Difference of osteoporotic bone fracture healing between pure magnesium and magnesium chloride (MgCl2) enriched calcium sulphate/phosphate cement (CSPC)

Calcium sulfate/phosphate cement (CSPC) is a calcium-based bioactive material which is degradable and used to repair bone defects, however, it is not recommended for patients with poor bone health due to the mismatch of time of bone regeneration and cement degradation. Previous studies suggested the addition of Magnesium (Mg) is a possible solution to enhance the performance of CSPC as Mg ions are beneficial to osteogenesis. However, the impact on bone healing induced by Mg is subtle since Mg2+ ions regulate both osteoblastic and osteoclastic activities. This study examined the healing effect of pure Mg-enriched CSPC (Mg-CSPC) and magnesium chloride (MgCl2) enriched CSPC (MC-CSPC). Mg-CSPC showed sustained release of Mg2+whereas MC-CSPC exhibited spike release of Mg2+and led to a higher rate of degradation. In vivo study in ovariectomized (OVX) rat model indicated a longer time of degradation in Mg-CSPC, which fully degraded at postoperative week 8. Mg-CSPC contained interconnective pores which allowed cell migration from the outer layers to the core of the cement and improved osteoinduction. On the other hand, MC-CSPC was fully degraded in less than 4 weeks after surgery and replaced by newly formed bone. In this study, MC-CSPC demonstrated a significantly higher rate of bone regeneration than Mg-CSPC and the optimum rate of bone regeneration was between weeks 4 to 7 after cementoplasty. Both histological and quantitative micro-CT analysis suggested MC-CSPC produced a higher quality of new bones and positively affected the surrounding bones. Taken together, this study suggests a fast release of Mg-contained scaffold is preferable for bone repair and the healing effect is continued even after complete degradation.