Fracture Biomechanics / Classification Flashcards

1
Q

Bone Macroarchitecture

A

Rigid endoskeleton (epiphysis, metaphysis, diaphysis)

Mineralized osseous tissue (marrow, endosteum, periosteum, nerves, vessels, cartilage)

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2
Q

Cortical bone

A

Shaft of long bones
Highly dense / relatively acellular
Develops in direct proportion to stress
Blood surrounds bone

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3
Q

Trabecular bone

A

Ends of long bones
Porous network
Large surface area
Bathed in blood

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4
Q

Microscopic bone anatomy

A

Cellular components + ECM (organic + inorganic)

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5
Q

Osteoblasts

A

Cover bone surfaces
Form organic matrix osteoid

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6
Q

Osteocytes

A

Osteoblasts incorporated into osteoid
(Bone cell)
Contain cytoplasmic projections

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7
Q

Osteoclast characteristics

A

Large, multinucleated cells
Function: bone resorption (control by local acid environment)
Form from blood monocytes

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8
Q

Organic components of ECM

A

95% Type I collagen
5% ground substance (Proteoglycans + glycosaminoglycans)

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9
Q

Inorganic ECM components

A

Hydroxyapatite (Ca-phosphate)
Laid down by osteoblasts as unmineralized osteoid —> mineralized by alkaline phosphates

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10
Q

Weak spot of bone during longitudinal growth

A

Zone of hypertrophy (where cells are stacked in rows)

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11
Q

Function of bone

A

Protection
Shape
Blood cell production
Mineral/fat storage
Movement
Acid-base balance

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12
Q

Bone formation

A

“Condensations” - aggregates of bone elements in fetal tissues - undifferentiated mesenchymal stem cells - osteoprogenitor cells

Intramembranous ossification (direct development from condensations)

Endochondral ossification (via cartilage intermediate)

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13
Q

Intramembranous ossification

A

Flat bones of skull

Osteoprogenitor cells in cell condensation —> osteoblasts —> produce bone matrix

Bony spicules form + fuse —> trabeculae —> unit to form spongy bone

OP cells in spongy area produce marrow + periosteum —> osteoblasts of periosteum produce compact bone

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14
Q

Endochondral ossification

A

OP cells —> chondrocytes —> growth of cartilaginous bone-to-be —> primary/secondary centers of ossification —> formation of articular cartilage and epiphyseal plate (growth/phsyeal plate)

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15
Q

Primary center of ossification forms …

A

Before or after birth
Forms diaphysis

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16
Q

Secondary center of ossification forms ..

A

After birth + forms epiphyses of long bones

17
Q

Hierarchical structure of bone designed to…

A

Maximize strength and lightness

18
Q

Bone structure corresponds to…

A

The forces it experiences

19
Q

Stress-strain curve

A

Elastic region —> yield point —> plastic region —> failure point

20
Q

Fracture biomechanics - forces

A

Tension (pulling away from center)
Compression (pushing toward center)
Bending
Shearing (two parts twisting towards each other)
Torsion (two parts twisting away)
Combined loading

21
Q

Tension (i.e. weight bearing) + bending results in …

A

Transverse fracture with butterfly fragment

22
Q

Bending of bone results in…

A

Transverse fracture +/- small fragment

23
Q

Torsion results in …

A

Spiral fraction

24
Q

Tension on a bone results in …

A

Transverse fractiure

25
Q

Compression results in …

A

Crushing injury

26
Q

Impact of loading rate on deformation

A

More rapidly a load is applied —> greater deformity

Slow loading allows time to adjust —> less damage

27
Q

Fracture descriptions

A

Open vs closed
Simple vs comminuted
Anatomical location
Displacement
Articular vs nonarticular
Physeal/growth plate injury

28
Q

Simple fracture

A

Two piece fracture
No fragments (comminution)
Transverse, oblique, or spiral
Less complicated to fix

29
Q

Comminuted fractures

A

> 2 pieces
Greater forces —> comminutation
Hit-by-car/gunshot/bite wound

30
Q

Fracture displacement

A

Described by distal fraction relative to proximal fragment
Medial v lateral
Cranial v caudal
Dorsal v palmar
Dorsal v plantar

31
Q

Salter Harris classification

A

P - I - Physis
M - II - Metaphysis
E - III - Epiphysis
B - IV - metaphysis + epiphysis
C - V - crushing

32
Q

Capital physeal fracture

A

Physeal injury of articular joint (acetabulum of femur)

33
Q

Sequelae of Physeal injury

A

Angular limb deformities

34
Q

Open fractures

A

Type I - fracture penetrates skin from within
Type II - wound < 1 cm, communicates with fracture
Type III - high energy trauma, major soft tissue damage +/- bone loss
IIIa - no major plastic procedures
IIIb - soft tissue insufficient for closure
IIIc - arterial injury needing repair, amputation

35
Q

Articular fracture

A

Distal/proximal portion of bone
Joint involvement

Exact anatomic reduction / rigid fixation required