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Show DISLOCAl‘lON OF THE HUMERUSe DISLOCATION or run HUMERUS. bones then stand in the relation to each other that is here represented. A is the scapula. B the acromion scapulas. C the humerus: while D may represent the lower part of the capsule. If the arm be thus raised, and there is a force suddenly raising the arm further, a spasmodic action of the muscles inserted into the scapula fix it, and then the arm THE SIGNS OF DISLOCATION of the shoulder are these :- .....M~\-. 3.- ._....,,_‘:_._.. ,..-_r.- - '_.:c4-:.'./V'.‘ 4:" 168 sauna" mum bone, C, comes in contact with the process, B, as here re- presented, and the force operating on the long lever of the arm, the head of the bone bursts through the capsule, D; tears the ligaments of the joint, and lodges in the axilla. Indeed, as to theplace of the head of the humerus in dislocation it depends on the direction of the force combined with the operation of the muscles. If, for example, while the hu~ merus is made to act like a lever, tearing up the ligaments of the joint, it at the same time receives an impulse in the. line E D; that is in the direction of the shaft of the bone, then will the head he urged deep into the axilla, or under the pectoralis major muscle. 169 1. There is a hollow in the middle of the deltoid muscle, and directly under the acromion process; because the head of the humerus is removed from the glenoid cavity of the scapula, and no longer serves to give roundness to the shoulder. 2. The head of the humerus is to be felt in the axilla. 3. The elbow cannot be pressed to the side without diflieulty and pain. (This howe 'er is an indication which becomes less distinct in old cases.) 4. The patient cannot make the circular motion of the arm. He raises his hand to his head awkwardly, and with pain. 5. There is an unusual bend or depression near the middle of the arm, from the change in the angle of insertion of the deltoides in consequence of the new direction of the bone. 6. The fore arm is not freely extended, and there is a tenseness in the biceps muscle. This proceeds from the origin of the long head of the biceps retaining its hold on the edge of the glcnoid cavity, while the tendon being engaged in the groove of the humerus must follow that bone, and consequently draw upon the belly of the muscle. VlUNl , M099? . \\ ‘ \ -\~>> .\\~\ , §§§ 7 7. There is a numbness of the arm sometimes, and the . , w " "WWW " pulse may be oppressed, or there may be oedema of the arm. This arises from the head of the humerus pressing 011 the axillary artery, or veins, or plexus of brachial nerves, and depends therefore on the accidental position of the head of the bone. POSITION OF THE HEAD OF THE HUMERUS. ~ " "7‘ "09mm 54M .. p.44, "-4 -- new-<9. 1. No force can be applied in a direction to dislocate the humerus, and push its head behind the scapula, for this very evident reason, that the chest prevents the necessary position A, The scapula, scan on the inside. B, An outline representing the humerus in its natural place. C, The humerus rcprcsonlcd dislocated. D, The humerus in outline representing the consogucnce ofpressing the elbow to the side, viz. that the of the humerus. 2. Neither can the arm bone be dislocated upwards, be- cause of the protection afforded to the joint by the prominence of the acromion and coracoid process; but chiefly, I head rises and presses against the neck qfthe scapula. believe, this is to be taken into consideration that there can vor. n. Y ._| |