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MI1 > Bone & Fractures > Flashcards

Bone & Fractures Flashcards

1
Q

What is the function of the skeleton?

A
  • Rigid supportive framework: Anchoring for organs/structures
  • Movement: muscles use bones as levers
  • Protection: CNS, organs
  • Mineral store: calcium, phosphate ions
  • Blood cell production: RBCs/WBCs
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2
Q

What are the 3 regions of bones?

A

Diaphysis
Metaphysis
Epiphysis

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3
Q

What is the difference between periosteum and endosteum?

A

Periosteum: Lining on the outside of the bone
Endosteum: Lining on the inside of the bone

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4
Q

Where is compact (cortical) bone found?

A

Outer layers of diaphysis and flat bones

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5
Q

What is the function of Harversian systems (osteons) and Haversian and Volkman’s canals?

A
  • Haversian systems (osteons): functional component of bone, lamelli form nested concentric cylinders
  • Haversian and Volkman’s canals: convey blood vessels through bone
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6
Q

What are the components of Haversian systems (osteons)?

A
  • Haversian canal: hole running parallel to long axis of bone
  • Lamelli: each ring around the canal
  • Lacunae: hollows containing osteocytes
  • Canaliculi: canals between lacunae, allow osteocytes to pass info, waste, O2
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7
Q

What are the characteristics of spongy (trabecular, cancellous) bone?

A
  • Forms meshwork
  • Trabeculae - few layers thick
  • Spaces lined with endosteum & filled with marrow
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8
Q

What is the difference between osteoblasts, osteoclasts and osteocytes?

A

Osteoblasts: Form new bone matrix
Osteocytes: Osteoblasts trapped inside bone matrix after forming new bone
Osteoclasts: Break down bone matrix

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9
Q

What are the 4 types of cells found in bone tissue?

A
  • Osteoprogenitor cells (osteoblasts, clasts, cytes)
  • Matrix
  • Fat cells
  • Hematopoietic cells: make RBCs, WBCs within bone marrow
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10
Q

What is bone matrix made up of?

A
  • Collagen fibres
  • Glycoproteins
  • Calcium salts
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11
Q

What are the components of bone matrix?

A
  • Lamelli: layers of matrix
  • Lacunae: hollows containing osteocytes
  • Canaliculi: canals between lacunae, allow osteocytes to pass info, waste, O2
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12
Q

What happens during bone remodelling?

A
  • Bone resorption by osteoclasts
  • Release of osteocytes within osteon, form osteoblasts to lay down new bone
  • Cell to cell communication
  • Muscle pull appears to be significant stimulus
  • Very specific cell responses to load rate, magnitude, timing of bouts
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13
Q

What is ossification?

A

Process of laying down new bone

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14
Q

What happens during ossification?

A

Osteoblasts secret matrix
- collagen fibres/glycoproteins
= osteoid

Osteoblasts secrete matrix vesicles
- enzyme accumulate Ca & phosphate ions in matrix
= bone mineral precipitation

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15
Q

What are the 2 forms of ossification?

A

Endochondral

Intramembranous

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16
Q

What is endochondral ossification and what does it enable?

A

Process of new cartilage being converted into bone, enables complex cartilaginous shapes to be ossified

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17
Q

When does endochondral ossification occur?

A
  • Formation of long bones in embryo
  • Growth in length of long bones
  • Found in epiphyseal plates in growing bones
18
Q

What are the 2 centres of endochondral ossification?

A

Primary centre:
- Near the centre of the diaphysis

Secondary centre:

  • Growth plate
  • Held between epiphysial bone plate and trabecular bone in metaphysis
  • Allows bones to increase in length while maintaining strength
19
Q

What is intramembranous ossification?

A

Process of bone matrix being laid down in fibrous tissue, doesn’t involve cartilage - formation of flat bones

20
Q

What happens during intramembranous ossification?

A

Osteoblasts lay down spicules of bone which combine together to form sheets of bone

21
Q

What are examples of flat bones?

A
  • Skulls, parts of face
  • Body of scapula
  • Ribs
22
Q

What happens during osteoporosis?

A
  • Osteoclasts more active than osteoblasts

- Bone loses mass, density, becomes porous and easy to break

23
Q

Why does osteoporosis occur?

A

Due to age or changes in hormonal levels

24
Q

What is one of the implications of osteoporosis?

A

Vertebral compression - slouched posture, rounded cervical vertebrae

25
Q

What happens in ageing bone?

A
  • Loss of 1% per year, 2-3% after menopause
  • Decreased Ca & fibres, causes bone to become more brittle
  • Cortical bone thins from inside out, greater internal space
  • Bigger Haversian canals, can withstand stress as well
  • Increase porosity, osteoblasts
26
Q

What are other age-related changes?

