Comparison of bone ingrowth between two porous titanium alloy rods with biogenic lamellar structures and diamond crystal lattice on femoral condyles in rabbits

The comparison of bone ingrowth between two types of porous titanium alloy rods with different micro-architectures including diamond crystal lattice (Re-rod) and biogenic lamellar configurations (Bi-rod) on femoral condyles was investigated in this study.Twelve rabbits were used. Re-rod (Re-rod group) and Bi-rod (Bi-rod group) were implanted randomly in femoral condyles of each rabbits respectively. Bone ingrowth of these two rods were investigated and compared. 4 and 12 weeks after the operation, X-ray, micro-CT and histological examinations were performed.No femoral condyle fracture and rod defluxion in the two groups was noted in the X-ray images during the observation period. Micro-CT images showed that all metal trabeculae in the Bi-rod group were covered by new bone at 4 and 12 weeks, whereas partial metal trabeculae in the Re-rod group were still uncovered at 12 weeks. Histological images showed that there was new bone growth in the centre and periphery of Bi-rods at 4 and 12 weeks, and there were several areas without new bone ingrowth at 4 and 12 weeks in the centre of Re-rods. In micro-CT analysis, the bone volume to total volume (BV/TV) of the volume of interest (VOI) of the Bi-rod group was higher than in the Re-rod group [(0.0794 ± 0.0021) % Vs (0.0521 ± 0.0032) % and (0.0875 ± 0.0039) % Vs (0.0702 ± 0.0028) % respectively, P < 0.05] at 4 weeks and 12 weeks. Whereas, the mean trabecular thickness (Tb.Th) values of VOI between the two groups were not significantly statistically different at 4 and 12 weeks. In histological analysis, the BV/TV of the VOI of the Bi-rod group was higher than in the Re-rod group [(0.0624 ± 0.0021) % Vs (0.0435 ± 0.0028) % and (0.0675 ± 0.0024) % Vs (0.0476 ± 0.0031) % respectively, P < 0.05] at 4 weeks and 12 weeks.These results showed that Bi-rods got better bone ingrowth in femoral condyles of rabbits compared with Re-rods.