Lecture 24 - Functional Anatomy of Shoulder Joint Complex

Question 1

What 7 structures compose the shoulder complex

Answer 1

1. Glenohumeral Joint
2. Labrum
3. Capsule
4. Ligaments
5. Scapulothoracic Joint
6. Sternoclavicular Joint
7. Acromioclavicular Joint

Question 2

What is the glenohumeral joint

Answer 2

A triaxial synovial joint that rotates around 3 axes/degrees of freedom

Question 3

What is the glenoid of the glenohumeral joint

Answer 3

It is concave and pear shaped structure that faces laterally, anteriorly and superiorly

Question 4

What is the humeral head of the glenohumeral joint

Answer 4

It is a convex structure that is larger articulates 1/3 with the glenoid fossa and faces superiorly, medially and posteriorly

Question 5

What is the glenoid labrum

Answer 5

It is a fibrocartilage ring (tissue) that surrounds the glenoid, deepens the fossa, and supplies a vacuum effect to seal and stabilize the glenohumeral joint

Question 6

Where does the joint capsule arise from and insert into?

Answer 6

The glenoid neck and labrum and inserts into the articular margin of the humeral neck

Question 7

How is the joint capsule reinforced

Answer 7

Superiorly and anteriorly by superior, middle and inferior glenohumeral ligaments

Question 8

Where does the superior glenohumeral ligament arise from

Answer 8

Its a robust thin tissue that is a small depression above lesser tubercle and blends with coracohumeral ligament that arises from margin of glenoid and labrum

Question 9

What is the function of the superior glenohumeral ligament

Answer 9

1) Provides restraint to inferior translations of humeral head when arms are adducted
2) Limits external rotation from 0-45 degrees abduction
3) Aids in stability anteriorly and inferiorly

Question 10

T or F: The superior glenohumeral ligament is not tensioned with biceps during throwing

Answer 10

F, it is

Question 11

What is the attachments of the middle glenohumeral joint

Answer 11

It arises from anterior superior glenoid and labrum and inserts into lower part of lesser tuberosity

Question 12

What are the 2 functions of the middle glenohumeral ligament

Answer 12

1. Limits external rotation when arm is at side
2. Provides restraint to anterior humeral translation with the arm in mid-range of abduction up to 45 degrees

Question 13

What is the attachment of the inferior glenohumeral ligament

Answer 13

Attaches from anterior/posterior mid glenoid and labrum (hammock type axillary pouch)

Question 14

What are the 2 functions of the inferior glenohumeral ligament?

Answer 14

1. Anterior band limits anterior translation when glenohumeral joint is abducted up to 90 degrees
2. During internal rotation the posterior band limits posterior translation of the humerus

Question 15

What is the attachment/insertion of the coracohumeral ligament

Answer 15

It attaches near root of the coracoid and inserts into the humerus and transverse ligament

Question 16

What are the 4 functions of the coracohumeral ligament

Answer 16

1. Limits external rotation below 60 degrees of flexion
2. Works with the superior glenoid ligament
3. Restraint for flexion and extension
4. Acts as a tunnel for the bicep

Question 17

T or F: The scapulothoracic joint is a true joint

Answer 17

F, it is a pseudojoint

Question 18

Where is the scapulothoracic joint found

Answer 18

1. Between anterior portion of the scapula and posterior thorax and rib cage (plane of scapula)

Question 19

Where is the sternoclavicular joint located

Answer 19

Between the medial end of the clavicle and lateral portion of the sternum (saddle-shaped)

Question 20

What is the most important ligament surrounding the sternoclavicular joint and why?

Answer 20

The posterior sternoclavicular ligament which increases anterior and posterior translation

Question 21

Where is the acromioclavicular joint located

Answer 21

Between he lateral end of the clavicle and medial end of the acromion

Question 22

How many degrees of freedom does the acromioclavicular joint have

Answer 22

3

Question 23

What 2 ligaments compose the acromioclavicular joint and their function

Answer 23

1. Conoid: Resists elevation and protraction
2. Trapezoid: Resists acromioclavicular joint compression and clavicle elevation/protraction

Question 24

Describe the Scapulohumeral Rhythm

Answer 24

180 degree of shoulder elevation is caused by humeral elevation while 60 degrees of that is due to scapular rotation (2:1 ratio)

Question 25

Force Couple

Answer 25

Occurs when 2 groups of muscles work together to produce a movement or provide joint stability

Question 26

Describe the Deltoid-Rotator Cuff Force Couple

Answer 26

During initial arm movement the larger deltoid has an upward and outward force caused by superior migration of humerus that is counteracted by inferior and medial directed force of the infraspinatus, subscapularis and teres minor (rotator cuff)

Question 27

What force couple produces the largest amount of force

Answer 27

Deltoid-Rotator Cuff

Question 28

Supraspinatus movement

Answer 28

Provides a direct compressing force on the humeral head into the glenoid maximally between 45-90 degrees of abduction (gone at 150 degrees)

Question 29

Infraspinatus and Teres Minor 2 Functions

Answer 29

1. Depress humerus allowing supraspinatus to compress and prevent sub-acromial compression 2. External rotator and eccentrically decelerates internal rotation (Concentrically -> lateral rotation)

Question 30

Do muscles work harder concentrically or eccentrically

Answer 30

eccentrically

Question 31

Subscapularis 2 functions

Answer 31

1. Active in all movements of humeral head that require compression and depression 2. Acts eccentrically to decelerate external rotation (concentric -> medial rotation)

Question 32

3 functions of the long head of the biceps

Answer 32

1. Increases glenohumeral compression with supraspinatus 2. Applies longitudinal compressive force during deceleration activities 3. Increases anterior stability in abduction/external rotation by resisting translational stress

Question 33

Describe the upper trapezius and serratus anterior force couple 4 functions

Answer 33

to produce upward movement of scapula during elevation by: 1) Rotating scapula for optimal glenohumeral joint function 2) Maintaining efficient length-tension of deltoid 3) Preventing impingement of rotator cuff from subacromial structures 4) Providing stable scapular base to enable appropriate recruitment of scapular-humeral muscles

Question 34

Describe how the serratus anterior/lower trap is involved with the upper trap/levator scapula in the upper trapezius and serratus anterior force couple

Answer 34

Lower portion of SA and LT work in conjunction with the UT and LS to create upward rotation of the scapula

Question 35

T or F: Lower trap and serratus anterior are the primary components of upward rotation and stabilization of the scapula when the shoulder is abducted past 90 degrees

Answer 35

T

Question 36

What happens to patients with impingement syndrome of the upper trapezius and serratus anterior force couple

Answer 36

Show decreased activity of serratus anterior and delay in firing lower traps and middle traps, so dominance occurs in the upper traps and levator scapula causing faulty scapulohumeral patterns