The optimal design of an implant to improve bone quality of implant surroundings based on stress analysis

Abstract

Research on how implant surface shape contributes to long-term stability after implantation is important in the field of orthopaedics. In particular, technology that controls various bone quality parameters and voluntary bone inducement in implant surroundings should be developed for the next generation of implants and this will improve the patient's quality of life (QOL). For this research, we focused on the inducement of the appropriate alignment for biological apatite (BAp) crystallites and related collagen (Col.) fibres as a bone quality parameter. In this study, we predicted that when stress is applied to bone, the BAp/Col. preferential alignment can be formed if osteocytes are in an environment that is aligned with the principle stress vector. We tested this idea by introducing grooves in the principal stress direction on the surface of an implant. This work thus analyzes the effect of stress transmission by a load at the proximal femur on the bone inside and near the grooves by using mechanical simulation in which groove angles can be changed on the implant surface. Coordinate data from the mechanical simulation of the combined bone/implant environment was verified against the coordinate data obtained by CT scans of actual canine bone. Results suggest that the tendency of stress transmission differs depending on the position and angle of the grooves and based on a vector diagram of the maximum and minimum principal stresses. The simulation was able to predict bone dynamics in vivo and enabled a best design of an implant to control the BAp/Col. alignment as an index of bone quality.