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102 Cards in this Set

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What are the 2 macroscopic bone types?
1) Cortical bone= compact bone
2) Cancellous bone= trabecullar bone
What bone is cortical (compact) bone?
In the shaft of the long bones
"cortex" - outer dense layer
Cortical bone is made up of _____ bone.
Lamellar bone - bone is layed down layer by layer, can remodel in a dramatic fashion when force is applied
-cancellous is lamellar too
Where is cancellous bone located?
-In center and ends of long bones
-flat bones
What are 2 microscopic types of bones?
1) Woven
2) Lamellar
When is woven bone laid down?
Occurs during rapid growth, rapid bone repair process, insertions of tendons/ligaments
What is woven bone?
Connective tissue stiffened by incorporation of mineral
-bundles of collagen fibers arranged similar to other CTs
Compare the mechanical properties of woven and lamellar bone.
Woven bone is inferior to lamellar bone
-woven bone is usually remodeled to become lamellar bone (long bones, fractures)
______ is the major portion of cortical and cancellous bone.
Lamellar
What is the rate of lamellar bone growth on a per day basis in optimal conditions?
****Osteoblats form1-2 um of lamellar bone per day
-slower rate of formation
-deposited layer by layer
Osteoblasts lay down lamellar bone then remodel to form ______.
Tunnels w/in bone- haversian systems/ secondary osteons
What is the outer fibrous layer covering bones (other than where bone is covered by articular cartilage?
Periosteum
What layer of bone is responsible for remodeling/ regeneration?
Periosteum- its the inner osteogenic layer
What provides blood supply to bone? (3) What does the blood flow in?
1) Branches from periosteum
2) Branches from endosteum
3) Nutrient foramen (long bones)
-In: Medullary cavity, haversian canals, Volkmann's canals
What 3 cell types are present in bone?
Osteocytes
Osteoblasts
Osteoclasts
What are the 4 components of bone?
1) Cells
2) Organic matrix (21% of wet weight)
3) Inorganic part of matrix (71% of wet weight)
4) Water (8% wet wt.)
What is the organic matrix comprised of?
Osteoid: 90% type I collagen, 10% non-collagens (osteonectin, osteocalcin, proteoglycans)
What makes the organic matrix of bone? What degrades it?
Osteoblasts make it
Osteoclasts degrade it
What is the organic matrix of bone comprised of?
Hydroxyapatite (Ca, P)
What governs the inorganic matrix? degrades it?
Governed by osteocytes
Degraded by osteoclasts
What are the 2 types of developmental bone formation?
1) Membranous bone formation
2) Endochondral bone formation
What is membranous bone formation?
Ossification by direct mineral deposition into organic matrix of mesenchymal CT
What bone is formed by membranous bone formation?
Skull, mandible, appositional growth of all bones
What is endochondral bone formation?
Cartilaginous template formed first, then transformed via calcification and replacement by bone
What are 2 types of bone growth that utilizes endochondral bone formation?
1) Longitudinal growth of long bones (growth plates)
2) Centrifugal growth of epiphyses
What are 3 types of growth cartilage?
1) Discoid growth plate
-longidtudinal growth
2) Spherical growth plate
-centrifugal growth
3) Apophysis
-traction epiphysis
Where are discoid growth plates located?
End of long bones (metaphyseal growth plate)
Where are spherical growth plates located?
-Cuboidal bones of carpus, tarsus
-epiphysis
What are 3 locations of apophyses?
olecranon process, calcaneal tuber, tibial tuberosity
What are the 5 zones of growth cartilage?
1) Resting or reserve
2) Proliferative
3) Hypertrophic
4) Calcified cartilage
5) Primary spongiosa of bone (replaces calcified cartilage)
What is Wolff's Law?
Bone adapts to the loads that are placed on it
-bone mass is increased where more bone is needed
What is the yield load of a load deformation curve?
Place where the load placed on the bone suddenly results in a lot more deformation- where levels off on graphs, bad thing
When examining a load deformation curve, what part is the stiffness?
Slope of the straight portion of the graph
What are the 3 factors that can be interpreted from a load deformation curve?
Stiffness
Yield load
Ultimate failure load
Stress is approximately equal to -_______.
