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HANDBOOK OF PHYSIOLOGY 



CIRCULATION II 



1 2 patients suffering from painful osteoporosis follow- 

 ing injury, found an increased blood flow amounting 

 to 5 to 60 per cent in the affected limb. Also, in severe 

 inflammatory processes an actual coalescence of 

 several Haversian canals takes place, the bony parti- 

 tion between them disappearing with the formation 

 of large spaces in bone containing numerous blood 

 \ essels and considerable vascular granulation. The 

 process is not confined to the Haversian system, but 

 also involves the spongy tabeculae. The marrow also 

 becomes extremely vascularized, as a result of the 

 proliferation of the existing vessels (71). 



reduction of blood supply. According to Haslhofer 

 (58) the richness of anastomoses in long bones pre- 

 vents bone infarction even when the blood supply to 

 the nutrient artery is interrupted. On the other hand, 

 Axhausen & Bergmann (2) present clinical instances 

 of aseptic bone necrosis which they ascribe to interrup- 

 tion of local blood supply. Also, Phemister (96, 97) 

 has published radiographic and pathologic descrip- 

 tions of lesions which he considers to be the result of 

 marrow infarction. 



Since the production of bone and marrow infarcts 

 in animals was generally considered impossible by 

 conventional means, earlier investigators resorted to 

 extensive stripping procedures or to the production of 

 multiple small emboli designed to occlude large num- 

 bers of capillaries. Thus, Brunschwig (17) attempted 

 to produce infarction of the marrow of the femur in 

 dogs by stripping the entire periosteum and simulta- 

 neously cutting the nutrient artery. Despite this ex- 

 tensive trauma, no evidence of infarction was seen in 

 adult dogs. Among the injection experiments are 

 those of Wollenberg (115) who injected talc into the 

 femoral artery of dogs and observed areas of necrosis 

 in metaphyses and epiphyses. Bergmann (6), on the 

 other hand, could find no changes in epiphyses, al- 

 though he saw widespread necrosis of cortical bone 

 after the injection of particles of silver suspended in 

 gum arabic, and Kistler (75-77) could find no in- 

 farcts following ligation of the nutrient artery of the 

 femur in rabbits. However, the injection of suspen- 

 sions of charcoal in acacia and of masses of aggluti- 

 nated bacteria, under unmeasured but admittedly 

 high pressure, produced areas of necrosis in the center 

 of the metaphyses. 



Huggins & Wiege (65) seem to have been the first 

 to report changes following occlusion of the nutrient 

 artery only. In both mature and immature rabbits 

 ligation of the nutrient vessels to the femur was fol- 

 lowed in all instances by infarction of the marrow. 



Although in a few cases there was some periosteal and 

 endosteal reaction above the operative site, no evi- 

 dence of bone infarction was found. In a recent study 

 Brookes (12) has shown that occlusion of the princi- 

 pal nutrient canal of the femur in day-old rabbits 

 produces an initial shortening, followed by equaliza- 

 tion, and then a final absolute shortening of 3 per cent 

 in the occluded femur. 



Variations in nutrition of the growth cartilage will 

 cause shortening or lengthening of long bones. Thus, 

 interruption of the medullary arteries and diversion 

 of blood to the growth cartilage presumably will ac- 

 count for the increased growth rate observed in long 

 bones affected by a variety of conditions, such as 

 fractures, chronic infections, and tumors (45). Occlu- 

 sion of the nutrient canal may result in diversion of 

 blood into the epiphyseal and metaphyseal arteries, 

 with possible ischemia of the diaphysis. It is probable 

 that while collateral circulation is developing in the 

 bone extremities, a diminution in the femoral blood 

 supply to the growth cartilages occurs, thus account- 

 ing for the growth lag of occluded femora noted by 

 Brookes (12) in the first 30 days. With the establish- 

 ment of a collateral circulation by means of anasto- 

 moses between the metaphyseal arteries and the 

 principal nutrient artery, blood flow near the growth 

 cartilage is increased bringing about equalization in 

 the length of occluded and normal femora in the 

 intermediate growth phase. In the final phase, 120 to 

 150 days, a relative decrease in the nutrition of the 

 growth cartilages must occur to account for the 3.7 

 per cent retardation in femoral growth seen at ma- 

 turity. The reason for this is not clear. However, it 

 seems probable that towards the end of growth the 

 collateral circulation is not quite able to furnish the 

 same quantity of blood to die medullary artery as 

 when the nutrient artery is also available as a supply 

 channel (12). These results may be compared with 

 the evidence of bone lengthening after fractures in 

 children (22) in whom presumably the same local 

 vascular mechanism is active that determined the 

 growth curve of occluded femora in rabbits. 



It is generally thought that the disturbances on the 

 venous side produced by obliterating the vein accom- 

 panying the nutrient artery is slight, because of the 

 profuse venous drainage at the bone extremities (57) 

 and at the surface of the diaphysis (16). 



Oxygen in the Blood of Bones 



Ham (53) has shown by measurements in the dog's 

 radius that bone cells, if they are to survive, can gen- 



