A synthetic bone implant macroscopically identical to cancellous bone.

Macroporous hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP) are widely used as synthetic bone replacement materials due to their high biocompatibility and osteoconductive properties. The level of porosity, pore size distribution, pore morphology, and the degree of pore interconnectivity in such grafts significantly influences the extent of bone ingrowth. It has been hypothesised that an ideal implant macrostructure may be similar in morphological characteristics to the inorganic matrix of the bone it is replacing. However, to date, clinically available synthetic materials differ structurally from cancellous bone. A method is described for the macrostructural replication of cancellous bone. Reproduction involves a multistage process requiring the manipulation of positive and negative forms of the inorganic matrix. By infiltration of a wax negative mould of cancellous bone with a ceramic slip, followed by removal of the wax, and firing, it is possible to produce a positive replica of the original cancellous macrostructure. Optimisation of slip preparation conditions (pH and percentage deflocculant addition) and sintering conditions have allowed successful replication of cancellous bone using several bioceramic compositions including HA, beta-TCP, and HA/beta-TCP.