38o 



HUMAN ANATOMY. 



-.^f^ 



.# 



femur becomes possible because of the firm connection between (a) the base of the 

 neck and the acetabulum through the unruptured portion of the capsule, and (d) 

 the two fragments through the attachment of muscles along the linea aspera. 

 These connections enable the limb to be used for traction, although the fracture 

 quite precludes the employment of circumduction and rotation. 



Allis summarizes the principles of his method by saying that the cardinal rule 

 applicable to every form of dislocation of the hip is : draw the head in the direction of 

 the socket ; apply a fulcrum at the upper part of the lever ; pry the head into the 



socket. 



The old view that the opening in the capsule was often a slit which required 

 enlargement before the head could be replaced has been shown (Allis and Morris) 

 to be fallacious. The inelastic character of the capsular fibres, the globular shape 

 of the femoral head, and the suddenness of application of the force (preventing 



stretching) make the rent in every 



case as large as the head ; it is not 



Fig. 398. infrequently larger. If, however, it is 



situated near the femoral attachment 

 of the capsule, it may leave a cuff of 

 the latter hanging from its pelvic ori- 

 gin over the acetabulum, and offering 

 a serious, if not insuperable, obstacle 

 to reduction. 



Congenital dislocation of the hip 

 may be unilateral or bilateral, and 

 while occasionally the result of intra- 

 uterine traumatism, is usually due to 

 an arrest of development of the ace- 

 tabulum. The head rests on the dor- 

 sum ilii, either directly upon the bone 

 or on the gluteus minimus. The cap- 

 sule is stretched and thickened to bear 

 the weight of the trunk. The tro- 

 chanters can be seen through the 

 glutei ; they are above Nelaton's line ; 

 there is usually lumbar lordosis to 

 compensate for the displacement pos- 

 teriorly of the centre of gravity. The 

 perineum is widened. 



Disease of the hip-joint is fre- 

 quent and grave. It may begin in 

 the epiphysis for the head, in the 

 synovial membrane, or, much more 

 rarely, in the articular cartilage. It 

 may be of any variety, but tuberculous disease outnumbers all others. 



Both the frequency and the gravity of disease of the hip-joint are due to : i, 

 the exceptional exposure of the joint to strains or traumatism on account of its im- 

 portance in carrying the weight of the trunk and in progression ; 2, the intra- 

 capsular situation of the upper femoral epiphysis ; 3, the relation of the joint to 

 some of the most powerful muscles of the body, so that great intra-articular pressure 

 is easily set up and with difificulty overcome ; 4, its enclosure by dense, unyielding 

 fibrous structures that increase tension after disease has begun ; 5, the thinness of 

 the non-articular plate of bone that separates it from the pelvis, and the presence 

 up to puberty of the Y-shaped cartilage which divides the acetabulum into three 

 bony segments (Fig. 353) ; 6, its deep situation, rendering the early symptoms in 

 many cases inconspicuous ; 7, the deprivation of fresh air and exercise, and often 

 of sunlight, involved in the immobilization of the joint. 



The disease is attended by certain symptoms having a definite anatomical basis : 

 I. Swelling, which is most easily demonstrated («) at the lower anterior portion of 

 the joint just internal to the ilio-femoral ligament, where the capsule is thin and the 



\ 



^■0 



Relation of the head of the femur to the innominate 

 bone in obturator luxation. 



