Upper Extremity Shoulder Complex Elbow Wrist (Hand)

1. Upper Extremity Shoulder Complex Elbow Wrist (Hand)

2. Shoulder Complex sternoclavicular acromioclavicular coracoclavicular scapulothoracic glenohumeral

3. Shoulder Girdle • an “open” mechanical system • R and L sides not directly attached so can move independently • sternoclavicular jt • acromioclavicular jt • scapulothoracic jt

4. Sternoclavicular Articulation • site of most movement of shoulder girdle • elevation/depression (up and down, 30-40o) • rotation (40-50o) • protraction/retraction (A/P, rowing, 30o) • articulation between the sternum and clavicle • a modified ball-and-socket joint • mobile in frontal and transverse plane • limited sagittal movement Interclavicular Ligament Clavicle Clavicle Sternoclavicular Ligament Articular disk Costoclavicular Ligament Costal cartilage Sternum

5. articulation between acromion process and distal end of clavicle Acromioclavicular Articulation coracoclavicular ligament serves as axis of rotation for associated scapular mvmts very dense capsule + AC ligaments provide support Bony Support -- WEAK!

6. 3 df protraction/retraction: acromion process moves on meniscus, scapula rotates about medial coracoclavicular ligament (conoid) 30-50º upward/downward rotation: clavicle moves on meniscus, scapula rotates about lateral coracoclavicular ligament (trapezoid) 60º elevation/depression: relative motion of acromion & clavicle with no rotation 30º AC Mvmts Note: mvmts @ AC joint will be opposite those at SC joint (e.g., AC elevation -- SC depression)

7. Scapulothoracic Articulation • “physiological” articulation (no bone-to-bone connection) between the anterior surface of the scapula (scapular fossa) and the thoracic wall • scapula rests on 2 muscles (serratus anterior and subscapularis) • 60º ROM

8. Shoulder Joint (aka glenohumeral) - articulation of humerus and glenoid fossa - designed for mobility (greatest ROM of any jt in body) - lacks bony and ligamentous support - shallow glenoid fossa (1/4 size of humeral head) -half-spherical humeral head

9. Supporting Structures for Shoulder • labrum • a lip of cartilage surrounding the joint • increases depth of fossa • increases contact area by 75% • assists in holding the humerus in place

10. coracohumeral ligament glenohumeral ligaments superior middle inferior these ligaments merge with the articular capsule

11. Shoulder depends on ligamentous and muscular contributions for support articular capsule 2X volume of humeral head - laxity anterior support capsule, labrum, glenohumeral ligaments 3 “reinforcements” in the capsule coracohumeral ligament, and fibers of the subscapularis and pec. major that blend into the jt capsule posterior support capsule, labrum, fibers from the teres minor & infraspinatus that blend into the capsule

12. ShoulderLigamentous Support • no ligament to prevent backward displacement • fossa angle slightly anterior • prevents backward displacement

13. Subacromial Arch coracoacromial ligament provides a “buffer” for the rotator cuff muscle tendons

14. Rotator Cuff Muscles Subscapularis Infraspinatus Supraspinatus 3 originate on posterior scapula (S I T) 4th originates on anterior scapula Teres Minor

15. Stabilizing Influence of Rotator Cuff • muscles have a large stabilizing component when active • all have a ‘large’ horizontal component • so play a significant role in stabilizing the humerus against the glenoid fossa

16. Bursae in Shoulder • sacs secreting synovial fluid • distributed throughout shoulder complex to reduce friction between tissues • e.g. subacromial bursae • cushions rotator cuff muscles (supraspinatus) from laying directly on acromion process • overuse can lead to irritation of bursae

18. Abduction/Flexion 1) primary movers 2) humeral head stabilization 3) orienting the glenoid fossa

19. Abduction/Flexion 1) Primary movers deltoid ~50%, rotator cuff ~50%

20. Abduction/Flexion 2) humeral head stabilization early: teres minor depresses head late: subscapularis & infraspinatus stabilize head >90º: supraspinatus remains active

21. Scapulohumeral Rhythm • scapular rotation to facilitate shoulder movements (abduction & flexion) • 1st 30 º of abduction or 45º of flexion -- scapula moves to a position of stability on thorax • beyond this initial range -- a 5:4 ratio of glenohumeral to scapular movements • for total ROM have a 2:1 ratio (e.g. 180 º of abduction have 120 º of glenohumeral mvmt and 60 º of scapular mvmt.

