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Bone replacement and osteosynthesis require materials which can at least temporarily bear high mechanical loads. ideally, these materials would eventually degrade and would be replaced by bone deposited from the host organism. to date several metals, notably iron and iron-based alloys have been identified as suitable materials because they combine high strength at medium corrosion rates. However, currently, these materials do not degrade within an appropriate amount of time. therefore, the aim of the present study is the development of an iron-based degradable sponge-like (i.e. cellular) implant for bone replacement with biomechanically tailored properties. We used a metal powder sintering approach to manufacture a cylindrical cellular implant which in addition contains phosphor as an alloying element. No corrosion inhibiting effects of phosphorus have been found, the degradation rate was not altered. implant prototypes were tested in an animal model. Bone reaction was investigated at the bone-implant-interface and inside the cellular spaces of the implant. newly formed bone was growing into the cellular spaces of the implant after 12 months. Signs of implant degradation were detected but after 12 months, no complete degradation could be observed. In conclusion, ironbased open-porous cellular biomaterials seem promising candidates for the development of selfdegrading and high load bearing bone replacement materials.

Open cell foams made on the basis of reticulated polyurethane foams are well known and widely used since decades. Polyurethane foams have been commercially produced since the 1950 s. [1] They are a practically ideal porous organic structure with porosities between 97 and 98%. First attempts to transfer these structures into ceramic foams by a powder slurry replication technique have been described by Schwartzwalder in 1961, [2] and nowadays such foams are produced in the order of 160 million parts per year for the use as filter in the cast shop. The replication technique has been transferred into the manufacturing of metal foams for the first time in 1966 in order to use them as porous battery electrodes. [3] In the 1970 s, notable work has been done by Russian research groups, where metal foams made by replication method were mainly used in catalysis or filtration applications. [4] Over the past ten years the method has been reinvented by various groups. Mainly open cell foams on the basis of highly alloyed steels were produced, [5][6][7][8] but also foams on the basis of copper [9] or titanium alloys for the use as permanent biomedical implant [10] or low alloyed steel for degradable implants [11] were investigated. In the present work, open cell metal foams have been developed on the basis of various steels like SUS 316L, SUS 314, 4110, SUS 430L, FeCrAl, mild steels and non-ferrous metals like molybdenum, tantalum and the titanium alloy Ti6Al4V. The present paper shows the main properties and applications of replicated PU based metal foams. ExperimentalThe replication method essentially involves three production steps: First, a reticulated polyurethane sponge is coated by slurry impregnation. Reticulated polyurethane foam samples with cell sizes of 10, 30, 45, 60, and 80 pores per inch (Foampartner Reisgies, Germany) were coated using double rubber rollers. Water-based slurries with PVA-binder or carbon acid binder and solids content between 87 and 90% were used. In the next step, the template is thermally removed and finally the debinded metal structure is sintered.Thus, the open network of the polymer foam is transformed into a metal structure. The processing in principle is rather simple, but however, in order to obtain defect-free structures with optimum properties every single processing step needs for proper development. Firstly, in order to obtain complete impregnation of the PU foams fine metal powders High porosity permeable materials have been manufactured on the basis of the highly uniform structure of foamed polyurethane since the 1950 s. This paper shows the development of open cell foams based on all kinds of steels, titanium alloys, and also open-cell molybdenum foams made by a powder metallurgical replication technique. Such materials show a wide range of physical and mechanical properties, which may be adapted to various requirements. The automotive industry, for example, needs high-temperature resistant materials with high permeability and good strength for catalytic conversion. For orthopaed...

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