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Fracture Healing

  Fracture Healing:  Four overlapping phases of bone repair: the inflammatory phase; the early callus phase; the mature callus phase; and the remodeling phase.

Inflammatory Phase

  • characterized by an inflammatory and marrow response
  • immediately following fracture to 3 to 4 days postfracture. 
  • release of proinflammatory mediators: interleukin 1 (IL-1), IL-6, tumor necrosis factor alpha (TNF-α):  peak expression 24 hours after injury with decline to baseline levels by 72 hours post-fracture. 

Early Callus Phase

  • predominated by mesenchymal and vascular infiltration and chondrogenesis
  • From few days to several weeks post-fracture 

Mature Callus Phase,

  • marked by endochondral ossification and primary bone (also called immature or woven bone) formation.
  • cartilaginous matrix is mineralized and primary bone is formed
  • fractures are typically considered healed during the late mature callus phase / early remodeling phase. 

Remodeling Phase

  • secondary bone (also called mature or lamellar bone) formation.
  • fractures are typically considered healed during the late mature callus phase / early remodeling phase. 
  • late remodeling can continue beyond 1 year

Chondrogenesis: divided into six phases: MSC proliferation, MSC condensation, chondrocyte formation, chondrocyte maturation, hypertrophic differentiation, and apoptosis.

Parathyroid hormone (PTH)

  • 
increases the calcium by indirectly stimulating bone resorption, increasing renal reabsorption of calcium, and increasing intestinal calcium absorption
FDA approved for treatment of osteoporosis in postmenopausal women

  • high-dose recombinant PTH (40 μg) has demonstrated accelerated cortical bridging in distal radius fractures (Aspenberg P, J Bone Miner Res 2010;25(2):404)

 

Vitamin D (800 IU) and calcium (1 g) has demonstrated increased callus formation in non-op proximal humerus fracture (Doetsch AM, Calcif Tissue Int 2004;75(3):183-188)