Schoulder Complex Biomechanics

Question 1

What are the sub-motions of angular joint movement ?

Answer 1

• roll : multiple points on a rotating articular surface contact multiple points on another articular surface
• slide : a single point on an articular surface contacts multiple points on the other articular surface
• spin : a single point on an articular surface contacts a single point on another articular surface

Question 2

Define the CONVEX/CONCAVE motion rule

Answer 2

In joints with fixed concave and moving convex surfaces (ex: glenohumeral joint, radiocarpal joint) the roll and the glide happen in opposite directions.
In joints with fixed convex and moving concave surfaces (ex : humeroradial joint, humeroulnar joint, MCP, IP joints) the roll and the glide happen in the same directions.

Question 3

Define agonist muscle

Answer 3

The agonist muscle is responsible for the movement, regardless of the contraction type.

Question 4

Define antagonist muscle

Answer 4

The muscle which is relaxed during the movement and responsible for the opposite action of the agonist.

Question 5

Define synergists muscle

Answer 5

Muscle which cooperate during the execution of a particular movement

Question 6

Define the scapular plane

Answer 6

It is 30° anterior to the frontal plane

Question 7

Name the static stabilizers of shoulder

Answer 7

• Coracohumeral ligament
• Glenohumeral ligament :
  
  • inferior
  • intermedius
  • superior
• articular capsule

Question 8

Name the dynamic stabilizers of the shoulder

Answer 8

The rotator cuff muscles :

• subscapularis
• supraspinatus
• infraspinatus
• teres minor

Question 9

What is the role of dynamic stabilizers of the shoulder ?

Answer 9

The stabilization of humeral head, the prevention of anterior translation and contracting the deltoid action

Question 10

Name and define the basic motions of scapula

Answer 10

• elevation : superior (upward) movement of the scapula
• depression : inferior (downward) movement of the scapula, return from elevation (passive)
• protraction : lateral slide of the scapula around the chest wall
• retraction : medial slide of the scapula around the chest wall
• upward and downward rotations

Question 11

Name the agonists of scapula elevation

Answer 11

1) upper trapezius
Origin : external occipital protuberance, ligamentum nuchae and spinous process of C-7 to T-12
Insertion : lateral one third of the clavicle

Question 12

Name the synergists of scapula elevation

Answer 12

1) rhomboid major
Origin : spinous process T2 to T5
Insertion : medial border of the scapula, between the spine of the scapula and the inferior angle

2) rhomboid minor
Origin : C7 to T1
Insertion : medial border of the scapula across the spine of the scapula

3) levatore scapula
Origin : transverse process of first through 4th cervical vertebrae
Insertion : medial border of scapula between the spine of the scapula and the upper angle of the scapula

Question 13

Name the agonists for scapula depression

Answer 13

1) lower trapezius
Origin : spinous processes from C7 to T12
Insertion : spine of the scapula

Question 14

Name the synergists of scapula depression

Answer 14

1) serratus anterior with origin fixed
Origin : external surface of upper eight to nine ribs
Insertion : anterior surface of medial border of scapula

2) pectoralis minor
Origin : ribs 3 to 5
Insertion : coracoid process

Question 15

Name the agonists of scapula protraction

Answer 15

1) serratus anterior
Origin : external surface of first eight to nine ribs
Insertion : anterior surface of medial border of the scapula

Question 16

Name the synergists of shoulder protraction

Answer 16

1) pectoralis minor
Origin : 3rd to 5th ribs
Insertion : coracoid process

Question 17

Name the agonists for scapula retraction

Answer 17

1) middle trapezius
Origin : medial portion of superior nuchal line of the occiput, ligamentum nuchae
Insertion : acromion

Question 18

Name the synergists for scapular retraction

Answer 18

1) rhomboid major
Origin : spinous processes T2 to T5
Insertion : medial border of the scapula from the spine to inferior angle of the scapula

2) rhomboid minor
Origin : spinous process C7 to T1
Insertion : medial border of the scapula from upper angle to spine of the scapula

Question 19

Name the agonists for upward rotation of the scapula

Answer 19

1) upper trapezius

2) lower trapezius

Question 20

Name the synergists for scapula upward rotation

Answer 20

1) serratus anterior

Question 21

Name the agonists for scapula downward rotation

Answer 21

1) rhomboid major

2) rhomboid minor

Question 22

Name the synergists for scapula downward rotation

Answer 22

1) levatore scapula

2) pectoralis minor

Question 23

What are the basic movements of the glenohumeral joint ?

Answer 23

• flexion / extension
• abduction / adduction
• horizontal abduction / adduction
• internal / external rotation
• internal / external rotation at 90°

Question 24

Describe the arthrokinematics of glenohumeral abduction

Answer 24

• convex humeral head rolls superiorly on concave glenohumeral fossa so the glide is inferior

Question 25

Which structure stabilize the humerus during abduction

Answer 25

The articular capsule tension

Question 26

What is the general principle of shoulder arthrokinematics ?

