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Bone Circulation

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Topic updated on 04/14/13 11:39am
Introduction
  • Bone receives 5-10% of cardiac output
  • Bones that receive tenuous blood supply
    • scaphoid
    • talus
    • femoral head
    • odontoid
  • Blood supply to long bone comes from three sources  
    • nutrient artery system
    • metaphyseal-epiphyseal system
    • periosteal system
Nutrient Artery System
  • High pressure system that branches from major systemic arteries
  • Enter the cortex through the nutrient foramen and enter the medullary canal
    • then branch into ascending and descending branches
      • then branch into arterioles and supply the inner 2/3 of mature bone via the haversion system 
Metaphyseal epiphyseal system
  • Arteries arise from periarticular vascular plexus
    • e.g. geniculate arteries
Periosteal System
  • Low pressure system that supplies the outer 1/3 of bone
    • connected by
      • Volkman's artery (perpendicular to long axis)
      • Haversion system (parallel to long axis)
Intracortical Vascularization
  • Intracortical vessels travel within canals
    • Primary Haversian canals
    • Secondary Volkmann canals
Direction of Arterial Flow
  • Normal intraosseous blood flow rate is 5-20ml/min/100g of bone 
  • Mature bone
    • flow is centrifugal (inside to outside)
      • because of high pressure nutrient artery system and low pressure periosteal system
  • Immature bone
    • flow is centripetal (outside to inside)
      • because low pressure periosteal system predominates
  • Factors increasing blood flow
    • hypoxia
    • hypercapnia
    • sympathectomy
Direction of Venous Flow
  •  Mature bone  
    • flow is centripetal (outside to inside)
      • cortical capillaries drain to venous sinusoids, which drain to the emissary venous system
Growth Plate
  • Perichondrial artery is the major source of nutrition of the growth plate 
Pathoanatomy
  • Fractures
    • patterns of blood flow following fracture
      • immediate phase
        • initial decrease in blood flow after fracture
        • flow is centripetal (outside to inside)
          • because high pressure nutrient artery system is disrupted
          • low pressure periosteal system predominates
    • hours to days
      • increase in blood flow (regional acceleratory phenomenon)
      • peaks at 2 weeks and returns to normal in 3-5 months
  • Intramedullary nails
    • unreamed intramedullary nails preserve endosteal blood supply
    • reaming devascularizes inner 50-80% of the cortex and delays revascularization of endosteal blood supply
    • loose fitting nails spare cortical perfusion and allow more rapid reperfusion
    • tight fitting nails compromise cortical perfusion and reperfusion is slow

 

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Qbank (2 Questions)

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(OBQ05.107) Disruption of which of the following interrupts the major source of nutrients to the growth plate? Topic Review Topic

1. Diaphyseal artery
2. Metaphyseal artery
3. Perichondrial artery
4. Synovial fluid
5. Synovial blood vessels

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