Iron Based Cellular Metals For Degradable Synthetic Bone Replace- ment

Degrading metal alloys have recently gained substantial scientific and clinical interest for their use as implant materials in bone surgery and cardiovascular surgery. In cardiovascular applications, iron has been used successfully in animal implantation studies and first clinical cases. Iron shows relatively long degradation timeframes, which in particular are needed in bone surgery. The aim of the present study was to investigate the usability of iron and iron based alloys with an open cell structure as degradable bone replacement material, which gives an osteoconductive surface for the stimulation of osseous integration on the one hand, and a degradation rate, which does not overburden the regeneration ability of bone on the other hand. Open cell metal PM foams exhibit a natural bone-like structure, which enables ingrowth of bone tissue and blood vessels. In order to determine the influence of alloying elements on biocompatibility and degradation times, various PM iron alloys were processed and tested in vitro. Observed degradation rates appear to be reasonable for the intended use as bone implant material. Open cell structures with a compressive yield of ~10 MPa were manufactured by a PM replication method and were implanted in the femur condylus of adult merino sheep for 6 and 12 months. This study shows that an open cell iron based bone implant material exhibits good biocompatibility and no inflammatory response. Therefore, iron based implant materials are considered a very promising approach for the design of new load bearing synthetic bone graft substitutes.