Biomech unit 4 Upper limb & Spine - deck 4

Question 1

What is the range of motion of each of the carpometacarpal, metacarpophalangeal and interphalangeal joints of the fingers is dependent on?

Answer 1

Their bone structure and the surrounding ligaments.

Question 2

State the movements permitted in the 2nd to 5th CMC joints in the fingers

Answer 2

• The 2nd and 3rd CMC joints are basically immobile
• The 4th and 5th CMC joints permit a small amount flexion-extension

Question 3

What is the range of motion permitted by the 4th and 5th CMC joints in the fingers ?

Answer 3

10 to 15 degrees at the 4th and 20 to 30 degrees at the 5th

Question 4

What movements do the MCP joints of the fingers allow?

Answer 4

Flexion-extension & Abduction-adduction

Question 5

What is the range of flexion-extension of the MCP joints in the fingers?

Answer 5

• Max flexion is 90 degrees
• Extension varies considerably depending on the laxity of an individuals ligamnets

Question 6

What movements are permitted by the DIP and PIP joints of the fingers?

Answer 6

Only flexion-extension

Question 7

Which of the DIP or PIP joints allows the most amount of flexion?

Answer 7

The PIP joints

Question 8

What is the range of flexion allowed by the PIP and DIP joints of the fingers ?

Answer 8

• PIP joints allow 100-110 degrees
• The DIP joints allow 90 degrees

Question 9

What is extension beyond the neutral position, with the fingers straight termed ?

Answer 9

Hyperextension

Question 10

What is range of extension permited by the DIP and PIP joints in the fingers?

Answer 10

It varies considerably between individuals and is dependent largely on ligament laxity just like in the MCP joints

Question 11

How does the structure and function of the MCP, PIP and DIP joints of the thumb compare to those of the fingers?

Answer 11

Structure and function is the same

However the MCP does not generally allow as large an amount of flexion as those of the fingers. The range varies from 30 to as much as 90 degrees. The amount of extension though is generally greater with normally around 15 degrees being possible.

Question 12

What joint of the thumb is of particular importance functionally?

Answer 12

The carpometacarpal (CMC) joint

Question 13

In what plane are flexion and extension of the thumb in terms of movement permitted by the CMC joint ?

Answer 13

In the plane of the palm

Question 14

Define what flexion and extension of the thumb permitted by the CMC joint is

Answer 14

• Flexion is when the thumb moves across the palm
• Extension is when the thumb moves away to the side from the palm

Remember that the movements of the thumb are described in relation to the plane of the palm (of the hand)

Believe the CMC joint allows this movement

Question 15

What is the range of motion of flexion-extension of the thumb permitted by the CMC joint ?

Answer 15

• 15 degrees of flexion
• 20 degrees of extension

Question 16

Describe what abduction of the thumb is and state the range of motion in degrees

Answer 16

• This is when the thumb moves away from the hand
• range of motion = 60 degrees

Believe the CMC joint allows this movement

Question 17

Is rotation of the thumb possible?

Answer 17

Yes to a small degree

(believe it is allowed by the CMC joint of the thumb)

Question 18

Describe the movements of the thumb which together achieve adduction of the thumb

Answer 18

• Flexion and rotation of the carpometacarpal joint and flexion of the metacarpophalangeal and interphalangeal joints (shown in fig. C&D)
• Adduction = if the thumb is moved across the palm so that the tip touches the base of the little finger

Question 19

How do the muscles in the forearm control movements of the digits?

Answer 19

Their distal tendons cross the wrist and are then inserted onto the digits

e.g. the flexor digitorum profundus originates from the anterior aspect of the ulna and has insertions on the distal phalanges, allowing it to flex the distal interphalangeal joints

Question 20

As the wrist changes position how does it affect the muscle tendons which cross the wrist ?

Answer 20

• It alters the functional lengths of the muscle tendons
• e.g. when the wrist is straight the fingers can be easily clenched into a tight fist, however, if the wrist is flexed first of all then it becomes difficult to fully flex the fingers.

Question 21

What is the the range of wrist flexion is dependent on?

Answer 21

Whether the fingers are straight or flexed. (this is the same idea as when wrist position changes the functional length of the muscle tendons so does finger position)

e.g. With the fingers extended the wrist can flex to almost 90º, but with the fingers clenched into a fist the range of wrist flexion is significantly reduced

Question 22

What bones form the spine spliting the bones into regions and state the number of each in each region ?

