Shoulder Flashcards
what type of joint is the SC?
functions as a saddle
structurally it is basically a planar
how is the SC joint stabilized?
- a disc between the clavicle and manubrium improves congruency
- Passive stabilizers
- Dynamic stabilizers
List the structures that passively stabilize the SC joint
- fibrous joint capsule
- A/P sternoclavicular ligaments
- Costoclavicular ligament (posterior and anterior bundle)
- interclavicular ligmanet
what motion does the fibrous joint capsule of the SC joint limit?
anterior and posterior translation of medial clavicle
what motion does the A/P sternoclavicular ligament limit?
Anterior = posterior translation of clavicle
Posterior = anterior translation of clavicle
what are the 2 portions of the costoclavicular ligmanet and what do they limit?
Anterior and Posterior bundle
limit elevation of clavicle
contribute to inferior glide of medial clavicle in elevation
shock absorption
what does the interclavicular ligament limit?
excessive depression and superior glide of clavicle
List the structures that dynamically stabilize the SC joint
- SCM
- Sternohyoid
- Sternothyroid
- Subclavius
what osteokinematic motions are available at the SC joint?
- elevation/depression
- protration/retraction
- anterior/posterior rotation
describe the arthrokinematics of the SC joint during elevation/depression
convex on concave
elevation = lateral clavicle rotates upward (superior roll, inferior glide)
depression = lateral clavicle rotates downward (inferior roll, superior glide)
describe the arthrokinematics of the SC joint during protraction/retraction
concave on convex
protraction = lateral clavicle moves anterior (anterior roll and glide)
retraction = lateral clavicle moves posterior (posterior roll and glide)
Describe the SC for the following:
closed pack
open pack
capsular pattern
closed pack = full posterior rotation (full arm elevation)
open pack = arm resting at side
capsular pattern = pain at end range with arm overhead
what is the joint type of the acromioclavicular (AC) joint?
planar synovial
T/F: an AC joint disc is always present
FALSE
it may or may not be there
List the passive structures that support the AC joint
- weak joint capsule
- Superior AC ligament
- Inferior AC ligament
- Coracoclavicular ligaments
- Trapezoid ligaments
- Conoid ligaments
what does the Superior Acromioclavicular ligmanet limit at the AC joint?
resists anterior clavicular/posterior acromion translation
reinforced by deltoid and trapzeius
what do the coracoclavicular ligmanets limit/resist at the AC joint?
limit superior clavicular/inferior scapular translation
and posterior rotation of clavicle
what is the primary function of the AC joint?
allow the scapula to rotate during arm movement
increases UE motion
positions glenoid beneath humeral head
maintains congruency of scapula on thorax
what osteokinematic motions are available at the AC joint?
- internal/external rotation
- A/P tilting (tipping)
- upward/downward rotation
describe the associated arthrokinematics for the osteokinematic motions at the AC joint
none are well defined
how is internal/external rotation of the AC joint important for motion at the scapula?
it maintains contact of scapula on curved thorax during protraction and retraction of clavicle
how is A/P tipping of the AC joint important to scapular motion?
important for maintaining contact of scapula on curved thorax during elevation and depression of clavicle
what is the significance of upward/downward rotation of the AC joint?
important for positioning of glenoid fossa in optimal position
describe the following for the AC joint:
closed pack position
open pack position
capsular pattern
closed pack = arm at 90 degrees
open pack = arm by side
capsular pattern = pain at end range with arm overhead
due to the structure of the AC joint, what injury is it susceptible to?
dislocation due to slopped nature of the articular coupled w/high probability of receiving large shear forces
can lead to development of posttraumatic OA
T/F: the scapulothoracic joint is a true anatomic joint and has all the assocaited structures expected of a synovial joint
FALSE
what osteokinematic motions are available at the scapulothoracic joint?
- primary
- elevation/depression
- protraction/retraction
- upward/downward rotation
- Secondary
- anterior/posterior tilting
- internal/external rotation
what motions occur at the SC and AC joint to allow for scapulothoracic protraction?
