Basic Science Of Fractures Flashcards Preview

Skin MS: Week 6 > Basic Science Of Fractures > Flashcards

Flashcards in Basic Science Of Fractures Deck (26):
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Composition of Bone

30% Organic --> Cells (2%)(Osteoblasts, osteocytes, osteoclasts), Matrix (Collagen)(98%)

70% Mineral --> Hydroxyapatite (95%), Mg, Na, K, F, Cl 

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Intramembranous ossification

•mesenchymal progenitor cells differentiate into osteoblasts, which then directly form bone

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Endochondral ossification

mesenchymal progenitor cells diffentiate into chondrocytes, initially forming a cartilage intermediate that is replaced as bone is regenerated

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•Cortical or compact bone

•Trabecular or cancellous bone

•Cortical or compact bone - diaphysis/long bones mainly

•Trabecular or cancellous bone - flatbones

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Structure of Cortical Bone

•Haversian system (fundamental functional unit of long bone)

•Nutrient arteries

•Periosteum (outer lining)

•Endosteum (inner lining)

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Structure of Trabecular Bone

More lattice

 

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2 Types of Bone

Woven bone (laid down quickly, immature, disorganized, not as strong) vs. Lamellar bone (stronger, more organized, mature)

 

*Get woven bone first --> lamellar bone

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Initial Injury

Trauma --> Injury to cells, blood vessels, bone matrix, and surrounding soft tissues --> Hematoma & Damage to blood vessels leads to osteocyte death, necrotic material at the fracture site

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Phases of bone healing

Inflammation, repairative, remodeling

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Bone regeneration during fracture healing is analogous to the process that occurs during __________, it involves both __________ and __________, which are interrelated and simultaneous

•Bone regeneration during fracture healing is analogous to the process that occurs during embryonic development, it involves both intramembranous ossification and endochondral ossification, which are interrelated and simultaneous

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Inflammatory Phase 

Release of inflammatory mediators from platelets and injured cells --> Vasodilation --> Edema

Migration of inflammatory cells (PMNs then macrophages and lymphocytes) - release of cytokinds, GSF, etc --> angiogenesis --> Fibroblast, osteoblasts, and chondrocytes appear and produce new matrix (osteoid) REPAIR & Monocytes → Osteoclasts which resorb necrotic tissue CLEANUP

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_______ = coccoon that surround fracture

Soft Callus

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Early repair

Migration of pluripotent mesenchymal cells - proliferate and differentiate

Pluripotent mesenchymal cells → Osteoblasts, Chondrocytes, Fibroblasts

Monocytes → Osteoclasts

--> 

Fibrous tissue, Cartilage, Immature bone =Soft Callus (less movement) --> less pain 

14

________ not involved in fracture repair

Osteocytes

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Transition from soft callus to hard callus

•___________ at periphery - proximal and distal to the injury site

•_________ occurs centrally - overlying the fracture site

•Fracture healing depends on the ______, _______, ________, and _________ of ______________ at the site of the fracture

•Intramembranous bone formation at periphery - proximal and distal to the injury site

•Endochondral bone formation occurs centrally - overlying the fracture site

•Fracture healing depends on the recruitment, proliferation, accumulation, and differentiation of pluripotent mesenchymal cells at the site of the fracture

16

•The ability of a structure to resist torsional and bending loads is _______________

•Advantage of External Callus is to___________ of the bone

•The ability of a structure to resist torsional and bending loads is proportionate to R4

•Increase cylinder of the bone

17

Clinical vs Radiographic Union

•Clinical union – fracture site becomes stable and pain free (according to pt)

•Radiographic union – plain radiographs show bone trabeculae or cortical bone crossing the fracture site, no radiolucency (according to xrays)

 

Which one we adhere to depends on location of fracture (i.e. clavicle clinical vs scaphoid radiographic)

18

Remodeling Phase

•Replacement of woven bone by lamellar bone

•Resorption of unneeded callus

•May continue for years!

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Variables that influence fracture healing

•Injury variables

•Patient variables

•Treatment variables

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Injury Variables

•Soft-tissue damage –Open vs. closed (infection)

•Bone comminution and displacement

•Location of bone injury (i.e. metaphysis has high blood supply - heal well vs. stress fracture in 5th metatarsal)

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Patient Variables

Age is the big one 

Illness (i.e. kidney failure, chemo)

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Treatment variables

Fracture stabilization

23

Fracture repair after internal plate fixation 

•Fracture gap closed by fixation

•No formation of external callus

•Lamellar bone forms directly across fracture line

 

Don't get normal healing (callus) - rely on hardware 

Different sequence of fracture healing

24

*Maturation of bone occurs _____ to ______

*Maturation occurs distal to proximal

25

3 important zones of bone growth

Proliferative zone

Hypertrophic zone - water, weakest

Metaphysis

 

**Sensitive growth cells are in distal area of growth plate 

 

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