232 APPLIED ANATOMY. 



rises but also goes backward, or the scapula comes forward, so that the end of the 

 clavicle may rest on the acromion process. In this dislocation the base of the cora- 

 coid process, on which the clavicle rests and to which it is bound by the conoid and 

 trapezoid ligaments, acts as a fulcrum. The scapula rotates on an anteroposterior 

 axis, passing through the base 6f the coracoid process, and as the inner portion of 

 the bone rises, its outer portion, that is, the acromion process, descends and is torn 

 from the outer end of the clavicle. 



The deformity produced by the upwardly projecting end of the clavicle is typical. 

 The luxation may be complete or incomplete. When incomplete the injury is con- 

 fined to the acromioclavicular joint; when complete the conoid and trapezoid ligaments 

 are partially or wholly ruptured. 



The joint usually possesses a poorly developed fibrocartilage and inclines upward 

 and outward so that the inclination favors the rise of the clavicle. When the conoid 

 and trapezoid ligaments are not ruptured they serve as the axis on which the scapula 

 rotates forward so that the outer end of the clavicle slips backward on the acromion 

 process. This led Hamilton to describe these luxations as backward luxations. In 

 rare instances the end of the clavicle seems to be displaced posteriorly without 

 rising above its normal level. We reported one such case in the Annals of 

 Surgery several years ago. Reduction of the displacement is easily effected, but 

 the same difficulty in keeping the bone in place has been experienced in this disloca- 

 tion as in dislocations of the inner extremity. Bandages going over the shoulder 

 and down the arm ,and under the elbow are commonly employed. The only sure 

 way of keeping the clavicle in its proper position is to operate and fasten it to the 

 acromion with wire or chromicised catgut. When the patient is put in bed the bones 

 are readily replaced. 



Downward dislocation though rare does seem to have sometimes occurred. 

 From the fact of the under surface of the clavicle resting almost or quite on the 

 coracoid process it is difficult to see how it is possible for this injury to take place. 

 It must take place while the scapula is violently twisted on the clavicle. The 

 displacement is readily reduced and shows but little tendency to recurrence. 



DISLOCATIONS OF THE SHOULDER. 



The dislocations of the shoulder are to be studied from the anatomical and not 

 from the clinical standpoint. A knowledge of the anatomical construction of the 

 various parts involved is to be applied to the explanation and elucidation of the 

 methods of production, the signs and symptoms observed, and the procedures neces- 

 sary for reduction. 



Classification, For our purpose there are two forms of dislocations of the 

 shoulder anterior and posterior. These two forms are entirely different and must 

 be studied separately. 



Anterior Dislocation. An anterior luxation is one in which the head of the 

 humerus is either on or anterior to the long head of the triceps muscle at the lower 

 edge of the glenoid cavity. 



Posterior Dislocation. A posterior luxation is one in which the head goes poste- 

 rior to the glenoid cavity and usually rests beneath the spinous process of the scapula, 

 hence this is called subspinous dislocation. 



When the head is luxated anteriorly it may pass so far inward as to rest between 

 the coracoid process and the clavicle; hence this form is called subclavicular. 



When the head does not pass so far inward, but rests on the anterior edge of the 

 glenoid cavity below the coracoid process, it is called a sub coracoid luxation. 



When it rests on the anterior and lower edge of the glenoid cavity, sometimes 

 on the long head of the triceps muscle or just anterior to it, it is called a subglenoid 

 luxation. 



ANTERIOR DISLOCATION OF THE SHOULDER. 



The head of the bone almost always comes out through the anterior portion of 

 the capsule and slips beneath the coracoid process. From this point it may shift its 

 position either a little farther inward, when it is called a subclavicular luxation, or a 

 little farther downward and outward, when it receives the name of subglenoid. 



