Development of Femur 



461 



means always, it passes inwards at a right angle from the shaft, the 

 head of the bone sinking even below the level of the top of the great 

 trochanter. At this time the compact wall becomes thinned, and 

 much of the cancellated tissue which it encases undergoes fatty 

 degeneration and absorption. Fracture of the femoral neck is, in such 

 circumstances, very apt to occur. 



The femur has five centres of ossification ; the centre for the 

 diaphysis, or shaft, extends also into the neck. This 

 is an important exception to the rule that only the 

 epiphysis of a long bone enters into the formation 

 of a joint ; in the case of the hip some of the dia- 

 physis is enclosed within the capsule. 



The knee-epiphysis begins to ossify in the ninth 

 month of fcetal life : a fact of importance in medical 

 jurisprudence. The head begins to ossify in the 

 first year, the great trochanter in the fifth, and the 

 lesser in the thirteenth year. 



The epiphyses join the shaft, in the inverse order 

 of their development, at the seventeenth, eighteenth, 

 nineteenth, and twentieth years. 



Increase in the girth of a bone depends upon 

 deposit in the periosteum ; increase in length by 

 growth in the junction-cartilages. As the lower 

 epiphysis of the femur is the last to join (twentieth 

 year), its integrity is very essential to the growth of Ossification of femur 

 the limb ; similarly, the scapular epiphysis of the 

 humerus(p. 260) is the important one in the growth of the arm. In ex- 

 cision of the knee-joint, the surgeon guards the lower junction-cartilage, 

 so as to diminish to the utmost the amount of the subsequent and 

 inevitable shortening of the limb. 



Fracture of the femur may occur in any part of the bone; 

 reference will be made here to certain special varieties of fracture 

 only. Before manhood the lower epiphysis may be ' unglued ' from 

 violence, and the bellies of the gastrocnemius, which arise from the 

 condyles, may tilt the upper border of the epiphysis back into the 

 popliteal space and against the artery. If there be difficulty in 

 keeping the surfaces in apposition, as I have known to happen, the 

 knee must be kept slightly bent, and, if necessary, the tendon of 

 Achilles divided, so as to relax all muscular traction. Complete dis- 

 placement of these wide surfaces rarely occurs. 



Fracture tJirough the epiphysis is apt to be followed by arrest of 

 growth of the bone, and by stiffness of the knee. 



In fracture above the condyles of the fully ossified bone there 

 is often no displacement whatever, especially if the plane be trans- 

 verse ; but if it be oblique, the lower fragment is most likely thrust 

 backwards, the plane of fracture passing from behind, downwards and 



