Blood supply of long bones

Blood supply of Bones

1. BLOOD SUPPLY OF BONES Dr Thouseef A Majeed MS Ortho PG VMKVMCH Salem

2. Types of bones

3. Anatomy of a long bone Copyright 2009 John Wiley & Sons, Inc.

4. Bone tissue cell types Osteogenic cells – unspecialized stem cells Osteoblasts – bone builders Osteocytes – mature bone cells derived from osteoblasts Osteoclasts – bone ‘breakers’ are multinucleate

5. Bone receives 5-10% of cardiac output Bones that receive tenous blood supply scaphoid talus femoral head odontoid

6. Blood supply to long bone comes from three sources    Nutrient artery system Metaphyseal and epiphyseal system Periosteal system

7. Copyright 2009 John Wiley & Sons, Inc.

8. Nutrient foramen Oblique canal situated in the diaphysis of long bones. Nutrient canals slope away from the knee for femur tibia and fibula. Canal facing towards elbow in radius, ulna, and humerus 90% of long bones have single nutrient foramen in middle third of the shaft

9. Nutrient artery system All long bones have one or more nutrient arterites that enter through a nutrient foramen High pressure system that branches from major systemic arteries Enter the cortex through the nutrient foramen and enter the medullary canal T hen branches into ascending and descending branches Each branch sends lateral oriented arteriolar branches Ascending and descending branches travels to the end of the bone they anastomosis with metaphyseal and epiphyseal vessels

10. With in the cortex they give rise to branches , Some extending longitudinally along the axis of long bone while others proceed radially and ultimately forms capillaries with in the haversion system . Some arterioles transfers the entire cortex to reach and anastomose with periosteal arteriolar network. With in the marrow , Some arterioles are short and profusely branched to supply the capillaries for the marrow . This system supplies the inner 2/3 of mature bone via the haversion system.

11. Metaphyseal system Derived from the neighboring systemic vessels. These arteries directly go into the metaphyses and reinforce the metaphyseal branches of the primary nutrient artery .

12. Layers of Epiphysis

13. Epiphyseal arteries The epiphysis has openings that permit passage of large number of vessels into and out of the ossification centers. Growth plate itself is avascular & receives nutrition from 2 sources. Epiphyseal vessels that supply resting, germinal, proliferating, and upper hypertrophic cell layers by diffusion Metaphyseal vessels that supply zone of provisional calcification.

14. In young child, epiphyseal vessels are separated from metaphyseal vessels. Following growth arrest of the cartilage plate, there is an anastomoses between epiphyseal vessels, metaphyseal vessels, & terminal branches of nutrient artery. Obliteration of epiphyseal blood supply results in necrosis of epiphysis & deprives deeper cartilage cells of growth plate for their nutrition .

15. Longitudinal growth ceases &collateral circulation is not quickly restored, permanent closure of epiphyseal plate occurs. Epiphyseal vessels are responsible for permitting longitudinal growth to occur. Metaphyseal vessels nourish  osteoprogenitor cells , which lay down bone on cartilage matrix.

16. Anatomy of periosteum Periosteum consists of two layers outer fibrous and inner cambium layer. The fibrous layer contains fibroblasts The cambium layer contains progenitor cells that develop into osteoblasts .

17. Periosteal System Low pressure system that supplies the outer 1/3 of bone Forms an extensive network of vessels covers entire length of the bone shaft. Periosteal vessels send small branches through minute channels in cortex to supply about outer 1/3 of cortex.

18. Periosteal arteries are the arteries of periosteum being especially numerous beneath the muscular and ligamentous attachment. Beneath the periosteum they divide into branches and thereby entering the Volkmann’s canals to supply the outer one third (1/3) portion of the cortex.

19. Paediatric Blood supply Circulation in pediatric bone differs from adult circulation due to requirements of growth & presence of epiphyseal plate. Terminal branches of nutrient artery, along with metaphyseal vessels, approach growth plate in a parallel relationship. Branches are so numerous as they reach growth plate that there is almost one vessel for each column of cartilage cells.

