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1. SHOULDER COMPLEX BIOMEHANICS

2. CONTENTS *Introduction/Components of the Shoulder Complex *Sternoclavicular Joint *Acromioclavicular Joint *Scapulothoracic Joint *Glenohumeral Joint -Static Stabilization -Dynamic Stabilization *Integrated Function of the Shoulder Complex -Scapulohumeral Rhythm

3. INTRODUCTION *Shoulder Complex composed of the CLAVICLE, SCAPULA + HUMERUS -links the UE  THORAX - Sternum *Articular structural design – indicate Primary Function : Wide ROM mobility Dynamic Stabilization

4. DYNAMIC STABILIZATION Exists when a moving segment/ set of segments is limited very little by passive forces : articular surface configuration, capsule /ligaments and instead relies heavily on active forces / dynamic muscular control Example – Shoulder Joint

5. COMPONENTS OF SHOULDER COMPLEX Sternoclacicular joint Acromioclavicular joint Glenohumeral joint Scapulothoracic joint – Functional joint Suprahumeral joint – Functional joint

6. ELEVATION: OF THE UPPER EXTREMTY The Combination of Scapular, Clavicular and Humeral motion that occurs when arm is raises forward/ to the side *Sagittal plane flexion *Frontal plane abduction *All motion in between Total Shoulder Complex Motion – Total Elevation = Motion of the scapula on Thorax [ 1/3 of total motion] +Motion of the GH joint [2/3 of total motion] INTEGRATED SHOUDLER COMPLEX FUNCTION: SCAPULOHUMERAL RHYTHM

7. STERNOCLAVICULAR JOINT *Connects UE to Axial Skeleton *Type: Plane Synovial joint /3 DOF *Has Joint capsule & Disc *Articular Surfaces -2 shallow saddle shaped surfaces Medial end of clavicle Notch of Manubrium sternum & 1 st Costal cartilage

8. Sternoclavicular Disc – Fibrocartilage disc *Increases congruence b/w the articulating surfaces *Improve joint stability *Absorb forces transmitted from lateral end of clavicle to SC joint

9. Sternoclavicular Joint Ligaments Strong Fibrous capsule – Fairly strong Anterior Sternoclavicular ligament Posterior Sternoclavicular ligament -Check Anterior & posterior translation of medial end of clavicle 4. Costoclavicular ligament – Bilaminar : Anterior/Posterior -Limits the elevation of lateral end of clavicle 5. Interclavicular ligament – Limits excessive depression of the distal clavicle and Superior gliding of the medial clavicle on the manubrium

10. Sternoclavicular Motions : Movements of Clavicle *Elevation & Depression (48/15) *Protraction & Retraction(15-20/30) *Anterior & Posterior Rotation (10/50)

11. ELEVATION & DEPRESSION OF THE CLAVICLE

12. PROTRECTION & RETRACTION OF THE CLAVICLE

13. ANTERIOR & POSTERIOR ROTATION OF CLAVICLE

14. 2. ACROMIOCLAVICULAR JOINT -Attaches Scapula to Clavicle Type: Plane synovial joint /3 DOF Articular Surfaces: Lateral end of Clavicle & Small facet on acromion of the Scapula

15. Acromioclavicular Joint – Ligaments 1.Joint Capsule - weak 2. Acromioclavicular Ligaments – Superior & Inferior 3. Coraco-clavicular ligaments Limits Superior/Inferior & Anterior / posterior Stability

16. Acromioclavicular Motions *Internal & External Rotation (30-60) *Anterior & Posterior Tilting /Tipping (60) *Upward & Downward Rotation(30/15)

17. INTERNAL & EXTERNAL ROTATION

18. Protraction & Retraction of the Scapula require Internal & External Rotation

19. ANTERIOR & POSTERIOR TILTING/ TIPPING

20. UPWARD & DOWNWARD ROTATION

21. 3. SCAPULOTHORACIC JOINT -Formed by the articulation of the scapula with the thorax -Not true anatomic joint -The SC joint + AC joint : interdependent with ST Movement at ST joint  AC joint movement /SC joint movement/Both

22. RESTING POSITION OF THE SCAPULA

23. Motions of the Scapula Upward & Downward Rotation (50-60) Elevation & Depression Protraction & Retraction Internal & External Rotation Anterior & Posterior Tilting

