Osteointegration of titanium and hydroxyapatite rough surfaces in healthy and compromised cortical and trabecular bone: In vivo comparative study on young, aged, and estrogen-deficient sheep

The osteointegration rate of titanium (Ti; TI01) and duplex Ti plus HA (HT01) coating systems with high surface roughness was investigated in healthy, aged, and oestrogen-deficient sheep. After having evaluated the bone quality, TI01 and HT01 rods were implanted in the tibial diaphyses (two implants for each tibia) and epiphyses (1 implant for each tibia) of five young (YOUNG), five aged (AGED), and five aged and ovariectomized (OVX) sheep. The iliac crest trabecular bone volume (BV/TV) and number (Tb.N) in OVX sheep were respectively 33.5\% and 28.5\% lower than in YOUNG sheep (p < 0.005) and lower than in the AGED group (BV/TV, -17\%; Tb.N, -13.5\%; not significant); in the OVX group the trabecular separation was 77.9\% higher than in YOUNG (p < 0.05) and 30.9\% higher than in AGED animals. Lumbar vertebrae L5 bone mineral density was significantly lower in AGED (8.9\%, p < 0.05) and OVX sheep (19.3\%, p < 0.0005) when compared with YOUNG animals. Five samples of five sheep from each group were analyzed for each observation. At 3 months, in cortical bone both affinity index and pushout test results showed no significant differences between the two materials in each group of animals. In trabecular bone, the affinity index of HT01 was significantly higher than that of TI01 in each group of animals (YOUNG, 90.7\%; AGED, 76.9\%; OVX, 49.9\%) with no significant differences between groups. In conclusion, the performance of TI01 and HT01 surfaces was high not only in YOUNG, but also in OVX animals and, therefore, they might be useful for aged and osteoporotic patients.