Glenohumeral joint-ppt.

MOHAMMAD AKEEL

1. GLENOHUMERAL JOINT`S STATIC STABILITY, DYANAMIC STABILITY & SCAPULO-HUMERAL RHYTHM MOHAMMAD AKEEL INTEGRAL UNIVERSITY

2. DEFINITION- The glenohumeral joint is a ball-and-socket type of synovial joint that permits a wide range of movement; however the mobility makes the joint relatively unstable.

3. ARTICULATION- The articular surfaces of the GH-joint are the large spherical head of the Humerus and the small Glenoid cavity of the scapula. The Glenoid fossa serves as proximal articular surface which is placed laterally, anterior to coronal plane & slightly upward tilt , looks like INVERTED DROP SHALLOW structure.

4. CAPSULE- a loose fibrous capsule surrounds the glenohumeral joint and is attached; Medially to the margin of the glenoid cavity. Laterally to the anatomical neck of the humerus . Superiorly, the capsule encloses on the root of the coracoid process so that the fibrous capsule encloses the proximal attachment of the long head of biceps brachii - supraglenoid tubercle of scapula.

5. LIGAMENTS- The fibrous membrane of the joint capsule is thickened and strengthened by ligaments. a . The glenohumeral ligaments has three fibrous bands- superior ,starts from Glenoid labrum to Anatomical neck & it limit anter -inferior translation. middle, Sarts from GL to Lesser tubercle & it limit anterior translation. inferior ,has 3- bands- 1. Anterior band , which limit anterior translation. 2 . Axillary band , which limit abduction over 90. 3 . Posterior band , which prevent post. Translation & limit internal rotation.

6. b . The coracohumeral ligament ; extends from coracoid process to anatotical neck of humerus . c . The transverse humeral ligament ; a broad fibrous band that runs more or less obliquely from the greater to the lesser tubercle of the humerus, bridging over the intertubercular groove .

7. INNERVATION The Glenohumeral Joint is innervated by; The suprascapular , Axillary , Lateral pectoral and Branches from the posterior cord of brachial plexus .

8. MOVEMENTS OF THE GLENOHUMERAL JOINT- The glenohumeral joint allows movements around three axes and permits: Flexion-extension Abduction-adduction medial and lateral Rotation Circumduction

9. STATIC STABILIY OF GH-JOINT At static/resting position, the Head of Humerus is stable against the Glenoid Fossa that is a Static Stability. As the Humeral head rest on fossa,the gravity acts on the Humerus parallel to shaft in downward direction ( Translatory Forces). It needs a vertical pull to maintain equilibrium and this vertical force is supplied by Deltoid, Supraspinatus & long head of Biceps & Triceps.

10. The LOG creates downward force on humerus . Given the magnitude of passive tension in the structure of the ROTATOR INTERVAL CAPSULE ( Superior Capsule, superior GH ligament & coracohumeral ligament ) that are taut when the arm is at the side. The resultant pull of both LOG & Rotator interval capsule creates a line of force that compress the humeral head into the lower portion of glenoid fossa , where the humeral head commonly sits when the arm is at the side.

11. The capsule has an airtight seal, which produces Negative intra- articular pressur e. This pressure creates a relative vaccum that resist inferior humeral translation caused by gravity. The degree of glenoid inclination influences the stability of the GH joint with the arm in dependent position.

12. DYNAMIC STABILITY OF GH-JOINT The normal Shoulder precisely constraints the Humeral head to centre of Glenoid cavity throughout most of the Arc of movement. For optimal shoulder stabilization the dynamic stabilizers must be working in an efficient synergistic fashion. 1.The Deltoid & GH Stablization - For ABDUCTION- Deltoid & Supraspinatus acts as a prime mover.The Anterior Deltoid helps in Flexion as a Prime mover. The deltoid muscle is an anterior stabilizer of the glenohumeral joint with the arm in abduction and external rotation.

13. 2.The Rotator cuff & GH Stablization - The Supraspinatus , Infraspinatus , Teres Minor & Subscapularis muscles (SITS) compose the rotator or musculotendinous cuff. Rotator cuff are important GH joint compressors.

14. Figure:- The action of line of the four segment of ROTATOR CUFF.

15. 3 . The Supraspinatus & GH Stablization - The action line of the supraspinatus muscle, unlike the action lines of the other three rotator cuff muscle, has a superior translatory component. The Supraspinatus has down movement which is capable of producing full range in GH Abduction while simultaneously stablizing the joint.

16. 4.The Head of Biceps Brachii & GH StabliLization - The Biceps muscle is capable of contributing to the force of flexion & can, if the humerus is laterally rotated, contribute to the force of abduction & anterior stablization .

17. Scapulohumeral Rhythm

18. The movement of the Humerus and the Scapula is not uniform over this range. Though,In the first 90 degrees of movement, the Humerus performs 50 degrees and the Scapula 40 degrees. after 135 degrees the remaining movement occurs at the Acromioclavicular and Clavicular joint.

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