Cartilage repair on magnesium scaffolds used as a subchondral bone replacement

Abstract

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.

Porous magnesium-based scaffolds for tissue engineering

“…Furthermore, histological studies showed no significant cartilage regeneration above the degraded magnesium scaffold. Similar results have also been observed using autografted cancellous bone as the replacement of the subchondral bone plate [118]. This finding is surprising since the autograft is believed to be the best and first option for regenerative tissue engineering due to its immunocompatibility.…”

“…Magnesium scaffolds were studied as the subchondral bone plate to induce cartilage repair [118]. Magnesium alloy (AZ91) with 75% porosity showed rapid degradation at twelve weeks postoperatively.…”

“…Application of autografts is mainly limited by inadequate availability, and donor bone site morbidity [119,120]. Comparison studies using autografted cancellous bone and magnesium scaffold for osteochondral defects confirm the necessity for the unconstrained access to nutrition and reparative cells from the bone marrow [118,120]. Therefore, the designed scaffolds should satisfy the need for local blood circulation and bone marrow accessibility.…”

“…Therefore, the designed scaffolds should satisfy the need for local blood circulation and bone marrow accessibility. On the other hand, in the untreated osteocartilage defect with the highest accessibility to bone marrow cavity, no reproduction of subchondral bone in the central part was observed [118]. Magnesium scaffolds with optimal porosity should provide appropriate mechanical support [47,48], osteoinductive properties, excellent biocompatibility [121], biodegradability and bioresorbability [122].…”

Histological and molecular evaluation of iron as degradable medical implant material in a murine animal model

“…The implants should be flexible to be compatible with minimally invasive techniques, and sufficiently sturdy to prevent collapsing or kinking. The mechanical stability of resorbable polymeric materials is not satisfactory and their degradation can provoke inflammation, whereas with metal alloys superior mechanical strength can be achieved [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] . Whereas magnesium stents tend to degrade too rapidly, this appears not to be the case for iron implants [25][26][27][28][29][30][31] .…”