Cartilage repair on magnesium scaffolds used as a subchondral bone replacement

Despite the availability of surgical and non-surgical techniques, the repair of articular cartilage lesions remains. a current clinical problem. Especially for the treatment of large osteochondral cartilage defects, the replacement of the subchondral bone plate is a crucial step for optimal cartilage repair. However, no artificial implant material can yet fully restore the properties of the subchondral bone plate. For optimal cartilage tissue repair, mechanical stability for the first two months is essential. Subsequently, a rapid degradation process of the implant material would allow optimal supply of nutrition to the regenerating tissue. To this end, we investigated whether the implantation of an open porous degradable scaffold made of a magnesium alloy (AZ91) could serve as a sufficient temporary replacement of the subchondral bone plate. The results show that this alloy degrades too rapid in vivo to allow sufficient cartilage repair above the scaffold. However, the surrounding cartilage tissue was not negatively affected by the rapid degradation process and new bone formation was observed at the rim of the degrading implant. In conclusion, magnesium scaffolds degrade in vivo but the initial high corrosion rate must be reduced to allow the formation of an appropriate cartilage tissue. Future research will therefore be directed to optimized alloys and additional coating with magnesium fluorides or calcium phosphates like hydroxyapatite.