Osseointegration of porous titanium modified by diamond-like carbon and carbon nitride

Abstract

High-porous implants capable of osteointegration are currently of great interest. Osseointegration is the establishment of bond strength between implant and host bone due to bone ingrowth into the porous structure. Ingrowth of bone tissue requires open interconnected pores and biocompatible surface, which is in direct contact with host tissues. Implants for orthopedics must have in addition a sufficient mechanical strength. In this work for in vivo experiments, cylindrical implants of 4.5mm diameter made of porous titanium (PTi) produced by the original technology were used. To improve osseointegration, on the implant surface the diamond-like carbon (DLC) or nitrogen-containing carbon (CN0.25) films were deposited using PVD technique. The PTi, PTi (DLC) and PTi (CN0.25) implants saturated by adhesion fraction of autologous bone marrow were implanted in rabbit right tibia and femoral condyles. Tensile strength study of native compact bone (σNB) and neogenic bone tissue (σBTS) at the implant–host bone interface showed the following: after 4weeks (σBTS/σNB)=0.39, 0.57 and 0.52, at 16weeks (σBTS/σNB)=0.46, 0.70 and 0.58 for PTi, PTi (DLC) and PTi (CN0.25), respectively. In all cases after 52weeks the neogenic bone tissue strength at the interface did not differ from the native bone strength. Histological studies of tissue formed in the implant pores, showed that after 4weeks a bone tissue of varying maturity was formed in the entire volume of implants: on the periphery of the implant it found bone trabecules ingrown from parent bed, and closer to the implant center a spongy immature bone tissue. In 16weeks the integration of parent bed bone and newly formed bone trabecules was determined. This process was most inhered to PTi (DLC). After 52weeks bone tissue integrated a 2/3 PTi (DLC) and 1/3 PTi (CN0.25) diameter of the implant. Our studies showed that all implants are biocompatible and osseointegrate with the native host bone. The porous titanium with DLC is the most effective and can be recommended for use in clinical trial.