Shoulder complex Flashcards
What are the joints contributing to the shoulder complex
Acromioclavicular (AC)
Sternoclavicular (SC)
Scapulothoracic (ST)
Glenohumeral (GH)
what are the bones contributing to the shoulder comple
Scapula
clavicle
humerus
sternum
Describe the glenoid fossa and its orientation in good posture
-small and shallow
-diected anterior-laterally about 5*
-glenoid labrum and articular cartilage add depth
(articular cartilage is thinner on the inside)
What is the resting position of the scapula
-superior angle at T2
-root at T3
-inferior angle T8
-Medial border 5-6cm from midline
-35* anterior to frontal plane
describe the orientation of the clavicle
-acts as a strut-keeps scapula at a constance distance from trunk/thoracic
-20* posterior to the frontal plane
Describe the orientation of the humerus
-head faces medial
-incline 135* to shaft (superiorly)
-retroverted 30* posteriorly
articular surfaces of the GH joint
head of hummus with glenoid fossa of scapula
(1/3 of the humeral head contacts the glenoid fossa at any given time)
What is hilton’s law
a joint capsule has nerve supply from branches of the nerves that cross that joint (innervate the muscles that cross that joint)
Describe the GH
-capsule innervation
-overall ligament structure
-capsule is innervated by C5,6
-has a lax structure to allow for large ROM
~arm at side causes an inferior fold/slack
~can be distracted about 1 in
GH ligaments
coracohumeral
glenohumeral (Superior, middle, and inferior)
Coracohumeral ligament
-coracoid process to greater tuberosity
-limites external rotation and inferior translation (when you pull down on the humerus)
-limits flexion and extension at the extremes
Superior Glenohumeral ligement
Runs under coracohumeral
limits inferior translation
-limits external rotation at 0 degrees (what my arm is at my side)
Middle glenohumeral ligament limits
-limits external rotation at 0 and 45 * of abduction
Inferior GH ligament
-thickest
-2-3bands of the ligament
~superior (“2-4 O’clock”)
~axillary pouch
~posterior (“7-9 o’clock”)
-ligament is like a sling for the humerus
-limits ER at 90* of abduction/prevents anterior translation
-limits IR at 90* of abduction/prevents
posterior translation
GH capsule/ligament influence on kinematics
-ER produced posterior translation
-IR produced anterior translation
-capsule tension counters and reverses humeral head movement
where are the GH joint bursae
-subscapular bursa: deep to tendon of subscapularis
-subacromial bursa/sub deltoid: in the subscromial space
GH joint classifcation
-diarthrosis
-ball and socket: enarthroses
-triaxial
-three degrees of freedom
what are the osteokinematic motions of the GH joint and ROM
-flexion 0-180
-Abd: 0-180
-external rotation 0-90 (90 when abducted and 0-60 when at side)
-internal rotation 0-65 (90 when Abd)
-horizontal Add 0-120
-horizontal abd 0-45
-extension 0-50
injuries to the GH joint
-dislocation; most common is anterior/inferiorly (mechanism or injury forced horizontal abduction and external rotation)
What are predisposing factors to a GH joint dislocation
-loose capsule
-small glenoid fossa
-no inferior musculature
-labrum does not provide a sufficient lip
associated injuries with the GH joint
-tear in capsule and labrum (bankart lesion) an anterior inferior dislocation (anterior inferior tear of capsule and labrum “3-6” o’clock)
-fracture portion of humeral head (Hillsach’s lesion)
(impaction fracture)
-SLAP lesion: superior labrum anterior to posterior tear (“10-2 o’clock” on face of clock)
What adds to the stability of GH joint
-dynamic musculature from the rotator cuff
-ligamentous: lax joint capsule does not provide much stability
-bony
-cohesion: synovial fluid bathes cartilage which adds cohesion
-intaarticular pressure in the closed capsule
Sternoclavicular joint classification and shape of the bones at the joint
diarthrosis
saddle joint
biaxial/triaxial?
2-3 degrees of motion
(frontal plane has convex moving on concave/clavicle moving on sternum and transverse plane has concave moving on convex/clavicle moving on sternum)
What are the SC joint ligaments
anterior and posterior sternoclavicular ligament
interclavicular ligament
costoclavicular ligament
Anterior and posterior sternoclavicular ligament
-attaches from the clavicle to the sternum on the anterior and posterior side
-reinforces the joint capsule
-prevents an anterior/posterior displacement of clavicle that could occur during protraction/retraction of scapula
-prevents upward and lateral clavicle displacement during a downward roll and upward glide (doing depression of clavicle)
describe the planes of the SC joint and their motions
-protraction/retraction are in the horizontal plane and the concave surface of the clavicle moves on the convex surface of the sternum
-elevation and depression are in the fontal plane and the convex surface of the clavicle moves on the concave surface sternum
Interclavicular ligament
-runs from one clavicle to another in the sternal notch
-prevents excessive upward glide during clavicle during depression
Costoclavicular ligament
-strong ligament that runs down and medial to 1st rub
-site of fulcrum of elevation/depression and protraction/retraction
Are there any accessory structures in the SC joint if so explain?
