Stages of Fracture Healing
• This occurs during approximately the first 10 days after the injury (see Figure 41-1, A).
• Hematoma forms around and within the broken bone.
• Platelets, inflammatory cells, and chemical mediators released as a result of the hematoma stimulate vascularization and recruit osteoblasts.
• The disruption of blood vessels at the fracture site results in resorption of the bony matrix within the fracture site, which causes the fracture to appear more visible on radiographs. Physicians should anticipate this and reassure parents this is a normal phase of fracture healing, even though the fracture on the radiograph may look “worse.”
• The hematoma is subsequently replaced with an interwoven collagen, which will serve as the scaffolding for new bone formation.
• This usually occurs between 10 and 14 days after the injury (see Figure 41-1, B).
• Enhanced vascularization and the differentiation of mesenchymal cells into cartilage, bone, or fibrous precursors
• As osteoblasts are recruited, bone mineralization occurs and the healing callus becomes visible on radiographs, usually at 2 to 4 weeks after injury.
• The reparative phase ends with radiographic union, which is when the radiograph demonstrates visible callus bridging over and filling in the fracture site; this follows clinical healing, which is when the fracture site is no longer painful to palpation. At this point the fracture is stable in that no further displacement (without trauma) is expected; however, the callus is still relatively weak, structurally disorganized, and not functionally ready for any abnormal stresses placed on the bone.
• Lengthiest phase of fracture healing; can continue for years (see Figure 41-1, C).
• Healing bone gradually returns to its pre-injury shape and strength.
• A protective splint or cast is advised in the early follow-up period.