Load
Strain is approximately equal to _______.
Deformation
What are the 2 regions of a stress-strain curve?
Elastic region: lots of stress w/ little increase in strain
Plastic region: Increase in strain with little stress
What are the 5 normal loads placed on a bone?
1) bending
2) Torsion
3) shear
4) Tension
5) compression
What are the 5 loading modes of bone?
1) Tensile
2) compressive
3) bending
4) torsion
5) shear
Stress is approximately equal to -_______.
Load
Strain is approximately equal to _______.
Deformation
What are the 2 regions of a stress-strain curve?
Elastic region: lots of stress w/ little increase in strain
Plastic region: Increase in strain with little stress
What are the 5 normal loads placed on a bone?
1) bending
2) Torsion
3) shear
4) Tension
5) compression
What are the 5 loading modes of bone?
1) Tensile
2) compressive
3) bending
4) torsion
5) shear
What are 2 ways fractures can result?
Single ultimate failure load
Repeated cyclic loading
What are 3 ways repeated cyclic loading can cause fractures?
1) Fatigue fracture
2) Site specific
2) Histologic evidence: microdamage
What are 2 specific sites that are prone to fracture?
Dorsal cortical metacarpal fracture
Distal metacarpal condylar fracture
What are the 2 types of bone healing?
1) Primary/ direct fracture healing
2) Secondary/ indirect fracture healing
What fractures will heal by primary/ direct fracture healing?
Rigid internal fixation, adequate reduction, sufficient blood supply
When bone heals via primary healing the fracture ends unite via ________.
Haversiain remodeling
When does secondary/ indirect fracture healing occur?
Small movement in fracture gaps
When bone heals via primary healing the fracture ends unite via ________.
Haversiain remodeling
What is secondary/ indirect fracture healing?
Fracture heals via periosteal, intercortical and endosteal callus formation= endochondral ossification
When does secondary/ indirect fracture healing occur?
Small movement in fracture gaps
What are the 7 events that occur during secondary/ indirect fracture healing?
1) hematoma-->
2) granulation tissue--->
3) Fibrous tissue--->
4) Fibrocartilage-->
5) Mineralized--->
6) Woven bone--->
7) Lamellar bone
What is secondary/ indirect fracture healing?
Fracture heals via periosteal, intercortical and endosteal callus formation= endochondral ossification
What are the 7 events that occur during secondary/ indirect fracture healing?
1) hematoma-->
2) granulation tissue--->
3) Fibrous tissue--->
4) Fibrocartilage-->
5) Mineralized--->
6) Woven bone--->
7) Lamellar bone
What are the 2 types of interfragmentary strain?
1) Elongation
2) Bending
How much elongation can granulation tolerate? Cartilage? bone?
Granulation tissue: 100%
Cartilage: 10-15%
Bone: 2% - can't tolerate much elongation before it fails
What degree of bending can granulation tissue tolerate? Cartilage? Bone?
Granulation tissue: 40 degrees
Cartilage: 5 degrees
Bone: 0.5 degrees
*Little tolerance to bending when healing
What are the 3 phases of bone healing?
1) Inflammatory phase
2) Reparative phase
3) Remodeling phase
What happens during the inflammatory phase of bone healing?
- vasodilation, leukocyte migration, chemotaxis
-mesenchymal cell proliferation, angiogenesis
When does the inflammatory phase of bone healing occur?
2-3 weeks post injury
What happens during the reparative phase of bone healing?
-Repair tissue highly vulnerable to interfragmentary motion
-periosteal & endosteal callus formation by endochondral and membranous ossification
How long is the reparative phase of bone healing?
2-12 months
-overlaps with inflammatory phase
What occurs during the remodeling phase of bone healing?
Osteonal remodeling
The remodeling phase overlaps with the ______ phase.
Reparative phase
When is it normal for the fracture gap to widen, as determined via radiographs?
2-3 weeks post injury
How can you determine the amount of interfragmentary motion of a bone via radiographs?
Size of callus
True or false. The size of the callus may predict the degree of fracture stability.
False, size of callus may NOT predict degree of fracture stability
How does complete healing of bone appear on a radiograph?
