Lecture 9: arthrology of the shoulder Test 3 Flashcards
articulations of the shoulder complex
Sternoclavicula = clavicle strut holding scapula
Acromioclavicular = firmly attaches the scapula to clavicle
scapulothoracic = not a true joint; interface between bones; movements linked to AC/SC; position of scam provides base for GH
glenohumeral = most distal and mobile portion of complex
describe the shoulder complex
series of kinematic links
cooperate to maximize ROM
weakened/painful or unstable link decreases the effectiveness of entire UE
how does the scapula move with elevation/depression
superior and inferior glide respectively
how does the scapula move with protraction and retraction
medial border slides ant/lateral with protraction
retraction = posterior medial
how does the scapula move with upward rotation
inferior angle rotates superior lateral direction, glenoid fossa faces upward = UE elevation
downward rotation = inferior angle rotates inferior medial direction with UE lowering
what articulates at the SC joint
medial end of clavicle with clavicular facet on sternum
superior border of the cartilage of the 1st rib
what is the basilar joint of the UE
SC joint
links axial to appendicular skeleton
characteristics of SC joint
extensive periarticular tissues
irregular saddle shaped
convex and concave with sternal facet reciprocally shaped
where are the longitudinal diameters of the SC joint
extend roughly in the frontal plane between superior and inferior points of articular surfaces
what are the transverse diameters of the SC joints
extend roughly in the horizontal plane between anterior and posterior points of the articular surfaces
periarticular tissues of the SC joint (i.e what are the structures like muscles, ligaments, etc around the joint)
anterior and posterior SC ligaments (reinforce capsules)
interclavicualr ligament
costoclavicular ligament
articular disc (only 50% of people)
SCM, sternothyroid, sternohyoid, and subclavis muscles
movement at the SC joint
3 degrees of freedom (sagittal, frontal, and horizontal)
elevates/depresses, protracts/retracts, and rotates
goal = place scapula in optimal position for head of humerus
all movements of the GH joint involve some movement at SC
clavicle rotates in all 3 degrees of freedom with UE elevation
osteokinematics of elevation and depression of clavicle
generally parallel to frontal plane
axis is near anterior posterior
35-45 degrees elevation
10 degrees depression
clavicular motion produces similar in scapula
arthrokinematics of elevation and depression of the clavicle
occur along the longitudinal diameter
elevation = convex surface rolls superiorly and glides inferiorly; CC ligament stretches and limits motion
depression: convex surface rolls inferiorly and slides superiorly; intraclavicular ligament/superior portion of the capsule stretches
osteokinematics of protraction and retraction of the clavicle
occurs neatly parallel to horizontal plane
axis = vertical
15-30 degrees each direction
associated with scapular retraction/protraction
arthrokinematics of the clavicle with protraction and retraction
occurs along SC joints transverse diameter
retraction = concave surface of clavicle rolls and slides posteriorly on convex surface of sternum; stretches anterior CC ligament and anterior capsule
protraction = occurs in an anterior direction; stretches posterior CC ligament and posterior capsule, involved in reaching forward
osteokinematics of rotation of the clavicle
around the bones longitudinal axis
UE elevation: posterior rotation 20-35 degrees (point on superior clavicle)
as UE returns, clavicle returns
arthrokinematics of the clavicle with rotation
spin of its sternal end relative to the lateral surface of the articular disc
axial rotation is linked with the overall kinematics of flexion and abduction (can’t be performed with the arm resting at the side)
what are the articulations for the acromioclavicular joint
lateral end of clavicle and acromion of scapula
clavicular facet on the acromion faces medial and slightly superior
articular disc of varying form is present in most AC joints
periarticular tissues of the AC joint
capsule is directly reinforced by superior and inferior AC ligaments
coracoclavicular ligament (extrinsic stability for AC)
2 parts of coracoclavicualr ligament = trapezoid ligament and conoid ligament (go from the coracoid process to the clavicle)
describe the kinematics of the AC joint
subtle movements between scapula and lateral clavicle
optimizes mobility and fit between scapula and thorax
motions are described scapula relative to the clavicle
movements present at the AC joint
3degrees of freedom
up/downward rotation
secondary motions = rotational adjustment motions; to fine tune position of scapula (horz and sagittal plane)
describe upward rotation of the scapula at the AC joint
swings upward and out relative to the end of clavicle with upward rotation
natural motion as part of elevation
up to 30 degrees
contributes significantly to scapulothoracic motion
describe downward rotation of the scapula at the AC joint
scapula rotates around clavicle to return to anatomical position
it looks like frontal plane but really is is the scapular plane