20. In final few mm before terminal arteriole reaches cartilage, it is encased in a tube of enchondral bone Children, while periosteum is actively engaged in circumferential bone growth, blood supply in this area is much more abundant than it is in adult

21. Venous drainage of bone Long bones posses a large venous sinus Long bones drains into central venous sinus ,from Central venous sinus through nutrient vein, periosteal veins and emissery veins it drains out Metaphyseal / epiphyseal veins – drain blood from the proximal and distal regions of the medullary cavity Periosteal veins – drain blood from the ends of long bones and the red bone marrow

22. Physiology of blood flow 5-20ml/min in 100gm of wet bone tissue 4-10% of resting cardiac output Metaphysis has highest blood flow stimulating factors sympathetic nerves acid metabolites increased or decreased CO 2 tension

23. Blood Flow throug the bone The direction and extent of blood flow with in the diaphyseal cortex remains controversial There are two theories behind this Centrifugal flow and centripetal flow Centrifugal flow With the blood entering the endosteal aspect from the medullary nutrient system and flowing through the periosteal surface .

24. Centripetal flow The medullary nutrient system is interpted ,the periosteal system provides a reverse supply and blood flow becomes centripetal (Towards the center)

25. Periosteal flow The role of periosteal vessels has not been clearly defined. Periosteal system originates mainly from the surrounding muscles and provide the blood supply to the outer one third to one half of cortex . At the outer aspect of the cortex many thin walled vessels with in the haversian canal are observed to be in continuity with arterioles with in the periosteum .

26. Metaphysal and Epiphysal flow The end of the long bones are supplied by vessels that enter the metaphysis and epiphysis through small foramina at the periphery. After entering the bone these arterioles branch into arterial arcades, forming a dense interlocking network The vessels becoming progressively smaller in caliber as they approach subchondral zone In subchondral zone they terminate as small capillary loops The epiphyseal,Metaphyseal arterioles anastomose with terminal twigs of medullary nutrient artery and contribute 20-40% of the total supply of the entire bone

27. Variations In Cortical Blood Flow In a normal extremities, not all blood vessels are functional at the same time. Blood transport occurs through a limited number of vessels, the other being considered in a resting state Under certain conditions(fracture of opposite extremities) a grater number of blood vessels become actively functional and demonstrate by micro angiographic methods.

28. Impairment of diaphyseal blood supply If the circulation in bone marrow and periosteum is interrupted , an increase in metaphyseal blood flow occurs If circulation through nutrient arteries and metaphyseal vessels are interrupted, proliferation of periosteal vessels and increased periosteal blood flow takes place(often accompanied by periosteal newborn formation) When the blood flow through the nutrient artery is interrupted, approximately 2/3 rd of the cortex becomes ischeamic and necrotic, outer third remains viable .

29. Reversal of venous blood flow Under certain circumstances blood flow through large peripheral veins can be reversed into alternative routes with in the medullary cavity When there is interferance with venous return through main veins of extremities , the medullary pressures with in the regional long bones are increased .so collateral venous return takes place through medullary venous channels.

30. Blood supply of head and neck of femur

31. Blood supply of scaphoid

32. Blood supply of talus

33. Applied aspects Periosteal stripping If the periosteum is stripped and left detached from the cortex and nutrient artery is preserved, only outer third of the cortex become ischeamic and necrotic ( often followed the development of periosteal newborn formation)

34. Intra medullary nail Unreamed intramedullary nails preserve endosteal blood supply Reaming devascularizes inner 50-80% of the cortex and delays revascularization of endosteal blood supply. Loose fitting nails spare cortical perfusion and allow more rapid reperfusion

35. Tight fitting nails compromise cortical perfusion and reperfusion is slow If the nutrient artery is supressed (intra medullary nailing) compensatory periosteal vascular proliferation occurs and the viability of cortex to a great extent . When the medullary nutrient blood supply is interepted + stripping of periosteum = entire thickness of cortex becomes necrotic

36. Nonunion scaphoid fracture neck of femur fracture Talus fracture Distal tibial fractures Should be fixed due to the nutrient artery divides into three ascending branches & a single descending branch. Bulk of muscle is more over proximal tibia than distal tibia

37. Osteomyelitis Hair pin arrangements of arterioles Sluggish flow Tortous blood vessels and skimming of bacteria

38. References Turek Apleys Inderbir Singh text book of histology

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