Hutchin

the front of the sternum, and its outer end on the acromion. son's patient was caught and rolled along between a locomotive and a platform; Morel-Lavallée's had his shoulder caught between the wheel of a cart and a pile of lumber; Lund's, while resting his left shoulder against a gate, was struck by the end of the shaft of his wagon upon the back of the right shoulder, and the right clavicle was dislocated. North's patient fell backward from a stool, striking on the shoulder; in this case the outer end of the clavicle was dislocated forward. Rombeau's patient was struck on the back by a locomotive; Richerand's patient fell from the third story of a building, striking upon the top of his shoulder; Newman's fell with a falling building, and Hulke's was knocked down by a horse.

The sternal end has always been displaced forward, and the only additional change in position that is mentioned is, in Morel-Lavallée's case, that it had moved rather upward than downward. The acromial end was displaced backward in four cases (once to a distance of three fingerbreadths), upward and outward twice, and once each forward and outward, downward, and incompletely upward. In Hutchinson's case the displacement is not described further than by saying that "when pressure was made on either end of the dislocated bone the other extremity rose perceptibly and protruded the skin."

In six of the cases reduction of both dislocations was effected and maintained, and the patients recovered with good use of the limb and but little deformity; in some of them mention is made of more or less persistent projection of the sternal end. Morel-Lavallée was unable to reduce the dislocation of the outer end, although he made direct traction upon it with a hook introduced through the skin. Lund, with the aid of chloroform, could only bring the bone "into fair position;" at the end of ten days the ends were found "fixed in their new position." In Newman's case, dislocation of the outer end under the acromion, reduction was impossible; the patient withdrew from the hospital on the tenth day, and remained disabled. The result in Hutchinson's case is not recorded.

Treatment-Reduction has usually been effected by drawing the shoulder outward and backward, and recurrence prevented by immobilizing it in a suitable position by means similar to those employed when the dislocation involves either end alone. Hulke used a guttapercha splint moulded over the clavicle and bound down by a bandage that crossed the shoulders and was made fast in front and behind to another about the waist.

CHAPTER XVI.

DISLOCATIONS OF THE SHOULDER.

ANTERIOR DISLOCATIONS; SUBCORACOID, INTRACORACOID.

ANTERIOR DISLOCATIONS.

The

Anatomy.-The bony surfaces which enter directly into the composition of the shoulder-joint are the glenoid cavity of the scapula and the postero-internal half of the globular head of the humerus. former is of irregularly oval shape, the more pointed end above and the broader one below, and is slightly concave, being deepened by a low fibro-cartilaginous rim, which is continuous throughout with the capsule, and above also with the tendon of the long head of the biceps. The cavity looks outward and forward in a direction nearly midway between the sagittal and frontal planes of the body when the scapula occupies its usual position, and changes its direction as the scapula is moved forward or backward around the chest, or is drawn upward or downward, or is rotated.

Against this shallow surface the head of the humerus rests, being held in place by atmospheric pressure, the tonicity of the muscles, and the

tension of thickened portions of the capsule in different positions of the limb. On the outer and anterior portion of the upper end of the humerus is the greater tuberosity, bounded internally in front by the bicipital groove which lodges the long tendon of the biceps in its passage downward and has upon its inner side the lesser tuberosity. Between the upper margins of these tuberosities and the globular articular head is a shallow groove, the anatomical neck.

The acromion and coracoid processes lie above, the one on the outer, the other on the inner side, and the strong coraco-acromial ligament uniting them closes in the upper part of the joint, but is separated from its cavity, as are also the two processes, by the interposed capsule and the tendon of the supraspinatus.

The surface of the head of the humerus that is covered by articular cartilage is about one-third of that of a sphere, and its centre meets the long axis of the shaft at The linear extent of the glenoid fossa, including

its fibro-cartilaginous rim, on a horizontal section is less than half as great as that of the head of the humerus; on a vertical section it is about two-thirds as great. The head of the humerus, therefore, simply rests against the fossa, and its displacement is but slightly opposed by the conditions of contact between them. The muscles which are most closely associated with the joint are the supraspinatus, infraspinatus, and teres minor, attached to the greater tuberosity in the order named from above downward, and the subscapularis, which, arising from almost the whole of the costal surface of the scapula, passes forward, broadly covering the inner side of the joint with its fibres and tendon, to be

Horizontal section through the shoulder-joint; A, in inward, B, in outward rotation. (HENLE.)

attached to the lesser tuberosity. The tendon of the long head of the biceps, starting from the upper margin of the glenoid cavity, passes upward and forward over the head of the humerus and then down the bicipital groove, carrying with it a prolongation of the synovial membrane of the joint. The deltoid, from its broad origin on the spine of the scapula, the acromion, and the clavicle, covers the joint superficially on its posterior, external, and anterior aspects; and the coraco-brachialis, the short head of the biceps, and the great vessels and nerves lie upon its inner side.

