Anatomical cbaracters of the dislocation into the axilla. — Sir Astley Cooper informs us that he dissected tvvo recent cases of this dis location :—" First case : A sailor fell from the• yard-arm on the ship's deck, injured his skull, and dislocated the arm into the axilla. He was brought into St. Thomas's Hospital in a dying state, and expired immediately after. On the next day the shoulder joint was rni nutely examined, and the following were the appearances found : —On removing the integu ments, a quantity of extravasated blood pre sented itself in the cellular membrane, lying immediately under the skin, and in that which covers the axillary plexus of nerves, as well as in the interstices of the muscles, extending as far as the cervix of the humerus, below the insertion of the subscapularis muscle. The axillary artery and plexus of nerves were thrown out of their course by the dislocated head of the bone, which was pushed back wards upon the subscapularis muscle. The deltoid muscle was sunken, with the head of the bone. The supra-and infra-spinati were stretched over the.: glenoid cavity and inferior costa of the scapula. The teres major and minor had undergone but little change of po sition ; but the latter, near its insertion, was surrounded by extravasated blood. The coraco-brachialis was uninjured. In a space between the axillary plexus and coraco-bra chialis, the dislocated head of the bone, co vered by its smooth articular cartilage and by a thin layer of cellular membrane, appeared. The capsular ligament was torn on the whole length of the inner side of the glenoid cavity, and would have admitted a much larger body than the head of the os humeri through the opening. The tendon of the subscapularis muscle which covers the ligament, was also extensively torn. The opening of the liga ment, through which the tendon of the long head of the biceps passed, was rendered larger by laceration, but the tendon itself was not torn. The head of the os humeri was thrown on the inferior costa of the scapula, between it and the ribs, and the axis of its new situ ation was about an inch and a hay below the centre of the glenoid cavity from which it had been thrown. The second case," adds Sir Astley Cooper, " which I had an opportunity of examining, was one in which the disloca tion had existed five weeks, and in which very violent attempts had been made to reduce the dislocated bone, but without success. The sub ject of the accident was a woman, fifty years of age. All the appearances were distinctly marked ; the deltoid muscle being 'flattened, and the acromion pointed ; the head of the bone could also be distinctly felt in the axilla. The skin had been abraded during the at tempts at reduction, and the woman apparently died from the violence used in the extension. Upon exposing the tnuscles, the pectoralis major was found to have been slightly lacer ated, and blood was effused amongst its fibres; the latissimus dorsi and teres major were not injured ; the supra-spinatus was lacerated in several places ; the infra-spinatus and teres minor were torn, but not to the same extent as the former inuscle ; some of the fibres of the deltoid muscle, and a few of those of the coraco-brachialis, had been torn, but none of the muscles had suffered so much injury as the supra-spinatus. The biceps was not in jured. Having ascertained the injury which the muscles had sustained in the extension, and, in some degree, the resistance which they opposed to it, I proceeded to examine the joint. The capsular ligament haci given way in the axilla, between the teres minor and sub scapularis muscles; the tendon of the sub scapularis was torn through at its insertion into the lesser tubercle of the os humeri, and the head of the bone rested upon the axillary plexus of nerves and the artery. Having de termined these points by dissection, I next," says Sir Astley Cooper, " endeavoured to re duce the bone, but finding the resistance too great to be overcome by my- own effbrts, I became very anxious to ascertain its origin. I therefore divided one muscle after another, cutting through the coraco-brachialis, teres major and minor, and infra-spinatus muscles. Yet still the opposition to my efforts re mained, and with but little apparent change. I then conceived that the deltoid must be the chief cause of my failure, and, by elevating the arm, I relaxed this muscle ; but still could not reduce the dislobation. I next divided the deltoid muscle, and then found the supra spinatus muscle my great opponent, until I drew the arm directly upwards, when the head of the bone glided into the glenoid cavity. The deltoid and supra-spinatus muscles are those which most powerfully resist reduc tion in this accident." This dissection ex plains the reason why the arm is sometimes easily reduced, soon after the dislocation, by raising it suddenly above the horizontal line; and placing the fingers under the head of the bone, so as to lift it towards the glenoid cavity, which will sometimes prove effectual, because, in this position, the muscles are relaxed, so as no longer to offer any resistance to reduction. Sir Philip Crampton has adduced an example of dislocation of the shoulder joint, which illustrates in a satisfactory manner the anatomy of a recent case of dislocation into the axilla.
