In a man lifting up suitcase, posterior dislocation of glenohumeral joint is prevented by:
Ans. (c) CoracobrachialisRef: Maheshwari 5th ed. / 88* Glenohumeral joint is the most important joint of shoulder complex.* It is a synovial ball and socket articulation between the head of the humerus and glenoid cavity of scapula.* Movements at this joint includes flexion, extension, abduction, adduction, medial rotation, lateral rotation and circumduction.* Posterior dislocation of glenohumeral (shoulder) joint would be prevented by the muscle which originate posteriorly and inserted anteriorly.# For Example: Corachobrachialis muscle originate from Coracoid process of scapula and inserted at Medial aspect of shaft of humerus.* The net vector of pull of this muscle would be anteriorly, opposing the posterior dislocation of shoulder joint.Origin & Insertions of Muscles Around Shoulder Joint:MuscleOriginInsertionDeltoidAnt. Fibres- Lateral l/3rd of anterior border of clavicleMiddle Fibres- Lateral border of acromionPosterior Fibres- Lower lip of crest of spineDeltoid Tuberosity of humerusCoracobra- chialisCoracoid process of scapulaMedial aspect of shaft of humerusLatissimus dorsiPosterior l/3rd of iliac crest, lumbar fascia, spine of lower 6 thoracic vertebrae, lower 4 ribs inferior angle of scapulaFloor of bicipital grooveBicepsLong head: supra glenoid tubercle of scapulaShort head: coracoids process of scapulaTuberosity of radiusThe classical clinical feature of posterior dislocation of shoulder is- arm is held in medial rotation and is locked in that position, and an examiner can not externally rotate it.
Deltoid
Latissimus dorsi
Coracobrachialis
Short head of biceps
Dislocation of Shoulder