the shoulder complex Flashcards
how many joints make up the shoulder?
3:
- sternoclavicular
- glenohumeral
- acromioclavicular
1 pseudo:
- scapulothoracic
what makes up the “shoulder girdle”
scapula
clavicle
manubrium
where is the manubrium?
sternal/ jugular notch b/n clavicular facets
- connection point b/n appendicular and axial skeleton
clavicle:
what does the outwards curve protect?
how does it help us absorb impact?
- major neurovasculature bundles travel up
- force travels from hand up to clavicle and scapula, then diffused through muscles
- sits above transverse plane, 20 degrees to frontal plane
what does the scapula provide regarding GH muscles and joint?
- location for GH muscles to originate
- stable base from which GH joint can operate
- works w clavicle to enhance shoulder ROM
significant muscle/group living on scapula:
- rotator cuff
- serratus anterior (vert border on thoracic aspect)
where does the long head of the biceps tendon originate?
supraglenoid tubercle
where does the long head of the triceps tendon originate?
infraglenoid tubercle
what does the labrum of the glenoid fossa allow for?
deepens fossa by 50%
“plane of scapula” or plane of scaption:
sits in middle of frontal and sagittal plane ~45 degrees b/n
where is the anatomical vs surgical neck of the humerus?
anatomical = immediately beneath head, where joint capsule of shoulder has insertion point
surgical = below, where fracture ysyally happens
how does the head of the humerus sit to articulate w the fossa?
rotate head back to sit on fossa
(laterally, superiorly, and anteriorly)
what is “angle of inclination” ?
what plane does is occur?
angle?
angle b/n humeral head and shaft relative to shaft
frontal plane
135 degrees
what is “angle of torsion” ?
what plane does is occur?
angle?
allows for?
torsion = twist
how humeral head is angled posterior relative to distal condyles
transverse plane (head in scapular plane while elbow neutral)
allows for greater ROM in abduction and ER before impinging
main movements of shoulder girdle:
elevation/ depression
protraction/ retraction
upward/ downward rotation
scapular tilting/ tipping
what joint connects the arm to the skeleton?
sternoclavicular
depression and elevation
due to:
ROM:
joints involved:
examples
upward/ downward scapular glide
up 60 degrees, down 5-10 degrees
psuedo, SC, AC
shrug vs crutches/ push out of chair
what do tilt and rotation help maintain scap contact w?
thorax
protraction/ retraction
measure of:
due to:
ex:
how far scapulae move away from spine
forward glide/ abduction of lat clavicle & scap
backward glide/ adduction of lat clavicle&scap
ex: reach arms forward vs pinch shoulder blades together
what joint motions are responsible for maintaining scapular contact w torax?
AC and SC
upward/ downward rotation
how does it allow for full GH flexion/ extension?
joints? movement?
upward rotation = scap moves superiorly and rotates underneath toward armpit to spot head of humerus
elevation/ depression of AC&SC
types of scapular tilt/tip:
named how?
- anterior-posterior
- medial-lateral
name according to where superior angle of scap goes
sternoclavicular joint:
connects?
what type?
DOF
manubrium & 1st rib - connection b/n axial and appendicular skeleton
synovial, complex, modified saddle
3 - elevation/ depression, protraction/ retraction, rotation
purpose of SC disc (4):
- separates joint into 2 cavities
- serves as a hinge = motion occurs b/n clavicle&dic and disc&sternum
- adds stability = reduce medial sliding to protect trachea
- reduces joint stress - has potential for arthritis
which capsular ligaments strengthen the SC capsule?
how?
which is extracapsular?
- A/P SC
- interclavicular = prevents upward displacement
- anteriorly, posteriorly, and superiorly
-costoclavicular = restricts clavicle elevation, rotation, medial/lateral motion
describe the costoclavicular ligament
- restricts clavicle elevation, rotation, medial/lateral motion
- 2 crossing heads = stronger, dissapates force
- origin of sternocleidomastoid - provides additional support
- reinforced by subclavius
what limits elevation vs depression of SC?
elevation = costoclavicular ligament and subclavius
depression = interclavicular ligament and first rib
predominant SC joint motion:
protraction/ retraction
- accompanied by scap pro/retraction
what movement does posterior SC rotation accompany?
due to?
