766 DISEASES OE THE SHOULDER-JOINT. 



upwards, the head of the bone being discovered in front of and above 

 the glenoid cavity of the scapula. As the biceps muscle antagonises 

 this movement, displacement can only occur when that muscle is 

 partially relaxed, as it would be, for instance, during simultaneous 

 flexion of the elbow-joint. For this reason luxation of the shoulder- 

 joint results most frequently from falls in jumping. A sudden check 

 to the movement of the lower portions of the leg may also bring it 

 about. Hertwig saw several such displacements, on account of 

 the feet striking against some obstruction in leaping. Excessive 

 movements of abduction may also result in the head of the humerus 

 being displaced inwardly beyond the glenoid cavity of the scapula. 



Symptoms. The accident is distinguished by excessive lameness, 

 which appears suddenly, and is most marked when the leg is being 

 moved. Passive movement of the joint is also interfered with. 

 Whilst there is much difficulty in flexing, and still more in extending, 

 the joint, abduction and adduction are abnormally easy, and the 

 leg appears shortened. Provided swelling be not excessive, dislocation 

 of the head of the bone can be discovered by palpation. Pressure 

 on the parts produces pain. Complications, like fracture of the scapula 

 or humerus, often coexist. 



Prognosis and course. The results of many observations seem 

 to indicate that even complete luxation, if early reduced, can be 

 cured in two to three weeks. Smith, after reducing a supposed 

 dislocation under chloroform, caused the horse to be moved, and it 

 then showed no distinct lameness ; eight days later it was nearly 

 sound. The diagnosis, however, in this case is not beyond question. 

 In other cases reduction, even under anaesthesia, being impossible, 

 chronic lameness remains. In working-horses, it is best to wait 

 for eight to fourteen days after reduction, and if in this time no 

 improvement is manifest, the animal should be slaughtered. 

 Reduction being easier in small animals, the prognosis is correspondingly 

 more favourable. 



Treatment. In large animals, which stand quietly, attempts 

 may be made to reduce the dislocation without casting. Siedam- 

 grotzky advises that one man should hold the animal's head, another 

 draw the leg forward, and a third press on the knee-joint to extend 

 it, whilst the operator endeavours to return the head of the humerus 

 to the joint cavity by strong pressure. Should this fail, the animal 

 must be cautiously cast and the attempt repeated. To produce 

 muscular relaxation anaesthesia is necessary, but if fracture of the 

 glenoid portion of the scapula coexist with luxation, the humerus 

 will not remain in proper position. A noose is passed round the 



