Degradation behavior of porous magnesium alloy scaffold under the low-intensity pulsed ultrasound intervention and their effect on bone defects repair.

Biodegradable porous magnesium alloy (pMg) scaffolds hold significant potential for repair of bone defects owing to favorable mechanical properties and biocompatibility. However, a critical challenge remains in matching the degradation rate of pMg scaffolds with the pace of bone regeneration. Low-intensity pulsed ultrasound (LIPUS) has emerged as a promising therapeutic strategy to enhance bone repair. In this study, femoral bone defects in Sprague-Dawley rats were implanted with pMg scaffolds, and LIPUS was applied to the defect sites post-operatively. This study primarily investigated the degradation behavior of pMg scaffolds in vivo experiments, as well as their reparative effects on bone defects under LIPUS intervention. In vivo analysis revealed that LIPUS intervention accelerated the degradation of pMg scaffolds by loosening the degradation layer, making it more susceptible to erosion. Concurrently, LIPUS enhanced the accumulation of beneficial calcium and phosphorus compounds on the surface of the pMg scaffolds. Furthermore, the pMg + LIPUS group exhibited enhanced bone formation and mineralization around the degradation site compared to the pMg group alone, attributed to the increasing osteocalcin (OCN) and type I collagen (COL-I) as well as reduction in osteolysis by pMg and LIPUS-induced osteogenesis effect. At the 24-week post-surgery, the hardness value (HV) of regeneration bone in the pMg + LIPUS group had a 15% increase compared to the pMg group and approached the HV of healthy bone. In conclusion, the promotion of bone tissue growth rate under the intervention of LIPUS in conjunction with the degradation rate of pMg scaffolds offers a novel clinical strategy for the repair of bone defects.