PRACTICAL CONSIDERATIONS : THE FEMUR. 



365 



Fig. 383. 



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may be insufficient to furnish reparative material. Any movement that might tear 

 the remaining connections between the fragments is, therefore, most undesirable. 

 The great length of the lower fragment, and the leverage thus exerted as a result of 

 any motion of the inferior extremity, together with the action of the powerful muscles 

 running from the pelvis to the thigh, make it especially difficult to keep the frac- 

 tured surfaces in close apposition, particularly if the small part of the neck is involved. 

 Impaction, even if very slight, may thus be a favorable circumstance, and should not 

 be broken up by rough handling. 



Intracapsular fractures, in spite of the scanty blood-supply, the presence of 

 synovial fluid, which is perhaps the most important unfavorable factor, and the mo- 

 bility of the lower fragment, do unite, but rather as an excep- 

 tion. As a rule, fractures at the base of the neck unite. 



Fracture of the shaft is most common at the middle, at 

 the point of greatest convexity of the forward curve, in spite 

 of the fact that here the bone is denser and its compact outer 

 wall thicker. At the upper third fracture is usually due to 

 indirect violence, at the lower third to direct violence. In the 

 former case it is apt to be oblique, in the latter transverse. 

 These lesions, as well as those of the lower end, just above the 

 condyles, will be considered in their relation to the muscles 

 that influence them (page 644). 



The lower epiphysis of the femur, the only one whose ossi- 

 fication begins before birth, — "with the exception of the occa- 

 sional early appearance of the osseous nucleus in the upper 

 epiphysis of the tibia" (Poland ), — is the last to join its diaphy- 

 sis, union occurring about the twentieth year. It has a cup- 

 shaped upper surface, which is higher externally. Its internal 

 level is just beneath the adductor tubercle. The epiphysis 

 includes all the articular surfaces of the lower end of the 

 femur. 



In the majority of the cases of disjunction of this epiphy- 

 sis the cause has been hyperextension of the tibia on the femur, 

 often combined with some twisting and traction upon the leg, 

 as when a boy hanging behind a cab has his foot caught be- 

 tween the spokes of a wheel. In twenty-seven out of sixty- 

 eight cases the lesion was caused in this way. 



The ligaments of the knee-joint are so powerful (as they 

 must be for security, on account of the shape of the bones that 

 enter into it) that when the leg is brought into .overextension 

 tremendous leverage is exerted on this epiphysis through the 

 crucial ligaments, the external and internal lateral ligaments, 

 and the popliteus muscle, aided by the gastrocnemius. Al- 

 though the latter is attached partly above the epiphyseal line, 

 the periosteum is torn off the lower end of the diaphysis down 

 to the extremely dense layer at the cartilaginous junction. 

 The muscle then becomes an important factor in carrying the 

 epiphysis forward — the usual displacement — and, aided by the 



popliteus, in rotating its posterior upper edge downward. The mechanism has been 

 compared to that of fractures of the radius in falls upon the hand, the posterior 

 ligament of the knee-joint bringing a cross-strain upon the epiphysis similar to that 

 conveyed to the radius by the anterior ligament of the wrist. 



The diaphysis projects into the popliteal space or through the skin, and has 

 caused grave injuries to vessels and nerves. Amputation has been required in a 

 large proportion of these cases, on account of these injuries or because of the de- 

 tachment of the periosteum and the suppuration that often follows it. The joint 

 is rarely involved, because the ligaments uniting the bones of the leg to the 

 epiphysis are more powerful than the cartilaginous connections of the latter with the 

 diaphysis. 



As might be expected, the chief growth of the femur taking place from this 



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Showing epiphyses of 

 femur. 



