THE FEMUR 



249 



in a fan-like radiation to the opposite side of the bone; the other, having origin in the lateral 

 (outer) portion of the shaft and arching upward and medially to end in the upper surface of the 

 greater trochanter, neck and head. These two systems intersect each other at right angles. 



"A. Medial (Compressive) System of Trabeculce. As the compact bone of the medial (inner) 

 part of the shaft nears the head of the femur it gradually becomes thinner and finally reaches the 

 articular surface of the head as a very thin layer. From a point at about the lower level of the 



FIQ. 247. Frontal longitudinal midsection of upper femur. 



lesser trochanter, 2| to 3 inches from the lower limit of the articular surface of the head, the 

 Irabeculao branch off from the shaft in smooth curves, spreading radially to cross to the opposite 

 "ide in two well-defined groups: a lower, or secondary group, and an upper, or principal group. 



'a. The Secondary Compressive Group. This group of trabeculae leaves the inner border of the 

 laft beginning at about the level of the lesser trochanter, and for a distance of almost 2 inches 

 long the curving shaft, with which the separate trabeculsG make an angle of about 45 degrees. 



