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AY BMSc Biomechanics > Unit 4: Biomechanics of the Upper Limb & Spine > Flashcards

Unit 4: Biomechanics of the Upper Limb & Spine Flashcards

1
Q

What is the major function of the upper limb?

A

To position the hand in space

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2
Q

What are the 3 synoviL articulations of the shoulder joint?

A

Glenohumeral
Acromioclaviclar
Sternoclavicular

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3
Q

What is the fourth bone-on-muscle-on-bone articulation?

A

Scapulthoracic

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4
Q

What forms the glenohumeral joint?

A

Humeral head & glenoid fossa of the scapula

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5
Q

What aids the stability of the glenohumeral joint?

A 
Glenoid labrum (thick cartilaginous rim)
Tharticulation is surrounded by a capsule and rotator cuff
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6
Q

What are the 4 muscles that make up the rotator cuff?

A

Subscapularis
Infraspinatus
Supraspinatus
Teres minor

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7
Q

How does the rotator cuff stabilise the joint?

A

Pushes on the humeral head preventing any anterior-posterior movement

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8
Q

What comprises the acromioclavicular joint?

A

Proximal acromoin of the scapula and distal clavicle

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9
Q

What stabilises the AC joint?

A

Superior & inferior AC ligaments

Coracoclavicular ligament

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10
Q

Why is there only a few degrees of motion at AC joint?

A

Restricted by thorax & muscle attachments

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11
Q

What is the only bony joint connnecting the shoulder girdle to the trunk?

A

Sternoclavicular joint

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12
Q

How does the clavicle move as the arm abducts?

A

Elevates by 4 degrees for every 10 degrees of arm elevation up to 90 degrees then the elevation is negligible

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13
Q

What determines the axis around which the clavicle rotates during elevation & depression?

A

Attachment of the costoclavicular ligament

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14
Q

What muscles separate the anterior surface of the scapula from the posterior thorax?

A

Serratus anterior

Subscapularis

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15
Q

What are the origins & insertions of the serratus anterior muscle?

A

Originates on the upper 8 or 9 ribs and inserts on the anterior surface of the scapula along its vertebral border

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16
Q

What is the purpose of the serratus anterior?

A

Holds scapula against thorax preventing “winging”

Strong abductor useful in pulling or pushing movements

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17
Q

What is the origin & insertion of the subscapularis muscle?

A

Originates from subscapular fossa and inserts on the lesser tubercle of the humerus

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18
Q

What is the function of the subscapularis muscle?

A

Medially rotate the humerus

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19
Q

What is shoulder elevation?

A

Movement of the humerus away from the side of the thorax in any plane

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20
Q

What is the normal range of forward flexion and abduction of the shoulder?

A

180 degrees

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21
Q

What is the normal range of backward extension of the shoulder?

A

60 degrees

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22
Q

What is the normal range of adduction with the arm moving in front of the trunk?

A

75 degrees

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23
Q

What is the normal range of horizontal flexion of the shoulder?

A

135 degrees

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24
Q

What is the normal range of horizontal extension of the shoulder?

A

45 degrees

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25
Q

What are the different movements of the shoulder?

A

Abduction/Adduction
Forward flexion/Backward extension
Horizontal flexion/Horizontal extension
Internal/External rotation

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26
Q

What is the range of motion of internal and external rotation of the shoulder?

A

90 degrees of each

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27
Q

What is the most common dislocation of the shoulder?

A

Anterior dislocation of the glenohumeral articulation

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28
Q

In what situation is their mostly likely to be an anterior dislocation of the glenohumeral articulation and why?

A

Heavy blow when arm is abducted and extended (arm acts as first class lever)

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29
Q

What are the 3 synovial articulations of the elbow?

A

Humeroradial articulation
Humeroulnar articulation
Proximal radioulnar articulation

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30
Q

What forms the humeroradial articulation?

A

Capitellum of the distal humerus & head of the radius

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31
Q

What forms the humeroulnar articulation/

A

Trochlea of the distal humerus & trochlear fossa of the proximal ulna

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32
Q

What forms the proximal radioulnar articulation?

A

Head of the radius & radial notch of the proximal ulna

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33
Q

Where does the axis of rotation pass through in the elbow?

A

Middle of the trochlea (roughly parallel to the line joining the lateral and medial epicondyles of the humerus)

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34
Q

What is the range of flexion-extension of the elbow?

A

140 degrees

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35
Q

Which articulation allows pronation & supination?

A

Proximal radioulnar articulation

36
Q

How are pronation & supination achieved?

A

Rotation of the head of the radius in the radial notch of the ulna inside the annular ligament (allows migration of the distal end of radius around the distal end of the ulna)

37
Q

What is the total range of pronation-supination?

A

150 degrees (70 pronation, 80 supination)

38
Q

What range of motion at the elbow is needed for daily activities?

A

100 degrees flexion (30-130)

100 degrees pronation-supination (50-50)`

39
Q

What is the olecranon process and what is it’s purpose?

A

Resembles a spanner - well suited to resist forces in the anteroposterior direction
Holds the trochlea like a nut

40
Q

What provides medial & lateral stability in the elbow?

A

Collateral ligaments (in particular medial CL prevents abduction)

41
Q

Which muscle assists the lateral collateral ligament in the elbow?

