Biomechanics of the vertebral body; trabeculae, cortical thickness and end plate Flashcards

1
Q

C3-C7 are wider where?

A

transversely than anteroposteriorly

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2
Q

They have a convex inferior surface and concave superiorly due to what?

A

the unicate process protruding upwards on the lateral borders

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3
Q

what does the atlas lack?

A

a vertebral body or spinous process

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4
Q

instead of a vertebral body to act as the weight bearing structure what does the atlas have?

A

lateral masses

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5
Q

in relation to the atlas what is on the lateral masses?

A

the transverse articular surfaces in which the atlas connects with the cranium via the occipital condyles

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6
Q

what is the strongest of the cervical vertebrae?

A

axis

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7
Q

what does the axis allow?

A

pivoting movement of the head due to its unique structure

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8
Q

what are the types of bone making up the lumbar vertebrae and what do they allow?

A

Outer cortical bone shell
Large section of cancellous bone deep to this.
Cancellous bone allows for dynamic compression where the cortical bone would just fracture if it alone was exposed to this

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9
Q

what are the trabecular systems surrounded by?

A

compact bone

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10
Q

bone is what?

A

hard and resilent

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11
Q

what is bone composed of?

A

65% mineral salts
23% collagen
10% water
2% non-collagen proteins

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12
Q

what is surrounding the bone?

A

a periosteum outer-layer; fibrous and osteogenic

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13
Q

cortical bone is what?

A

relatively dense and compact

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14
Q

in vertebrae what does cortical bone form?

A

a surrounding shell, around the trabecular bone

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15
Q

what is the main role of cortical bone?

A

provide strength

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16
Q

what does cortical bone contain?

A

osteon around haversian canals, give space for blood vessels and nerves

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17
Q

what is the functional unit of trabecular bone?

A

trabeculae

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18
Q

what is trabecular bone?

A

vertebral body core

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19
Q

trabeculae form what?

A

interconnected, open porous network

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20
Q

what are the pores filled with in trabecular bone?

A

bone marrow and blood vessels

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21
Q

what does trabecular bone lack?

A

haversian canals

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22
Q

where does trabecular bone get its nutrients?

A

via diffusion from bone marrow

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23
Q

what is the main role of trabecular bone?

A

transfer mechanical force

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24
Q

characteristics of cortical bone?

A

harversian systems, denser, compact, surrounding shell, heavy, provide strength

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25
Q

characteristics of trabecular bone?

A

lacks haversian canals, more surface area, porous (3D network), core, lighten bone, transfer forces

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26
Q

weight of the body produces what?

A

an axial compressive force on the vertebral column

27
Q

what percentage of weight is transferred to trabecular bone in the vertebral body?

A

25%-90%

28
Q

what vertebrae are under most stress?

A

thoracocolumbar and lower lumbar region

29
Q

anterior flexion of the trunk does what to the COG?

A

shifts the COG forward and creates shearing forces on the vertebrae

30
Q

to maintain anterior flexion of the trunk what is happening?

A

erector spinae muscles are acting to counteract and stabilise this movement, in doing so they are exerting a compressive force on the vertebrae

31
Q

what is wolffs law?

A

bone function changes cause bone structure modification

32
Q

limitations of wolffs law?

A

Fails to account for hormonal activity governing the activity of osteoclasts and osteoblasts in defining bone density

To combine hormonal influences and mechanical forces as stress on bone the Mechanostat theory and Utah Paradigm was formed.

33
Q

in areas of stress, trabecular bone reacts in what ways?

A

Areas with most stress develop more dense trabeculae

Thicker trabeculae

Closer more uniform spacing of trabeculae

Along areas of stress trabecular patterns form as a direct function of stress

34
Q

where is the vertical system found?

A

the vertebral column with the exception of the IV discs

35
Q

what is the vertical system composed of?

A

large cylindrical struts of trabecular bone in vertical arrangement in the central zone of the vertebral body

36
Q

what is the functional role of the vertical system?

A

to resist acial compression for weight bearing

37
Q

what does the vertical system resist?

A

shocks and jars perpendicular to the vertebral column

38
Q

the vertical system has the most resistance to what?

A

atrophy out of the trabecular systems

39
Q

what are the primary systems?

A

vertical system

40
Q

what are the secondary systems?

A

horizontal and oblique systems

41
Q

how many oblique systems are there?

A

4, 2 superior, 2 inferior

42
Q

what to oblique systems resist?

A

torsion, they are woven together

43
Q

oblique systems along with vertical resist what?

A

bending and shear

44
Q

horizontal systems resist what?

A

muscular tension produced to counteract movements

45
Q

superior oblique runs where?

A

runs from superior articular process through pedicle to lower surface of the vertebral body

46
Q

inferior oblique runs where?

A

runs from inferior articular process through pedicle to upper surface of the vertebral body

47
Q

oblique systems absent where?

A

in anterior surface of vertebral body making it more prone to fracture

48
Q

the vertebral body is made up of what?

A

a shell of cortical bone with an inner core of cancellous bone

49
Q

a solid block of cortical bone is likely to what?

A

to fracture along cleavage planes when dynamic force is applied to it.

50
Q

without the addition of cancellous bone in the centre the cortical bone would be what?

A

be a shell which is also likely to collapse when force is applied.

51
Q

the cancellous bone forms what?

A

vertical and transverse trabeculae which act as the internal architecture of the bone. They form ‘cross beam’ like structures meaning tension is held both transversely and vertically in the vertebral body.

52
Q

the strength of a vertebral body is dependent on what 4 factors?

A

bone mass, the trabeculae architecture, the size of the vertebral body and the thickness of the cortical ring.

53
Q

which spine has the largest thickness?

A

lumbar spine (290um)

54
Q

what is the second largest thickness of spine?

A

cervical spine (285um)

55
Q

what thickness is the thoracic spine?

A

244um

56
Q

the vertebral bodies cortical shell is thicker where?

A

anteriorly thicker and thinner posteriorly

57
Q

is the cartilagenous end plate thick or thin?

A

very thin; 1mm

58
Q

how thick is the IVD?

A

7-10 mm

59
Q

where is the CEP thinnest?

A

in the central region adjacent to the nucleus pulposus

60
Q

what does the CEP contain?

A

osseous component and a hyaline cartilage and cartilaginous component

61
Q

what is the function of the CEP?

A

maintaining the integrity of the vertebral bodies

62
Q

what does the CEP absorb?

A

Simultaneously absorbs hydrostatic pressure that results from mechanical loading of the spine

63
Q

what does the CEP prevent?

A

Prevent the highly hydrated nucleus from bulging into the adjacent vertebral bone

64
Q

the CEP degenerates with what?

A

Degenerates with ageing- calcification