Exam 3 lecture: shoulder

Question 1

what is scapulohumeral rhythm?

Answer 1

arm trunk mechanism

Question 2

what are the 4 important joints of the shoulder complex?

Answer 2

scapulocostal
sternoclavicular
acromioclavicular
glenohumeral

Question 3

what type of joint is the glenohumeral joint?

Answer 3

ball and socket / enarthrosis

Question 4

what is the effect of the depth of the glenoid fossa on stabilty?

Answer 4

the glenoid fossa is shallow –> less static stability

Question 5

t or f: the head of the humerus is larger than the glenoid fossa.

Answer 5

true

Question 6

what is the significance of the glenoid fossa being anteverted?

Answer 6

there is little anterior stability

Question 7

what happens if the glenoid fossa is retroverted?

Answer 7

there would be less posterior stability

Question 8

what increases the glenohumeral socket depth and size?

Answer 8

the labrum

Question 9

what is the labrum made of?

Answer 9

fibrocartilage

Question 10

t or f: the labrum completely encircles the glenoid fossa (i.e. makes a complete O shape)

Answer 10

true

Question 11

what is a Bankart lesion?

Answer 11

anterior detachment of the joint capsule from the labrum

Question 12

what is a SLAP lesion?

Answer 12

superior labrum anterior posterior;
commonly seen in throwing athletes;
biceps or cuff msl detaches from superior labrum

Question 13

what are common causes of labral damage?

Answer 13

dislocation, increased mobility, overuse

Question 14

what is the shape of the humeral head?

Answer 14

1/3 of a sphere

Question 15

what is the position of the humeral head? (i.e. anteverted vs. retroverted)

Answer 15

retroverted (b/c the glenoid fossa is anteverted)

Question 16

what is the effect of the humeral head being retroverted?

Answer 16

there is less resistance to anterior translation, and more resistance to posterior translation

Question 17

what attaches to the greater and lesser tubercles?

Answer 17

rotator cuff msls

Question 18

what attaches to the intertubercular sulcus?

Answer 18

biceps long head, transverse lig, subscapularis and pectoralis msls

Question 19

in which directions is the glenohumeral joint strong?

Answer 19

anterior and inferior

Question 20

in which directions is the glenohumeral joint weak?

Answer 20

posterior (no posterior ligs)

Question 21

what are the 4 ligaments of the glenohumeral joint in order of importance?

Answer 21

inferior GH lig
middle GH lig
super GH lig
coracohumeral lig

Question 22

which glenohumeral ligament is the strongest?

Answer 22

inferior GH lig

Question 23

which glenohumeral ligament is the most injured?

Answer 23

inferior GH lig

Question 24

what are the two parts of the inferior GH lig?

Answer 24

anterior and posterior

Question 25

what is the function of the coracohumeral lig?

Answer 25

resist distraction and inferior translation w/arm at side

Question 26

what is the function of the superior GH lig?

Answer 26

main resistor of distraction, external rotation, and adduction of arm w/arm at side

Question 27

what is the function of the middle GH lig?

Answer 27

resist distraction and external rotation w/arm abducted 45-60˚

Question 28

what is the function of the inferior GH lig?

Answer 28

most important lig w/arm abducted >90˚; folds like an accordion

Question 29

what happens to the GH joint capsule when the arm is dependent?

Answer 29

lax/folded capsule

Question 30

what happens to the GH joint capsule when the arm is abducted?

Answer 30

taught/unfolded capsule

Question 31

what is resting position of the arm?

Answer 31

dependent position = hanging at side, 0˚

Question 32

what is tight packed position of the arm?

Answer 32

abducted and externally rotated

Question 33

what are static stabilizers of the glenohumeral joint?

Answer 33

capsule/ligs - IGHL most important | labrum

Question 34

what are the dynamic stabilizers of the glenohumeral joint?

Answer 34

rotator cuff, esp. w/arm abducted, biceps, trices, pec minor

Question 35

when is the GH jt most vulnerable to dislocation?

Answer 35

abduction and external rotation / FOOSH

Question 36

which direction are most dislocations?

Answer 36

anterior

Question 37

what is the suprahumeral joint?

Answer 37

between the coracoacromial arch and the humeral head

Question 38

what are the contents of the suprahumeral joint?

Answer 38

subacromial bursa rotator cuff tendon (esp. supraspinatus) biceps brachii long head

Question 39

what are the 3 parts of the coracoacromial arch?

Answer 39

coracoid, acromion, coracoacromial lig.

Question 40

what muscles and actions decrease risk of impingement at the suprahumeral joint?

Answer 40

external rotation inferior translation cuff and biceps

Question 41

what muscles and actions increase risk of impingement at the suprahumeral joint?

Answer 41

``` internal rotation superior translation deltoid, internal rotators, triceps (long head), pectoralis minor kyphosis shoulder hiking ```

Question 42

what is the progression of the acromioclavicular joint as you age?

Answer 42

fibrocartilaginous symphysis @ birth 2 cavities w/fibrocartilaginous disc @ 3-4 yrs meniscus @ 20 yrs degenerated by 20-30 yrs, not always symptomatic

Question 43

what is a common site for shoulder separation?

Answer 43

acromioclavicular joint

Question 44

what are the extracapsular ligs of the acromioclavicular joint

Answer 44

coracoclavicular ligs (conoid, trapezoid) - most important stabilizers

Question 45

what forces do the coracoclavicular ligs resist?

Answer 45

distractive forces

Question 46

what causes distraction at the AC joint?

Answer 46

``` abduction & horizontal abduction flexion external rotation lifting (i.e. suitcase) pull up or chin up ```

Question 47

what causes compression at the AC joint?

Answer 47

adduction horizontal abduction pushing pushup

Question 48

why can dislocation of the sternoclavicular joint be lethal?

Answer 48

b/c it can block the airway

Question 49

what are the supportive muscles of the SC joint?

Answer 49

pectoralis major, trapezius, SCM, subclavius

Question 50

what is the role of subclavius?

Answer 50

extensile/contractile lig to add stability to proximal end

Question 51

why is the interclavicular ligament so unique?

Answer 51

b/c it supports both R and L SC joints.

Question 52

what is the most important ligament of the sternoclavicular lig?

Answer 52

costoclavicular lig

Question 53

what does the costoclavicular lig resist?

Answer 53

anterior: distraction, depression, elevation, external rotation of clavicle @ SC jt. posterior: compression, depression, elevation, internal rotation @ SC jt

Question 54

why is the clavicle important?

Answer 54

connects the upper limb to the axial skeleton

Question 55

t or f: the clavicle moves with the scapula.

Answer 55

false. the clavicle moves similarly to the humerus

Question 56

what is the significance of the clavicle moving similarly to the humerus?

Answer 56

less torsion/bending

Question 57

what are the 3 phases of scapulohumeral rhythm?

Answer 57

phase 1 = 0-30˚ phase 2 = 30˚-90˚ phase 3 = 90˚ - 180

Question 58

what are the motions to watch during scapulohumeral rhythm

Answer 58

humerus @ GH (accounds for 120˚ total) scapula (60˚ external rotation) clavicle @ SC (results in 60˚ distal elevation) acromion @ SC (20˚ total rotation w/distal clavicle

Question 59

how much of the motion of the shoulder joint is in the GH jt?

Answer 59

2/3