Unit 3- shoulder Flashcards
trapezoid ligament
extends superolaterally from superior surface of coracoid process to the trapezoid line on the clavicle (lateral)
conoid ligament
extends vertically from the base of coracoid process to conoid tubercle of the clavicle
motions at the AC joint
how scapula moves on distal clavicle
- upward and downward rotation
- internal and external rotation
- anterior tilt and posterior tilt
motions at the ST joint
cooperation between AC and SC motions
- elevation and depression
- protraction and retraction
- upward and downward rotation
motions at the SC joint
- elevation and depression
- protraction and retraction
- forward and backward rotation
elevation at the ST joint
combination of elevation of SC and downward rotation at AC
depression at the ST joint
combination of depression of SC and upward rotation at AC
protraction at ST joint
protraction at SC and IR at AC
retraction at ST joint
retraction at SC and ER at AC
upward rotation of ST
elevation of SC and upward rotation of AC
SC joint articulations
medial end of clavicle, clavicular facet on sternum, superior border of cartilage of first rib
AC joint articulations
acromion and lateral end of clavicle
GH joint
large convex head of humerus and shallow concavity of the glenoid fossa
superior GH ligament
from supraglenoid tubercle to above the lesser tubercle
-becomes taut in adduction, restrains inferior and AP translation
shoulder elevation: contribution from clavicle
- posterior rotation
- retraction
- elevation
shoulder elevation: contribution from scapula
- upward rotation
- internal rotation
- posterior tilt
shoulder elevation: contribution from humerus
- elevation (abd or flexion)
- external rotation
ratio for humerus to scapula movement
2:1 GH to ST movement
passive stabilization of the shoulder
- structures of the superior capsule, supraspinatus tendon and rotator interval capsule
- vacuum pressure of capsule (negative intraarticular pressure)
- glenoid inclination/gravity (slight upward tilt of fossa)
rotator interval
provides stability against anterior translation
space between supraspinatus and subscap tendon on the head of the humerus
-contains coracohumeral ligament and superior GH ligament
GH ligament
inferior (a/p bands, axillary pouch)
middle
superior
angle of torsion
axis through humeral head in relation to axis through condyles (approx 30 degrees)
angle of inclination
axis through head and neck relative to shaft (130-150 degrees)
glenoid labrum
attachment site for GH ligaments and long head of biceps tendon
superior GH ligament
resists anterior and inferior translation when arm is at side
middle GH ligament
resists anterior translation when arm is abducted at the side and up to 60 degrees
inferior GH ligament
major restrain is with arm abd beyond 45 degrees resisting inferior translation
anterior band: resists anterior translation when arm is ER and abd
posterior band: resists posterior translation when arm is IR and abd
dynamic stabilization of GH
function of:
- force of prime movers
- force of gravity
- force of muscle stabilizers
- articular surface geometry
- passive capsuloligamentous structures
- friction
- force of joint reaction forces
supraspinatus as a prime GH joint mover
- action line runs superior, parallel to rotator interval
- large ability to abduct arm and compress joint (drives humeral head into glenoid to stabilize so deltoid can take over) due to greatest MA of RTC muscles
- with gravity, contributes to inferior glide of humeral head during abduction (offsets vertical torque of deltoid)
dynamic stabilization of the GH due to RTC
during movement of the arm, the axis of rotation of the humeral head only moves a few millimeters within the glenoid
dynamic stabilization of the GH during ER
infraspinatus and teres minor cause ER
humerus goes posteriorly, glides forward and is stabilized by tension in subscap
role of long head of biceps in GH stabilization
attaches to superior labrum and capsule, pulls humeral head down when it contracts and stabilized the humeral head as the shoulder flexes
role of gravity in GH stabilization
facilitates inferior glide, can approzimate and acts as a stabilizer depending on position of arm
ST elevators
upper traps, levator scap, a little rhomboids
ST depressors
lower traps, lats, pec minor, subclavius
protractors at ST joint
serratus anterior
retractors at ST joint
middle traps
also lower traps and rhomboids
abductors at GH joint
anterior and middle deltoid, supraspinatus
flexors at GH joint
coracobrachialis, anterior delt, long head of biceps
upward rotators at ST joint
serratus anterior and traps **force couple
middle traps does retraction while upper and lower do upward rotation with serratus
