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Magnesium Sponges as Resorbable Bone Implants Manufactured by Investment Casting

Friday (26.10.2018)
10:30 - 10:50
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Large bone defects, caused by inflammations, tumours and traumas after accidents, must be treated with an implant or transplant. However, bone autografts, which can be cut off from the same person’s hip, need a second surgery, which increases the risk of complications like inflammations. By contrast, only one procedure is needed, if resorbable implants are used. The shape in the investment casting process will be generated by fused deposition modelling, which has the additional benefit in producing patient individual implants. The pore sizes should be in the range of 150 500 µm in order to obtain an osteoconductive environment and promote bone ingrowth behaviour. Magnesium, as a biodegradable material, has several advantages as an osteosynthetic material. It is used for different metabolic and enzymatic reactions in the body and is also part of the bone structure. Moreover, magnesium has mechanical properties, especially the stiffness, similar to those of bone. As a result, stress shielding occurs more unlikely. Nonetheless, adapting the degradation of the magnesium implant towards the bone ingrowth behaviour is still challenging. To tailor the degradation behaviour, magnesium can be alloyed. The cellular structures, investigated in the present study, were cast with the magnesium alloys LAE442 and MgLa2. Using the alloy LAE442, it was possible to produce structures with pore sizes as low as 400 µm. However, with the alloy MgLa2 only pore sizes down to 500 µm could be realised. Moreover, the degradation behaviour can be adapted using biocompatible coatings. In the present study, the magnesium sponges were coated successfully with magnesium fluoride, calcium phosphate and polylactic acid. Furthermore, the as-cast implants had a sufficient strength for the use in the rabbit tibia, where they are investigated in future in vivo studies. Using the alloy LAE442 instead of MgLa2 and smaller pores, the strength could be enhanced further.

Stefan Julmi
Leibniz Universität Hannover
Additional Authors:
  • Dr. Christian Klose
    Leibniz Universität Hannover