GH elevation (anytime you bring arm up)
tightening of trapezoid and conoid ligaments
when does the conoid become an axis?
effect?
as it tightens during second 90 degrees of shoulder elevation
improves GH elevation
what arthrokinematic motions does the SC joint do?
all
- roll
- glide
- spin
resting vs close packed position of SC
resting = arm by side
closed packed = hiked up by ear bc conoid has locked the AC joint and created axis, provides rest of ROM
acromioclavicular joint
type:
DOF:
primary function:
plane synovial joint
3
(lined w fibrocartilage)
increases ROM of humerus in glenoid - allows scapula to maintain thoracic contact throughout ROM
**no muscular connections move this
which capsular ligaments strenghten AC capsule? in which ways?
superior and inferior AC ligaments
inferiorly and superiorly (often gets damaged)
which ligaments are key in AC joint stability?
coracoclavicular - stronger than AC ligament, limits excessive AC motion
1. conoid = checks superior clavicular motion
2. trapezoid = prevents lateral clavicle motion on acromion
osteokinematic AC motions:
aka?
scapular motions
- elevation/ depression
- abduction/ adduction
- upward/ downward rotation - allows clavicle to rise and roll
small but key adjustments done by AC:
- keep fossa and head aligned during GH elevation
- M/L tilt move vertebral border toward/ away from posterior thorax
- A/P tilt
AC resting vs closed packed position:
resting = arm by side
close packed = 90 degrees abduction (after that conoid provides axis for SC to anchor for max ROM)
Scapulothoracic
type:
what does it show/ represent?
(separated by?)
is it needed?
psuedo joint
represents articulation b/n scap and thorax
- scapula = concave
- thorax = convex
(bursa, serratus anterior, subscapularis, fascia)
- needed for full GH motion
ST function:
- enhance shoulder ROM**
- stability = length-tension relationship of rotator cuff/ deltoid
- position glenoid to receive humeral head
- absorb shock - FOOSH
- push out of chair
2 muscles jobs during initial abduction:
supraspinatus = primary role is first 30 degrees (sucky rotator)
deltoid = stabilize by lifting up and pulling humerus into fossa
combined motion of what joints directly results in ST motion?
AC and SC
ST joint motions:
SC = 30 degrees joint elevation
AC = 30 degrees joint upward rotation
= 60 degrees
- protraction/ retraction = AC and SC determine if joint can move
where is the subscapular bursa?
function?
- lies over anterior joint capsule, beneath tendon of subscapularis muscles
- communicates w joint capsule to maintain neg pressure w/n joint - try to keep joint in place - balanced flow
glenohumeral joint
type:
DOF:
mobile?
ball and socket, synovial
3 (flex/ex, ab/duction, med/lat rotation0
highly mobile = unstable
what/ where is the labrum?
fibrocartilanginous rim attached to glenoid, continous w long head tendon of biceps
- protects the edges of the bone
GH joint capsule:
size/shape/thickness
attaches where?
ligaments and tendons separate or blend??
large fibrous cylinder, thin&loose
attached from glenoid rim to anatomical neck
ligaments and tendons blend
inferior axillary recess:
where?
function?
= bottom armpit space
need extra space/ laxity in capsule for head to move into glenoid fossa
“redundant inferiorly”
GH reinforcements:
- superior/middle/inferior GH ligaments
- coracohumeral ligament
- long head of triceps/ biceps (hold up humeral head)
- rotator cuff tendons (hold head in socket) blend w capsule
superior GH ligament
relative size:
where:
supports?
limits:
smallest thickening of capsule
base of coracoid process to MGHL, biceps tendon, & labrum
supports hanging arm
limits anterior translation and external rotation to 45 degrees of abduction + (inferior translation in adduction)
middle GH ligament
where:
limits:
supports?
area of strength or weakness?
attached to anatomical neck (medial to lesser tuberosity)
limits ER b/n 45-90 degrees of abduction
supports hanging arm
area of weakness
(feeds into subscapularis bursa, “foramen of weitbrech)
function of superior and middle GHL:
stop too much external rotation (a vulnerable position for shoulder)
ex: foosh, arm caught and pulled too far
inferior GH ligament
relative size:
where:
how is it “redundant”?
what degree of abduction does primary support begin at?
thickest of GH capsule
from labrum or glenoid neck
2 bands = cradle/ sling to keep arm up
above 90 degrees abduction
coracohumeral ligament
origin/insertion:
limits:
supports?
originates on (posterolateral) coracoid
inserts on greater tuberosity (lateral to bicipital groove)
limits:
- external rotation when arm is neutral
- posteroinferior shift of humeral head
supports hanging arm
where are long heads of biceps and triceps?
biceps = supraglenoid tubercle
triceps = infraglenoid tubercle
rotator cuff tendons: (4)
SSIT:
Subscapularis
Supraspinatus
Infraspinatus
Teres minor
which rotator cuff tendon prevents external rotation and why?
subscapularis = active INTERNAL rotator + passive stabilizer
which rotator cuff tendons limit internal rotation?
infraspinatus and teres minor = active EXTERNAL rotators
what does the coracoacromial arch form?
what tendons does it protect?
a roof over GH joint
protects
- supraspinatus
- long head of biceps
- subacromial bursa
- superior capsule
how many GH bursae are there &what are the 2 most noteable?
