interface when using the transcortical model. Both smooth and porous-surfaced implants were evaluated at several time periods to determine the effects of placement in the medial versus left cortex, proximal versus distal placement, and left versus right femur. The smooth-surfaced implants demonstrated a significant effect due to proximal versus distal placement within the femur only. There were no other significant comparisons. Porous-surfaced implants demonstrated no significant effects due to placement within the femur. The results demonstrate the necessity for careful study design when evaluating smooth surfaced implants; however, paired comparisons in either the medial versus lateral cortex or left versus right femur will provide unbiased comparisons between the implants.