Biomech unit 4 Upper limb & Spine - deck 5

Question 1

What does the thoracic (or dorsal) spine consist of and where is it located in the body?

Answer 1

It consists of the twelve vertebrae located in the posterior part of the thoracic region of the trunk (the chest).

Question 2

What is each thoracic vertebrae attached to ?

Answer 2

A pair of ribs (Left and right side of the vertebrae)

Question 3

How does each rib articulate with each thoracic vertebrae?

Answer 3

The head of each rib articulates with the body and the tubercle of each rib articulates with the transverse process

Question 4

What 3rd articulation do the 2nd to the 9th ribs have with the thoracic vertebrae?

Answer 4

They also articulate with the body of the vertebrae above

Question 5

What do the articulations between the ribs and thoracic vertebrae allow?

Answer 5

The ribs to move up and down as we breathe.

Question 6

What does the articulations of the ribs with the thoracic vertebrae do in terms of the movement allowed in the thoracic region ?

Answer 6

The ribs give added rigidity to the thoracic spine which effectively limits its mobility to only a very limited degree of flexion and extension and little rotation.

Question 7

What does the lumbar spine consist of ?

Answer 7

5 vertebrae

Question 8

How do the vertebrae in the lumbar spine differ from vertebrae in other regions of the spine ?

Answer 8

• The vertebrae in the lumbar spine have larger bodies
• This is because the lumbar vertebrae are subjected to significantly greater loads than the vertebrae in the rest of the spine.

Question 9

What part of the spine do the sacrum and coccyx form ?

Answer 9

They form the distal portion of the spine, they lie below the lumbar vertebrae

Question 10

Describe the shape and what forms the sacrum

Answer 10

It is a single triangular-shaped bone that has resulted from the fusion of five separate vertebrae

Question 11

What is the coccyx and what forms it ?

Answer 11

It is a single bone that has resulted from the fusion of four or five vertebra.

Question 12

What is the sacrum the link between ?

Answer 12

The lumbar spine and the pelvic girdle

(The pelvic girdle consists of paired hipbones, connected in front at the pubic symphysis and behind by the sacrum; each is made up of three bones—the blade-shaped ilium, above and to either side, which accounts for the width of the hips; the ischium, behind and below, on which the weight falls in sitting; and the pubis, in front.)

Question 13

The junction between the lumbar spine and the sacrum is very mobile - T or F?

Answer 13

True

Question 14

Other than the lumbar spine what is the sacrum joined to?

Answer 14

It is also joined to the 2 inominate bones of the pelvis (R and L inominate bones)

Question 15

State what the inominate bones of the pelvis are

Answer 15

The bone formed from the fusion of the ilium, ischium, and pubis; the hip bone.

Question 16

State the type of joint which joins the sacrum to the inominate bones and also state the range of motion allowed at these joints

Answer 16

2 Fibrous joints joint them, they only allow a small amount of relative motion

Question 17

The range of motion of the spine is large - T or F?

Answer 17

True

Question 18

What factor is the biggest influence on the ROM permitted in the spine

Answer 18

Range of motion is particularly dependent upon age, in old age the range is around half that in youth.

Question 19

What are all movements of the spine a result of ?

Answer 19

The combined movement of several vertebrae, the amount of motion between adjacent segments is generally small and does not occur independently

Question 20

State what flexion and extension of the spine is

Answer 20

• Flexion occurs when bending forwards
• Extension occurs when bending backwards

Question 21

Describe how the range of flexion-extension of the spine permitted between adjacent segments of the spine between different regions of the spine varies

Answer 21

• It is greatest in the cervical spine, with a total range of flexion-extension of around 21 degrees between C4 and C5
• It is smallest in the thoracic spine, with a total range of around 3 degrees between T9 and T10.

Question 22

The maximum amount of flexion and the maximum amount of extension between adjacent segments in the spine also varies

This is particularly true in the lumbar spine where the maximum range of flexion averages about 10 degrees and the maximum range of extension averages only around 4 degrees

Question 23

Describe how during actual movements the motion of the spine is complex and often combined with motion in other parts of the skeletal system.

Answer 23

For example, during forward bending the first 50 to 60 degrees of flexion occurs in the lumbar spine with any further flexion being achieved by the tilting of the pelvis forward.

Question 24

Describe what lateral bending of the spine is

Answer 24

This is the motion from side to side in the frontal plane.

Question 25

Describe the distribution of lateral bending permitted in the different segments of the spine

Answer 25

It has a similar distribution to that of flexion and extension, with the cervical spine being the most mobile and the thoracic spine the least

Question 26

Between what 2 bones of the spine is there no lateral bending permitted?

Answer 26

Between C1 & C2

Question 27

Describe how the distribution of rotation of the spine permitted in each segment of the spine varies

Answer 27

The amount of rotation about the longitudinal axis of the spine generally decreases down the spine

Question 28

Between what 2 bones is there no rotation permitted ?

Answer 28

Between the atlas (C1) and the occipital (OC) bone of the skull

Question 29

Between what 2 bones of the spine is the most rotation permitted and why?

Answer 29

Between the atlas (C1) and axis (C2), because of their unique structure

Question 30

The loadings on the spine are mainly due to what 3 things?

Answer 30

1. the weight of the upper body 2. muscle activity 3. externally applied loads.

Question 31

What region of the spine carries the highest loadings and how does this regions vertebrae differ because of this ?

Answer 31

* The lumbar region * The vertebrae are larger in the lumbar region than the cervical or thoracic

Question 32

Lower back pain in the lumbar region is very prevelant, what is it usually due to ?

Answer 32

* Bad posture during standing or sitting * or by bad bending or lifting techniques

Question 33

What do bad postures do to loadings on the spine? give examples

Answer 33

Bad postures increase loadings on the spine e.g. pic shows a bar chart of the comparative loads on the third lumbar intervertebral disc for different postures. The load during standing is defined as 100% during upright standing. Note that during sitting the loading is actually larger than during upright standing and how slumping (bad posture) forwards can almost double the load.

Question 34

Explain specifically why bad posture increases the loading on the lumbar spine?

Answer 34

Consider the position of the upper body relative to the lumbar spine In Pic the vertical arrow shows the direction of the weight of the upper body in two cases: 1. The moment arm of the upper body mass about the lumbar spine is increased in the case of relaxed sitting (bad posture) due to the backward tilt of the pelvis. 2. The flexion moment produced by the upper body weight and the moment arm must be counterbalanced by an extension moment produced by the posterior back muscles. The larger the moment arm is the greater the muscle forces need to be. 3. The muscles produce a compressive load on the spine which increases with increasing muscle force. Thus any change in posture that causes the upper body to be in a position offset from the lumbar spine effectively increases the load that it must carry.

Question 35

Describe how lifting technique of a weight affects loading on the lumbar spine

Answer 35

The load on the lumbar spine is increased in accordance with the increase in the moment arm produced by weight of the object being lifted. Illustrated in the difference in loading between good and bad lifting techniques: The moment arms of the weight of both upper body and the object are greater with bad lifting technique (not bending the knees and not having the object close to the body) this means the centre of mass is acting further away and therefore the moment arms of the weight of the upper body and object are increased