Bone Healing/Grafting Flashcards
What are the three long bone blood supply sources in mature animals?
Principle nutrient artery
Metaphyseal arteries
Periosteal arteries
What are the long bone blood supply sources in immature animals?
Epiphyseal and metaphyseal arteries
What occurs in terms of blood supply with fractured bone?
Development of extraosseous blood supply
What are the two types of bone healing?
Direct- primary osteonal reconstruction
Indirect- callus formation
When does indirect bone healing (callus formation) occur?
Unstable mechanical environment and motion between fracture fragments
- > 1mm gap between fragments
- impaired blood supply or revascularization
What are the three stages of indirect bone healing?
Inflammation
Repair
Remodeling
When does the inflammation stage of indirect bone healing occur?
IMMEDIATELY after fracture, lasts 3-4 days
What occurs in the inflammation stage of indirect bone healing?
Clot at fracture site
- Osteoinductive growth: angiogenesis, bone formation
- Abundant mast cells: vasoactive substances (new vessel formation)
When does the remodeling phase of indirect bone healing occur?
Around 2 months
What occurs during the remodeling phase of indirect bone healing?
Clot differentiates into granulation tissue, gain strength, soft callus, mesenchymal cells become osteoblasts (lay down fibrocartilage)
What is the governing law of remodeling?
Wolfe’s law
Compression- osteoblasts
Tension- osteoclasts
What is the difference of direct and indirect bone healing?
Direct bone healing fills fracture sites with no callus formation
How long does it take to gain mechanical strength?
6-12 months
What size are the fracture gaps with direct gap healing?
< 1 mm
What size are fracture gaps with direct contact healing?
< 0.01 mm
What is contact healing initiated by?
Cutting cones of osteclasts directly followed by osteoblasts
How far do cones travel per day? (micrometers/day)
50-100
What are characteristics of cancellous bone healing?
More stable than cortical bone
No callus formation
Fracture gap filled then cortical shell
Fractured zone of hypertorphy will heal how?
Continued growth of physeal cartilage
Fractured zone of proliferation will heal how?
Endochondral ossification
What is a disadvantage to physeal fractures?
Premature physeal closure (stunted growth)
What are factors that affect fracture healing?
Location of fracture Stability Method of fixation Biological environment Blood supply Biomechanical vs. Biological Osteosynthesis
What is biological osteosynthesis?
Restores overall length and alignment
Limits soft tissue disruption
What are the different types of repairs used on fractures?
Intermedullary pins with wire
Cast/splints/no fixation
Bone plates
External skeletal fixator
Which repairs utilize indirect healing?
IM pins/wires
Casts/splints/no fixation
External skeletal fixator
What repair heals by direct healing?
bone plates
What effect does IM pins/nails have on the blood supply?
Disrupts endosteal blood supply and medullary blood flow
What effect does bone plates have on the blood supply?
Disrupt perioseal bone supply
What does improper bone implants do to blood supply?
damage blood supply
When are bone grafts used?
Bone loss
Arthrodesis
Delayed/non-union fractures
Old age
What are the three bone graft origins?
Autograft
Allograft
Xenograft
What are the three functions of bone grafts?
Osteogenesis (osteoblasts)
Osteoinduction (mesenchymal cells)
Osteoconduction
What are the three bone graft types?
Cancellous
Cortical
Combination
What is the gold standard of bone grafts?
Autogenous cancellous bone graft
What does Autogenous cancellous bone graft promote?
Osteogenesis
What are the four phases of cancellous graft?
Inflammatino (hours)
Revascularization (1-2 weeks)
Osteoconduction (2-4 weeks)
Mechanical support (up to 12 weeks)
Where are autograft cortical bone grafts used?
Ribs
ulna
Fibula
Ilial wing
What patients are cortical bone grafts indicated in?
Devascularized comminuted fractures
OSA patients and limb sparing procedures where dz is caught early and hasn’t metastasized
What are the phases of cortical bone graft effects?
Osteoclasts move into graft and resorb bone
Osteoblasts follow and lay down new bone
Mechanical strength of graft maintained
Termed “creeping substitution”
