Table 1: Definition of terms and common examples.

Term	Definition	Example
Osteoconduction	The process by which an implanted scaffold passively allows ingrowth of host vasculature, cells and tissue	Resorption of calcium sulfate or phosphate cements
Osteoinduction	The process by which exogenous growth factors promote differentiation of host MSCs to form chondroblasts and osteoblasts that form new bone	Bone morphogenetic proteins
Osteogenesis	The synthesis of new bone by donor cells derived from either the host or graft donor	Various autografts, stem cell transplants
Fracture nonunion	A bone fracture that is at least nine months old in which there have been no signs of healing for three months (US FDA definition)3
Hypertrophic nonunion	Fracture nonunion with the presence of callus, typically due to inadequate immobilization of fracture ends	See Figure 1
Atrophic nonunion	Fracture nonunion without the presence of callus, typically due to impaired healing from vascular, nutritional, immunogenic, or metabolic impairments	See Figure 2
Growth factor	A naturally occurring protein or hormone that stimulates cellular differentiation, proliferation and/or growth	Transforming growth factor beta, insulin-like growth factor
Mitogen	A growth factor that specifically induces cellular mitosis	Bone morphogenetic proteins, vascular endothelial growth factors, fibroblast growth factors
Ceramic	An inorganic compound formed at high temperatures that contains metallic and non‐metallic elements with a crystalline structure	Alumina, Zirconium, Hydroxyapatite, Calcium phosphates
Glass	An inorganic solid compound formed at high temperatures with a non-crystalline or amorphous structure	Poly(methyl methacrylate)