432 THE INFERIOR EXTREMITY 



movement renders the relaxed ilio-femoral ligament tense,, and 

 it may be used as the fulcrum of a lever which has the femoral 

 shaft for its long arm and the neck for its short arm. The 

 movement of lateral rotation levers the head forwards over 

 the posterior margin of the acetabulum, and, by completing 

 the circumduction and finally extending the limb, the head is 

 made to travel medially and upwards into its socket. 



2. In the anterior group the method followed is much the 

 same as the foregoing, but the movements are carried out in 

 the reverse direction. The tense ilio-femoral ligament maintains 

 the femur in a position of extension, abduction, and lateral 

 rotation, and it must be relaxed by flexing the abducted thigh 

 in order to release the head from its pubic position. As the 

 thigh is elevated, the head descends to the level of the acetabulum, 

 and it is made to travel laterally by circumducting the fully 

 flexed thigh in a medial direction. Finally, the limb is extended, 

 and this movement carries the head forwards and medially into 

 the acetabulum. 



(3) PATHOLOGICAL DISLOCATIONS of the hip-joint are preceded 

 by atrophy of the surrounding muscles from disuse and by soften- 

 ing of the articular capsule. Sometimes, as in advanced tubercle, 

 the acetabular margin or the head of the femur is much eroded. 

 In these cases the joint cavity is often distended by fluid or 

 granulations, and the thigh is maintained in the position of semi- 

 flexion, since the capacity of the hip -joint is greatest in that 

 attitude. When the limb is adducted, the head of the bone 

 gradually perforates the weakened capsule, but this causes so 

 little pain that it may escape notice until the general condition 

 has been recovered from. 



It should be pointed out that pathological dislocations of 

 the hip-joint are always posterior, owing to the position of the 

 limb at the time of their occurrence. 



The Surgical Approach to the Hip-Joint is planned 

 so as to give good exposure while doing little damage. The 

 operation of excision yields excellent results, sometimes even 

 in cases of advanced tuberculous disease. As a rule a posterior 

 dislocation is present, or there may have been erosion of the 

 neck of the femur, so that the head lies loose in the acetabulum. 

 On this account the joint is best approached from behind 

 Kocher's postero-lateral route. 



The upper half of the incision corresponds to the lower 

 two-thirds of the line joining the posterior superior iliac spine 