A
  • Thinning of articular cartilage
  • Calcification
  • Disk changes
  • Reduced transfer of nutrients
  • Parathyroid hormone > calcitonin
27
Q

How are fractures classified in terms of the mechanism of the break?

A
  • Greenstick: Bent
  • Spiral: Twisted
  • Comminuted: Broke into lots of pieces
  • Transverse: Clean, flat, horizontal break
  • Compound: Break is through the skin
  • Vertebral compression
28
Q

How are fractures classified in terms of the end result of the fracture?

A
  • Closed vs open (compound)
  • Simple vs multi-fragmentary
  • Stable vs unstable
  • Displaced vs undisplaced
  • Articular vs extra-articular: involving/not involving the joint
  • Complications, e.g. near vessels, nerves etc
  • Impacted (compacted): shunted into itself
29
Q

What are the mechanisms of injury for fractures?

A
  • Unloaded
  • Tension (pulling away)
  • Compression
  • Bending
  • Shear (two pieces of bone moving laterally away from each other)
  • Torsion
30
Q

What are the physical signs of a fracture?

A
  • Abnormal movement
  • Crepitus (grating between bone ends)
  • Deformity
  • Bruising around fracture
  • Tenderness
  • Pain on stressing the limb (bending/longitudinal compression)
  • Impaired function
  • Swelling
31
Q

What other tissues can be injured by a fracture?

A 
Joints
Ligaments
Soft tissues (blood vessels, nerves, muscles, skin, viscera)
32
Q

What are the types of paediatric fractures?

A
  • Greenstick
  • Buckle (torus)
  • Epiphysial fractures
33
Q

What are the 6 steps of fracture healing?

A

1) Increase in blood flow:
- WBCs, fibro/osteoblasts
- Blood clot (procallus)
- Periosteum confines space, speeds healing process
2) Osteoblasts lay down bone
3) Formation of bony callus:
- 6-8 weeks
- Cast removed
- Primarily trabecular bone, very susceptible to re-fracture
4) Modelling
5) Remodelling
6) Healed fracture - 2 years

34
Q

What occurs during stage 1 of fracture healing?

A

Inflammatory (first few days)

  • Large hematoma
  • Leukocytes/macrophages remove dead muscle/bone fragment
  • Delicate fibrin network bridges fracture fragments
  • Stimulates growth of osteoblasts
35
Q

What occurs during stage 2 of fracture healing?

A

Callus (following 2 weeks)

  • Fibrin network organised and reinforced by collagen fibres
  • Capillaries bring O2/nutrients
  • Osteoblasts form fibrocartilaginous matrix (osteoid)
  • Osteoid becomes calcified, soft callus becomes visible (2-3 weeks)
  • Osteoid is mineralised, fracture fragments cemented together - hard callus (6-12 weeks)
36
Q

What occurs during stage 3 of fracture healing?

A

Remodelling (12-18 months)

  • Osteoclasts remove immature woven bone
  • Osteoblasts lay down lamellar bone along lines of mechanical stress
  • Lamellar bone contains Haversian systems, making it much stronger
37
Q

What are some of the early complications of fractures?

A
  • Wound infection
  • Fat embolism
  • Shock lung (actue respiratory distress syndrome)
  • Chest infection
  • Disseminated intravascular coagulation
  • Compartment syndrome
38
Q

What are some of the late complications of fractures?

A
  • Deformity
  • Osteoarthritis of related joints
  • Avascular necrosis
  • Traumatic chondromalacia
  • Complex regional pain syndrom
39
Q

What are the reasons for fractures not healing?

A
  • 10% of the time biological (natural problem)

- 90 of the time technical (not set right)

40
Q

What are some of the complications for failure in fracture healing?

A
  • Mal-union: heals with residual deformity
  • Delayed union: takes longer
  • Non-union: fracture gap fills with scar tissue instead of bridging callus
  • Pseudoarthrosis: movement is excessive around fracture site, cavity forms with synovial fluid
  • Rotation of bone segments (bad)
  • Some angulation or displacement is OK
41
Q

What is the treatment for fractures?

A
  • Reduction
  • Stabilisation
  • Immobilisation of fracture site
  • Rehabilitation of soft tissues and joints
42
Q

What are the methods of reduction?

A
  • Traction: e.g. Hamilton Russell traction
  • External splints/braces/Plaster of Paris (POP), fibreglass
  • External fixation: drilled through skin into bone
  • Internal fixation: drilled into bone under skin

MI1 (18 decks)

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