Sternoclavicular Joint
What type of joint is the SC joint?
What about its articulation?
Synovial joint with fibrocartilage with 3 DOF
saddle joint
what kind of movements do the AC allow compared to the SC joint
more subtle motions and fin tune position of the scapula
What is the resting position of the scapula
30- 40 degrees IR, 10 degrees of Ant tilt, 5-10 degrees of upward rotation (sometimes)
what is shoulder motion?
Ratio: 2° of glenohumeral motion to 1° of scapular rotation overall motion (2:1) after first 30 degrees pf the setting phase
Lesions or detachments of the glenoid labrum are common where? common with dislocations of the shoulder
what leads to this creating a cycle of more injuries?
anterior -inferior
instability
what is the arthokinematic motion of the SC joint
elevation=roll superior and glide inferior
depression=roll inferior and glide superior
protraction= concave clavicle rolls and slides anteriorly
retraction=concave clavicle surface rolls and slides posteriorly
what are the motions and axes of those motions?
IR/ER- S/I axis (transverse plane)
Ant/Post tilt- M/L axis (sagittal plane)
what happens with the AC and SC joints of scapulohumeral motion?
Scapulothoracic upward rotation = SC joint elevation + AC joint upward rotation
what gives compression and stability of the GH?
Superior capsular lig, coracohumeral lig, supraspinatus tendon
Rotator cuff has a resultant force vector horizontal to the
With a complete rupture of the AC joint does the clavicle go up?
No, the shoulder goes down
Describe the long axis of the clavicle
posterior rotation 30- 35 degrees with should flexion and abduction
What decelerates the arm when throwing a baseball?
External rotators, biceps, abductors eccentrically
what motion is happening at scapula protraction or retraction at the AC and SC joint
SC protraction or retraction respectfully
AC internal or external rotation respectfully
What is happening during abduction?
deltoid causes superior translation, supraspinatus rolls head superiorly and adds compression, infraspinatus subscapularis and teres minor inferiorly translation
What is a Bankart lesion?
A detachment of the anterior inferior labrum from the anterior glenoid rim
Caused by repeated anterior shoulder subluxations
Anterior dislocations can damage the connective tissue ring around the glenoid labrum
Also damages the connection between the labrum and the capsule
Describe the motion of the scapular during flexion or abduction
30 - 35 degrees of elevation, 15- 30 degrees of retraction, and 30-35 degrees of posterior rotation
What are the downward rotators of the scapula?
•Rhomboids
•Levator Scapulae
•Deltoid – when arm fixed
what is scapular dyskinesis
what can happen because of this?
Reduced fluidity and uncomfortable movement
Downward rotation during first half of abduction
Inability to abduct past 150 degrees
Excessive IR, anterior tilt or elevation
Leads to impingement
A “Dumper” - eccentric serratus, lower trap,
Winging- rhomboid
compressing of subacromial space
what makes a force couple with upward rotation of the scapula
Lower trap and serratus anterior
What does the coracoclavicular ligament do with shoulder abduction?
tension is created in ligament and rotates clavicle posteriorly to allow full upward rotation of AC joint
What are the ligaments at the SC joint
What do the ligaments do - think about the motion
Ant/Post sternocavicular ligaments and costoclavicualr ligament (resist elevation) and interclavicular ligament (resist depression)
also gives support
What muscles cause internal rotation of the scapula?
•Deltoid
•Teres Major
what are the ultimate motions of the scapula are to do what?
Orient the glenoid fossa for optimal contact with the humeral head of moving arm, to add a range of elevation to arm, and provide a stable base for controlled motions b/w humeral head and glenoid fossa
what creates dynamic stabilization of humerus?
Infraspinatus, subscapularis, middle GHL, a coracohumeral lig add to rigidity during ER
If too rigid prevents arthrokinematic motion
What can cause shoulder impingement?
Rotator cuff tear
tight posterior or inferior capsule
lack or ER
improper scapulohumeral motion
posture
instability
abnormal shape of the acromion or coracoacromial arch