shoulder anatomy Flashcards
what are the movements at the SCJ and how are they defined?
- elevation/depression
- protraction/retraction
- posterior rotation
defined by movement at the distal clavicle
describe SC elevation/depression
convex on concave limited by the CC ligament
describe SC depression
convex on concave limited by the interclavicular ligametn
describe SC retraction
concave on convex limited by CC ligament and anterior capsule
describe SC protraction
concave on convex limited mostly by the posterior capsule
describe axial movment of the clavicle
during abd/flx around 90/100, the clavicle spins posteriorly 20-35
what does the coracoclavicular ligament do? what are the two parts
suspends the scapula from the clavicle
how is motion described at the scapula? what are the motions?
by motion occuring at the distal clavicle; up and down rotation primarily, but also IR/ER and AP tilting
what are the physiologic motions associated with scapular upward and downward rotation?
upward: flexion and abduction
downward: extension and adduction
what are the muscles that make up the scapulothoracic joint?
subscap, serratus anterior, ES
what is the average resting position of the scapula in all three planes?
anterior tilt, IR, upward rotation
what two component motions are necessary for scapular elevation?
SC elevation, AC down rotation
what two component motions are associated with scapular protraction?
SC protraction and AC IR
scapulothoracic upward rotation is made of which component motions?
SC elevation and AC up rotation
what are the approximate orientations of the GHJ components
scapular plane: approx 30
physiologic GH head retroversion: 30
clavicle posteriorly oriented : 20
what are the capsular ligaments of the GHJ and what motions do they resist
superior: adduction
middle: ER
inferior: inferior and A/P translations
what is most unique about the inferior GHL?
it is a cradle-like pouch composed an anterior band, posterior band, and axillary pouch
the cocking phase of throwing stresses which part of the GHJ the most?
anterior band of inferior capsule
which external capsule ligament provides GH capsule stability
CHL
when is the SGHL taught and what motions does it resist?
- adduction
- inferior + AP humeral head translation
when is the MGHL taught and what motions does it resist?
- anterior translation of the humerus (esp in slight abd)
- ER
when is the CHL taught and what motions does it resist?
- adduction
- inferior translation of humerus + ER
when is the axillary pouch taught and what motions does it resist?
- 90 abd
- AP + inferior translation
when is the anterior band of the IFGHL taught and what motions does it resist?
- 90 abd + full ER
- anterior translation of humerus
when is the posterior band of the IFGHL taught and what motions does it resist?
- 90 abd + full IR
- inferior translation of the humerus
what are three major components of the subacromial space
supraspinatus tendon, subacromial bursa, and long head biceps tendon
what are the motions at the GHJ?
three degrees of freedom plus a fourth (horizontal abd/add)
what motion is associated with GH abd and why?
ER so that the greater tubercle can pass under the acromion
what are the three kinematic principles of full shoulder abduction
- 2:1 rhythm
- 60 degree scap up rotation
- clavicle retraction
- scap posterior tilt and ER
- clavicle posterior rot 20-35
- GH ER
what innervates the serratus anterior?
long thoracic (C5-7)
what innervates the rhomboids and levator scap?
dorsal scap (C5)
what innervates the supra and infraspinatus?
suprascapular nerve (C5-6)
what innervates the subscapularis?
upper and lower subscapular nerves (C5,6)
what innervates the lats?
thoracodorsal C6-8
what innervates teres major?
lower subscapular nerve (C5,6)
what innervates the deltoid and teres minor?
axillary nerve (C5,6)
what innervates pec major and minor?
lateral pectoral C5-7 and medial pectoral C8,T1
what provides sensation to the SCJ
supraclavicular C3,4
what are ST elevators?
UT, LS, rhomboids
what are ST depressors?
LT, lats, pec minor, subclavius
what are ST protractors?
SA
what are ST retractors?
MT, rhombs, LT
what are ST up rotators?
delt, all traps, SA
what are the three components of the detoid-RTC force couple and why do they matter?
- deltoid
- supraspinatus
- other RTC
though the deltoid is a big mover, the RTC fixes the humeral head in the glenoid and directions the rotation of the head; otherwise, the humerus would just ram the acromion (60% more)
