Biodegradable Magnesium Screws Accelerate Fibrous Tissue Mineralization at the Tendon-Bone Insertion in Anterior Cruciate Ligament Reconstruction Model of Rabbit

Abstract

The incorporation of tendon graft into bone tunnel is one of the most challenging clinical issues in anterior cruciate ligament (ACL) reconstruction. As a biodegradable metal, Mg has appropriate mechanical strength and osteoinductive effects, thus may be a promising alternative to commercialized products used for graft fixation. Therefore, it was hypothesized that Mg based interference screws would promote tendon graft-bone junction healing when compared to Ti screws. Herein, we compared the effects of Mg and Ti screws on tendon graft healing in rabbits with ACL reconstruction via histological, HR-pQCT and mechanical analysis. The histological results indicated that Mg screws significantly improved the graft healing quality via promoting mineralization at the tendon graft enthesis. Besides, Mg screws significantly promoted bone formation in the peri-screw region at the early healing stage. Importantly, Mg screws exhibited excellent corrosion resistance and the degradation of Mg screws did not induce bone tunnel widening. In tensile testing, there were no significant differences in the load to failure, stress, stiffness and absorption energy between Mg and Ti groups due to the failure mode at the midsubstance. Our findings demonstrate that Mg screws can promote tendon graft healing after ACL reconstruction, implying a potential alternative to Ti screws for clinical applications.

Biodegradable Magnesium‐Based Implants in Orthopedics—A General Review and Perspectives

“…When Mg‐based screws were used to fix the tendon graft in the drilled bone tunnel after anterior cruciate ligament (ACL) reconstruction, the surrounding trabecular bone quality was greatly improved,47–49 most likely attributed to the high concentration of Mg ions (>15 × 10 −3 m ) and high pH, which reduces the fusion of pre‐osteoclast cells and the activity of osteoclasts (Figure 4), thereby inhibiting osteoclastogenesis 50. Consistently, Mg screw also improved healing in a femoral intra‐condylar fracture model, demonstrating with better osseointegration and increased bone volume and bone mineral density at fracture gap, as compared to those fixed with PLA screws 51…”

“…As mentioned above, the traditional permanent metallic and resorbable polymeric interference screws have several drawbacks including high Young's modulus91 and unfavorable acidic degradation products,92 which may lead to bone tunnel enlargement and impaired tendon‐bone integration after ACL reconstruction, respectively. Mg‐based interference screws have recently been applied to fix the tendon graft in the drilled bone tunnel during ACL reconstruction in rabbits 46,48,77,81,82…”

Translational status of biomedical Mg devices in China

“…They proposed that the stimulation of BMP-2 and VEGF by Mg ions was responsible for the fibrochondrogenesis of Mg [33]. Wang et al [34,35] also used Mg-based interference screw to promote tendon graft incorporation in rabbits bone tunnel. While in order to improve the poor mechanical strength of Mg, Wang designed one kind of Mg alloys (Mg–Zn–Sr) and tested its potential for ACL reconstruction.…”

Injectable Magnesium-Zinc Alloy Containing Hydrogel Complex for Bone Regeneration

“…If degenerated too fast, it may lose its function before the bone heals completely, while lower degradation rate leads to negative effects on early bone healing. In addition, the shapes of calvarial defects caused by bone resorption are always irregular and changing over time, so the "intramedullary nail" used in long bones, or the screws, etc., are unable to be applied (Wang et al, 2017). Therefore, there is an unmet need to develop plastic magnesium alloys with promising degradability, especially for calvarial defects.…”