The capsule extends from the free margin of the fibro-cartilaginous rim of the glenoid fossa, or from the surface of bone immediately outside of it, to the anatomical neck of the humerus. At the upper part its scapular insertion is at the base of the coracoid process and separated from the glenoid fossa by the tendon of the biceps; on the posterior and inner portion of the humerus it extends somewhat beyond the cartilaginous surface along the projection upon which the head rests. Between the two tuberosities the synovial membrane by which it is lined is prolonged down the bicipital groove, and is reflected over the long tendon of the biceps. The capsule is reinforced at some points by thickenings of itself which are known as ligaments and by the tendons of the scapular muscles; on the inner side it is perforated by the tendon of the subscapularis, and there shows a gap through which the cavity of the joint communicates with the subscapular bursa, a large pouch lying against the inner side of the neck of the scapula and the root of the coracoid process, between them and the upper part of the subscapularis. This opening lies just in front of the upper part of the anterior (inner) margin of the glenoid fossa, has the form of a slit or crescent, and is usually large enough to

admit the end of the finger. When the synovial membrane has been dissected away the gap has the form shown in Figs. 39 and 40, and is partly occupied by the tendon of the subscapularis. The portion of the

capsule which forms its upper margin is called the gleno-humeral ligament, or, to adopt the subdivisions described by Farabeuf,' the supragleno-suprahumeral, the portion forming the lower margin is the supra

The interior of the shoulder-joint from behind. gleno-suprahumeral ligament. 3, supragleno-præhumeral ligaments. 4, pragleno-subhumeral ligament. 5, upper edge of the tendon of the subscapularis; 5', its lower part. B, biceps tendon. C, coracoid. E, spine of scapula. G, glenoid fossa.

(FARABEUF.) 1, coraco-humeral ligament. 2, supra

gleno-præhumeral, and the portion immediately below the latter is the præegleno-subhumeral. These different portions are shown in Figs. 39 and 40, which are copied from Farabeuf's paper. Of them the one

1 Farabeuf: Bull. de la Soc. de Chirurgie, 1885, p. 391.

that forms the lower margin of the gap, the supragleno-præhumeral, is often of slight strength and underlies and is intimately adherent to the tendon of the subscapularis.

The coraco-humeral ligament is a strong wide band extending from the root and outer border of the coracoid process over the top of the joint to the neck of the humerus above the greater tuberosity, and is intimately connected with the capsule and the tendon of the supraspinatus. It is thought to play an important part in determining the position taken by the limb when dislocated, and the manoeuvres by which the dislocation can be reduced.

The tendon of the supraspinatus passes between the acromion and the head of the humerus and is attached to the upper part of the greater tuberosity; it is blended with the capsule and is separated from the acromion by a bursa. Below it come the tendons of the infraspinatus and teres minor, passing to the lower and middle facets respectively and also blended with the capsule.

Outside the capsule is a loose layer of connective tissue which separates it and the tendons of the outer muscles from the under surface of the deltoid; within the layer is the subdeltoid bursa, extending under the acromion, which deserves special mention because of the fact that when the tendon of the supraspinatus is torn away from its attachment in a dislocation and retracts under the acromion with the adherent capsule, this bursa is thereby opened and placed in communication with the cavity of the joint, and the upper portion of the capsule is thus greatly lengthened. The influence of these new conditions in favoring recurrence of dislocation has been discussed in Chapter III.

With respect to the nerves and arteries it is only necessary to speak of the circumflex nerve and of the arterial branches which pass outward, the two circumflex and the subscapular. The circumflex nerve winds around behind the neck of the humerus to its outer side, to be distributed to the deltoid muscle and to the integument covering it. It may be so injured in a dislocation that the deltoid will be paralyzed, perhaps permanently.

The circumflex and subscapular arteries pass outward to be distributed among the muscles of the scapula and upper part of the arm; when in a dislocation the head of the humerus presses the axillary artery inward, those branches are put upon the stretch because they are prevented by the attachment of their branches to the tissues from moving inward as freely as the main trunk does, and consequently they may be ruptured or torn away from the side of the main artery. This accident may be the consequence of the dislocation itself, or of the efforts to reduce it.

The movements of the joint are not only very free but they are also effected by the gliding of one surface over the other, not by simple rolling, and consequently the capsule is loose and is thrown into folds on the side toward which the limb is moved. Above and on each side these folds are drawn back by the attached muscles in the line of their contraction and thus are kept from being caught between the articular surfaces; meanwhile, on the opposite side of the joint the capsule is made tense not only by the separation of its scapular and humeral points