24. UPWARD & DOWNWARD ROTATION

25. ELEVATION & DEPRESSION

26. PROTRACTION & RETRACTION

27. Scapular Elevation coupled with Anterior tilting Scapular Depression coupled with posterior tilting To follow the Convex Thorax

28. 4. GLENOHUMERUAL JOINT Most Mobile / Unstable Joint of the human body Type: Ball-and-Socket Synovial Joint / 3 DOF Articular Surfaces: The large head of humerus - Distal The smaller Glenoid fossa – Proximal Less Articular Congruency  Less Joint Stability More susceptible to Degeneration / Instability

29. GLENOID FOSSA *Orientation of Glenoid Fossa- Slightly upward & anterior/ posterior Anteversion – GF faces anterior (10) Retroversion – GF faces posterior (10) *Vertical curve > Horizontal curve *Concavity increased by articular cartilage + GL

30. HEAD OF THE HUMERUS – Anatomical resting position Head faces medially + superiorly + posteriorly In relation to the shaft of the humerus & the humeral condyles When the arms hang at the side – the inferior surface of the humeral head rests on only a small inferior portion of the Glenoid fossa

31. HEAD OF THE HUMERUS – Angle of inclination Formed by an axis through the humeral head and neck in relation to a longitudinal axis through the shaft of the humerus (N=130-150 in frontal plane)

32. HEAD OF THE HUMERUS – Angle of Torsion Formed by an axis through the humeral head and neck in relation to an axis through the humeral condyles(N= 30 posterior) Posterior Torsion Retrotorsion Retroversion

33. Normal Retroversion of Head of Humerus

34. Reduced Retroversion / Anteversion of head of humerus

35. Increased Retroversion of head of humerus

36. GLENOID LABRUM - Increases the total articular surface of the Glenoid fossa by increasing the depth / concavity of the fossa by approx. 50% FUNCTIONS *Provides resistance to humeral head translation *Protects Bony edges *Reduces joint friction *Dissipation/spreading of joint contact forces *Provides attachment site for GH ligaments & Long Head -Biceps

37. Shoulder Joint - Anatomy

38. Shoulder Joint - Anatomy

39. GLENOHUMERAL LIGAMENTS & JOINT CAPSULE When arm dependent at the side Joint Capsule - Loose Taut superiorly Slack anteriorly & inferiorly --------------------------------- Tightens with Humeral abduction + ER (Closed packed Positon)

40. GLENOHUMERAL LIGAMENTS: Superior Glenohumeral Ligament Middle Glenohumeral Ligament Inferior Glenohumeral Ligament Complex [Anterior band + posterior band] Coracohumeral Ligament

41. Gleno Humeral Ligaments- At Rest

42. GHL – At 45 Humeral Abduction + Neutral rotation

43. GHL – At 90 Humeral Abduction + Neutral rotation

44. GHL – At 90 Humeral Abduction + External rotation

45. GHL – 90 Humeral Abduction + Medial rotation

46. ROTATOR INTERVAL CAPSULE

47. CORACOACROMIAL ARCH The coracoacromial/suprahumeral arch is formed by the coracoid process, the acromion, and the coracoacromial ligament that spans the two bony projections

48. BURSAE A fluid filled sac / thin cushions/tiny water balloon, located at points of friction between a bone and the surrounding soft tissue such as skin, muscles, ligaments & tendons for lubrication / to reduce the friction Subacromial Bursa Subdeltoid Bursa Subcoracoid Bursa Subscapular Bursa

49. Glenohumeral Motions : Osteokinematics & Arthrokinematics OSTEOKINEMATICS 3 DOF Flexion /Extension [ 120 /50] Abduction/ Adduction [ 90-120 ] Medial Rotation/Lateral Rotation Scaption: Abduction in the plane of the scapula

50. ARTHROKINEMATICS

51. STATIC STABILIZATION

52. In the dependent arm *Bony geometry - articular surfaces alone can not maintain joint stability *With the humeral head rest on the GF: Gravity acts caudally/downwards *To maintain equilibrium  Cranially directed force needed -Active contraction / passive tension in Deltoid/ Supraspinatus/ Long head of Biceps ???- Relaxed -RIC: Rotator Interval Capsule *Superior Capsule *Superior Gleno Humeral ligament *Coracohumeral ligament -Glenoid Inclination: Anatomical

53. Inadequate Static stabilization : heavily loaded arm Supraspinatus Activation Paralysis of Supraspinatus  Gradual subluxation of GH joint

54. DYNAMIC STABILIZATION Muscles of Shoulder Complex- Dynamic stabilizers *Deltoid *Supraspinatus *Infraspinatus *Teres Minor *Subscapularis *Long Head of Biceps brachii

55. Shoulder Complex Anatomy - Attachments and Actions

56. DELTOID

57. * Deltoid – a prime mover for GH Abduction [+ Supraspinatus] *Anterior Fibers  GH - Flexion Middle Fibers  GH - Abduction Posterior Fibers  GH – Extension * Resolution of Deltoid muscle force vector : -Fx Component :Parallel to long axis of the humerus  Larger  Stabilizer -Fy Component: Perpendicular to long axis of the humerus  Smaller Mobilizer

58. *Fx – Parallel muscle force component of Deltoid – if unopposed Cause the humeral head to impact the coracoacromial arch before much abduction occurs *Fy – perpendicular muscle force component of Deltoid – Not effective Not be able to cause much abduction Until the equilibrium of the translatory forces are achieved

59. * Theoretically: 1 Inferiorly directed contact force of the arch = Fx component of the Deltoid Impingement of Subacromial structures  PAIN Prevent much motion

60. * Theoretically : 2 The Inferior pull of the Gravity Can not offset the Fx component of the Deltoid The Resultant Force [ Effort Force] >> The Gravitational Force [ Resistance Force] Rotation

61. HOW ARM ELEVATION IS BEEN ACHIVED??? The Deltoid can’t independently ELEVATE the Arm Another Force / Set of Forces – to work synergistically with the Deltoid For the Deltoid to work effectively To Produce the desires ROTATION ?????

62. ROTATOR CUFF

63. Rotator Cuff – Muscle force vectors

64. Resolution of RCM Force Vectors

65. *Fy ITS – Perpendicular force component Cause some Humeral rotation Compresses the head of the humerus into the Glenoid fossa *Fx ITS – Parallel force component  Critical : The Inferior translatory pull of ITS Nearly Offsets The Superior translatory pull of the Deltoid  Additional : Teres Minor + Infraspinatus – Lateral Rotation of Humerus Subscapularis - Medial Rotation of Humerus

66. The action of the deltoid and the combined actions of the Infraspinatus , Teres minor , and Subscapularis muscles approximate a force couple The nearly equal and opposite forces for the deltoid and these three rotator cuff muscles acting on the humerus approximate an almost perfect rotation of the humeral head around a relatively stable axis of rotation

67. * Supraspinatus : Fx – Parallel force component – Superior translatory Not able to offset the upward dislocating Deltoid action Fy – Perpendicular force component - Compressive Effective Stabilizer of GH joint  Independent Abductor : Larger Moment Arm Gravity : Stabilizing Synergist

68. * Long head of the Biceps Brachii Force of Flexion – Neutral Humerus Force of Abduction – Humerus LR Reinforce Superior & Middle Glenohumeral ligaments

69. Summary : Dynamic Stabilization *FOG *Force of the prime movers - Dynamic *Force of the muscle stabilizers *Articular Surface Geometry *Passive Capsule + Ligaments Forces *Force of Friction *Joint Reaction Forces 9-10 Times the Weight of the UE

70. INTEGRATED FUNCTION OF THE SHOULDER COMPLEX - SCAPULOHUMERAL RHYTHM

71. *The Shoulder Complex acts in a coordinated manner to provide the smoothest & greatest ROM possible to the UE *The GH motion alone can not achieve full range of elevation of the humerus *The remainder of the range is contributed by the scapula on the thorax through the SC & AC joint motions

72. Significance of Scapulo-Humeral Rhythm Distributes the motions b/w the joints Allow a large ROM with less compromise of stability 2. Maintains joint congruency 3. Maintains good muscle length - tension relationship Prevent Active Insufficiency

73. DEFINITION – Scapulo-Humeral Rhythm An overall ratio of 2 degree of Glenohumeral motion to 1 degree of Scapulothoracic motion during arm elevation [ Flexion/Abduction/Scaption] This Combination of concomitant Glenohumeral & Scapulothoracic motion is commonly referred to as SCAPULOHUMERAL RHYTHM

74. PHASES OF SCAPULO-HUMERAL RHYTHM PHASE – 1 :[0- 30] Degree Elevation GH Joint – 30 Degree ST Joint [ Clavicular Motion] – Minimal 0-5 Degree PHASE – 2 : [30-90] Degree Elevation GH Joint – 40 Degree ST Joint – 20 Degree PHASE – 3 : [90-180] Degree Elevation GH Joint – 50 - 60 Degree ST Joint – 30 - 40 Degree

75. Scapulo Thoracic Contribution : to ELEVATION of the Humerus -By upward rotation of the Glenoid fossa 50-60 degree from its resting position Gleno-Humeral Contribution : to ELEVATION of the Humerus -100-120 of Flexion / 90-120 of Abduction Maximum Range of ELEVATION : 150-180 Lateral Rotation – 50

76. Sternoclavicular + Acromioclavicular Contributions ST upward Rotation Coupled with Clavicular Posterior Rotation + Clavicular Elevation At SC joint

77. ST upward rotation Coupled with Scapula – Posterior Tilting [20-30] + Initially-Scapular Int. Rotation & End Range – Scapular Ext. Rotation [25] At AC Joint

78. Integrated movement during elevation

79. 50% From SC Joint : 20 30 Degree of ST upward Rotation 50% From AC Joint : 20-30 Degree of ST upward Rotation ------------------------------------------------- Variations in Scapulohumeral Rhythm GH Motion : ST Motion Ratio -- 1.25:1  2.69:1

80. 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

81. MUSCLES OF ELEVATION & DEPRESSION

82. ELEVATORS *Deltoid *Supraspinatus *Infraspinatus *Teres Minor *Subscapularis *Upper & Lower trapezius *Serratus Anterior * Rhomboids – Minor & Major

83. DELTOID *Scapular plane abduction- anterior and middle deltoid *Posterior deltoid has smaller MA and thus less effective in frontal plane abduction *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 up to 90 degrees only.

84. Supraspinatus * Primary function - to produce abduction with deltoid muscle. [MOBILIZER] * Secondary function : acts as a ‘steerer’ of humeral head and helps to maintain stability of dependent arm. [STABILIZER]

85. Infraspinatus + Teres minor + 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, [I +T] work to pull the humeral head down , and during the middle range , act to externally rotate for clearing greater tubercle under coracoacromial arch . * Subscapularis helps as internal rotator when arm is at side and during initial range and With more abduction, its inter rot capacity decreases.

86. UPPER AND LOWER TRAPEZIUS + SERRATUS ANTERIOR *This force couple produces upward rotation of scapula. *When the trapezius is intact and the Serratus anterior muscle is paralyzed active abduction of the arm can occur through its full range, although it is weakened. *When the trapezius is paralyzed (even though the Serratus anterior muscle may be intact), active abduction of the arm is both weakened and limited in range with remaining range occurring exclusively at the GH joint. *Without the trapezius (with or without the Serratus anterior muscle), the scapula rests in a downwardly rotated position as a result of the unopposed effect of gravity on the scapula.

87. How SA and trap work with deltoid?? 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, as upward scapular rotators, prevent the undesired downward rotatory movement of the scapula by the middle and posterior deltoid segments that are attached to the scapula.

88. Rhomboid It works eccentrically to control upward rotation of the scapula produced by the trapezius and the Serratus anterior muscles. It adducts the scapula with lower traps to offset the lateral translation component of the Serratus anterior muscle.

89. DEPRESSORS *Latissimus Dorsi *Pectorals – Major & Minor *Teres Major

90. CLINICAL CONNECTION: PATHOMECHANICS * RCI – Rotator Cuff Injury -Stain /tear of RC muscles -Common in baseball pitcher/swimmers/racket sports -Degeneration/improper lifting * Shoulder Dislocation * Glenoid Labrum Tear  Shoulder Dislocation

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