A

Anconeus muscle

42
Q

What is the origin and insertion of the anconeus muscle?

A

Origin - lateral epicondyle of the humerus

Insertion - olecranon & superior portion of ulnar shaft

43
Q

What is the most likely mechanism for n anterior dislocation of the elbow?

A

Fall on outstretched hand

44
Q

Why are the joint forces at the elbow large?

A

arge muscle forces for activities pull the 2 sides of the joinnt together
Muscles have small moment arms

45
Q

What are the 8 carpal bones of the wrist?

A 
Scaphoid 
Lunate 
Triquetrium 
Pisiform
Trapezium 
Trapezoid 
Capitate
Hamate
46
Q

Which is the only carpal bone that is easily palpated?

47
Q

What is the pisiform the insertion point of?

A

Flexor carpi ulnaris

48
Q

What does flexor carpi ulnaris do?

A

Flexes and adducts the wrist

49
Q

Why is the pisiform bone important?

A

Increases the lever arm of the flexor carpi ulnaris

50
Q

What forms the radiocarpal joint?

A

Articulation of the lunate & scaphoid at the distal end of the radius

51
Q

What is a condyloid joint?

A

When an oval shaped condyle fits into an elliptical depression

52
Q

What movements does the radiocarpal joint allow?

A

Flexion & extension
Abduction & adduction
Circumduction

53
Q

What is found in the ulnocarpal space?

A

Triquetrium articulates with the distal ulna (attached at its apex to styloid process of the ulna & at base to ulnar notch of the radius)

54
Q

What degree of flexion does the wrist allow?

A

80-90 degrees

55
Q

What degree of extension does the wrist allow?

A

70-80 degrees

56
Q

At which joint does 60% of flexion occur?

A

Midcarpal joint

57
Q

At which joint does 67% of extension occur?

A

Radiocarpal joint

58
Q

What degree of abduction does the wrist joint allow?

A

15-20 degrees

59
Q

What degree of adduction does the wrist allow?

A

35 degrees

60
Q

What range of motion of the wrist is needed for daily activities?

A

10 flex - 35 extension

61
Q

If the wrist joint is fused what position provides best functional capacity?

A

Fixed extension of 15 degrees

62
Q

Which is the most free moving CMC joint?

A

First carpometacarpal joint (between trapezium and first MC)

63
Q

What is the significance of the the first CMC joint?

A

Allows the thumb to oppose fingers (saddle joint)

64
Q

What type of joint are MCP joints?

A

Condyloid joints (rounded distal heads of the metacarpals and the concave proximal ends of the phalanges)

65
Q

What type of joint are the PIPs & DIPs?

A

Hinge joints

66
Q

What is the maximum amount of flexion the MCP’s are capable of?

A

90 degrees

67
Q

What is the maximum amount of flexion possible at the PIPs?

A

100-110 degrees

68
Q

What is the maximum amount of flexion at the DIPs?

A

90 degrees

69
Q

What is flexion & extension of the thumb?

A 
Flexion = moves across the palm 
Extension = moves away from the side of the palm
70
Q

What is the range of flexion & extension of the thumb?

A

15 degrees flexion

20 degrees extension

71
Q

What degree of abduction is the thumb capable of?

A

60 degrees

72
Q

Where are the principles muscles that control the movements of the digits located?

A

The forearm

73
Q

What is the origin & insertion of the flexor digitorum profundus?

A

Origin - anterior aspect of ulna

Insertion - distal phalanges

74
Q

What is the function of the flexor digitorum profundus?

A

Flexes the DIPs

75
Q

How many vertebrae make up the spine?

A

7 cervical
12 thoracic (dorsal)
5 lumbar
5 sacral & 4 coccyx (fused)

76
Q

What are the 3 points of articulation between vertebrae?

A

Via intervertebral discs

2 facet joints

77
Q

What is the nucleus pulposus?

A

Lies at the centre of discs
Formed by strongly hydrophilic gel enmeshed in a random collagen matrix
Internal pressure balances the applied compressive stress (water movement to compensate)

78
Q

What is the annulus fibrosus?

A

Tough layer which surrounds the nucelus pulposus
Composed of collagen fibres which form lamellae
This arrangement resists high bending & torsional loads

79
Q

Describe the structure of the axis (C2)

A

Has a dens process which protrudes superiorly from the body

80
Q

Describe the structure of the axis (C1)

A

Has no body but is composed of a ring within which an oval fossa articulates with the axis

81
Q

At what region of the spine is the greatest flexion possible?

A

Cervical spine

82
Q

What is the total range of flexion between C4 & C5?

A

21 degrees

83
Q

At what region of the spine is the least flexion possible?

A

Thoracic spine (3 degrees between T9/10)

84
Q

Which segments of the spine are most and least mobile when lateral bending?

A

Most mobile = cervical

Least mobile = thoracic

85
Q

At which point in the spine is there no lateral bending?

A

Between C1 & C2

86
Q

At which point in the spine is there most rotation?

A

Between C1 & C2 (decreases going down the spine)

87
Q

As the moment arm of the upper body weight increases does the loading on the spine increase or decrease?

A

Load on the spine increases as the moment arm increases

AY BMSc Biomechanics (4 decks)

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