Material-based therapy for bone nonunion

Bone nonunion has become one of the most severe sequelae of fractures, infections, bone tumors, or revision arthroplasty owing to its high morbidity and disability rate. Recently, bone nonunion has received considerable attention from plastic surgeons. There are different treatment methods for nonunion depending on its classification according to the etiology and pathological types. Bone tissue engineering provides advanced platforms for the treatment of bone nonunion via the use of material scaffolds with sufficient mechanical strength. Meanwhile, it promotes bone regeneration and osseointegration by the addition of various growth factors or drugs. This review describes in detail the classification and leading causes of nonunion, as well as the clinical treatment methods and basic research progress, including the design of metal and bioactive material scaffolds. Future challenges in engineering, material science, and three-dimensional printing are also summarized. This article may provide new perspectives of the clinical translation for the treatment of bone nonunion by understanding the pathogenic mechanism and the rational application of bioactive scaffolds.