Biological interface study of HA/ZrO2 graded composite in a dog lumbar vertebra bone defect model

摘要

This study compared bony fusion in autologous bone grafting with HA/ZrO2 graded composite in terms of mineral depositions, histological characteristics, and biomechanical properties of bonding interface. Twenty-four beagle dogs were established four places of bone defect in two adjacent lumbar vertebral bodies (L4 and L5) and were successively implanted with HA/ZrO2 graded composite (group A), HA/ZrO2 unilayer composite (group B), pure ZrO2 (group C), and pure HA (group D). After operation, lumbar vertebral specimens were respectively harvested per time at week 6, 12, and 16. Then, the bony fusion interface was evaluated by fluorescence microscope and computer image analysis system to measure mineral apposition rates (MAR). Histological analysis of specimen was used to determine bone bonding rates (BBR) and possible foreign body reactions associated with each groups. And interface bonding force between implant and autogenous bone was quantified with biomechanical push-out test. Compared with other groups, group A led to significantly higher MAR from week 6 to 12 (p<0.05). Histologically, new bony tissue and hyaline cartilage were seen around the HA/ZrO2 graded composite, accompanied by mild chronic inflammation. And the BBR of HA/ZrO2 graded composite were the highest (p<0.05), while reaching (90.3 +/- 3.8) % at week 16. Moreover, the biomechanical push-out tests revealed that the maximum interface shear strength of group A was respectively (2.64 +/- 0.16) MPa, (2.95 +/- 0.19) MPa, and (3.45 +/- 0.23) MPa at week 6, 12, and 16, which all possessed significantly statistical differences with other three groups (p<0.05).