Quantification of porosity, connectivity and material density of calcium phosphate ceramic implants using micro-computed tomography

Abstract

Calcium phosphate ceramics have been widely investigated in orthopaedic tissue engineering and surgery as bone extensor. Attention has been given to manufacturing of a porous ceramic that mimics the trabecular bone structure for better osteoconduction. Although different methods have been applied to manufacture the porous structure, they have been unable to quantify the pores and their interconnection within the ceramics. With the advances in biomedical imaging technologies, the study attempted to quantify the pore structure of different ceramics using high-resolution micro-computed tomography (micro-CT). Three kinds of ceramic blocks with product names (BSC, ChronOS and THA, respectively) were synthesized by three methods from three different manufactures and evaluated in the study. The specification claimed that the porosity of the ceramic ranged from 40 to 80%. Six blocks of each ceramic were evaluated by conventional water immersion method and μCT. The pore size and connectivity of the pores were evaluated with standardized protocols. By the water immersion method, the porosity of three ceramics ranged from 60 to 78%. The three-dimensional analysis of the pores by μCT showed that the porosity of the ceramics was 26.2% for BSA, 59.9% for ChronOS, and 67.7%for THA. The pore connectivity was 2.7 for BSC, 59.9% for ChronOS, and 7.1 for THA. The ChronOS had more functional pores (200-400μmin diameter) than the BSC (52.8%) and THA (43.2%) did (p < 0.05). It was shown that the distribution of the pore size of three different ceramics has different characteristics. We speculated that different combinations of structure parameters may have different in vivo properties in osteogensis, whereas the chemical properties of the ceramics cannot be neglected in the in vivo performance. Providing objective information on the functional pores, the micro-CT evaluation serves as a good standard for specification of the ceramic-related implants in the future characterization of scaffold biomaterials for orthopaedic and related medical applications. © 2007 Springer-Verlag Berlin Heidelberg.