2. Dislocation forwards.—This species of dislocation is much rn ore distinctly marked than the former. The acromion is more pointed, and the hollow below it, from the depression of the deltoid, is more considerable. The head of the os humeri can be felt through the skin and pectoral muscle, and its con vexity seen, in thin persons, just below the clavicle ; and when the arm is rotated, the protuberance may be observed also to rotate and accompany the motions of the arra. The coracoid process of the scapula is placed above and on the outside of the head of the bone, which we know is covered by the pectoris major muscle. The elbow is thrown out more from the side, and furthei. back than it is in the case of dislocation into the axilla (fig. 436.).
Much difference of opinion seems to pre vail as to whether the arm is lengthened or shortened, as the result of' this dislocation of the head of the hurnerus forwards. Mal gaigne and Dupuytren both assert that the arm on the dislocated side is longer than na tural; Sir A. Cooper expresses himself in opposite terms ; he says, that in the disloca tion forvvards and inwards of the head of the humerus, the arm is shortened. In our experience we have never found in the living subject the arm shortened ; and in the speci men from whichfig. 436. has been taken, the centre of the new glenoid cavity is several lines below the centre of the original cavity, and the arm therefore must have been by, so much, longer than natural. The direction of inwards towards the middle of the clavicle. The pain attending this accident is less than it is in the case where the head of the bone is thrown into the axilla, because the nerves of the axillary plexus are less compressed ; but the motions of the joint are much imore materially affected. The strongest diagnostic marks of the dislocation are these. The elbow is separated from the side arid thrown backwards, and the head of the humerus can be felt to move below the clavicle when the arm is rotated. Sir Philip Crampton has adduced the following example of the ordinary dislocation forwards, in which the head of the bone vvas thrown at once on the neck of the scapula, without previously passing into the axilla.
" James Wilson, azt. 30, fell into a lime kiln, in the immediate neighbourhood of the Meath Hospital, while the lime was still burning ; he was drawn up by ropes, but just as he reached the top of the shaft, the rope broke, and he again fell to the bottom, a dis tance of about fifteen feet, on the ignited stones. It appeared, on exanaination,rnade in the Mew h Hospital, that in addition to several extensive burns and lacerations, there was a dislocation of the humerus, under the pectoral mus cle. Mr. Macnamara, without assistance, re duced the dislocation, by merely drawing the arm gently forwards and downwards with one hand, while he pushed the head of the bone towards the glenoid cavity with the other. The man died in the course of
the day, from the conjoint effects of the burn and the fall. Eighteen hours after death the shoulder joint was dissected by Mr. Macna mara, from whom I take the description of the appearances, with the advantage of having the preparation before me while I write. The dislocation was unattended with rup ture of any muscle, or the separation of any tendon from its insertion into the bone ; by a slight effort the dislocation was reproduced, and the pectoral muscles being removed, the polished head of the bone was now seen lodged on the cervix of the scapula, at the root of the coracoid process, but extend ing nearly as far as the notch in the superior margin of the scapula. The head of the bone had passed out through a rent in the capsu lar ligament, over the upper edge of the tendon of the subscapularis, detaching this muscle from its connection, which is at this point but slight, with the inner surface of the scapula, and pushing its fibres downwards, so that they formed a curVe, which partly embraced the neck of the humerus (fig. , ing in the capsular ligament through which it no injury. The cellular substance cover ing their tendons was deeply ecchymosed, so as to mark their course most distinctly. 437.). The supra-, andorinfra-sirMna,tu. s mus cles were on the stretch, but 'had suffered On replacing the head of the bone, the open 's , ,,,,, ,, Fig. 437.
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‘ •1 Dislocation forwards and inwards. (Sir P. ton's case.) had escaped from its socket, could be dis tinctly seen. It was formed, by a separation of the ligament from the interior side of the brim of the glenoid cavity from top to bottom, it was bounded at the top by the tendon of the supra-spinatus, and at the bottom by the inferior edge of the tendon of the suhscapu laris ; the rent was continued as far as the root of the lesser tubercle of the os humeri, and was of sufficient extent, but no more, to per mit the head of the bone to pass easily through it. The inferior part of the capsular liga ment, however, the part corresponding to the axilla, was perfect. The great blood vessels and nerves lay to the sternal side of the head of the humerus, and were forced a little out of' their course. The axis of the head of the bone in its disturbed position was scarcely a quarter of an inch higher than the axis of the glenoid cavity.