FLOW OF BLOOD THROUGH BONES AND JOINTS 



1657 



found in nutritional diseases such as scurvy and 

 rickets, and septic infarction with abscess formation 

 in tuberculosis and other forms of bacteremia (23). 



Arterial blood from the terminal arborizations in 

 the cortex, derived from the medullary arterial sys- 

 tem, empties into a vascular lattice contained in the 

 canals of Havers and Volkmann (16). Here the circu- 

 lation is probably very sluggish and, besides move- 

 ment up and down the diaphysis, blood may be 

 shifted into either medulla or periosteum depending 

 upon functional variations in opposing muscles and 

 hematopoietic activity in the marrow. According to 

 Branemark (11) blood flow in bone capillaries is 

 fairly steady and the velocity is greater than in mar- 

 row capillaries. Externally, the vascular lattice of the 

 cortex connects with the osteogenic capillary layer; 

 internally, with the medullary sinusoids. The former 

 route to the systemic veins is direct and probably 

 drains most of the blood circulating in the cortex. The 

 latter route is indirect, through the sinusoids, into the 

 central venous sinus, and thence via the nutrient vein 

 at the bone extremities into periarticular veins (16). 



Lamas et al. (80) have pointed out that a relatively- 

 slow blood flow in bone should be expected, since 

 none of the three functions of long bones, mechanical 

 support of the body, storage of calcium salts, and 

 hematopoiesis, needs a rapid circulation. In this con- 

 nection, it may be noted that the arrangement of 

 blood vessels within bone favors a slow circulation. 

 Thus, the nutrient artery describes many curves 

 before entering bone and after dividing into ascend- 

 ing branches which run through the marrow, it ends 

 in wide blood spaces close to the epiphyses. These 

 blood spaces are in close contact with thin-walled 

 veins of wide caliber. This arrangement of blood 

 vessels reduces the pressure and speed of circulation 

 in the arteries, and enables the vein to carry sub- 

 stances quickly away from the blood spaces: hence 

 the efficacy of therapeutic injections into marrow. 



Few quantitative studies of blood flow through 

 bone have been made, [ones (73), who studied the 

 uptake rate of a radioactive colloid which is highly 

 selected by marrow cells, found a minimal circula- 

 tion through the red marrow in the rabbit amounting 

 to 7 per cent of the circulating blood volume per min. 

 A corresponding value for man would be about 

 300 ml. 



The blood flow through human bone has been 

 studied by measuring the rate of clearance of I 131 from 

 bone marrow (94). Xo apparent correlation was 

 found between marrow clearance rates and hemo- 

 globin level, leucocyte count, body temperature, or 



blood pressure. The intravenous injection of hexa- 

 methonium bromide, a ganglionic blocking agent, 

 reduced the clearance rate of marrow, and this ap- 

 pears to be directly related to the fall in blood pres- 

 sure. Conversely, the injection of Paredrine resulted in 

 a distinct increase in the clearance rate from the 

 marrow, presumably as a result of the sympathomi- 

 metic action of the drug. A decreased flow through 

 the perfused tibia of the dog can be produced by 

 stimulating sympathetic nerve fibers or by adding 

 Adrenalin to the perfusion fluid (39). 



Plethysmographic measurements of blood flow 

 through the normal humerus of man have been made 

 by Edholm et al. (41). They report a blood flow 

 through the nutrient artery of 0.5 to 1.0 ml per 100 ml 

 of bone per min. They point out that this value may 

 represent only half the total flow, for the periosteal 

 vascular supply is not included. They calculate on the 

 basis of these measurements that the total skeletal 

 blood flow should be 74.5 ml per min, although they 

 concede that this is bound to be an underestimation, 

 for bones with an active marrow are more vascular 

 than the humerus. The above measurements are much 

 lower than the values of 3.5 to 41 ml per 100 g bone 

 per min found in perfusion experiments using the 

 tibia of the dog (40). 



hyperemia. Blair (7) has suggested that alternating 

 ischemia and hyperemia maintain normal bone calcifi- 

 cation and aid healing after a fracture. In this con- 

 nection it should be noted that hyperemia has long 

 been thought to be the physiological basis for localized 

 deossification. Thus, Leriche & Policard (83) state: 

 "If by any process whatever, the activity of the circu- 

 lation is increased in the vicinity of bone, the latter 

 becomes rarefied." Also, Greig (52) has written: 

 "Every trauma of bone is followed by a reactionary 

 local hyperemia, and every disease resulting in bone 

 rarefaction or decalcification is accompanied by a 

 more or less copious and prolonged increase of the 

 arterial and capillary circulations." De Lorimer et al. 

 (87) interpret their radiological studies showing areas 

 of bone rarefaction as being the result of localized 

 reflex hyperemia. They believe this may be produced 

 by trauma even of minor degree as in simple contu- 

 sions, sprains, or overenergetic physical therapy, or 

 by infection or neoplasms. 



Although the above statements seem to rest more 

 on logic than on observable facts, it seems clear that 

 vascular resorption of bone is related to definite circu- 

 latory changes. Thus, Miller & cle Takats (91), who 

 carried out plethysmographic studies of blood flow on 



