Assessment of the degradation rates and effectiveness of different coated Mg-Zn-Ca alloy scaffolds for in vivo repair of critical-size bone defects

Nan Zhang,Dewei Zhao,Jinglong Yan,Huanxin Xie,Yuefei Wang,Yunfeng Wu,Jiahui Yang,Na Liu,Yaming Wang,Jinpeng Zhuang,Ye Ji,Changlong Zhou

doi:10.1007/s10856-018-6145-2

Abstract

Surgical repair of bone defects remains challenging, and the search for alternative procedures is ongoing. Devices made of Mg for bone repair have received much attention owing to their good biocompatibility and mechanical properties. We developed a new type of scaffold made of a Mg-Zn-Ca alloy with a shape that mimics cortical bone and can be filled with morselized bone. We evaluated its durability and efficacy in a rabbit ulna-defect model. Three types of scaffold-surface coating were evaluated: group A, no coating; group B, a 10-μm microarc oxidation coating; group C, a hydrothermal duplex composite coating; and group D, an empty-defect control. X-ray and micro-computed tomography(micro-CT) images were acquired over 12 weeks to assess ulnar repair. A mechanical stress test indicated that bone repair within each group improved significantly over time (P < 0.01). The degradation behavior of the different scaffolds was assessed by micro-CT and quantified according to the amount of hydrogen gas generated; these measurements indicated that the group C scaffold better resisted corrosion than did the other scaffold types (P < 0.05). Calcein fluorescence and histology revealed that greater mineral densities and better bone responses were achieved for groups B and C than for group A, with group C providing the best response. In conclusion, our Mg-Zn-Ca-alloy scaffold effectively aided bone repair. The group C scaffold exhibited the best corrosion resistance and osteogenesis properties, making it a candidate scaffold for repair of bone defects.

Highlights

Treatment of critically sized and large defects in long bones of humans caused by trauma, infection, or a tumor remains a challenging undertaking for orthopedic surgeons [1, 2]
We showed that, relative to the routine healing period for a bone fracture, our uncoated scaffold degraded much more rapidly and had completely degraded by 8 weeks post implantation
The probable reason for the rapid degradation is the presence of body fluids and soft tissue found in the region of the bone defect

Summary

Introduction

Treatment of critically sized and large defects in long bones of humans caused by trauma, infection, or a tumor remains a challenging undertaking for orthopedic surgeons [1, 2]. Available repair modalities include autogeneic, allogeneic [3, 4], and vascularized bone grafts [5]. The most intriguing advantage of a Mg alloy is that it can be tuned to resorb after completion of the bone-healing process, which would eliminate the need for a second surgery to remove it, thereby reducing the risk of infection, discomfort, and cost. The use of a Mg-alloy scaffold to repair a large segmental bone defect has not been reported. We fabricated a scaffold made of a Mg-Zn-Ca alloy that is

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Results

Conclusion