Sir P. Crampton observes, " the anatomy of the recent case of dislocation forwards set tles the long disputed question as to whether or not the humerus can be dislocated primi tively in any other direction than dozvnwards, or into the axilla ; it is plain, that in the case of Wilson, the head of the bone was thrown at once forwards, into the situation into which it appears under the clavicle ; as the inferior portion of the capsular ligament was not ruptured, and the attachment of the sub scapularis and teres minor muscles to the in ferior costa of the scapula remained undis turbed." Mr. Key has given the following account of the appearances observed in dissection of the right shoulder joint of a patient who had had for seven years an unreduced dislocation of the head of the humerus, in the direction for wards and inwards. The specimen is pre served in the museum attached to St. Thomas's Hospital. The head of the bone was thrown on the neck and part of the venter of the scapulm, near the edge of the glenoid cavity, and immediately under the notch of the su perior costa : nothing intervened between the bead of the humerus and the scapula, the subscapularis muscle being partly raised from its attachment to the venter. The head was situated on the inner side of the coracoid process, and immediately under the edge of the clavicle, without having the slightest con nection with the ribs; indeed, this must have been prevented by the situation of.the sub scapularis and serratus magnus muscles be tween the thorax and humerus. The tendons of all the muscles attached to the tubercles of the humerus were perfect, and are shown in the specimen preserved. The tendon of the biceps was not torn, and it adhered to the capsular ligament. The glenoid cavity was completely filled up by ligamentous structure, -still however preserving its general form and " character ; the tendons of the supra- and infra spinati and teres minor muscles adhered by means of bands to the ligamentous structure occupying the glenoid cavity, and, to prevent the effects of friction between the tendons and the glenoid cavity in the motions of the arm, a sesamoid bone had been formed in the substance of the tendons ; the newly formed socket reached from the edge of the glenoid cavity to about one-third across the venter ; a complete lip was formed around the new cavity, and the surface was irregularly co vered with cartilage. The head of the bone had undergone considerable change of form, the cartilages being in many places absorbed, and a complete new capsular ligament had been formed." The accompanying wood-cut (fig. 438.) is taken frorn a scapula preserved in the museum of the College of Surgeons in Dublin, and re sembles much the specimen alluded to by Mr. Key. The newly formed socket reached from the edge of the glenoid cavity, to about one third across the subscapular fossa; a deep cup was formed for the reception of the dislocated head of the humerus ; the inner margin of this cup was fully half an inch above the level of the subscapular fossa; the glenoid cavity had lost all cartilaginous investment ; it was rough on its surface from bony deposition, and its inner margin was elevated somewhat into a sharp ritlge, so as to form part of the margin of the new articular cavity for the head of the humerus.
3. Dislocation backwards of the head of the humerus on the dorsum of the scapula, the result of accident. — In this dislocation the arm is directed from above downwards, inwards, and forwards. The deformity of the joint is well seen by viewing it in front, where a deficiency is noted of the normal roundness of the articu• lation. When we look at the shoulder side ways,the head of the humerus may be seen to form a remarkable saliency behind the posterior angle of the acromion. In this dislocation the head of the bone is thrown on the posterior surface of the scapula immediately below the spine of this bone, and there forms a very re markable protuberance, and when the elbow is rotated as far as practicable this protuberance ves also. The dislocated head of the bone may be easily grasped between the fingers, and distinctly felt resting below the spine of the scapula; the motions of the arm are impaired, but not to the same extent as in the other luxations of the shoulder, and the longitudinal axis of the humerus may be observed to run upwards, backwards, and to a point, evidently behind the situation of the glenoid cavity. ln Guy's Hospital Reports* Sir A. Cooper has published a case of this species of dislocation, from which we abstract the following, Case. —" Mr. Key has given me the par ticulars of the following case. Mr. Complin
was 62 years of age, and had been the sub ject of epileptic fits; one of them, which was particularly severe, occurred one morning while he was in bed, and in his violent con vulsive strugglings his shoulder became dis located on the dorsum of the scapula, present., ing the ordinary symptoms of this accident in which dislocation had never been reduced." The circumstance most peculiar in this case was, that the head of the bone could by ex tension be drawn into its natural situation in the glenoid cavity ; but so soon as the force ceased to be applied it slipped back again in the dorsum of the scapula, and all the appear ances of dislocation were renewed. The se cond peculiarity consisted in a sensation of crepitus as the bone escaped from its socket, so as to lead to a belief that the edge of the glenoid cavity had been broken off. The patient was unable to use or even to move the' arril to any extent, nor could he by his own efforts elevate it from his side, and although he lived seven years after the occurrence of the epileptic fit, he never recovered the use of the limb. Mr. Key sent the following note of the dissection of the dislocated shoulder in this case to Sir A. Cooper The dislocation of Mr. Complin's shoulder arose from muscu lar action alone in a paroxysm of epilepsy, and during his life it was thought probable' that a portion of the glenoid cavity had been broken off, or a piece of the head of the os humeri, or perhaps the smaller tubercle, and that either of these injuries would account for the head of the bone not remaining in its na-4 tural cavity when reduced. But the inspec tion, post-mortem, proved that the cause of' this symptom was the laceration of the tendon of the subscapularis muscle, which was found to adhere to the edge of the glenoid cavity, and* was much thickened and altered in its cha-. racter front its laceration, and from its very imperfect and irregular union. The muscles of the dorsum scapulm were diminished, by being thrown out of use, and the tendon of the long head of the biceps muscle was entire, but glued down by adhesion." Upon further ex amination of the scapula and os humeri, Sir A. Cooper found the muscles and the situation of the bones to be as follows :—" The head of the os humeri was placed behind the glenoid cavity of the scapula, and rested upon the posterior edge of that articular surface, and upon the inferior costa of the scapula, where it joins the articulation. When the scapula was viewed anteriorly, the head of the os hu meri was placed in a line behind the acromion but below it, and a wide space intervened be tween the dislocated head of the bone and the coracoid process, in which the fingers sunk deeply towards the glenoid cavity of the sca pula. When viewed posteriorly, the head of the os humeri was found to occupy the space between the inferior costa and spine of the scapula, which is usually covered by the infra spinatus and teres minor muscles. The tendon of the subscapularis muscle, and the internal portion of the capsular ligament, had been torn at the insertion of that muscle; but the greater part of the posterior portion of the capsular ligament remained, and had been thrust back with the head of the bone, the back part of which it enveloped. The supra spinatus muscle was put upon the stretch, the subscapularis was diminished by want of ac tion, and the infra-spinatus, and teres minor muscles were shortened and relaxed, as the head of the bone carried their insertions back wards. The tendon of the long head of the biceps muscle was carried back with the head of the bone, and elongated; but it was not torn. As to the changes in the bones, the head of the os humeri, and the outer edge of the glenoid cavity of the scapula, were in di rect contact, the one bone rubbing upon the other when the head of the os humeri was moved ; and this accounted for the sensation of crepitus at the early period of the disloca tion, as there was no fracture. The glenoid cavity was slightly absorbed at its posterior edge, so as to form a cup, in which the head of the bone was received, and this latter bone and the articular cartilage had been in some degree absorbed where it was in direct contact with the scapula, as well as changed by attrition during the seven years the patient lived." The surface of the original glenoid cavity, instead of being smooth and cartilaginous, vvas rough and irre gular, having elevations at some parts, and depressions at others. The extremity of the acromion was sawn off, to look for any little fragment of bone which might have been broken off, but not the smallest fracture could be per ceived.