Quantitative characterization of porous commercial and experimental bone graft substitutes with microcomputed tomography

A large number of resorbable bone graft substitutes are being marketed as porous, but the total porosity being referred does not take into account many of the biologically important physical aspects of porosity. Therefore, to allow the direct comparison of different commercial products, there is a need to adopt guidelines for a standardized characterization. The aim of the study was to assess a microcomputed tomography-based method for the characterization of porous biomaterials to allow head-to-head comparison of these materials. The study included two commercial biomaterials (Actifuse(®) and ChronOs(®)) and three experimental biomaterials (sintered bioactive glass microspheres, porous alginate (Alg), and porous Alg/hydroxyapatite composite). In addition to porosity and pore size distributions, the interconnectivity of the pores was assessed by an iterative blocking of interconnections. The biomaterials were characterized in their original morphologies (granules or cones). Differences between the materials were demonstrated. Actifuse(®) had the broadest distributions of pores and interconnections. ChronOs(®) had a substantial fraction of closed pores (10%). Other materials had closed porosity below 1%. Due to the thinner walls of the lattice, the Alg-based materials had high total porosity (>80%). Discrepancies were found between the porosity values reported by the manufacturers and the values obtained in this study. The proposed method is plausible for the systematic characterization of porous biomaterials.