322 Anatomy Applied to Medicine and Surgery. 



2. Dislocation into the vicinity of the Sciatic 



Notch. The same kind of accidents may cause 

 this, as are responsible for the dorsal iliac variety, with 

 the exception that the limb at the time of the receipt of 

 the injury is less flexed and less rotated inwards than in 

 the case of the dorsal iliac variety. The condition of the 

 soft parts is much the same in each of these forms of dis- 

 location. The head, however, in this variety, rests in the 

 vicinity of the great sciatic notch (often upon the spine of 

 the ischium), while the great toe of the dislocated limb is 

 generally pointing towards the ball of the great toe of the 

 sound limb. Bigelow describes what he calls a disloca- 

 tion "below the tendon of the obturator internus," in 

 which this tendon lies between the head of the femur and 

 the acetabulum. 



3. Dislocation into the Thyroid Foramen is 

 generally caused by falls or violence received, when the 

 limbs are abducted or widely separated. When, in this 

 form of dislocation, the head of the femur leaves the ace- 

 tabulum, it slips, generally, forwards, so as to rest on the 

 thyroid foramen. The limb is slightly flexed and abduct- 

 ed, and the foot points forward, or is somewhat everted. 

 There is lengthening of the limb from half an inch to two 

 inches. The psoas, iliacus and the adductors are over- 

 stretched and tense, whereas, the posterior external rota- 

 tors are not much affected. The flexion and abduction 

 are attributed to the influence of the Y ligament by 

 Bigelow, though Gunn states, that it is impossible for the 

 head of the bone to occupy the thyroid foramen without 

 complete rupture of this ligament. The abduction is in 

 all probability due, partly to the head of the femur rest- 

 ing on the inclined plane formed by the ascending ramus 

 of the ischium and the descending ramus of the pubes, 



