Fracture Healing (and disruptors of this process) Inflammatory Stage (0-7d) • Fracture disrupts local blood vessels -> formation of hematoma -> Inflammatory reaction & release of cytokines -> activation of osteoprogenitor cells and mesenchymal differentiation into cartilage-producing chondrocytes at fracture site Soft Callus Stage (wks 1-3) • Chondrocytes lay down cartilage in place of the hematoma -> bridging the fracture site more stability Hard Callus Stage (wk 3 - mo 3) • Mineralization of cartilaginous matrix by osteoblasts forms bony callus -> Incr fracture-site stability Remodeling (mos - yrs) • Osteoclast-osteoblast coupled bone remodeling: Callus along the trajectory of mechanical forces is fortified, while callus not in line with mechanical forces is reabsorbed Factors that may disrupt fracture healing - Tobacco & Alcohol abuse - Incr healing time, mechanisms unclear - Metabolic / Endocrine disorders - Corticosteroids & prolonged NSAlDs - Block the inflammatory response that promotes healing - Vascular Insufficiency / Compromise - Trauma or pre-existing vasculopathy - Fluoroquinolones - Causes formation of an immature callus - Infection - Increases risk for non-union - Inadequate fixation of fracture - Too loose = hypertrophic non-union, Too rigid = atrophic non-union - Rifampicin & topical gentamycin - Toxic to osteoblasts - Vitamin D Deficiency - Insufficient Ca2+ & PO4- absorption from GI tract, bone mineralization. #Fracture #Healing #Stages #Orthopedics #msk #Staging #pathophysiology #diagnosis #disruptors
