Influence of different surface machining treatments of resorbable magnesium alloy implants on degradation - EDX-analysis and histology results

The surface of cylindrical MgCa0.8 implants were differently machined which leads to smooth implants, sandblasted and threaded cylinders. 16 implants of each group were implanted into the medial femoral condylus of New Zealand White rabbits (totally n = 48). Each half of the implants remained for three and six months, respectively. After euthanasia 5 mu m thin slices were produced, stained and evaluated through a semi quantitative scoring. Two specimen of each surface were used for EDXanalysis. Specified areas were examined for the appearance of predetermined elements. The EDX-analysis showed phosphorus in the edge layer of the implants. It appeared at all surface varieties. Magnesium could be found in the bone near the implants. It decreased with increasing distance to the implant site. The appearance of phosphorus indicates a possible new bone formation in the periphery of the implants. This also points to a good biocompatibility and a possible osteoinductive tendency. All bone preparations developed a fibrotic layer around the implant. It was strongest in sandblasted implants. The layer decreased from three to six months. Within the layer macrophages appeared most frequently at both defined times. They contained ingested implant material. Lymphocytes, plasma cells and foreign body cells appeared most frequently in sandblasted implants at both points in time. After six months, foreign body cells occurred exclusively at sandblasted implants.