Shoulder Complex

Question 1

scapulohumeral rhythm

Answer 1

ratio of 2 degrees of GH to 1 degree of scapular motion during arm elevation/ABD

Question 2

ideal shoulder girdle posture

Answer 2

• slightly elevated and relatively retracted scapula

- results in glenoid fossa facing slightly upward

Question 3

pathologies that can reduce muscular support of shoulder girdle

Answer 3

• isolated paralysis of upper trap
• stroke
• muscular dystrophy
• Guillain-Barre

Question 4

effect of gravity of scapulothoracic posture

Answer 4

results in depressed, protracted and excessively downwardly rotated scapula

Question 5

consequences of poor shoulder girdle posture

Answer 5

• depressed clavicle; superior dislocation of SC joint

- compressed subclavian vessels or brachial plexus

Question 6

long term paralysis of UT may result in ____

Answer 6

• inferior subluxation/dislocation

- seen with flaccid hemiplegia

Question 7

rounded shoulders

Answer 7

• slight depression, downward rotation, and protraction of scapula
• can lead to biomechanical stress on SC and GH
• predisposes individual to impingement

Question 8

potential causes of rounded shoulders

Answer 8

• general laxity
• muscle tightness
• fatigue or weakness
• GH joint capsule tightness
• abnormal cervicothoracic posture
• habit

Question 9

function of rhomboids + lower trap during retraction

Answer 9

• these muscles share similar actions but act as antagonists to one another
• elevation tendency of rhomboids is neutralized by depression tendency of lower trap
• result is pure retraction

Question 10

relationship of deltoid and supraspinatus in paralysis of deltoid

Answer 10

supraspinatus is typically able to perform full ABD of GH joint, but ABD torque is significantly reduced

Question 11

relationship of deltoid and supraspinatus in paralysis or complete rupture of supraspinatus

Answer 11

• full ABD is difficult, but achievable in some cases

- in other cases, full ABD is not possible du to weakness and altered AK at GH joint

Question 12

force couples for upward rotation

Answer 12

• serratus anterior + upper and lower traps

- contract simultaneously to produce upward rotation during GH ABD

Question 13

scapular winging

Answer 13

• excessive IR of scapula
• visualized during arm elevation
• could be secondary to pathology or poor neuromuscular control of the scapulothoracic muscles

Question 14

how does the supraspinatus control AK of ABD of GH joint?

Answer 14

• drives superior roll of humeral head
• compresses humeral head against glenoid
• creates a semi-rigid spacer above the humeral head, restricting excessive superior translation of the humerus

Question 15

how do the infraspinatus, teres minor, and subscap control AK of ABD of GH joint?

Answer 15

exert a depression force on the humeral head

Question 16

how does the infraspinatus and teres minor control AK of ABD of GH joint?

Answer 16

ER humerus

Question 17

goal of reverse shoulder arthroplasty for people with severe RC degeneration

Answer 17

• shift the AOR medially and inferiorly in relation to the scapula
• allows deltoid to increase ABD leverage due to increased tension

Question 18

what is scapular dyskinesis?

Answer 18

any abnormal position or movement of the scapula

Question 19

scapular dyskinesis is typically seen as…

Answer 19

• reduced upward rotation
• excessive downward rotation, IR, anterior tilt, or elevation of scapula
• occurs with overhead movement of the GH joint

Question 20

scapular dyskinesis alters the ____ of muscles’ actions and distorts ____ resulting in increased stress

Answer 20

• effectiveness

- AK

Question 21

prevalence of injury in SC joint

Answer 21

• does not undergo degenerative changes to the same degree as other shoulder joints
• only 1% of dislocations in the body occur here

Question 22

prevalence of injury in AC joint

Answer 22

susceptible to trauma and degenerative changes

Question 23

prevalence of injury in GH joint

Answer 23

subject to degenerative changes, instability (esp in anterior dislocation), and derangement