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EDKP-206 > Lecture 14 - Shoulder Biomechanics > Flashcards

Lecture 14 - Shoulder Biomechanics Flashcards

1
Q

What makes up the shoulder complex?

A
  1. Bone structure
  2. Joints and supporting structures
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2
Q

What is the bone structure?

A
  • Bones of the shoulder complex
  • Connects to the rest of the body via sternum and thorax
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3
Q

What are the bones of the shoulder complex?

A
  1. Clavicle
  2. Scapula
  3. Humerus
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4
Q

What are the joints of the shoulder complex?

A
  1. Sternoclavicular joint
  2. Acromioclavicular joint
  3. Scapulothoracic joint
  4. Glenohumeral joint
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5
Q

What are the supporting structures of the shoulder complex?

A
  1. Labrum
  2. Capsule
  3. Ligaments and musculature
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6
Q

What is the clavicle?

A
  • Crank shaped
  • Convex towards sternum
  • Concave towards humerus
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7
Q

What is the function of the clavicle?

A
  1. Attaches shoulder to axial skeleton
  2. Force transmission to scapula
  3. Contributes to ROM
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8
Q

What is the scapula?

A
  • Sits between T2 and T7
  • Can palpate acromion and coracoid process
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9
Q

What is the function of the scapula?

A

Muscle attachment

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10
Q

What is the alignment of the scapula?

A
  • Superior aspect 30-45 degrees anterior to frontal plane
  • Slight anterior inclination and upward rotation
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10
Q

What increases the depth of the glenoid fossa?

A

Fibrocartilaginous labrum (50% increase)

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11
Q

What does the labrum help with: mobility or stability?

A

Stability

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12
Q

What is the role of the tubercles on the humerus?

A

Externally rotate humerus for greater tubercle to clear acromion process and acromioclavicular ligament

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13
Q

What is the role of the intertubercular groove?

A

Radial nerve runs along it

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14
Q

What type of joint is the sternoclavicular joint?

A

Synovial

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15
Q

What type of joint is the acromioclavicular?

A

Synovial

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16
Q

What type of joint is the scapulothoracic joint?

A

Special

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17
Q

What type of joint is the glenohumeral joint?

A

Synovial

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18
Q

What is the role of the sternoclavicular joint?

A

Connects upper limb and axial skeleton

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19
Q

What are the 3 rotatory motions?

A
  1. Elevation/depression
  2. Protraction/retraction
  3. Upward/downward rotation
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20
Q

What is the seesaw affect of the clavicle due to the sternoclavicular joint?

A

Rotation of the joint about an axis causes the head and opposite end of clavicle to move in opposite directions

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21
Q

What are the ligaments of the sternoclavicular joint?

A
  1. Anterior sternoclavicular
  2. Posterior sternoclavicular
  3. Interclavicular
  4. Costoclavicular
  5. Intraarticular disc
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22
Q

What are the 3 rotatory motions of the acromioclavicular joint?

A
  1. Internal/external rotation
  2. Anterior/posterior tipping
  3. Upward/downward rotation
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23
Q

What does the acromioclavicular joint also allow?

A
  1. Additional ROM of the scapula on the thorax
  2. Force transmission through the upper extremity
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24
Q

What supports the acromioclavicular joint?

A
  1. Capsule
  2. Coracoacromial ligament
  3. Coracoclavicular ligaments
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25
Q

What is the function of the coracoacromial ligament?

A

Provides protection (doesn’t cross the joint)

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26
Q

What is the function of the coracoclavicular ligaments?

A
  1. Trapezoid
    -> Prevents medial displacement of acromion
  2. Conoid
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27
Q

What are the two translational movements of the scapulothoracic joint?

A
  1. Elevation/depression
  2. Abduction/adduction
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28
Q

What are the 3 rotational movements of the scapulothoracic joint?

A
  1. Upward/downward rotation
  2. Internal/external rotation
  3. Scapular tilt
29
Q

What provides stability of the scapulothoracic joint?

A
  1. AC joint
  2. SC joint
30
Q

What are the 5 essential functions of the scapulothoracic joint?

A
  1. Increase ROM of shoulder (enhance reach)
  2. Maintain favorable length-tension relationship for deltoid function (>90 degrees)
  3. Maintain GH stability for overhead work
  4. Shock absorption
  5. Permits elevation of body
31
Q

What is the glenohumeral joint?

A
  • Ball and socket
  • Most mobile (but costs stability)
32
Q

What are the supporting structures of the glenohumeral joint?

A
  1. Labrum
  2. Capsuloligamentous complex
33
Q

What is the function of the labrum?

A
  1. Deepens the glenoid fossa
  2. Increases articular contact
    -> Increase stability and decreases stress
34
Q

What makes up the capsuloligamentous complex?

A
  1. Capsule
  2. Glenohumeral ligaments
    a) Superior
    b) Middle
    c) Inferior
  3. Coracohumeral ligament
35
Q

What does the capsule of the capsuloligamentous complex do?

A
  • Encircles joint
  • Provides protection against excessive rotation and translation
36
Q

How many degrees of freedom exist at the glenohumeral joint?

