Exam 3 lecture: shoulder Flashcards
what is scapulohumeral rhythm?
arm trunk mechanism
what are the 4 important joints of the shoulder complex?
scapulocostal
sternoclavicular
acromioclavicular
glenohumeral
what type of joint is the glenohumeral joint?
ball and socket / enarthrosis
what is the effect of the depth of the glenoid fossa on stabilty?
the glenoid fossa is shallow –> less static stability
t or f: the head of the humerus is larger than the glenoid fossa.
true
what is the significance of the glenoid fossa being anteverted?
there is little anterior stability
what happens if the glenoid fossa is retroverted?
there would be less posterior stability
what increases the glenohumeral socket depth and size?
the labrum
what is the labrum made of?
fibrocartilage
t or f: the labrum completely encircles the glenoid fossa (i.e. makes a complete O shape)
true
what is a Bankart lesion?
anterior detachment of the joint capsule from the labrum
what is a SLAP lesion?
superior labrum anterior posterior;
commonly seen in throwing athletes;
biceps or cuff msl detaches from superior labrum
what are common causes of labral damage?
dislocation, increased mobility, overuse
what is the shape of the humeral head?
1/3 of a sphere
what is the position of the humeral head? (i.e. anteverted vs. retroverted)
retroverted (b/c the glenoid fossa is anteverted)
what is the effect of the humeral head being retroverted?
there is less resistance to anterior translation, and more resistance to posterior translation
what attaches to the greater and lesser tubercles?
rotator cuff msls
what attaches to the intertubercular sulcus?
biceps long head, transverse lig, subscapularis and pectoralis msls
in which directions is the glenohumeral joint strong?
anterior and inferior
in which directions is the glenohumeral joint weak?
posterior (no posterior ligs)
what are the 4 ligaments of the glenohumeral joint in order of importance?
inferior GH lig
middle GH lig
super GH lig
coracohumeral lig
which glenohumeral ligament is the strongest?
inferior GH lig
which glenohumeral ligament is the most injured?
inferior GH lig
what are the two parts of the inferior GH lig?
anterior and posterior
what is the function of the coracohumeral lig?
resist distraction and inferior translation w/arm at side
what is the function of the superior GH lig?
main resistor of distraction, external rotation, and adduction of arm w/arm at side
what is the function of the middle GH lig?
resist distraction and external rotation w/arm abducted 45-60˚
what is the function of the inferior GH lig?
most important lig w/arm abducted >90˚; folds like an accordion
what happens to the GH joint capsule when the arm is dependent?
lax/folded capsule
what happens to the GH joint capsule when the arm is abducted?
taught/unfolded capsule
what is resting position of the arm?
dependent position = hanging at side, 0˚
what is tight packed position of the arm?
abducted and externally rotated
what are static stabilizers of the glenohumeral joint?
capsule/ligs - IGHL most important
labrum
what are the dynamic stabilizers of the glenohumeral joint?
rotator cuff, esp. w/arm abducted, biceps, trices, pec minor
when is the GH jt most vulnerable to dislocation?
abduction and external rotation / FOOSH
which direction are most dislocations?
anterior
what is the suprahumeral joint?
between the coracoacromial arch and the humeral head
what are the contents of the suprahumeral joint?
subacromial bursa
rotator cuff tendon (esp. supraspinatus)
biceps brachii long head
what are the 3 parts of the coracoacromial arch?
coracoid, acromion, coracoacromial lig.
what muscles and actions decrease risk of impingement at the suprahumeral joint?
external rotation
inferior translation
cuff and biceps
what muscles and actions increase risk of impingement at the suprahumeral joint?
internal rotation superior translation deltoid, internal rotators, triceps (long head), pectoralis minor kyphosis shoulder hiking
what is the progression of the acromioclavicular joint as you age?
fibrocartilaginous symphysis @ birth
2 cavities w/fibrocartilaginous disc @ 3-4 yrs
meniscus @ 20 yrs
degenerated by 20-30 yrs, not always symptomatic
what is a common site for shoulder separation?
acromioclavicular joint
what are the extracapsular ligs of the acromioclavicular joint
coracoclavicular ligs (conoid, trapezoid) - most important stabilizers
what forces do the coracoclavicular ligs resist?
distractive forces
what causes distraction at the AC joint?
abduction & horizontal abduction flexion external rotation lifting (i.e. suitcase) pull up or chin up
what causes compression at the AC joint?
adduction
horizontal abduction
pushing
pushup
why can dislocation of the sternoclavicular joint be lethal?
b/c it can block the airway
what are the supportive muscles of the SC joint?
pectoralis major, trapezius, SCM, subclavius
what is the role of subclavius?
extensile/contractile lig to add stability to proximal end
why is the interclavicular ligament so unique?
b/c it supports both R and L SC joints.
what is the most important ligament of the sternoclavicular lig?
costoclavicular lig
what does the costoclavicular lig resist?
anterior: distraction, depression, elevation, external rotation of clavicle @ SC jt.
posterior: compression, depression, elevation, internal rotation @ SC jt
why is the clavicle important?
connects the upper limb to the axial skeleton
t or f: the clavicle moves with the scapula.
false. the clavicle moves similarly to the humerus
what is the significance of the clavicle moving similarly to the humerus?
less torsion/bending
what are the 3 phases of scapulohumeral rhythm?
phase 1 = 0-30˚
phase 2 = 30˚-90˚
phase 3 = 90˚ - 180
what are the motions to watch during scapulohumeral rhythm
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
how much of the motion of the shoulder joint is in the GH jt?
2/3