articular disc
-reinforces the join t
-attaches superomedially to the upper aspect of sternal end of clavicle and inferolaterally to the first costocartilage
-supports the joint and prevents the medial clavicle from going superiorly
-resists force to dislocate clavicle medially
-increases the distance between the two articular surfaces for greater motion
What are the osteokinematic motion so the SC joint
Protraction: anteriorly 0-30
Retraction: posteriorly 0-15
Elevation: superiorly 0-45
depression: inferiorly 0-10
Rotation:
-posterior: associated with elevation 0-40-50
-anterior: associated with depression back to neutral
Characterize the AC joint
-other structures that might be present
-joint capsule
Plane synovial joint (flat surfaces the move on each other and sit at an angle- not a diarthrotial joint)
-little mobility between clavicle and acromion
-moves with scapula
-articular disc are sometimes incomplete
-joint capsule is thin and loose to allow sliding
AC joint osteokinematic motions
-upward/downward rotation
-rotation adjustments in horizontal and sagittal plan
AC joint arthrokinematic motions
gliding and sliding to adjust the clavicle
AC joint ligaments
Coracoclavicular
-trapezoid
-conoid
coracoclavicular ligaments
-prevent superior dislocation of clavicle on the distal end
-transmit forces from the scapula to the clavicle
-produce and limit longitudinal rotation of the clavicle
AC joint injuries
Seperation: step off deformity
-scapula lifts down away from the clavicle so that the lateral end of the clavicle appears elevated (acromian gets driven below the distal clavicle) due to a shearing force
Scapulothoracic joint
-not a true joint but rather a physiological joint
-extrinsic muscles of the shoulder
-maintain position of the scapula and produce the movements
-trapezius and serrates anterior provide major control of the scapula
what are the osteokinematic motions of the ST joint
abduction (protraction)
adduction (retraction)
elevation
depression
rotation: superior(upward/lateral) /inferior (downward/medial)
tilting: around the medial lateral axis in the frontal plane
what are the arthrokinematic motions of the ST joint
gliding or sliding
rotation
explain the force couples produced at the glenohumeral joint during shoulder abduction
Force couple 1:deltoid and supraspinatus (and rotator cuff)
-accounts for 120* of total motion
-the rest of the rotator cuff will cause the inferior glide of the humeral head
Force couple 2: upward rotation of the scapula produced by the serrates anterior and trapezius
-accounts of the 60* of total motion
Explain the scapula humeral rhythm
and its role for motion
-for every 2 degrees of GH there is 1 degree of ST
-occur simultaneously
-role:
1. limits active insufficiency of deltoid and supraspinatus
2. glenoid support for the humeral head
3. prevents impingement agasint the coracoacromian arch
4. provides stable base for intrinsics or muscles that cross the scapula and humerus
Describe phase 1 of sacpulohumeral rhythm
-0-90*
-elevation of lateral end of clavicle occurs as scapula upwardly rotates about 30*
-elevation is limited by costoclavicular tautness medially
describe phase 2 of scapulohumeral rhythm
-90-180*
-coracoclavicular ligament tightness producing posterior clavicular rotation
-scapular rotation is allowed to continue without further clavicular elevation
what is the suprahumeral space and what is inside it
-interval between the head of the humerus and the coracoacromial arch
-also called the subacromial space
-contents (superficial to deep)
1. subacromial bursa
2. supraapsinatue tendon
3. super joint capsule
4. biceps brachii long head tendon
Impingement syndrome
-painful arch 60-120* (during which there is the longest external moment arm where the rotator cuff must work the hardest to pull the humeral head down so it doesn’t pinch)
-irritation of supraspinatus tendon, biceps long head tendon, subdeltoid bursa infraspinatus tendon
Impingement syndrome epidemiology (what can be factors that cause it)
-tightness of the inferior joint capsule therefore the hummus cannot go down
-weakness in the rotator cuff therefore it cannot pull down the humeral head or compress to allow for full motion
-timing: when they are calling on the muscles/retrain them to turn these muscles on during the correct time in the motion
-overuse: Rotation cuff gets tired so it will not cause the inferior glide
What are signs of altered shoulder mechanics
-pain
-limited ROM
-limited force production
-Decreases quality of motion
