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Abstract

The interconnections in a porous biomaterial are the pathways between the pores. They conduct cells and vessels between pores. Thus they favour bone ingrowth inside ceramics. The aim of our study was to determine the effect on bone ingrowth of interconnections in two ceramics: hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP) with the same porosity of about 50% and a mean pores size of 100-300 microm and a mean interconnection size of 30-100 microm. In vitro, four discs for osteoblast culture were studied after 14 and 28 days of incubation. The results show that human osteoblasts can penetrate interconnections over 20 microm in size, and colonize and proliferate inside macropores, but the most favourable size is over 40 microm. In vivo, eight cylinders were implanted in the middle shaft of both rabbit femurs for 12 or 24 weeks. The histomorphometric results show that interconnections in porous ceramics favour bone ingrowth inside the macropores. In the HA group the rate of calcification and bone ingrowth do not differ, and chondroid tissue is observed inside pores. But in beta-TCP, the calcification rate and the bone ingrowth increased significantly. At week 12 significant correlation between new bone ingrowth and the size of the interconnections is observed between new bone ingrowth and the density of pores. In conclusion we notice that in vivo a 20 microm interconnection size only allows cell penetration and chondroid tissue formation; however the size of the interconnections must be over 50 microm to favour new bone ingrowth inside the pores. We propose the concept of "interconnection density" which expresses the quantity of links between pores of porous materials. It assures cell proliferation and differentiation with blood circulation and extracellular liquid exchange. In resorbable materials, pore density and interconnection density are more important than their size, contrary to unresorbable materials in which the sizes and the densities are equally important.

Biomimetic Materials by Freeze Casting

“…42,100,101 Hybrid composites are another alternative for bone replacement materials with higher strength and toughness. 19,31 The use of a biodegradable polymer as the impregnated phase may allow the organic phase to degrade over time so that porosity is created in situ to promote new bone ingrowth.…”

A review of protein adsorption on bioceramics

“…The works that are in progress mainly cover two aspects. One focuses on studying the biological events that occur in vivo between bioceramics and living tissues [34][35][36][37][38]. The other tries to reveal the mechanisms of apatite layer formation or the regeneration process on the implanted bioceramics [18,39].…”

Potential Bone Replacement Materials Prepared by Two Methods

“…Implant porosity has a direct effect on osteogenesis and integration with natural bone [5,6]. The pores must be interconnected with an interconnection size of at least 50 µm which is needed to promote bone ingrowth [7]. Hulbert et al determined that a minimum pore size of at least 100 µm was required for significant ingrowth of bone into an implant [8].…”