Answer 26

There is a ratio of 2:1 between shoulder elevation and scapula upward rotation

Question 27

Describe the scapula humeral rhythm

Answer 27

Phase 1 : 30° total elevation Humerus abduction 0° to 30° Clavicle elevation 0° to 5° Scapula minimal medial movement Phase 2 : 90° total elevation Humerus abduction from 40° up to 90° Clavicle elevation 15° elevation Scapula 20° lateral rotation Phase 3 : from 90° to 180° total elevation Humerus 60° abduction + 90° lateral rotation Clavicle 30° to 50° posterior rotation + 15° elevation Scapula 30° to 40° lateral rotation

Question 28

Consider the clavicle in the scapular rhythm, what permits the 60° of scapula upward rotation ?

Answer 28

- elevation and retraction of the sternoclavicular joint - upward rotation of acromioclavicular joint - posterior rotation of the clavicle

Question 29

What happens to scapula during shoulder abduction ?

Answer 29

- posterior tilt (sagittal plane) | - external rotation (horizontal plane)

Question 30

Why are posterior tilt and external rotation of the scapula helpful for during shoulder abduction

Answer 30

Keep a safe distance between the humeral head and the acromion

Question 31

What happens to humerus during shoulder abduction ?

Answer 31

Humerus externally rotates. This allows the greater tubercle of the humerus to move posterior to the acromion and therefore increases the subacromial space

Question 32

Which structures provide a dynamic centralization of the humeral head ?

Answer 32

- Subscapularis tendon - infraspinatus tendon - capsule tension

Question 33

During shoulder abduction, what are the muscles implied in the scapulothoracic movement and how ?

Answer 33

- serratus anterior - upper trapezius - lower trapezius They rotate the scapula upwards - serratus anterior - lower trapezius They create the posterior tilt of the scapula and maintain it against the thorax

Question 34

During shoulder adduction, what are the muscles implied into the scapulo thoracic movement and how ?

Answer 34

- rhomboid major - rhomboid minor - levatore scapulae - pectoralis minor Work together during shoulder adduction

Question 35

Which muscle is the glenohumeral joint prime mover ?

Answer 35

Middle Deltoid

Question 36

Which muscle is the main synergists in glenohumeral abduction ?

Answer 36

The supraspinatus

Question 37

Name the agonists for shoulder external rotation

Answer 37

1) Posterior fibers of the deltoid Origin : spine of scapula Insertion : deltoid tuberosity

Question 38

Name the synergists of shoulder external rotation

Answer 38

- infraspinatus Origin : infraspinous fossa of scapula Insertion : greater tubercle of humerus - teres minor Origin : upper 2/3rd of lateral border of scapula Insertion : greater tubercle of humerus

Question 39

Name the agonists for shoulder internal rotation

Answer 39

- Anterior fibers of Deltoid Origin : lateral third of clavicle Insertion : deltoid tuberosity

Question 40

Name the synergists for shoulder internal rotation

Answer 40

1) latissimus dorsi Origin : inferior angle of scapula, spinous processes of last six vertebras, last three or four ribs, thoracolumbar aponeurosis and posterior illiac crest Insertion : intertubercular groove of humerus 2) teres major Origin : inferior angle and lateral 1/3rd of scapula Insertion : crest of the lesser tubercule of humerus 3) subscapularis Origin : subscapular fossa Insertion : lesser tubercle of the humerus 4) pectoralis major Origin : medial half of clavicle, sternum, cartilage of six first ribs Insertion crest of greater tubercle of the humerus

Question 41

Name the agonists of shoulder flexion

Answer 41

1) Deltoid anterior fibers Origin : medial third of clavicle Insertion : deltoid tuberosity

Question 42

Name the synergists of shoulder flexion

Answer 42

1) upper fibers of pectoralis major 2) biceps brachii Origin : coracoid process (short head), supraglenoid tubercle of scapula (long head) Insertion : tuberosity of the radius and aponeurosis of the biceps brachii 3) coraco brachialis Origin : coracoid process Insertion : medial surface of mid-humeral shaft

Question 43

Name the agonist for shoulder extension

Answer 43

1) deltoid posterior fibers

Question 44

Name the synergists of shoulder extension

Answer 44

1) latissimus dorsi 2) teres major 3) pectoralis major 4) triceps brachii Origin : infraglenoid tubercule of the scapula (long head), posterior surface of proximal half of humerus (lateral head), posterior surface of distal half of humerus (medial head) Insertion : olicrenon process of the ulna

Question 45

Name the agonists for shoulder horizontal adduction

Answer 45

Deltoid anterior fibers | Pectoralis major upper fibers

Question 46

Name the agonists of shoulder horizontal abduction

Answer 46

Deltoid posterior fibers

Question 47

What are the ROM of the shoulder ?

Answer 47

``` Shoulder flexion : 180° Shoulder extension : 45° Shoulder abduction : 180° Shoulder adduction : 0° Shoulder external rotation at 90° : 90° Shoulder internal rotation at 90° : 70° ```