37
Q

What are the 3 DOF?

A
  1. Flexion/extension
  2. Adduction/abduction
  3. Internal/external rotation
38
Q

What occurs when elevation takes place)

A
  • Reduces subacromial space
  • Requires rotation of humerus in GH joint in frontal/sagittal plane
39
Q

What is the coracoacromial arch?

A
  1. Coracoacromial ligament
  2. Sub-acromial space
  3. Roof of the GH joint
    -> Narrow with elevation and internal rotation
40
Q

What is the function of the coracoacromial arch?

A
  1. Protection of muscles, tendons and bursae
  2. Prevention of superior dislocation of humerus
41
Q

What is impingement?

A
  • Irritation of structures in the subacromial space
  • Sustained or intermittent compression
  • Narrowing of sub-acromial space
42
Q

What provides static stability of the glenohumeral joint?

A
  1. Superior capsule
  2. Coracohumeral ligament
  3. Inactive supraspinatus
43
Q

What provides dynamic stability of the glenohumeral joint?

A
  1. Rotator cuff muscles
  2. Biceps
  3. Deltoids
44
Q

What are the muscles of the rotator cuff?

A
  1. Supraspinatus
  2. Infraspinatus
  3. Subscapularis
  4. Teres minor
45
Q

What do the dynamic stabilizes of the GH joint help with?

A
  • Neutralize upward movement
  • Compress humerus head into glenoid fossa
  • Force couples
46
Q

What are the primary movers of the arm?

A
  1. Deltoid
  2. Supraspinatus
47
Q

What occurs during total shoulder movement?

A
  • Contribution from all 4 joints
  • Scapular elevation is the movement of the scapulothoracic “joint” which indirectly elvetaes the sternoclavicular joint
48
Q

What is the scapulohumeral rhythm?

A

Scapulothoracic and glenohumeral joints move simultaneously

49
Q

What is the ratio of the scapulohumeral rhythm?

A

2:1 (GH:ST)

50
Q

What is the role of the scapula in arm elevation?

A
  1. Posterior tilt
  2. Upward rotation
  3. External rotation
51
Q

What is the role of the humerus in arm elevation?

A
  1. Anterior flexion
  2. Abduction
52
Q

What happens during arm-trunk elevation?

A
  • Upward rotation of the scapula forces elevation of the clavicle
  • Scapula moves more than clavicle
53
Q

What is the total ROM of upward/downward rotation?

A

60 degrees

54
Q

What is the contribution to 180 degree arm elevation by the joints?

A

GH: 120 degree (abduction)
ST: 60 degree (upward rotation)
SC: 30 degree (elevation)
AC: 30 degree (upward rotation)

55
Q

What are the 3 groups of the muscles of the shoulder complex?

A
  1. Axioscapular and axioclavicular
  2. Scapulohumeral
  3. Axiohumeral
56
Q

What classifies the axioscapular and axioclavicular muscles?

A

Posses an attachment on the axial skeleton and on the shoulder girdle

57
Q

What is the role of the axioscapular and axioclavicular muscles?

A

Moving the sternoclavicular and scapulothoracic joints

58
Q

What are a few important axioscapular and axioclavicular muscles?

A
  1. Trapezius
  2. Serratus anterior
59
Q

What is the role of the trapezius?

A

Adducts and upwardly rotates the scapula (each section has unique functions)

60
Q

What is the force couple for upward scapular rotation?

A
  • Upper/lower trapezius (+ serratus anterior)
  • Muscles pulling in different directions crease a net torque but no net force
61
Q

What is the role of the serratus anterior?

A

Active when pushing anteriorly

62
Q

What is winging of the scapula?

A

Cause: Weakness of the serratus anterior/injury to nerves
Types: Medial and Lateral

63
Q

What is the role of the scapulohumeral muscles?

A
  • Provide motion and dynamic stabilization of the GH joint
  • Critical to mobility
64
Q

What are the important scapulohumeral muscles?

A
  1. Deltoid
  2. Supraspinatus
  3. Infraspinatus
  4. Teres minor
  5. Subscapularis
  6. Teres major
  7. Coracobrachialis
65
Q

What is the function of the deltoid?

A

Causes humerus and humeral head to translate superiorly

66
Q

What is the function of the supraspinatus?

A

Causes abduction of the humerus and compression of the humeral head

67
Q

What is the function of the infraspinatus, subscapularis and the teres minor?

A
  • Initially pull humeral head downwards and then externally rotate humerus
  • Muscles work to compress humeral head in glenoid fossa during arm elevation
  • Force couple with deltoid
68
Q

What classifies the axiohumeral muscles?

A
  • Attach to thorax and humerus
  • Large PCSA for additional strength
69
Q

What are the 2 important axiohumeral muscles?

A
  1. Pectoralis minor
  2. Latissimus dorsi
70
Q

What is the joint reaction force of the shoulder?

A

Compressive load maximum at 90 degree shoulder abduction

71
Q

What can help alleviate shoulder pain/weakness?

A

Simple interventions (exp: holding a child closer to your body)

EDKP-206 (16 decks)

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