458 



SURGJCAL APPLIED ANATOMY, [chap. xix. 



the tension of the Y ligament, and of the ilio-psoas 



muscle. 



Nos. 2 and 3. The dislocations forwards. If the 



head after leaving the acetabulum simply moves a 



little forwards along 

 the inner edge of the 

 socket, the thyroid lux- 

 ation is produced. If 

 it goes farther and 

 moves upwards, the 

 pubic displacement will 

 result. The latter dis- 

 location is therefore 

 but an advanced form 

 of the first - named. 

 Whether the head will 

 remain in the thyroid 

 foramen or ascend on 

 to the pubes depends 

 on whether extension 

 and rotation outwards 

 accompanies the dis- 

 placement. If these 

 occur the pubic form 



. is produced. In these 



F;g. 42. Dislocation upon the Pubes . .* . 



(Bigelow). injuries the pectineus, 



gracilis, and adductors 



will be more or less torn, while the ilio-psoas, glutei, and 

 pyriform muscles are much stretched. The obturator 

 nerve may be stretched or torn, and in the pubic 

 luxation the anterior crural nerve may be involved. 

 The abduction and eversion of the limb noticed in 

 these luxations depend partly upon the position of 

 the head of the bone, fixed more or less by the 

 Y ligament, and partly upon the action of the gluteai 

 muscles and some of the small external rotators, 

 which are tightly stretched, The flexion of the 



