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Bone Healing, Grafting, Nonunions - Coggle Diagram

- - - - Contact healing
        
        Occurs where there is direct cortical contact
        
        Bone modeling unit cutting cone
        
        Osteoclast, blood vessels, osteoblasts
        
        Rate of bone resorption/formation = 50-80 µm/day
        
        Osteoclasts follow Haversian canals nearest fracture
        
        Cross fracture, followed by capillary buds
        
        Osteoblasts deposit osteoid across fracture
      - Gap healing
        
        Gaps 200-500 μm filled with blood clot
        
        Capillary buds form after 2 weeks
        
        Osteoblasts deposit lamellar bone in gap
      - Not necessary for good outcome
        
        Goal for intraarticular fractures
      - Proceeds slowly
      - No callus formation
      - no cartilage intermediary
      - Requires
        
        Anatomic reduction
        
        Absolute rigid stability
    - - Cutting cones cross new bone in gap
      - Deposit new bone parallel to weight bearing axis
  - - - Interfragmentary strain is high
      - Vascularity is poor
      - Fracture gap is large Stages of Indirect Healing
    - - Large callus forms away from neutral axis
      - Progression of tissue laid down
      - granulation => fibrous/cartilage => increased bone stability, decreased motion => decreased strain
      - Osteoclastic resorption
      - increased gap width decreases strain
        
        Strain reduced to < 1% => bone forms !!!
    - - Hematoma forms
      - activated cells (platelets, MΦs,PMNs) clear dead bone, debris, bacteria
      - Growth factors stimulate
        
        angiogenesis
        
        cell migration
        
        differentiation
        
        GFs involved
        
        PDGF
        
        Interleukins
        
        TGF
        
        PGE
      - Granulation tissue forms
        
        Inhibited by
        
        NSAIDs
        
        cytotoxic drugs
    - - 2a. Soft Callus
        
        Fibroblasts produce stroma for vascular ingrowth
        
        high PO2 osteoblast activity
        
        Cartilage where PO2 is low
        
        big callus size = stability
        
        Tissues bridge fracture
        
        interfragmentary strain drops
      - 2b. Hard Callus
        
        Granulation tissue mineralizes
        
        Endochondral ossification
        
        Osteoblasts from the periosteum produce osteoid –
        
        intramembranous ossification
        
        Neovascularization is essential
    - - Woven bone replaced by lamellar cortical bone
      - Wolff’s Law = bone will adapt to the loads under which it is placed
      - Dynamization increases load sharing by bone
      - Reduce callus diameter
      - Re-establish medullary canal
- - - - ∆L - increase stability => callus formation
      - L - osteoclastic resorption of bone fragment
- - - - If reduction is OK
        
        Need to maintain fixation
        
        Restrict activity
      - If reduction is not good
        
        Add stability – ESF
        
        Replace implants
      - If malaligned
        
        Replace implant after realignment
        
        Graft
  - - - Types
        
        Hypertrophic
        
        Mildly hypertrophic
        
        Oligotrophic
      - Treatment
        
        Realign if necessary
        
        Apply stable fixation (compress)
        
        Use callus as graft
    - - Types
        
        Dystrophic - no vascular supply
        
        Necrotic
        
        Defect
        
        Atrophic - movement at fracture site
      - Treatment
        
        Open approach
        
        Remove tissue from fracture site
        
        Remove sclerotic ends
        
        Open medullary canal
        
        Realign, if necessary
        
        Add bone graft
        
        Apply rigid fixation
        
        May need more treatment (grafting)
      - Common Causes
        
        Poor immobilization
        
        Inadequate reduction
        
        Impaired blood supply
        
        Presence of infection
        
        Large bone defect