Functional Anatomy of the Shoulder Complex Flashcards
what is the shoulder complex composed of
what type of joint is the glenohumeral joint
GH joint, scapulothoracic joint, sternoclavicular joint, acromioclavicular joint, labrum, capsule, ligaments
triaxial synovial joint
the GH joint rotates around __ axes
how does the GH joint’s mobility compare to other joints in the body
what does the GH joint consist of
3
more mobility than any other single joint in the body
humeral head and glenoid fossa
T or F: the humeral head is 3-4 times larger than the glenoid fossa
what is the glenoid labrum
what does the glenoid labrum do
T, only 1/3rd of it articulates with the glenoid fossa
a fibrocartilage ring surrounding the glenoid
deepens the fossa and has a vacuum effect to seal the joint and assist with stability
where does the GH joint capsule arise from and insert
the inferior capsule is ___ and ___ which allows for full ___
arise: the glenoid neck and labrum
insert: articular margin of the humeral neck
loose and redundant, abduction
the GH joint capsule is superiorly and anteriorly reinforced by what 3 ligaments
does the joint capsule provide a lot of stability
superior, middle and inferior GH ligaments
no because it is thin and loosely surrounds the joint
where does the superior GH ligament arise from
the superior GH ligament blends with what other ligament
the superior GH ligament is a primary stabilizer to what movements when the shoulder is in what position
margin of the glenoid and labrum in a small depression above the lesser tubercle
coracohumeral
inferior and anterior posterior translation when adducted
the superior GH ligament limits ER in what degrees of abduction
it is tensioned with the biceps during which motion
the superior GH ligament is a secondary stabilizer when the arm is in what position
0-45
throwing
abduction
where does the middle GH ligament arise from and insert to
what are the two functions of the middle GH ligament
arise: anterior superior glenoid and labrum
insert: lower part of the lesser tuberosity
limits ER when arm is adducted, provides restraint to anterior humeral translation with the arm in mid range of abduction up to 45 degrees
where does the inferior GH ligament attach
what are the two bands it has called
the inferior GH ligament has a __ type axillary pouch
from anterior/posterior mid glenoid and labrum
anterior and posterior
hammock
what are the two functions of the inferior GH ligament
where does the coracohumeral ligament attach and insert
anterior band limits anterior translation when GH joint is abducted up to 90, during IR the posterior band limits posterior translation
attach: near root of the coracoid
insert: humerus and transverse ligament
what are the functions of the coracohumeral ligament
T or F: the scapulothoracic joint is a true joint
limits ER below 60 degrees, works with superior glenoid ligament, restraint for flexion and extension, acts as a tunnel for the bicep
F, is a pseudo joint
where is the scapulothoracic joint located
where does the scapula rest superiorly and inferiorly on the thoracic vertebrae
what can injury to this joint result in
between the anterior portion of the scapula and the posterior thorax and rib cage
superiorly: at the 2nd thoracic vertebral level
inferiorly: at the 7th thoracic vertebrae
scapular winging
why is the scapulothoracic joint angled at 30-45 degrees from the coronal plane
what is this position known as
to place the glenoid fossa anteriorly
scaption
where is the sternoclavicular joint located
what shape is this joint
T or F: the SC joint is unstable but very rarely dislocated
between medial end of the clavicle and lateral portion of the sternum
saddle
T
what is the most important ligament surrounding the sternoclavicular joint
this ligament causes significant increases in what type of translation
the posterior sternoclavicular ligament
anterior and posterior translation greater than that of any other surrounding ligament
what type of joint is the acromioclavicular joint
how many degrees of freedom does the AC joint have
which ligaments provide medial stability to the AC joint
synovial planar
3
conoid and trapezoid (coracoclavicular)
the conoid runs ___ between coracoid process and clavicle
what movements does the conoid resist
the trapezoid runs __ and __ between the coracoid process and clavicle
what movements does the trapezoid resist
vertically
elevation and protraction
superiorly, laterally
AC joint compression and clavicle elevation and protraction
what is scapulohumeral rhythm
what is the ratio of scapulohumeral rhythm
contributions made by multiple joints to create should elevation
2 degrees of GH motion for 1 degree of scapular movement (others have said 1.25:1 or 4:1)
what are force couples
which force couple produces the largest amount of force
two or more muscle groups on opposite sides of a joint that work in concert to provide joint stability or movement in a joint segment
deltoid-rotator cuff force couple
during initial arm movement, the deltoid in the deltoid-RC force couple produces forces in which 2 directions
what does this cause
this is counteracted by which forces from the RC muscles
upwards and outwards force
superior migration of the humerus
inferior and medial directed force
what type of force does the supraspinatus have on the humeral head
what does this force do
between what degrees is this force maximal
after you reach ___ degrees this force is gone
a direct compressing force
compresses the humeral head into the glenoid
45-90
150
what are the 2 functions of the infraspinatus and teres minor when they work together as force couples
depress the humerus allowing the supraspinatus to compress and prevent sub-acromial compression
external rotators and eccentrically decelerate internal rotation
the subscapularis is active in all movements of the humeral head that require ___ and ____
the subscapularis acts ___ to decelerate ___
the subscapularis is commonly injured in which types of sports
compression, depression
eccentrically, external rotation
sports requiring OH movement of the shoulder
which tendon is one of the most commonly torn in the body
which muscle is the only muscle that is an IR concentrically
supraspinatus
subscapularis
the long head of the biceps increases GH ___ with the ___
the long head of the biceps increases ___ stability in ____ and ____ by resisting translational stress
compression, supraspinatus
anterior, abduction, external rotation
the upper trap and serratus anterior work together to produce what movement during elevation
what are the 4 crucial functions of the upper traps and serratus anterior force couple
upwards rotation of the scapula
allows for rotation of scapula for optimal GH function
maintains efficient length tension of the deltoid
prevents impingement of RC from subacromial structures
provides stable scapular base enabling appropriate recruitment of scapular-humeral muscles
in the upper trap and serratus anterior force couple, the lower traps and serratus anterior cause what movements when the shoulder is abducted past 90
upwards rotation and stabilization of the scapula
what changes would you see in the upper trap and serratus anterior force couple in a patient with impingement syndrome
what do these changes result in
decreased activity of serratus anterior
delay in firing of lower and middle traps
dominance of upper traps and LS
faulty scapulohumeral patterns
what are the anterior-posterior RC force couples
what do these force couples do
anterior-subscapularis and posterior-infraspinatuc and teres minor
create inferior dynamic stability, compresses the GH joint, stabilize fulcrum to all rotation of the humeral head on the glenoid
