412 



SURGICAL APPLIED ANATOMY. [Chap. xix. 



the Y ligament, and in the forward displacements in 

 front of it. 



The anatomy of eacli form. Nos. 1 and 2. 



The dislocations backwards. Here the femoral head, 

 having been displaced in the way indicated, is carried 

 towards the dorsum or sciatic notch by the glutei, 



hamstring, and ad- 

 ductor muscles. 

 The bone having 

 taken a general 

 direction back- 

 wards, the height to 

 which it ascends de- 

 pends mainly upon 

 the nature of the 

 dislocating force, 

 and also upon the 

 extent of the rup- 

 ture in the capsule, 

 and the laceration 

 of the obturator 

 internus tendon 

 and other small 

 . external rotators. 



Fig. 40. Dislocation upon the Dorsum ilii m, , , , . , 



(Bigeiow). The dorsal disloca- 



tion is, therefore, 



a more advanced grade of the sciatic. The more 

 extreme the flexion and inward rotation at the time 

 of the accident the more likely is the dislocation to be 

 sciatic. More moderate flexion and inward rotation 

 will produce a luxation upon the dorsum. In the 

 dorsal luxation the head is above the obturator 

 internus tendon, while in the sciatic form it is below 

 it (Bigeiow). Morris has been able to find but one 

 case of direct dislocation of the femur backwards on 

 to the ischium. In every instance it passes first in a 

 downward direction, and then backwards. 



