Quantity and Quality of Regenerated Bone in Grooves Aligned at Different Angles from the Implant Surface

Abstract

The quantity and quality of regenerated bone strongly depends on the direction and amplitude of in vivo principal stress; therefore, in vivo stress distribution near bone implants should be optimized on the basis of the morphology of the interface between an implant and bone tissue. In this study, grooves were created on the implant surface in order to improve the surface morphology of the implant for optimizing in vivo stress distribution near the implant. The preferential alignment of the biological apatite (BAp) c-axis, which is a parameter of bone quality and controls the mechanical function of bones, is closely related to stress distribution; therefore, the direction of principal stress should be matched with the direction of the groove on the implant surface. Hip implants were prepared with grooves aligned at different angles from the surface; the grooves were located on the stem portion. These implants were inserted in a beagle femur to investigate the dependency of the quantity and quality of newly formed bone in the grooves on the groove angle. The degree of preferential alignment of the BAp c-axis of the regenerated bone in the grooves strongly depends on the angle of the groove to the principal stress vector that was estimated previously to an animal experiment. The regenerated bone forms anisotropic BAp orientation in response to the principal stress in the grooves; therefore, the direction of the grooves has to be designed on the basis of the stress distribution near the implant.