Biomechanics of Shoulder Complex- Dr Gurjant Singh (PT)

Notes for Biomechanics of Shoulder Co0mplex

1. Biomechanics of Shoulder Complex Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

2. Introduction Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR The shoulder is composed of 3 Synovial Joints : The Sternoclavicular joint ( SC) The Acromioclavicular joint (AC) The Glenohumeral joint (GH) The scapulothoracic joint also functions as joints in the shoulder complex .

3. Components of shoulder complex Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

4. STERNOCLAVICULAR JOINT Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

5. STERNOCLAVICULAR JOINT Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR SC joint is a complex saddle joint . Movement of the clavicle at the SC joint inevitably produces movement of the scapula under conditions of normal function , because the scapula is attached to the lateral end of the clavicle. The SC articulation consists of two saddle-shaped surfaces, one at the sternal or medial end of the clavicle and one at the notch formed by the manubrium of the sternum and first costal cartilage.

6. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

7. Sternoclavicular disc Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR It is a fibrocartilaginous disc to increase the congruency b/w incongruent articular surfaces. The disc diagonally transects the SC joint space and divides the joint into 2 separate cavities. The disc is considered part of the manubrium in elevation/depression and thus the upper attachment of the disc serves as pivot point and the disc acts as the part of the clavicle in protraction/ retraction with lower attachment serving as pivot point.

8. Sternoclavicular joint capsule and ligaments Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR S C joint is supported by fibrous capsule 3 ligaments : Sternoclavicular ligament Costoclavicular ligament Interclavicular ligaments ANTERIOR POSTERIOR ANTERIOR LAMINA POSTERIOR LAMINA

9. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

10. Sternoclavicular motions Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR 3 rotatory degrees of freedom : Elevation/depression Protraction/retraction Anterior/posterior rotation of clavicle 3 degrees of translatory motion at the SC joint (very small in magnitude): Anterior/posterior Medial/lateral Superior/inferior

11. Elevation/depression of clavicle Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Clavicular elevation= upto 48 degrees Cl avicular depression= less than 15 degrees

12. Protraction/retraction of clavicle Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR protraction= 15-20 degrees Retraction= 20-30 degrees

13. Anterior and Posterior Rotation of the Clavicle Posterior rotation= 50 degrees Anterior rotation= less than 10 degrees Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

14. Acromioclavicular Joint Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

15. AC JOINT Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Plane synovial joint 3 rotational and 3 translational degrees of freedom The primary function of the AC joint is to allow the scapula additional range of rotation on the thorax and allow for adjustments of the scapula outside the initial plane of the scapula in order to follow the changing shape of the thorax as arm movement occurs. In addition, the joint allows transmission of forces from the upper extremity to the clavicle.

16. AC articulating surface Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

17. AC joint Capsule and ligaments Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Superior acromioclavicular ligament Inferior acromioclavicular ligament Coracoclavicular ligament TRAPEZOID (LATERAL) CONOID ( M E D IAL)

18. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

19. The capsule of the AC joint is weak and cannot maintain integrity of the joint without reinforcement of the superior and inferior acromioclavicular and the coracoclavicular ligaments. Superior AC ligament is reinforced by aponeurotic extensions from deltoid and trapezius . Trapezoid portion : oriented more horizontally. It resists posterior forces on distal clavicle Conoid portion : oriented more vertically. It resists superior and inferior forces Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

20. AC motions Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR 3 rotatory motions: Internal/external rotation Anterior and posterior tipping Upward and downward rotation 3 translatory motions: Anterior/posterior Medial/lateral Superior/inferior

21. Internal/external rotation Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Vertical axis

22. Anterior and posterior tipping Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Oblique coronal axis

23. Upward and downward rotation Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Upward rotation=30 degrees Downward rotation=17 degrees Oblique A-P axis

24. Scapulo-thoracic joint Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

25. ST JOINT Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR It is not a true anatomic joint. The functional ST joint is part of a true closed chain with the AC and SC joints and the thorax. The linkage of the scapula to the AC and SC joints, however, actually prevents scapular motions both from occurring in isolation and from occurring as true translatory motions. Eg. When the arm is abducted, scapula undergoes upward rotation, external rotation and posterior tipping (all movts in combination).

