LECTURE 7A: SHOULDER ANATOMY Flashcards
4 joints in the shoulder complex
Gleno-humeral joint (golf ball and T)
Acromio-clavicular joint
Sterno-clavicular joint
Scapulo-thoracic joint
What is the primary function of the shoulder?
position hand in space to permit upper limb to interact w/ environment and perform wide range of activities
what is the secondary function of the shoulder?
- suspend UE
- provide sufficient fixation for motion of UE/trunk
- serve as fulcrum for arm elevation (scaption, abduction, flexion)
The GH joint is a ____ joint
true synovial, ball and socket
capsular pattern of the GH joint
ER, ABD, IR
Closed packed position of shoulder
90 ABD or full, full ER
open packed position of shoulder
55 degrees of abduction, 30 degrees of adduction, (maybe slight IR)
What is the last motion you get when you injure shoulder
Internal rotation
passive structures of the GH joint
- labrum
- capsule
- ligaments
active structures of the GH joint
rotator cuff
scapular muscles
muscles blend into each other!
What stabilizes the GH joint?
concavity of glenoid fossa (negative pressure, adhesions)
labrum
ligaments
muscles
mechanoreceptors
labrum is ___ and _____, and made of __cartilage
avascular, aneural
made of fibrocartilage
labrum aids in ____ to glenoid
attaching GH ligaments
T or F: capsule is large, loose, and not very stable
true
normal volume of the shoulder capsule
10-15 ml
fluid volume in GH capsule with adhesive capsulitis
5-10 ml
fluid volume with GH capsule with capsular laxity
up to 30 mL
GH ligaments are _____ rather than isolated structures
capsular thickenings (not super concrete, not very stable!)
superior GH ligament is taut when
arm by side (0 degrees abduction)
SGHL is covered by
coraco-humeral ligament
some people (30% of people) don’t have a middle GH ligament. What does the MGHL do?
true (supposed to provide 2ndary restraint to anterior translation)
When this ligament is incompetent, humeral head will sublux inferiorly
SGHL
inferior GH ligament is the main static stabilizer of the ____
abducted shoulder
(also rotation in abduction –> IGHL fans out to support humeral head)
inferior GH ligament is made of
- anterior band
- posterior band
- axillary pouch
inferior band of the inferior GH ligament fans and rotates ___ with rotation
anterior (hammock)
posterior ligaments are ___
THIN, not helpful that much
(mostly stable through muscles)
Provides stability to humeral head when arm abducted 90° and IR
posterior band of IGHL
MAIN JOB OF rotator cuff
the transverse abs of the shoulder! CORSET
stabilizes GH joint when other large mm contract, assist with arm elevation
rotator cuff acts as force couple with ___ muscle
deltoid
3 jobs of the rotator cuff
- control motion
- rotate humeral head
- STABLIZE HUMERUS IN GLENOID (CORSET)
what are the 3 force couples of the shoulder
- Rotator cuff – deltoid
- Upper/lower trapezius – serratus anterior
- Anterior – posterior rotator cuff
Dynamic stability of GH joint achieved through contraction of RC muscles and ____
biceps
___ couple offers compression of convex-concave joint surfaces, decreasing translation
anterior/posterior RC force couple
T or F: passive structures are reinforced through direct attachment of RC tendons to provide dynamic stability
T
can you have all the muscles in the shoulder and it still play out of tune?
yes! like a band, need everyone in tune.
NM control via proprioception
with your arm by the side, subacromial space is about ____ mm
10-11 mm
when arm elevates, sub acromial space is ____
narrowed
most narrow at 60-120 degrees elevation
If you ahve osteophyte, acromion hook, swollen rotator cuff tendon, what happens with the shoulder sub-acromial space?
impingement
position of the GH joint (ER vs IR) changes impingement. Why?
The tubercles! greater and lesser w/ all mm attachements
ER: not under acromion, escape! cleared
IR: under acromion, LESS SPACE
What tendon is the most involved in overuse syndromes
supraspinatus
Muscle imbalances and capsular stiffness can ____ superior migration of humeral head
increase
Glenoid covers ____of humeral head
quarter to a third
AC joint is a ___ joint
true synovial, plane joint (glides
closed pack of AC joint
90 degrees abduction
capsular pattern of AC joint
extreme ROM ends (elevation)
* AC doesnt matter if someone rolls in with like 90 degrees of elevation
Main articulation that suspends UE from trunk
AC joint
primary support for AC joint
Coraco-clavicular ligament
(2 parts: conoid and trapezoid)
someone “separated” their shoulder - what did they tear?
coraco-clavicular
Only joint that connects shoulder girdle to axial skeleton
sterno-clavicular joint
sterno-clavicular joint is a ___ joint
true synovial, saddle/plane joint
closed packed position of sterno-clavicular joint
max elevation and protraction
capsular pattern of the sterno-clavicular joint
extreme end ROM (especially elevation and horz ADDuction)
AC joint ___dislocation 9X more common than ____dislocations, although only 3% of shoulder injuries overall (sterno-clavicular joint)
Anterior dislocation 9X more common than posterior dislocations, although only 3% of shoulder injuries overall
AC and SC joints are mainly controlled by -__ structures
passive!
scapulothoracic joint has stability through
no real passive just active structures
B/c of bony arrangement, SC joint inherently weak. secured by ___
super strong ligaments
scapulo-thoracic joint is considered a ___ joint
false joint
OPP: Scapulo-thoracic Joint
w/ arm at neutral – scapula positioned 30-45° IR, slight upward rotation and 5-20° anterior tipping
review scapulo-humeral rhythm: 3 phases
phase 1:
-30 degree humeral elevation (clavicle 0-5)
phase 2:
-humerus: 40 abduction
-scapula 20 upward rotation + min protraction/elevation
-clavicle: 15 elevation
phase 3:
-humerus: 60 abduction, 90 ER
-scapula: 30 upward rotation
-clavicle: 30-50 posterior rotation, up to 15 elevation
what is reverse Scapulo-humeral Rhythm
- scap moves more than humerus (2:1 rhythm)
- often seen in patients with adhesive capsulitis, RC tears
- patient appears to be hiking shoulder w/ minimal abduction
Sympathetic nerve supply originates from___ to ___
Sympathetic nerve supply originates from T2-8
you see a lot of biceps tendinopathy and supraspinatus tendinopathy. Why?
not very well vascularized (kinda avascular)
-perfusion can change w/ positions
Nerve supply of shoulder: Embryologically derived from
C5-C8
ac joint: C4
Where is the vascular supply to the shoulder complex from?
mostly axillary artery branches
What artery supplies both heads of biceps
brachial artery
GH joint:
CPP
OPP
Capsular pattern
CPP: 90-90 or full ER/ABD
OPP: 55 abd, 30 horz ADD, neutral rotation or maybe tiny bit IR
capsular: ER > ABD> IR
AC joint:
CPP, OPP, Capsular pattern
CPP: 90 ABD
OPP: unknown (arm at side?)
Capsular: pain w/ extreme ROM/elevation
SC joint:
CPP, OPP, Capsular pattern
CPP: full elevation/protraction
OPP: arm at side? unknown
capsular: extreme ROM
ST joint:
OPP, CPP, Capsular pattern
CPP: none
OPP: 5-20 anterior tip, slight upward rotation, 30-45 IR
capsular: none