what are rotational adjustment motions at the AC joint
pivoting or twisting type motions of the scapula around the lateral end of the clavicle
optimally align the scapula against the thorax
horizontal plane: vertical axis; medial border moves away (IR of glenoid fossa)
sagittal plane: medial-lateral axis; inferior angle pivots away (anterior tilt) or reverse (posterior tilt)
kinematics of AC joint with protraction
AC joint IR in the horizontal plane
helps align the anterior surcease of the scapula with the thorax curved surface
kinematics of AC with elevation of scapula
“shrugging” is accompanied by anterior tilt
what would happen if there were no scapular adjustments with movements
the scapula would have to follow the clavicle exactly and could not adjust to the thorax
describe the scapulothoracic joint
not a true joint: no direct contact, but separated by layers of muscles
scapula is seated between 2nd and 7th ribs; medial border 6 cm lateral to spine
motions of the scapulothoracic joint
large UE ROM largely dependent on scapular motion
10 degrees anterior tilt
5-10 degrees upward rotation
30-40 degrees internal rotation
muscles that separate the scapulothoracic joint
subscapularis
serratus anterior
erector spinae
describe elevation/depression at the scapulothoracic joint
composite SC and AC
scapulothoracic elevation is a summation of elevation at SC and downward RT at the AC joint
how can you describe protraction/retraction at the scapulothoracic joint
summation of horizontal motions at SC and AC
protracting the clavicle around SC joint; varies with the amount of IR
describe upward/downward RT at the scapulothoracic joint
integral part of UE elevation
places the glenoid fossa in a position to support/stabilize the head of the humerus
summation of clavicular elevation and SC/scapular upward RT
full 60 degrees of upward RT
describe the kinematics of scapulothoracic upward rotation
summation of elevation at the SC joint and upward RT at the AC joint
general features of the glenohumeral joint
large convex head
shallow concavity = glenoid fossa
head positioned medially, superiorly, and posteriorly (normal retroversion)
in anatomical position describe the inferior portion of the capsule of the shoulder
slackened
called axillary pouch
what lines the inner wall of the GH joint
synovial membrane
head of humerus and glenoid fossa are lined with
articular cartilage
potential volume of space in GH joint
2x size of the humeral head
primary stabilizers of GH joint
passive tension with embedded ligaments
active forces produced by local muscles (specifically rotator cuffs)
LHB crosses superiorly over the head of the humerus
function of the capsular ligaments of the GH joint
limites extremes of RT and translation
help keep a negative intra-articualr pressure in GH joint
describe the makeup of capsular ligaments
fibrous connective tissue
interlacing collagen fibers
thickening of capsule in complex bands
function of superior capsular ligament
resists ER/inferior and anterior translations
function of the middle capsular ligament
stabilizes most motions
especially restraint in 45-90 abduction and extremes of ER
slack in IR
blends with subscap
function of the inferior band of capsular ligament
3 portions
taught in 90 degree abd
hammock like
supports the suspended humeral head
resists inferior/anterior-posterior translation
what is the strongest portion of the capsule
anterior is the strongest/thickest portion of the capsule
primary ligamentous restraint to anterior translation (abd and neutral)
ABD and ER forceful dynamic activities are especially stressful
coracohumeral ligament: where does it attach, when is it taught, what does it blend with, and what does it restrict
from the coracoid process to the greater tubercle
blends with the superior capsule and supraspinatus tendon
taut in anatomical position
restraint inferior translation and ER humeral head
significance of the rotator cuffs
significant structural support to the capsule
blends with capsule
belly of muscles close to the joint
protects and acts as an active stabilizer
4 rotator cuff muscles
subscapularis = thickest/anterior to capsule
supraspinatus, infraspinatus, and teres minor = posterior to the capsule
regions of vulnerability for rotator cuff muscles
rotator interval: triangular space formed by the tendons of subscapularis and supraspinatus and the coracoid process
common site for dislocation
reinforced by LHB, coracohumeral ligament, and sup/mid capsular ligaments
origin of the LHB
supraglenoid tubercle and labrum , intracapsular tendon crossed the humeral head, inter tubercle groove on anterior humerus
LHB resists whats
restricts anterior translation of the humeral head
the force generated through the tendon across the dome of the humeral head resists anterior translation - needed in ABD
describe the glenoid labrum
fibrocartilaginous ring
50% depth is from this structure
stabilizer
tissues that reinforce/deepen the GH joint
joint capsule/GH ligaments
coracohumeral ligament
rotator cuff muscles
LHB
glenoid labrum
describe the static stability of the GH joint
at rest the humerus is stable on the glenoid fossa
like a ball on an inclined surface