26. Resting position of scapula Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR 2 inches from midline b/w 2 nd and 7 th rib. Internally rot -30-45 degrees from coronal plane. (sup. View) Ant tipped -10-20degrees from frontal plane( side view) Upward rotated - 10-20 degrees from sagittal plane( post view)

27. MOTIONS OF THE SCAPULA Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Upward / downward rotation Elevation/depression Protraction/retraction

28. UPWARD ROTATION Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Approx. 60 degrees of upward rotation of the scapula on the thorax is typically available. Upward rotation of the scapula is produced by clavicular elevation and posterior rotation at the SC joint and by rotations at the AC joint .

29. ELEVATION/DEPRESSION Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Elevation and depression of the scapula are produced by elevation/depression of the clavicle at the SC joint and requires subtle adjustments in anterior/posterior tipping and internal/external rotation at the AC joint to maintain the scapula in contact with the thorax.

30. PROTRACTION/RETRACTION Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Protraction and retraction of the scapula are produced by protraction/retraction of the clavicle at the SC joint, and by rotations at the AC joint to produce internal rot & ant tipping .

31. GLENO-HUMERAL JOINT Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

32. GH ARTICULATING SURFACE Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Scapula - Glenoid fossa is facing upwards and 6-7 degrees retroverted . The radius of curvature of the fossa is increased by articular cartilage that is thinner in the middle and thicker on the periphery, which improves congruence with the much larger radius of curvature of the humeral head. Humerus The head faces medially, superiorly, and posteriorly with regard to the shaft of the humerus. ANGLES: Angle of inclination=130-150 degrees Angle of torsion=30 degrees posteriorly

33. Angle of i n cl i n a tion Angle of torsion Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

34. Because of the internally rotated resting position of the scapula on the thorax, retroversion of the humeral head increases congruence of the GH joint. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

35. GLENOID LABRUM Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Enhance the depth or curvature of the fossa by 50%. It is a redundant fold of dense fibrous connective tissue with little fibrocartilage. It is attached to glenohumeral ligament.

36. GH ligaments Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Superior GH lig. Middle GH lig. Inferior GH lig. Coracohumeral lig

37. Function of GH ligament Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Limits ant and inf translation in arm at degrees of abduction Superior GH Lig Limits anterior translation at arm 45 degrees abduction Middle GH Lig Limits ant translation beyond 45 degrees abduction + external rotation Anterior band of IGHL Limits posterior translation with arm 45 degrees abd+ internal rotation Posterior band of IGHL

38. Static Stabilization of the GH Joint in the Dependent Arm- UNLOADED ARM PASSIVE TENSION IN THE ROTATOR INTERVAL CAPSULE AIR-TIGHT CAPSULE producing negative intraarticular pressure GLENOID INCLINATION -There is slight upward tilt of glenoid fossa either due to anatomically or due to upward rotation of the scapula. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

39. Unloaded Arm Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

40. Loaded Arm- Static Stabilization Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR SUPRASPINATUS ACTIVITY STARTS when the passive tension in rotator interval capsule is insufficient as in loaded arm.

41. Dynamic Stabilization Of GH Joint Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR The Deltoid and Glenohumeral Stabilization The majority of the force of contraction of the deltoid causes the humerus and humeral head to translate superiorly; only a small proportion of force is applied perpendicular to the humerus and directly contributes to rotation (abduction) of the humerus. It also produces a shear force rather than a compressive force The deltoid cannot independently abduct (elevate) the arm. Another force or set of forces must be introduced to work synergistically with the deltoid for the deltoid to work effectively.

