2025, Vol. 29 ›› Issue (34): 7261-7268

Comparison of Mg-Li-Gd alloy and stainless steel intramedullary nail for fixation of femoral annular hemi-defects in rats

Wang Jingshuai1, Zhang Xiaotong2, Zhang Yange1, Wan Zedong1, Kong Lingwei1, Cao Haiying1, Jin Yu1   

Abstract: BACKGROUND: With the increasing demand for orthopedic implants, the search for materials with good biocompatibility and degradability has become a research hotspot. Magnesium-lithium-gadolinium (Mg-Li-Gd) alloy has good degradability, biocompatibility, and mechanical properties, providing ideal supporting conditions for fracture healing.
OBJECTIVE: To evaluate the effects of Mg-Li-Gd alloy implants on bone healing in rats.
METHODS: A circular half-defect model was made on the lateral side of the right mid-femoral segment in 28 SD rats, and the rats were randomly divided into two groups. The stainless steel group was fixed with a stainless steel intramedullary nail, and the magnesium alloy group was fixed with an Mg-Li-Gd alloy intramedullary nail, with 14 rats in each group. At 2, 8, and 14 weeks after surgery, right femur X-ray and Micro-CT examinations, as well as hematoxylin-eosin staining, immunohistochemical staining, and western blot assay were performed.
RESULTS AND CONCLUSION: (1) X-ray film: At 2 weeks after surgery, the osteotomy lines of both groups were clear, the density of the intramedullary nail in the magnesium alloy group was close to that of bone tissue, and the density of the intramedullary nail in the stainless steel group was higher than that of bone tissue. At 8 weeks after surgery, the osteotomy lines of both groups were blurred, and the intramedullary nail in the magnesium alloy group had corroded and degraded. At 14 weeks after surgery, the osteotomy lines of both groups disappeared, and the intramedullary nail in the magnesium alloy group further corroded and degraded. (2) Micro-CT: At 2 weeks after surgery, callus began to form in both groups; 8 weeks after surgery, the stainless steel group entered the callus remodeling stage, and a relatively dense bone structure was formed at the bone defect site, and the magnesium alloy group showed obvious callus hyperplasia at the bone defect site. At 14 weeks after surgery, the stainless steel group showed a mature bone remodeling process, and thick cortical bone was formed at the bone defect site, and thinner cortical bone was formed in the magnesium alloy group. (3) Hematoxylin-eosin staining: At 2 weeks after surgery, a large number of osteoblasts, osteocytes, a small number of osteoclasts and trabecular structures were observed in the magnesium alloy group, while relatively few osteoblasts and osteocytes were observed in the stainless steel group. At 8 weeks after surgery, a large number of osteoblasts, osteocytes, and mature trabecular structures were observed in the magnesium alloy group, while a large number of osteocytes and lamellar bones were observed in the stainless steel group. At 14 weeks after surgery, lamellar bones were observed in the magnesium alloy group, while mature bone tissue was observed in the stainless steel group. (4) Immunohistochemical staining and western blot assay: At the same time point, the expression levels of bone morphogenetic protein 2, osteocalcin, and RUNX2 proteins in the magnesium alloy group were higher than those in the stainless steel group. (5) The results showed that compared with stainless steel materials, Mg-Li-Gd alloy had no obvious advantage in promoting the formation of fracture healing structure.

Key words: magnesium alloy, bone defect, biocompatibility, degradable material, bone healing, Mg-Li-Gd alloy, femoral annular hemi-defect model, bone mineralization