Shoulder Anatomy Flashcards
what is in the shoulder complex?
clavicle
scapula
humerus
why is stability sacrificed in the shoulder joint?
so it can have more mobility
how many degrees of freedom does the shoulder joint have?
3
what is on the end of the long bone?
articular cartilage
what kind of CT is the fibrous capsule?
dense irregular
what is the purpose of the joint capsule?
adds stability
lowers friction
what gives the shoulder the greatest stability?
muscles
what is dynamic stability?
when a joint is more dependent on muscles than other structures to give stability
what is special about the scapulothoracic joint?
its not a true joint
a/w movement of the sc and ac joints
what are the movements of the scapula?
elevation/depression
protration/retraction
upward/downward rotation (look at the inferior angle to identifty this motion)
what forces hold the scapula to the thorax?
ATM
link with AC and SC jt
muscles
what are functions of the scapula?
orient glenoid fossa to arm
add ROM to the arm
provide a stable base for the controlled rolling and sliding of the articular surface
what type of jt is the sternoclavicular jt?
plane (saddle shaped surfaces)
has 3 degress of motion
incongruent
what are motions at the sternoclavicular jt?
elevation/depression
protraction/retraction
rotation
how is the motion described for the sternoclavicular jt?
in terms of the distal portion of the clavicle
protraction/retraction of the sternoclavicular jt is a/w which movement of the scapula?
ab/adduction
which direction does sternoclavicular jt rotate?
posteriorly only!
what kind of joint disc is in the sternoclavicular jt?
fibrocartilage
which ligaments are involved at the SC joint?
anterior and posterior SC ligament costoclavicular ligament (major constraint on SC motion) interclavicular ligament
what is the function of the SC joint?
protects the brachial plexus and subclavian artery (pass between clavicle and 1st rib)
what is the sequence of brachial plexus?
roots trunks divisions cords nerves
what levels are involved in the brachial plexus?
c5-t1
which type of joint is the AC joint?
plane
what is the primary function of the AC joint?
maintain relationship b/w clavicle and scapula
allow scapula additional ROM on the thorax in latter stages of elevation
what are the articulation surfaces in the AC joint?
- convex facet of lateral end of clavicle
2. concave facet on acromion of the scapula
which ligaments are involved in the AC joint?
- superior and inferior AC ligaments
- coracoclavicular ligament
- coracoacromial ligament
what are the motions of the AC joint?
- scapular rotation
- winging of the scapula
- tipping of the scapula
what motion is altered in pathological winging?
flexion/abduction (scapula does not round around thorax)
what motion is altered in pathological tipping?
elevation/depression (scapula does not round around thorax)
what are the 2 parts of the coracoclavicular ligament?
- trapezoid
- conoid
(separated by fat and a large bursa)
which clavicular jt is more likely to get injured?
AC (sprains, subluxations, dislocations)
what is the function of the AC joint?
prevent superior dislocation of the clavicle
also provides horizontal stability
also prevent excessive rotation of the scapula
transmits compression forces to the stronger SC joint
what is the position of the humeral head?
posterior torsion (retrotorsion)-30 degrees
what is the angle of inclination of the humerus?
135 degrees (angle of direction of head compared to rest of the body)
what is the glenoid labrum?
dense, fibrous CT that provides excess depth to the socket
when does the GH joint tighten?
during motion
at rest, it is large and loose-2x the size of the humerus
what are the GH ligaments?
superior/middle/inferior GH ligament (not as strong)-forms a Zshape coracohumeral ligament (inserts on greater tubercle)
what is the most important role of the coracohumeral ligament?
passive support against gravity
what is the role of the coracoacromial arch?
protect bursa against trauma
prevents superior dislocation of the humeral head
what are the joint motions of the shoulder jt?
roll, slide, spin
which muscle supports for static stabilization?
supraspinatous muscle
if more force is needed, deltoid also contracts
which are the primer movers for abduction?
deltoid
supraspinatous
what is the primer movers for GH flexion?
anterior deltoid
what is a major role of the rotator cuff?
muscles produce inferiorly directed force which offsets the superior pull of the deltoid
provide stability
reduce forces of the humeral head moving in the glenoid fossa
which two muscles are responsible for external rotation?
infraspinatous
teres minor
which muscle is responsible for internal rotation?
subscapularis
which muscle is responsible for humeral stability against gravity?
suprascapularis then deltoid
which muscles cause the scapula to upwardly rotate?
trapezius and serratus anterior