superior capsular structures (superior capsular ligament, CH ligament, and tendon of supraspinatus)
there is a resultant compressive force
describe the forces of the rotator cuff and significance
RC has horizontal forces to help if there is a load added to the arm
muscular forces act as a rope that holds the scapula in position of the slightly upward fossa
disruption can cause humeral head to drift inferiorly due to plastic deformation of SCS = subluxation or dislocation
what is the coracoacromial arch
formed by the coracoacromial ligament and acromion process
roof of the GH joint
creates subacromial space between the arch and the humeral head
average of 1 cm in adults with arm at rest by side
what does the coracoacromial arch contain
supraspinatus muscle and tendon
subacromial bursa (direct extension of synovial membrane of the GH joint)
LHB
superior capsule
where are the bursa of the GH joint
situated where significant frictionless forces develop such as between tendons, capsules and bones, muscles and ligaments, or 2 adj muscles
what 2 bursa are superior to the humeral head
subacromial bursa (above SS) = protects SS from acromial bone
sub deltoid bursa = limitse friction forces between the deltoid and the SS tendon/humeral head
kinematics of the GH joint
3 degrees of freedom
4th motion defined: horizontal abd/add (starts at 90 degrees abd - vertical axis)
anatomic position = 0 degrees
describe abd/add of the GH joint
ABD:
rotation of humerus in frontal plane; AP axis
120 degrees NLs at GH joint
simultaneous 60 degrees upward scapular rotation
convex head of humerus rolls superiorly, slides inferiorly
larger head does not roll of due to this sliding
add is reverse
describe dynamic stability of the GH joint
part of the SS tending blends with superior capsule
active contraction pulls the capsule tight and prevents it from being pinched between the humeral head and the undersurface of the acromion
at 90 deg ABD humeral head stretches ICL (axillary pouch) which acts like a hammock supporting the head of the humerus
describe the height of the subacromial space and the significance
impacted bu GH arthrokinematics and scapular motion
critical minimum must be maintained for lack of compression of contents in the space:
7.5 mm at 20 deg ABD
2.6 mm at 85 deg ABD
5mm at 150 deg ABD
clinical significance of the arch representing the subacromial space
arc is where SS potential compression is at 35-70 deg
what is adhesive capsulitis
excessive thickening or stiffness in ICL
limits inferior slide of humeral head
superior roll leads to jamming of the humeral head against the coracoacromial arch
what is impingement syndrome
unnatural and repeated compression/abrasion may damage the SS tendon, subacromial bursa, LHB tendon, or superior parts of the capsule
over time repeated compression may lead to this syndrome
arthrokinematics of humerus with flex/ext
arthro = spinning motion of humeral head in fossa
describe the surrounding structures of the GH joint with flexion and extension
most surrounding structures are taut
tension in posterior capsule may cause slight anterior translation of humerus in extremes of flexion
how much range of flexion and extension is present in the shoulder with flexion and extension
120 degrees GH flexion/180 includes scapula
extension = 65 degrees active, 80 passive
how does the scapula move with flexion and extension of the shoulder
slight anterior tilt of the scapula, stretch of capsular ligaments
how does the humerus move with ER of the shoulder
axial rotation o the humerus in the horizontal plane
ER/IR ROM present in shoulder
75-85 degrees IR
60-70 degrees ER
with ABD of 90 degrees, ER of up to 90 (variable)
neutral = in IR?
roll/slide of humerus with ER
ER rolls posteriorly and slides anteriorly
reverse for IR
describe the principle of scapulohumeral rhythm
natural coupling of GH ABD and Scapulothoracic Upward RT
after 30 degrees of ABD, rhythm is consistent
ratio = 2:1; for every 3 deg of ABD there are 2 deg at the GH joint and 1 deg at the ST upward RT
full arch of 180 degree movement = 120 at GH and 60 at ST
describe the ST and SC joints during full abduction
60 degrees of movement at the ST joint is a combo of elevation at SC joint and upward RT at AC
SC joint elevates 30 deg during the 180 arch
how does the clavicle move at the SC joint during ABD
clavicle retracts
starts at 20 deg posterior to the frontal plane
retracts another 15-20 degrees with ABD
describe the tilt of the scapula with ABD and what these movements help with
as full abd occurs, the scapula tilts posteriorly and slightly rotates outward
at rest = anterior tilt of 10 degrees, IR 30-40 deg
with ABD it posteriorly tilts 20 deg
these movements help keep the scapula flush with the thorax, orients the fossa, and moves the coracoacromial arch away from the advancing humeral head
describe the rotation of the clavicle with ABD
rotates posteriorly along its own axis
20-35 degrees during full ABD
those with subacromial impingement showed reduced RT
describe the movement of the humerus with ABD
naturally ER with ABD
allows greater tubercle to pass posterior to the acromion
25-50 degree range; majority occurs before 70-80 degrees of ABD
