REGION OF THE HIP. 



S9 



femur leaves its socket it passes down either anteriorly or posteriorly and we have 

 either an anterior or a posterior luxation. 



The attachment of the iliofemoral ligament immediately above the acetabulum 

 and of the ischiofemoral directly below also tend to prevent the head's emerging at 

 these places and favor its going anteriorly or posteriorly. Anterior luxations may be 

 either low or high. The primary luxation is a low one into the thyroid foramen. 



Nelaton's line 



Anterior superior spine 



Acetabulum 



Tuberosity of ischium 



FIG. 512. Innominate bone, resting on its inner side, to show the wedge-shaped formation of its outer sur- 

 face. The apex of the wedge is NtHaton's line, running from the anterior superior spine to the tuberosity of the 

 ischium; the anterior plane inclines downward and forward toward the pubis and the posterior plane inclines 

 downward and backward on the ilium. 



If then the thigh is rotated outward the head rises, and it becomes a pubic luxation. 

 Posterior luxations may also be either high or low. The primary luxation is a low 

 one either on the spine of the ischium or in the sciatic notch, and by rotation of the 

 thigh inward it becomes a high one on the dorsum of the ilium (Fig. 513). In cer- 

 tain very rare cases in which there has been an 

 excessive amount of twisting the rotation is 

 extreme and a form of dislocation called in- 

 verted is produced; it will be explained later. 

 Mechanism of the Production of 

 Luxations. The following should be borne 

 in mind : 



1 . The neck of the femur makes with the 

 shaft an angle of approximately 128 degrees. 



2. In speaking of inward and outward ro- 

 tation is meant inward and outward rotation 

 of the shaft of the femur. Thus if the head 

 (and neck) is pointing inward and we rotate 

 the shaft inward, the head rotates outward pos- 

 teriorly. If, however, we rotate the shaft in- 

 ward while the head is pointing outward then 

 the head moves inward anteriorly. Thus it is 

 seen that in rotating the shaft inward the head 

 is moved inward or outward according to its 

 original position. 



3. That while actually the axis of the 

 head and neck does not coincide with a line 

 drawn transversely through the condyles, 

 but inclines forward at an angle of 10 or 12 

 degrees, nevertheless for practical purposes 



we may consider that it does so coincide and normally points directly inward. 



4. The position of the greater trochanter can be recognized by its being directly 

 above the external condyle, and the position of the head by its being directly above 

 the internal condyle. 



5. The muscles may be disregarded in the production of luxations, and the 

 action of only the bones and ligaments considered. 



6. A luxation results from the capsule being made tense or even ruptured by a 

 leverage action of the bones, and the head then being thrust out on the anterior or 

 posterior plane. 



FIG. 513. Diagram illustrating the position 

 of the head in high and low dislocations on the an- 

 terior and posterior planes. 