8
subacromial and subdeltoid
where are subacromial and subdeltoid bursae?
function?
separate or continous?
over supraspinatus tendon and deltoid beneath acromion
decrease friction in joint (w/o = impingement)
continuous
GH joint osteokinematic DOF’s:
- ab/duction
- in frontal plane
- horizontal = in transverse plane - flexion/ extension in sagittal plane
- medial/ lateral rotation in transverse plane (affected by forearm pronation/ supination)
what does movements does max GH flexion elevation require?
- GH rotation
- posterior scapular tilting
- upward rotation
arthrokinematic GH movements:
- flexion/extension = spin (anterior/posterior slide)
- ab/duction = superior/inferior roll, inferior/upward glide
- lateral/ medial rotation = posterior/anterior roll, anterior/ posterior glide
GH resting position:
20-30 degrees of horizontal adduction
55 degrees of flexion
GH closed packed position:
full abduction, external rotation
what is the bicipital grrove?
where biceps tendon is restrained by coracohumeral and transverse humeral ligament
(humerus moves on tendon during shoulder motion)
setting phase:
what is the ratio of degrees of humerus to scapula movement after this?
early phase of abduction - first 30 degrees
2:1
what joint provides first 120 degrees?
remaining 60 degrees?
GH
AC + SC
where does axis of rotation of scapula migrate during elevation?
start at root of scap spine, moves laterally toward AC joint
scapular stabilizer muscles (1 inch punch):
- serratus anterior = primary scapular protractor (usually too weak/ tight)
- trapezius (shrug/retract/depress)
- rhomboid major/ minor
- pectoralis minor (scap depression +downward rotation)
- levator scapulae (elevator/ depressor, both = neck extender)
glenohumeral stabilizers:
main function?
for initial abduction
1. supraspinatus
2. infraspinatus/ teres minor
3. subscapularis (depends on arm positionpassive support at insertion)
4. biceps (hold humerus head up and in) /triceps brachii (stabilize - cradle ligaments)
“large mover” muscles:
deltoid (heads on clavicle, acromion process, scap)
latissimus dorsi (big flat)
teres major (+ lats = handcuff muscles)
pectoralis major (heads on clavicle&sternum)
coracobrachialis (off coracoid process)
passive stabilization at
SC and AC
GH and scapulothoracic
SC and AC = ligamentous support - bony configuration
GH and ST = muscular support
dynamic stabilizers:
upper trapezius = low activity at rest
rotator cuff = compressive stabilizers
biceps = compress humeral head
deltoid
rotator cuff muscles
- supraspinatus
- infraspinatus
- teres minor
when arm up, which muscles work together like couples yoga
deltoid and rotator cuff - synergistic
what happens when serratus anterior, upper and lower trap fire (synergistic)?
upward scapular rotation = scapula rolls so inferior angle moves towards axilla
what happens when pec minor, levator scapulae and rhomboids fire (synergistic)?
downward scapular rotation = guide inferior angle of scap towards vertebra
what allows the rotator cuff to maintain long moment arm over a greater range?
scapular rotation
does supraspinatus or deltoid have greater leverage?
suprapinatus = bc lever arm length is constant throughout elevation ROM (deltoids increases)
what is needed for perfect shoulder elevation?
upper t spine - full extension
GH - full flexion and abduction
ST - full upward rotation
AC&SC = full ROM
joint stabilization
ratio of peak isokinetic torques for medial/lateral rotators:
3:2
(pecs, teres major, subscapularis) : (infraspinatus, teres minor)
ratio of peak isokinetic torques for adductors to abductors:
2:1
(lat dorsi, teres major, pec major) : (deltoid, supraspinatus)
ratio of peak isokinetic torques for extensors to flexors:
5:4
what muscles might cause functional deficiency?
serratus anterior
- limit upward scap rotation
- long thoracic nerve palsy?
trapezius
- limit shoulder elevation
- spinal accessory nerve palsy?
what is total shoulder motion a result of?
- balance b/n joints
- functioning and synchronization of muscles
