Biocompatibility, Osteoconduction and Biodegradation of Porous Hydroxyapatite, Tricalcium Phosphate, Sintered Hydroxyapatite and Calcium Carbonate in Rabbit Bone Defects

Abstract

AbstractThe biocompatibility, osteoconduction and biodegradation characteristics of calcium phosphate ceramics is controversial. Few comparative studies have controlled for material properties as well as biological influences. In this study, we compared the in-vivo response of implants made porous (500 μm pores) using the Replamineforu™ process and composed of hydroxyapatite (HA), sintered hydroxyapatite (SHA), tricalcium phosphate (TCP) or calcium carbonate (CC). In ten rabbits, rod-shaped implants (5mm d × 10m 1) of each material were randomly press-fit into two bilateral defects of either the bicortical iliac crest or unicortical proximal tibial metaphysis. Explants were harvested at 1 to 9 months, sectioned midsagitally with half embedded in plastic for qualitative histomorphometry, and the other half decalcified and stained for histology. The acute and chronic inflammatory response was minimal for all implants. The osteoconduction properties were similar for the calcium phosphate materials, resulting in repair of the cortical defects within three months with partial bony fill of the medullary canal. CC completely degraded by three months, causing incomplete defect closure in some cases. TCP partially degraded in the medullary canal, but remained when surrounded by bone in the cortex. HA and SHA did not degrade. In summary: