BIOMECHANICS OF SHOULDER joint Upper extremity.pptx

BIOMECHANICS OF SHOULDER joint Upper extremity

1. BIOMECHANICS OF SHOULDER

2. 5- 2 The Shoulder Joint #S houlder joint is a complex joint composed of clavicle, scapula & humerus . #It links the upper extremity to the thorax or axial skeleton.

3. SHOULDER COMPLEX consists of 3 joints: -STERNOCLAVICULAR JOINT -ACROMIOCLAVICULAR JOINT -GLENOHUMERAL JOINT

4. Joint between medial end of clavicle and superolateral aspect of manubrium . Links the upper extremity directly to thorax. True synovial joint, has a fibrocartilagenous articular disc which divides it into 2 compartments. Stabilizers of SC Joint: - Costoclavicular ligament - Interclavicular ligament - Sternoclavicular ligaments Sternoclavicular ligaments -prevents anterior and posterior translations. STERNOCLAVICULAR JOINT

5. Costoclavicular ligament -limits upward and posterior displacement of clavicle. Interclavicular ligaments -restraint SC Joint superiorly. Articular Disc -prevents medial displacement of clavicle while carrying objects at the side as well as inferior displacement of clavicle via articular disc.

6. Joint between lateral end of clavicle & acromion of scapula. Synovial joint ACROMIO-CLAVICULAR LIGAMENT : - Superior AC Ligament - Inferior AC Ligament :Restraints axial rotation & posterior translation of clavicle. ACROMIOCLAVICULAR JOINT

7. Joint between glenoid fossa of scapula and head of Humerus. Glenoid fossa faces slight anteriorly. The GH joint is a ball-and-socket synovial joint with three rotational and three translational degrees of freedom . GLENOHUMERAL JOINT

8. Angle b/w long axis through the shaft of humerus and the axis passing though the centre of the humeral head . Normal value is 130-150 deg. In frontal plane. Angle of Inclination:

9. The angle b/w the axis through the humeral head and neck & an axis the humeral condyles in the transverse plane. The humeral head is normally angled posteriorly approximately 30 (angle of torsion) with regard to an axis through the humeral condyles. Angle of torsion

10. Capsule and Ligaments - GLENOID LABRUM- -Increases total available articular surface by increasing depth or curvature of glenoid fossa. GLENOHUMERAL CAPSULE- -Large & loose capsule surrounding GH joint. -Taut superiorly & slack anteriorly and inferiorly when the arm at the side of the body.

11. GLENOHUMERAL LIGAMENTS- -Reinforce GH capsule 1 ) Superior GH lig . 2) Middle GH lig .- 3) Inferior GH

12. CORACO-HUMERAL LIGAMENT : - Resraints inf.translation of humeral head in dependent arm. CORACO-ACROMIAL ARCH: - Osteo-ligamentous vault-covers humeral head,forms a space with in which lie the subacromian bursa,rotator cuff &a portion of long head of biceps. -consist of coracoid process posteriorly , acromian process anteriorly and coracoacromial lig . Superiorly. -Functions:1)protection of humeral head

13. against the impingement 2)prevents humeral head from dislocating superiorly. BURSAE : Subacromial or Subdeltoid Bursae . Permits frictionless movement b/w humerus & supraspinatus tendon.

14. KINEMATICS OF SHOULDER COMPLEX STERNO-CLAVICULAR JOINT: 3 Rotatory degrees of freedom of SC Joint : 1)Elevation & Depression of clavicle : Around AP axis. :ROM-Elevation:48 deg. -Passive depression:15 deg. :Lateral clavicle rotates upward in Elevation & downward in Depression. 2)Protraction & Retraction of clavicle :Around vertical( supero -inferior) axis. :ROM-Protraction:15-20 deg. -Retraction:20-30 deg. :Lateral clavicle rotates anteriorly in Protraction & posteriorly in Retraction.

15. 3)Anterior& Posterior Rotation of Clavicle : :Occurs around a longitudanal axis through clavicle intersecting SC & AC joints. :Clavicle rotates posteriorly from its neutral position and then , rolls anteriorly from its fully rotated position. : ROM:Posterior Rotation:50 deg. :Anterior Rotation:10 deg.

16. ACROMIO-CLAVICULAR JOINT : 1)INTERNAL/EXTERNAL ROTATION : :Occurs around vertical axis through AC Joint. :Brings glenoid fossa anteromedially ( Int.rotation ) & posterolaterally ( Ext.rotation ). :Maintain contact of scapula with horizontal curvature of thorax when clavicle protracts &retracts as a result of humeral elevation. :Normal value:30 deg. 2)ANTERIOR/POSTERIOR TIPPING :Tilting of scapula in relation to clavicle.

17. :Occurs around an oblique “coronal axis” through AC Joint. :Anterior Tipping:Acromion process tips forward & inf. Angle tips backward. :Posterior Tipping:Acromion Process tips backward & inf. Angle tips forward. :Normal value:60 deg. 3)UPWARD/DOWNWARD ROTATION :Rotation of glenoid fossa upward or downward. :Upward rotation: Coracoid process move inferiorly but restricted due to tension in coraco-clavicular ligament. :Normal value:30 deg.

18. GLENO-HUMERAL JOINT : * FLEXION/EXTENSION : -Occurs around coronal axis passing through axis of humeral head. -Flexion:0-120 deg. -Extension:0-50 deg. * ABDUCTION/ADDUCTION : -Occurs around an AP Axis passing through humeral head. -Abduction:0-120 deg.(with the movement of scapula) -Adduction:120-0 deg.

19. * MEDIAL/LATERAL ROTATION : -Occurs around a long axis parallel to shaft of humerus & passing through the centre of humeral head. -Normal value:0-90 deg. *SCAPTION/SCAPULAR ABDUCTION : -Abduction/elevation of humerus in the plane of scapula.

20. MUSCLES * FLEXION :Clavicular fibres of Pectoralis major :Anterior fibres of Deltoid : Coracobrachialis :Short head of Biceps * EXTENSION :Posterior fibres of Deltoid : Lattisimus Dorsi : Teres Major : Sternocostal head of Pectoral major * ADDUCTION :Pectoralis major : Lattisimus dorsi :Long head of Triceps : Teres major : Coracobrachialis

21. * ABDUCTION :Deltoid (Middle fibres ) : Supraspinatus : Serratus Anterior :Upper & lower fibres of Trapezius . * MEDIAL ROTATION :Pectoralis major :Anterior fibres of Deltoid : Lattisimus Dorsi : Teres major : Subscapularis * LATERAL ROTATION :Posterior fibres of Deltoid : Infraspinatus : Teres minor :

22. KINETICS OF SHOULDER COMPLEX Kinetics include the forces which produces the motions & stability of GH Joint during rest and motions. STATIC STABILIZATION OF GH JOINT -Includes stabilization of humeral head when the arm is at the side unloaded & loaded. -Arm unloaded at the side:Resultant pull of LOG and Rotator Interval capsule creates a line of force which compresses humeral head against lower portion of glenoid fossa .

23. -Airtight seal of capsule-creates – ve intraarticular pressure which prevents inf. translation of humerus by force of gravity. -Degree of glenoid inclination-upward tilt of scapula produces a partial bony block against humeral translation. -If the arm is heavily loaded- Supraspinatus recruited which has attachments to rotator interval capsule.

24. DYANAMIC STABILIZATION OF GH JOINT * DELTOID : -Role of stabilization in elevation activities (abduction & flexion). -Resultant action line all 3 segments of Deltoid is Fd resolved into Fx (large translatory ) Fy (small rotatory component). -Isolated action of Deltoid causes more superior humeral translation and less rotation (i.e. abduction) of humerus . -Deltoid needs other sets of forces to work synergistically with deltoid to work effectively as it can’t abduct the arm alone.

25. * ROTATOR CUFF(SITS): -Action lines of ITS has Fy component ( rotatory component) which compresses humeral head into lower portion of glenoid fossa & Fx component( translatory component) causes inf. Translation which offsets sup. Translation component of Deltoid. -Functions of ITS: 1]Stabilizing role. 2]Provides ext.rotation that occurs with elevation of humerus . -Action of Deltoid & combined force of ITS creates a force couple which produces a perfect spinning of humeral head around relatively axis of rotation.

26. * SUPRASPINATUS : -Action line of Supraspinatus has Fx component(smaller translatory force) & Fy component(larger rotatory component). - Fx force is offset by gravity. - Fy is larger than that of ITS. -Independently produce a full or nearby GH abd . while simultneously stabilising the joint. -Resultant of gravitational & supraspinatus forces contributes to inferior gliding of humeral head during Abd . of arm.

27. *LONG HEAD OF BICEPS: -Contributes to force of flexion. -If arm is laterally rotated, it contributes to Abd . Force contribution. -It centres the head of humerus in fossa & reduce vertical(sup. & inf.) and ant.translations .

28. Combined Scapulo -humeral motion has following functions: 1]Distributes the motion b/w joints permitting a large ROM with less compromise of stability than would occur if the same range occurred at one joint. 2]Maintains the glenoid fossa in an optimal position in relation to head of humerus which increases joint congruency while decreasing shear forces. INTEGRATED FUNCTION OF SHOULDER COMPLEX

29. 3]Permits the muscles acting on humerus to maintain a good length-tension relationship while minimising or preventing active insufficiency of GH muscles. # SCAPUL0-HUMERAL RHYTHM (ST&GH C ontributions : -States that, scapula on the thorax contributes to elevation( flexion&elevation ) of humerus by upward rotation of scapula. -Overall ratio of 2 deg of GH to 1 deg of ST motion during arm elevation is commonly used & this combination of GH & ST motion is referred to as “SCAPULO-HUMERAL RHYTHM”. GH:ST motion=2:1

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