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Enhancement of Fracture Healing

  • fracture healing = specialized type of wound healing with bone regeneration
  • incidence of delayed healing in USA = 5 to 10%

Causes

  • inadequate immobilization
  • distraction
  • repeated manipulations
  • excessive early motion
  • excessive periosteal stripping
  • other soft tissue damage
  • contamination/infection
  • anatomical structure e.g. NOF, scaphoid, talus

2 aspects

  1. biological interventions
  2. mechanical interventions

Biological enhancement

Local approaches

  • stimulate bone healing = osteogenic, osteoconductive, osteoinductive methods

Osteogenic methods

  • autogenous bone graft (Macewen 1881)
  • allograft
  • autogenous bone marrow graft
    • haematoma forms around graft
    • release of bio-active materials
    • necrosis of graft & an inflammatory response, development of a fibro-vascular stroma with host derived blood vessels & osteogenic precursor cells
    • graft is penetrated by osteoclasts - graft resorption
    • a few cells from the graft may survive but main function is osteoconductive properties + osteoinduction d/t factors which stimulate the local inflammatory response with # healing
    • cancellous graft allows more rapid revascularization & leads to better incorporation than cortical bone
    • inlay grafts are better than onlay grafts
    • rigid fixation enhances graft survival & revascularization
    • bone of endochondral origin eg. tibia have > rate of revascularization compared to bone of membranous origin eg. iliac blade but must be securely fixed
    • once the graft is adherent to the host bed, fixation plays no further role
    • concern with allograft - infection, blood borne disease, histocompatibility.
  • bone marrow - contains osteogenic precursors
  • marrow derived mesenchymal cells in the future

Osteoconductive methods

  • supports the ingrowth of vascular tissue & osteogenic cells
    • Ca based ceramics - HA (marine coral), tricalcium phosphate
    • Ca-collagen grafts
    • bio-active glass
    • synthetic polymers - inorganic Ca & phosphate paste which is injected into the # site & hardens

Osteoinductive methods

  • process that supports formation of osteoprogenitor cells with the capacity for new bone formation
  • can get bone formation at extra-skeletal sites
    • BMP (bone morphogenic proteins)
    • fibroblast growth factors
    • platelet derived growth factor
    • transforming growth factor-beta
      • the above are growth factors
      • these are cytokines which modulate & regulate fracture healing

Systemic approaches

  • humoral factors
    • #’s heal faster & with more callus in head injuries
  • prostaglandins
    • anabolic effect, esp PGE2
    • effect blocked by indocid ie. anti-prostaglandin
  • circulating osteogenic substances

Mechanical enhancement

  • Rx of a fresh # may differ from the Rx of a non-union
  • # healing is retarded by over-distraction or instability
  • controlled micromotion or controlled rythmic distraction may enhance # healing
  • in general, motion at a # site will cause formation of callus: hypermotion = hypertrophic non union

Effects of weight bearing

  • Sarmiento - improved # healing
  • Some report no difference in healing with weight bearing
  • early stability improves blood flow, intra-medullary reaming + a tight fitting nail decreases blood flow
  • electrical stimulation - most research has been with non-unions, may be beneficial
  • electromagnetic stimulation - useful in delayed union
  • ultra-sound - has a role in # healing