Case.—" In the year 1808, a labouring man was brought into the County of' Dublin In firmary in a dying state : the persons who carried him stated that he had been engaged in digging under the foundation of a house that had been burned ; that a part of a par tition wall fell upon him, and that they- had found hitn buried under the rubbish : the man did not survive more than two hours. On examining the body eighteen hours after death, it was observed, that in addition to the injury of the head, which had proved fatal, the right humerus was dislocated into the axilla. To
this part I directed the whole of my attention. I made a careful dissection of the joint, pre viously to reducing the dislocation, and was so fortunate as to obtain a drawing of the parts, executed upon the spot, by a distin guished artist. On removing the integuments of the axilla, the cellular membrane, which was extensively ecchymosed, formed a kind of cap, closely embracing the head of the os humeri, which, when the axilla was cleared, was seen lodged on the inferior costa of the scapula, or rather, on its neck ; the head of the bone, in escaping from its socket, had pushed the teres minor downwards, and burst through the lower part of the subscapularis muscle, some of the fibres of which closely embraced the neck of the bone, while, the bulk of the us cle wa,s pushed upwards, and detached from the inner surface of the scapula (fig. 434.).
The neck of the humerus, therefore, was in some degree embraced by the divided fibres of the subscapularis muscle, while a portion of its head rested on the neck and part of the venter of the scapula, without the interven tion of any muscular substance. The short head of the biceps, and the coraco-brachialis, were forced to describe a curve outwards, over the neck of the humerus on the sternal side, while the long head of the triceps crossed the neck of the bone obliquely on the dorsal side ; this strangulation of the head of the bone, by the surrounding muscles, was made niost apparent when extension was applied to the fore-arm. The biceps and triceps seemed then to close behind the head of the bone, and interpose themselves between it and the glenoid cavity ; the tendon of the long head of the biceps remained in its groove, but the sheath in which it runs was partially ripped up. The capsular ligament was com pletely torn from the lower part of the neck of the humerus, to the extent of more than half its circumference, the torn edge appear ing like a crest over the head of the bone. The great nerves and blood vessels of the arm were forced to describe a curve backwards, by the pressure of the head of the bone, which was in contact with them. But the greatest injury had been sustained by the articular muscles,' as they have been called, which lie on the back of the scapula. The tendons of the supra-spinatus, the infra-spinatus, and the teres minor, were completely torn off front the humerus, carrying with them, however, a scale of bone, which was ascertained to be the surface of the greater tubercle into which they are inserted." In order to ascertain the nature of the ob stacles which oppose the reduction of the dislocated humerus, the scapula was fixed, and the arm being raised to nearly a right angle with the body, extension was slowly ap plied to the arm by pulling at the wrist; it then appeared that so long as the hand was held supine, the head of the bone remained immovable; the chief resistance appearing, to be caused by the closing of the biceps and triceps behind the head of the bone. The muscles of the back of the scapula being de tached from the greater tubercle, could of course afford no resistance; but, on turning the hand into the prone position, and giving a motion of rotation inwards to the whole limb, the extension being still maintained, the bead of the bone glided easily into its socket. The appearances observed in this case are nearly identical with those which are described by Mr. Henry Thompson, in the Medical Ob servations and Inquiries, while they differ materially from those which were found by Sir Astley Cooper ; establishing an important fact, which, indeed, might have been inferred d priori, that in apparently similar dislocations of the humerus, there may be very different kinds as well as degrees of lesion, and conse quently very different causes of resistance to reduction. " In Mr. Thompson's ease," Sir P. Crampton adds, " as in mine, the head of the bone was found lodged on the inside of the neck of the scapula, between the subscapu laris and teres major muscles ; but during the eighteen days which had elapsed since the injury had been received, the cellular substance of tlw axilla had formed a kind of capsular ligament, which embraced the head of the bone, and contained a small quantity of mucus resembling synovia. In Mr. Thompson's case, the capsular ligament was completely torn from the whole circumference of the humerus. In mine it was detached to the extent of more than half the circumference. In both cases, the attachments or the ten dons of the supra- and infra-spinatus muscles were torn off with the part of the bone they were inserted into ; in both cases, some fibres of the subscapularis muscle embraced the neck of the bone." In Sir Astley Cooper's cases, on the contrary, although the tendon of the subscapularis was torn through, the supra- and infra- spinatus muscles retained the connection with the greater tubercle, and " until this muscle was relaxed, by raising the arm, the humerus could not be reduced by any effbrts which he (Sir Astley) could make." In cases of dislocation of the humerus into the axilla, which have been left long unreduced, the longitudinal axis of the limb passing from below upwards, is much altered, being thrown the head of the bone is found altered in its form, the surface towards the scapula being flattened, a complete capsular ligament en virons the head of the os humeri. The glenoid cavity is filled entirely by ligamentary matter, in which are to be found small portions of bone. These must be of new formation, as no portion of the scapula or humerus is broken. A new cavity-is formed for the head of the os humeri on the inferior costa of the scapula, hut this is shallow, like that from which the os humeri had escaped.