FLOW OF BLOOD THROUGH BONES AND JOINTS 



1653 



Periosteal arteriole 

 and venae comitantes' 

 Periosteal 

 capillaries 



Medullary 

 artery 



Cortical 

 - x " capillaries 



Endosteal 

 capillaries 



Medullary 

 sinusoids 



Central 

 enous sinus 



fig. 2. The blood vascular organization of diaphyseal tu- 

 bular bone represented diagramatically in transverse section. 

 [From Brookes (14).] 



fig. 3. A longitudinal section of cortical bone showing the 

 anastomosing and branching Haversian canals. The com- 

 municating canals between the Haversian canals are demon- 

 strated. [From Jaffe (70).] 



nally, they do not run vertically for more than short 

 distances soon deviating from a straight line. The 

 canals form a continuously anastomosing and ramify- 

 ing network (fig. 3). Beneath the articular cartilage 

 at the upper and lower ends of a bone, the canals run 

 transversely to the long diameter of the bone. Near 

 the surface of the bone, Haversian canals communi- 

 cate with the canals of the ground lamellae which 

 open to the external surface of the bone, and the 

 innermost canals lead into the medullary cavity. Re- 



cently the term "macrocanalicular system" has been 

 used to refer to the system in mineralized tissue which 

 is made up of Haversian and anastomosing Volkmann 

 spaces (68). It is generally stated that one or two 

 capillaries are present in an Haversian canal (79). A 

 single endothelial tube surrounded by a slight 

 adventitia has been described in Volkmann's canals. 



Lexer (86) had emphasized the role of the periosteal 

 arteries in bone nutrition, but more recent studies 

 indicate that the periosteal circulation may be scanty 

 (20), periosteal arteries being found rarely or only 

 with difficulty (i). Also, the notion of a periosteal 

 arterial penetration of compact bone has recently 

 been rejected as a result of microradiographic analy- 

 sis in the rabbit ( 16), and in the rat and human fetus 

 (13, 14). This opinion is further strengthened by a 

 study of nonischemic adult tubular bone (15). Ac- 

 cording to certain investigators (13-16), normal 

 diaphyseal blood flow is centrifugal, that is, passing 

 from the medullary arterial system outward through 

 the cortex into the periosteal and interfascicular capil- 

 laries of muscle. Drainage of compact bone is effected 

 either by way of periosteal capillaries or through 

 medullary sinusoids and the central venous channel. 

 Apparently, the vascular systems of bone and peri- 

 osteum are united, but only at the capillary level. 

 This would explain the survival of outlying bone cells 

 seen by Marneffe (88) in rat diaphysis nourished by 

 the periosteum alone. It also provides a basis for the 

 development of a collateral circulation as found in 

 Johnson's experiments in dogs (72). 



The obliquity of Haversian canals has been noted 

 by Cohn & Harris (29) and others. Brookes (13), 

 studying rat femora and tibiae as a whole, was able 

 to show how cortical vascular obliquity is in opposing 

 senses at either end of a long bone, the two regions 

 meeting by abrupt directional changes. In the adult 

 human tibia this change takes place at the inferior 

 metaphysis and may well be a factor in the delayed 

 healing of fractures at this site, where a rich venous 

 outflow would predispose to recurrent hematoma 

 formation. 



It seems likely that the normal arterial supply to 

 cortical capillaries is mediated by medullary end 

 arteries. This conception is supported by the findings 

 of Eletto (42) who noted the lack of anastomoses be- 

 tween branches of the principal nutrient artery in the 

 medulla. It would help to explain the occurrence of 

 irregular bone cell necrosis in the cortex produced by 

 the injection of particulate suspensions (75, 76), or by 

 interruption of the principal nutrient artery (10). 

 Epiphyses also seem to contain discrete circumscribed 