42. The Rotator Cuff and Glenohumeral Stabilization Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR ROTATOR OR MUSCULOTENDINOUS CUFF MUSCLES ARE: Supraspinatus (S) Infraspinatus (I) Teres minor(T) Subscapularis(S)

43. INTEGRATED FUNCTION OF SHOULDER COMPLEX Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

44. SCAPULAR UPWARD ROT = 60 DEGREES SCAPULA not only upwardly rotates but also posteriorly tips to 30 degrees. GLENO-HUMERAL CONTRIBUTION = 100 to 120 of flexion and 90 to 120 of abduction. TOTAL MOVEMENT IN ELEVATION= OF 150-180 DEGREES The overall ratio of 2 of GH to 1 of ST motion during arm elevation is commonly used, and the combination of concomitant GH and ST motion most commonly referred to as scapulohumeral rhythm. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Scapulothoracic and Glenohumeral Contributions

45. Sternoclavicular and Acromioclavicular Contributions The major shift in the axis of rotation( for scapular upward rotation) happens because the ST joint motion can occur only through a combination of motions at the SC and AC joints. When the axis of scapular upward rotation is near the root of the scapular spine , ST motion is primarily a function of SC joint motion; when the axis of scapular upward rotation is at the AC joint, AC joint motions predominate; when the axis of scapular upward rotation is in an intermediate position , both the SC and AC joints are contributing to ST motion. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

46. Integrated movement during elevation Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

47. Upward Rotators of the Scapula The motions of the scapula are primarily produced by a balance of the forces between the trapezius and serratus anterior muscles through their attachments on the clavicle and the scapula. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

48. TRAPEZIUS WITH SERRATUS Anterior -forms a force couple for scapular upward rotation INITIATION Of scapular rotation- upper trap + middle traps AT THE END RANGE = Lower traps Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

49. MUSCLES OF ELEVATION Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

50. DELTOID Scapular plane abduction- anterior and middle deltoid Maintenance of appropriate length-tension relationship of deltoid is dependent on scapular position/movement and stabilization. For example: when scapula cannot rotate , there is more shortening of deltoid and thus loss of tension, which causes elevation to upto 90 degrees only. Supraspinatus Primary function is to produce abduction with deltoid muscle. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

51. Infraspinatus, teres minor and subscapularis These muscle function gradually increases from- 0-115 degrees of elevation after which (115-180 degrees) it dropped. In the initial range of elevation , these muscles (infrasp and t.minor) work to pull the humeral head down , and during the middle range, these muscles act to externally rotate for clearing greater tubercle under coracoacromial arch. Subscapularis helps as internal rot when arm is at side and during initial range With more abduction, its inter rot capacity decreases. Then it acts with other Rotator Cuff muscles to promote stability by compression. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

52. How SA and traps work with deltoid?? Serratus anterior produces upward rotation, posterior tipping and external rotation of scapula , which is necessary for upward elevation of arm. The serratus anterior and trapezius muscles are prime movers for upward rotation of the scapula. These two muscles are also synergists for the deltoid during abduction at the GH joint. The trapezius and serratus anterior muscles maintain an optimal length-tension relationship with the deltoid and permit the deltoid to carry its heavier distal lever through full ROM. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

53. Pectoralis major muscle Clavicular head Sternal head Flexion of shoulder Depression of shoulder Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

54. Teres Major and Rhomboid Muscle Function Teres major- adducts, medially rotates, and extends the humerus. It is active primarily during resisted activities. In order for the teres major muscle to extend the heavier humerus rather than upwardly rotate the lighter scapula , the synergy of the rhomboid muscles is necessary to stabilize the scapula. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

55. The muscles noted previously can be divided into functional groups Flex ors Pectoralis major B iceps brachii A nterior deltoid Extens ors P osterior deltoid T eres major Latissimus dorsi Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

56. Deltoid Supraspinatus Trapezius , Serratus anterior. Adductors Subscapularis Infraspinatus Teres minor Pectoralis Latissimus dorsi Teres major Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Abduc t ors

57. Subscapularis Latissimus dorsi Anterior fiber of the deltoid Pectoralis major Teres major. External rotators Infraspinatus Teres minor Posterior fibers of the deltoid. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR Internal Rotators

58. REFERENC ES Joint structure and function. Lavangie and Norkin, 5 th edition Biomechanics of the Locomotor Apparatus. F. Pauwels Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR

59. Dr. Gurjant Singh, MPT, (PhD) Assistant Professor, MMIPR THANK YOU