1 1.1 1.1.1 1.1.2 1.1.3 1.2 2 2.1 2.2 3 4
Biology of fracture healing in unstable fractures 73 Healing under uncontrolled motion 73 Inflammatory phase 73 Repair phase 75 Remodeling phase 76 Healing under restricted motion 77 Biology of fracture healing in stable 78 fractures Contact healing 79 Gap healing 80 Stimulation of fracture healing 81
Radiographic evaluation of fracture healing 88 Implant removal Bibliography 92 91
Dominique J Griffon
Fracture healing interfragmentary strain, deﬁ ned as the deformation occurring at the fracture site relative to the size of the gap. However, bone formation can only occur in a stable biomechanical environment with an interfragmentary strain lower than 2% [2, 3] . Various processes occur to overcome this unfavorable situation. They include initial contraction of muscles surrounding the fracture, resorption of fragment ends, orderly repair with tissues suitable for the mechanical envi ronment, and formation of a prominent external callus.
1.1.1 Inﬂ ammatory phase
Fracture healing shares many similarities with soft-tissue healing but its ability to be completed without the formation of a scar is unique. Therefore, any tissue other than bone which persists within a fracture gap represents incomplete healing  . If adequate vascularity is present, the pattern of fracture repair is dictated by the biomechanical environment. Indeed, bone can only be produced after restoration of mechanical stability. This may be achieved by a natural process of healing or by osteosynthesis, with partial or complete stabilization of the fracture fragments. These healing mechanisms have unique histological features, and each can occur in isolation or in concert with the other to achieve bone union.
Interfragmentary strain, deﬁ ned as the deformation occurring at the fracture site relative to the size of the gap, inﬂuences the type of tissue which forms in the fracture gap.