Resorbable polymer-ceramic composites for orthopedic scaffold applications
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abstract
In current state-of-the-art resorbable orthopedic implant materials, loss of strength occurs before substantial mass loss in the degradation process. Materials such as 1:1 PLA:PGA copolymers become too weak to carry any load long before significant amounts of bone have grown to replace the eroded prostheses. An alternative is a two-stage implant material that is both load bearing and osteoconductive; a property of a material to encourage bone already being formed, to lie closely to or adhere to its surface. To achieve this, an interpenetrating network of osteoconductive material and strong (but degradable) biocompatible material is needed. In comparison to conventional prosthesis or scaffold manufacturing routes, rapid prototyping (RP) techniques are an attractive means of fabricating these two-stage implants. A poly butylene terephthalate polymer blend scaffold with 150-300 urn diameter interconnected pores was built using RP and coated with a thin coating of tricalcium phosphate (TCP) or hydroxy apatite suspension in a polycaprolactone matrix. Tissue culture results showed that scaffolds with such thin coatings were more conducive to growth of the cells, perhaps due to a more open scaffold, where the cells can proliferate more easily compared to the other types. The interpenetrating combination of the two biodegradable materials was designed to allow rapid bone in-growth while providing support. This preliminary study validates our hypothesis that the RP process combined with thin coating of HA can tailor an implant to the needs of a specific patient.