Answer 22

• 24 unfused vertebrae (7 cervical, 12 thoracic, 5 lumbar)
• The sacrum (5 fused vertebrae) and the coccyx (4 fused vertebrae)

Question 23

State the 5 regions of the spine

Answer 23

1. cervical
2. thoracic
3. lumbar
4. sacrum
5. coccyx

Question 24

What are the main differences between each region of the spine ?

Answer 24

The vertebrae are slightly different in structure, as is the overall structure, function and range of motion in each region

Question 25

Does all the unfused vertebraes (the first 24) structure resemble eachother?

Answer 25

Yes - except the first two, C1 & C2

Question 26

Describe the structural features of a typical unfused vertebrae (so not C1 or C2)

Answer 26

• Vertebral body - a flat, rounded body placed anteriorly and centrally
• The neural arch - an arch of bone that forms the spinal foramen
• A spinous process - projects inferiorly in the posterior mid-line
• Two transverse processes - project laterally

Question 27

What passes through the spinal foramen?

Answer 27

The spinal cord

Question 28

What do the spinous and transverse processes of vertebrae provide?

Answer 28

They provide anchorage sites for the ligaments and muscles which stabilise and move the spine

Question 29

What points does each unfused vertebrae articulate with adjacent vertebrae by ?

Answer 29

3 articulation points:

• The main articulation is at the vertebral body via an intervertebral disc
• The other 2 articulations are facet joints.

Question 30

What type of joint are facet joints ?

Answer 30

Synovial joints

Question 31

Describe the position of the facet joints of the vertebrae

Answer 31

They are positioned on either side of the arch

Question 32

What forms the facet joints of the vertebrae ?

Answer 32

The upper facets of the vertebrae articulate with the lower facets of the vertebra above, and the lower facets articulate with the upper facets of the vertebra below.

(upper facet = superior articular process, lower facets = inferior articular processes)

Question 33

What is the function of the intervertebral discs ?

Answer 33

Dual role of bearing and distributing loadsand ofrestraining excessive motion.

Question 34

Describe the structure of an intervertebral disc

Answer 34

• It is cylindrical in shape
• It is made up of the inner nucleus pulposus and the outer annulus fibrosis

Question 35

What is the position of the nucleus pulposus in the intervertebral discs ?

Answer 35

It lies in the centre of the disc, except in the lumbar region where it lies slightly posterior

Question 36

Describe the structure of the nucleus pulposus

Answer 36

It is formed by a strongly hydrophilic (waterloving) gel that is enmeshed in a random collagen matrix

Question 37

What does the hydrophilic gel in the nucleus pulposus do?

Answer 37

It produces a high water content and an elevated nucleus pressure

Question 38

Why does there need to be a high internal nucleus pressure?

Answer 38

To balance the applied compressive stress on the intervertebral disc

Question 39

What happens when the applied compressive stress on an intervertebral disc is increwased or decreased?

Answer 39

If the applied stress is increased water is driven out of the disc until a new steady state is reached. Likewise, when the applied stress is decreased the disc rehydrates.

Note this mechanism is not capable of maintaining a constant level of hydration over a long period of time. The reduction in hydration over time results in a decreased disc height which is evident in the loss of standing height over the day which can be as much as 1 cm.

Question 40

Describe what makes up the annulus fibrosis and state the position of it

Answer 40

It is a tough layer which surrounds the nucleus pulposus. It is composed of collagen fibres. These form concentric layers (lamellae) with alternating orientations of the collagen fibres

Question 41

What does the arrangement of concentric layeral (lamaella) with alternating orientations of collagen fibres allow the intervertebral disc to be able to do?

Answer 41

Allows it to resist high bending and torsional loads.

Question 42

What is the most mobile region of the spine ?

Answer 42

The cervical region

Question 43

What makes up the cervical region of the spine and what does it form?

Answer 43

7 unfused vertebrae make up the cervical region, this forms the neck

Question 44

What are the 2 most mobile vertebrae in the cervical spine ?

Answer 44

• C1 (atlas)
• C2 (axis)

Question 45

Describe how the structure of the atlas (C1) vertebrae differs from a typical vertebrae

Answer 45

The atlas has no body but is composed of a ring within which an oval fossa articulates with the axis.

(Pic shows a facet for the dens which I think is the oval fossa)

Question 46

Describe how the structure of the axis (C2) vertebrae differs from a typical vertebrae

Answer 46

The axis has an articular process, the dens, which protrudes superiorly from the vertebral body

Question 47

What is the name and type of joint formed by the articulation between the dens of C2 and the oval fossa of C1?

Answer 47

• Atlanto-axial joint - this is a synovial joint
• It is formed between the anterior tip of the dens and the oval fossa of the atlas