SC = protraction
AC = slight IR
what motions occur at the SC and AC joint to allow for scapulothoracic upward rotation?
summation of SC elevation and AC upward rotation
what is the angle of inclination of the GH joint?
130-150 degrees in frontal plane
what is the angle of torsion of the GH joint?
30 degrees posterior in the transverse plane
what is retroversion describing at the GH joint?
the posterior orientation of humeral head with regards to the condyles
increased humeral retroversion may result in what?
increased ER ROM and reduced IR ROM
observed a lot in dominant arm of throwing athletes
list the passive structures that support the GH joint
- Glenoid labrum
- Joint capsule
- S/M/I GH ligaments
- Coracohumeral ligament
describe the characteristics of the GH joint capsule
- significant laxity, minimal stability provided
- reinforced by thicker external ligaments
- inferior portion is slack in ADD position creating an axillary pouch
what is the clincial significance of a tight posterior GH capsule?
linked to shoulder impingement
tightness may produces increased anterior humeral head translation which decreases the subacromial space
what does the superior glenohumeral ligament limit?
ER, anterior and inferior translation at O degrees of abduction
slackens when abducted beyond 35-45 degrees
what does the middle GH ligament limit?
anterior translation from 45-90 degrees abduction
and extremes of ER
what does the inferior GH ligament limit?
primary stabilizer beyond 45 degrees of abduction
stabilizes during combing abduction w/rotation
what does the coracohumeral ligament limit?
downward dislocation
inferior translation and ER of humeral head w/arm hanging at side
list the dynamic structures that support the GH joint
Rotator cuff
what are 2 places the rotator cuff does not reinforce the GH joint?
- inferiorly
- region between subscapularis and supraspinatus (rotator cuff interval)
describe the arthrokinematics for each osteokinematic motion at the GH joint
convex on concave
(roll and glide will be opposite for every motion)
how does shoulder flexion impact the GH joint capsule?
causes tension throughout capsule
slight anterior translation may occur at end range flexion due to tension in posterior capsule
in order for full GH abduction to occur, what else must occur?
ER
what is the closed pack position for the GH joint?
90 degrees abducted and full ER
OR
full abduction and ER
what is the open pack position for the GH joint?
abducted 55 degrees, then horizontally adducted 30 degrees with slight ER
what is the capsular pattern for the GH joint?
ER > ABD > IR
what is the ratio of motion in the scapulohumeral rhythm?
2 degrees of glenohumeral
to
1 degree of scapular motion
what is the ideal shoulder girdle position?
slightly elevated and relatively retracted scapula
*results in glenoid fossa facing slightly upward
List some pathologies that reduce musclar support of the shoudler
- Stroke
- muscular dystrophy
- Guillan-Barre
- impinged nerve
how does gravity effect scapulothoracic posture?
results in depressed, protracted, and excessively downward rotated scapula
what is the impact that rounded shoulders can have on an individual’s shoulder complex?
can lead to biomechanical stress on SC and GH
slight depression, downward rotation and protraction of scapula
can lead to stressed portions of joint, subluxations at worse and compression of arteries and nerves
describe how the rhomboids and traps function together
pure retraction
traps tend to elevate scapula and rhomboids tend to depress scapula = neutralized and pure retraction
describe how the deltoid and supraspinatus function together
work to acheive full abduction
if the deltoid is paralyzed, is full abduction of GH possible?
yes, but torque is reduced
if the supraspinatus is paralyzed is full GH abudction possible?
yes but only through compensations and in very specific cases
describe how the supraspinatus and mid trap function together
middle trap functions to stabilize scapula
while supraspinatus ER the shoulder
what would occur if the middle trap was paralyzed?
scapular dyskinesis
scapula would move into IR as the GH ER
describe how the serratus anterior, upper trap and low trap function together
contract simulataneously to produce upward rotation of scapular during GH abduction
how does the infraspinatus, teres minor and subscapularis stabilize the GH joint?
exert a depressive force on humeral head
what is scapular dyskinesia?
any abnormal position or movement of the scapula
alters effectiveness of muscle actions and distorts arthrokinematics resulting in stress