Bridging of bone & remodeling of the callus
What are the 4 ultimate goals of bone healing?
1) Reconstruction of original cortices
2) Early return of total limb function
3) Rapid bone union
4) Prevention of fracture disease
What are 6 ways that bone healing can predispose the bone to fracture disease?
1) Soft tissue contracture
2) Loss of muscle
3) Osteopenia
4) Loss of joint function- prevent OA
5) Contralateral limb disease
-breakdown or laminitis
6) Malunion / nonunion
What type of bone healing is most desirable?
Primary fracture healing by Haversian remodeling rather than secondary healing by callus formation
What are 3 ways to try and provide the right circumstances for primary healing?
1) Rigid fixation
2) Adequate reduction
3) Preservation of blood supply
What are 4 advantages of the biologic effect of plating?
1) Direct bone union if fracture compression
2) Stress protection
3) Rigid fixation
4) Adequate reduction
What is the disadvantage of the biologic effects of plating?
Disrupt periosteum & fracture hematoma to apply
What are the 3 types of bone plating techniques?
1) Compression
2) Neutralization
3) Buttress
**What are the properties of compression bone plates?
-tension band (on tension surface of bone)
-Pre-stressing (overbending)
-Load sharing
**What are the properties of neutralizing bone plates?
- protect the repair
- medial buttress intact
**What are the properties of buttress bone plates?
- no load sharing
-Acts as a splint or bridge to maintain length of limb
- no holes in bridge
What are the 2 ways to preserve blood supply?
1) Preserve Periosteum
2) Preserve soft tissue attachments
What are the 2 components of biologic osteosynthesis?
Closed reduction & external fixator
What are 3 advantages to biologic osteosynthesis?
1) Encourage early callus growth (indirect union) to move load from implant to bone
2) Emphasize preservation of blood supply over anatomic reconstruction- "spatial alignment"
3) Provide for early dynamization to stimulate callus growth
Why is biologic osteosynthesis difficult in horses?
Large biomechanical often dictates fixation technique (i.e. plating)
Dynamization is only possible in _____ animals.
Smaller animals
-Often happening inadvertently in horses
What is dynamization?
Strategic reduction in rigidity of fixation to allow for MICROmotion of fracture ends
-stimulates vascular and callus growth by interfragmentary micromotion
-has ability to adjust degree of fixation to enable dynamization
________ allows for stages removal when using dynamization therapy.
External skeletal fixator
What are the 3 main functions of bone grafts & replacements?
1) Osteogenesis
- by fresh osteoblasts
2) Osteoinduction
-growth factors, cytokines
3) Osteoconduction
-matrix scaffold
What are the 4 types of bone grafts and replacements?
1) Autogenous fresh cancellous bone grafts
-tuber coxae, sternum
2) Cortical bone (less common)
3) Bone replacements (osteoconductive only)
-Hydroxyapatite, tricalcium phosphate
4) Growth factors
-bone morphogenetic protein-2 (BMP-2)

What is a type I open fracture?
Small skin laceration without bone exposure, no gross contamination
What is a type II open fracture?
Skin laceration w/ little tissue loss, minimally exposed bone, minimal gross contamination
What is a type III open fracture?
Extensive laceration, significant tissue loss, extensive gross contamination
What are the different configurations for fractures?
-fissure/hairline/greenstick
-transverse, oblique, spiral, comminuted/compound, avulsion
Give some examples of a fracture location?
Diaphyseal, metaphyseal, physeal, epiphyseal
-intra-articular
What are the 5 components to fracture classification?
1) Complete vs incomplete
2) Displaced vs non-displaced
3) Open vs closed
4) Configuration
5) Location
What is a type I salter harris fracture?
Complete separation of the physis
What is a type II salter harris fracture?
Physeal fractures breaks out in metaphysis
what is a type III salter harris fracture?
Intra-articular fracture through epiphysis and physis
What is a type IV salter harris fracture?
Intra-articular fracture extending through epiphysis, physis, and metaphysis
What is a type V salter harris fracture?
Crushing injury leading to closure of physis in limited area
What is a type VI salter harris fracture?
periosteal bridge between metaphysis and epiphysis slows growth on affected side?