410 SURGICAL APPLIED ANATOMY. [Chap. xix. 



General facts. In all these dislocations of the 

 hip, (a) the luxation occurs when the limb is in the 

 position of abduction ; (6) the rent in the capsule is 

 always at its posterior and lower part ; (c) the head 

 of the bone always passes at first more or less directly 

 downwards ; (d) the Y ligament is untorn, while 

 the ligamentum teres is ruptured. 



(a) It is maintained that in all luxations at the 

 hip, the pelvis and femur are in the mutual position 

 of abduction of the latter at the time of the accident. 

 The direction of the neck of the femur and of the 

 acetabulum, and the position of the cotyloid notch, all 

 favour dislocation in the abducted posture. The 

 lower and inner part of the acetabulum is very 

 shallow, and the lower and posterior part of the 

 capsule is very thin. In abduction, the head of the 

 bone is brought to the shallow part of the acetabulum; 

 it moves more than half out of that cavity ; it is 

 supported only by the thin weak part of the capsule, and 

 its further movement in the direction of abduction is 

 limited only by the pectineo- femoral ligament, a 

 somewhat feeble band. In abduction the round 

 ligament is slack, and in abduction with flexion both 

 the Y ligament and the ischio-femoral ligaments are 

 also relaxed. In the position of abduction, therefore, 

 no great degree of force may be required to thrust the 

 head of the bone through the lower and posterior part 

 of the capsule, and displace it downwards. 



(b) The above being allowed, it will be understood 

 that the rent in the capsule is always at its posterior 

 and lower parts. " Generally the rupture is jagged 

 and irregular, but will be found to extend more or 

 less directly from near the shallow rim of the aceta- 

 bulum, across the thin portion of the capsule to the 

 femur near the small trochanter, and then to run 

 along the back of the ligament close to its attachment 

 to the neck of the bone " (Henry Morris). 