22. Abduction/Flexion 3) orienting the glenoid fossa requires protraction, elevation, upward rotation with posterior clavicular rotation upper trapezius and serratus anterior responsible muscles

23. Adduction & Extension Primary Movers: If no resistance then use eccentric actions of abduction/ flexion muscles BUT if resistance (e.g. weight machine or swimming) main contributors are sternal portion of pectoralis major latissumus dorsi teres major

24. Adduction & Extension Accompanying movements: retraction, depression, downward rotation with anterior clavicular rotation Pectoralis minor depresses & downwardly rotates Mid & lower trapezius retracts Rhomboid downwardly rotates & retracts

25. Internal & External Rotation Important to many sport skills plus a necessary movement to accommodate mvmt when arm is at 90º or greater abduction or flexion External rotation: infraspinatus & teres minor primary muscles on posterior side insert posteriorly on humerus Internal rotation: subscapularis & teres major primary muscles on anterior side insert posteriorly on humerus (also lat. Dorsi and pect. major)

26. Horizontal Ab-/Adduction Similar musculature as for flexion and abduction BUT more sig. contribution from pec. major & ant. deltoid for hor. adduction infraspinatus, teres minor, & pos. deltoid for hor. abduction

27. Muscular StrengthShoulder Complex STRONGEST adduction extension flexion abduction internal rotation external rotation WEAKEST

28. Loads on Outstretched Arms T = Fd moment arms a = 0 cm b = 20 cm c = 30 cm shoulder torque A. 0 N cm B. 700 N cm C. 1050 N cm C The moment arm(d) is the perpendicular distance from the line of action of the weight to the axis of rotation. B A if segment weight = 35 N c b

29. Shoulder Loading • ergonomists recommend workers seated at desk use arm position with 20 degrees or less of abduction and 25 degrees or less of flexion

30. Shoulder Girdle Injury • sternoclavicular joint • low rate of injury • sprain caused by force which displaces shoulder anteriorly • dislocation of medial end of clavicle medially, superiorly, and either anterior or posterior • posterior dislocation particularly dangerous because trachea, esophagus, veins, etc. located behind • dislocation in adults but usually fracture in children

31. Shoulder Girdle Injury • acromioclavicular joint • force applied laterally to acromion process • commonly known as shoulder separation • range from mild sprain of AC ligament to complete AC dislocation with tearing of clavicular attachments of deltoid and trapezius & complete rupture of coracoclavicular ligament • displaces the acromion anteriorly and inferiorly while clavicle does not move (95% of all dislocations for this joint) • scenario - fall on an outstretched arm to break a fall • force of impact transmitted through humerus such that entire scapula is displaced relative to unmoved clavicle

32. Shoulder Injuries • Dislocation or subluxation • frequent due to lack of stability • usually occur when shoulder abducted and externally rotated • anterior-inferior dislocations most common (90%) • when arm is abducted, extended, and externally rotated • usually caused by a large external force • age of 1st dislocation inversely related to rate of recurrence • i.e. the younger you are the more likely you are to have a recurrence

33. Detecting a torn Rotator Cuff Tendon using an Arthrogram Inject dye into joint to see if it leaks out where the rotator cuff tendon is supposed to be

34. Detecting a torn Rotator Cuff Tendon using an MRI

35. Soft tissue injuries Often associated with overarm motions such as throwing Preparatory phase -- shoulder abducted to 90, shoulder ext rotation, scapular retraction, and elbow flexion Anterior capsule and subscapularis muscle are susceptible to strain or tendinitis at the insertion on the lesser tubercle

36. Extreme External Rotation in Overarm Pitching • external rotation terminated by forces from • anterior joint capsule & ligaments • subscapularis • pectoralis major • triceps brachii • teres major • latissimus dorsi

37. Acceleration Phase • explosive phase characterized by • initiation of elbow extension • shoulder internal rotation • maintenance of shoulder abduction at 90 • shoulder transverse adduction • scapular protraction • posterior capsule and labrum susceptible to injury as anterior shoulder is tightened driving the humeral head backwards

38. Follow-Through Phase • Rotator cuff works to decelerate shoulder’s internal rotation • infraspinatus and teres minor very susceptible to muscle strain or tendinitis

39. Rotator Cuff Impingement • impingement of supraspinatus tendon • 2 theories • GENETIC:too narrow a space between acromion and humeral head • OVERUSE: repeated stretching of supraspinatus weakens its ability to stabilize the humerus leading to deltoid pulling humerus up and impingement of tissues

40. Swimmer’s Shoulder • recovery • near maximum tension in serratus anterior during recovery to rotate scapula and facilitate overhead arm movements • fatigued serratus will not rotate scapula so rotator cuff muscles impinged

41. Swimmer’s Shoulder“Impingement Syndrome” • @ hand entry • shoulder forced into extreme abduction, flexion and internal rotation • allows prox head of humerus to rub across the supraspinatus tendon • can “impinge” the supraspinatus tendon between humerus and coracoacromial ligament • increased internal rotation when elbow is held in place and arm pushes back • head of humerus is thrust forward close to ligamentous structure of shoulder joint where contact can occur • increase likelihood of impingement

42. Swimmer’s Shoulder (cont.) • at completion of arm pull • shoulder adducted such that supraspinatus tendon is stretched over the head of the humerus • cuts off blood supply to tendon