Abstract
In order to improve hydroxyapatite (Ha) quality as a bone substitute, two types of Ha were developed based on a new and original technique: Ha with graduated porosity (G-Ha) and porous “carbonated” Ha (C-Ha). Ha cylinders were implanted into the femoral diaphysis of NZW rabbits. Before implantation the materials were characterised by XRD, porosimetry, SEM and thermic and mechanical analysis. Macroscopic, radiographic and histologic analysis were performed on the specimens at standard intervals after surgery (1-3-6- and 12 months).
G-Ha proved to be morphologically more similar to bone tissue because of the graduated porosity that mimes the two natural components of bone (cortical-scarce porosity and spongious-high porosity). The C-Ha was chemically more similar to bone because of the CO3- substitution, which is a normal substitute in natural bone.
Both materials achieved good mechanical strength, in particular the pseudo-cortical portion of G-Ha. Interconnected porosity was also observed in both materials. Newly formed bone appeared earlier in C-Ha (1–3 months). At 1 year C-Ha demonstrated quiescent bone and significant degradation. The G-Ha was scarcely reabsorbed but showed active osteogenesis in the surrounding living bone. Graduated porosity improved the mechanical interaction with bone over time, while the carbonation improved the temporal interaction and Ha resorption.
Porous Ha was found to be a promising bone substitute and also a reliable drug-delivery carrier.
