Schoulder Complex Biomechanics Flashcards
What are the sub-motions of angular joint movement ?
- 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
Define the CONVEX/CONCAVE motion rule
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.
Define agonist muscle
The agonist muscle is responsible for the movement, regardless of the contraction type.
Define antagonist muscle
The muscle which is relaxed during the movement and responsible for the opposite action of the agonist.
Define synergists muscle
Muscle which cooperate during the execution of a particular movement
Define the scapular plane
It is 30° anterior to the frontal plane
Name the static stabilizers of shoulder
- Coracohumeral ligament
- Glenohumeral ligament :
- inferior
- intermedius
- superior
- articular capsule
Name the dynamic stabilizers of the shoulder
The rotator cuff muscles :
- subscapularis
- supraspinatus
- infraspinatus
- teres minor
What is the role of dynamic stabilizers of the shoulder ?
The stabilization of humeral head, the prevention of anterior translation and contracting the deltoid action
Name and define the basic motions of scapula
- 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
Name the agonists of scapula elevation
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
Name the synergists of scapula elevation
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
Name the agonists for scapula depression
1) lower trapezius
Origin : spinous processes from C7 to T12
Insertion : spine of the scapula
Name the synergists of scapula depression
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
Name the agonists of scapula protraction
1) serratus anterior
Origin : external surface of first eight to nine ribs
Insertion : anterior surface of medial border of the scapula
Name the synergists of shoulder protraction
1) pectoralis minor
Origin : 3rd to 5th ribs
Insertion : coracoid process
Name the agonists for scapula retraction
1) middle trapezius
Origin : medial portion of superior nuchal line of the occiput, ligamentum nuchae
Insertion : acromion
Name the synergists for scapular retraction
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
Name the agonists for upward rotation of the scapula
1) upper trapezius
2) lower trapezius
Name the synergists for scapula upward rotation
1) serratus anterior
Name the agonists for scapula downward rotation
1) rhomboid major
2) rhomboid minor
Name the synergists for scapula downward rotation
1) levatore scapula
2) pectoralis minor
What are the basic movements of the glenohumeral joint ?
- flexion / extension
- abduction / adduction
- horizontal abduction / adduction
- internal / external rotation
- internal / external rotation at 90°
Describe the arthrokinematics of glenohumeral abduction
- convex humeral head rolls superiorly on concave glenohumeral fossa so the glide is inferior
Which structure stabilize the humerus during abduction
The articular capsule tension
What is the general principle of shoulder arthrokinematics ?
There is a ratio of 2:1 between shoulder elevation and scapula upward rotation
Describe the scapula humeral rhythm
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
Consider the clavicle in the scapular rhythm, what permits the 60° of scapula upward rotation ?
- elevation and retraction of the sternoclavicular joint
- upward rotation of acromioclavicular joint
- posterior rotation of the clavicle
What happens to scapula during shoulder abduction ?
- posterior tilt (sagittal plane)
- external rotation (horizontal plane)
Why are posterior tilt and external rotation of the scapula helpful for during shoulder abduction
Keep a safe distance between the humeral head and the acromion
What happens to humerus during shoulder abduction ?
Humerus externally rotates. This allows the greater tubercle of the humerus to move posterior to the acromion and therefore increases the subacromial space
Which structures provide a dynamic centralization of the humeral head ?
- Subscapularis tendon
- infraspinatus tendon
- capsule tension
During shoulder abduction, what are the muscles implied in the scapulothoracic movement and how ?
- 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
During shoulder adduction, what are the muscles implied into the scapulo thoracic movement and how ?
- rhomboid major
- rhomboid minor
- levatore scapulae
- pectoralis minor
Work together during shoulder adduction
Which muscle is the glenohumeral joint prime mover ?
Middle Deltoid
Which muscle is the main synergists in glenohumeral abduction ?
The supraspinatus
Name the agonists for shoulder external rotation
1) Posterior fibers of the deltoid
Origin : spine of scapula
Insertion : deltoid tuberosity
Name the synergists of shoulder external rotation
- 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
Name the agonists for shoulder internal rotation
- Anterior fibers of Deltoid
Origin : lateral third of clavicle
Insertion : deltoid tuberosity
Name the synergists for shoulder internal rotation
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
Name the agonists of shoulder flexion
1) Deltoid anterior fibers
Origin : medial third of clavicle
Insertion : deltoid tuberosity
Name the synergists of shoulder flexion
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
Name the agonist for shoulder extension
1) deltoid posterior fibers
Name the synergists of shoulder extension
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
Name the agonists for shoulder horizontal adduction
Deltoid anterior fibers
Pectoralis major upper fibers
Name the agonists of shoulder horizontal abduction
Deltoid posterior fibers
What are the ROM of the shoulder ?
Shoulder flexion : 180° Shoulder extension : 45° Shoulder abduction : 180° Shoulder adduction : 0° Shoulder external rotation at 90° : 90° Shoulder internal rotation at 90° : 70°
