BONE INGROWTH BEHAVIOR OF HYDROXYAPATITE-COATED, POLYETHYLENE-INTRUDED AND UNCOATED, SANDBLASTED PURE TITANIUM IMPLANTS IN AN INFECTED IMPLANTATION SITE - AN EXPERIMENTAL-STUDY IN MINIATURE PIGS

We studied the dynamics of bone tissue ingrowth into the pores of hydroxyapatite-coated (plasma-spraying technique) and uncoated wire meshes of pure Ti in an infected implantation site. Samples of the test materials were implanted into the femora of 15 adult Gottingen minipigs. Just before implantation they were contaminated with Staphylococcus aureus. The pigs were killed after 4, 8, 12 or 24 weeks. Undecalcified ground sections of bone tissue were prepared and stained with toluidine blue for comparative histological evaluation. The hydroxyapatite-coated implants already demonstrated advanced new bone formation after 4 weeks. By 12 weeks most of the implant pores were filled with newly formed bone although all samples showed macro- as well as microscopic signs of persistent infection. Comparable reactions of the uncoated implants could be observed only after 24 weeks. Signs of degradation of the hydroxyapatite coating were seen in contact with soft tissue. This was more extensive in the infected than in the uninfected site. The results and possible clinical consequences are discussed.