Biocompatibility and degradation behaviour of degradable magnesium sponges coated with bioglass - method establishment within the framework of a pilot study

Aim of the present study was to establish methods for the evaluation of biocompatibility and degradation behaviour of coated magnesium sponges in cancellous bone. So bioglass coated sponges of the magnesium alloy Ax30 were implanted into the femurs of rabbits for an observation period of 6, 12 and 24 weeks, respectively. In the follow up clinical and radiographical examinations and in vivo mu-computed tomographies (XtremeCT) were taken regularly. After euthanasia ex vivo mu-computed tomographies (mu CT80) and histological examinations were executed. As result the greater trochanter proved to be a suitable implantation site and all coated magnesium sponges were tolerated well. The radiographs showed no development of gas or severe bone alterations. The XtremeCT depicted the proceeding degradation and accumulations of gas, but turned out to be not as meaningful in exact determination of bone and sponge changes. Better results regarding the degradation state of the sponges were provided by the mu CT80 at the end of the test. After all implantation periods different sized implant residues and newly formed bone around the implant were found. The histological examinations resulted in new bone formation and a mild, decreasing inflammation. The bone-implant-interface could not be evaluated at all localisations, since the remaining implants partly coiled up during microtome sectioning. In conclusion the chosen methods are suitable for usage in further studies. But supplement of the cutting and grinding method according to Donath is required to examine the bone-implant-compound.