Avascular necrosis
Encyclopedia
Avascular necrosis is a disease where there is cellular death (necrosis
) of bone components due to interruption of the blood supply. Without blood, the bone tissue dies and the bone collapses. If avascular necrosis involves the bones of a joint
, it often leads to destruction of the joint articular surfaces (see Osteochondritis dissecans
).
, excessive steroid
use, post trauma, caisson disease (decompression sickness), vascular compression, hypertension
, vasculitis
, arterial embolism
and thrombosis
, damage from radiation
, bisphosphonates (particularly the mandible), sickle cell anaemia, Gaucher's Disease
, and deep diving
. In some cases it is idiopathic
(no cause is found). Rheumatoid arthritis
and lupus
are also common causes of AVN. Prolonged, repeated exposure to high pressures (as experienced by commercial and military diver
s) has been linked to AVN, though the relationship is not well-understood.
and are the first to die after reduction or removal of the blood supply, usually within 12 hours. Experimental evidence suggests that bone cell
s (osteocytes, osteoclasts, osteoblasts etc.) die within 12–48 hours, and that bone marrow fat cells die within 5 days.
Upon reperfusion, repair of ischemic bone occurs in 2 phases; First, there is angiogenesis
and movement of undifferentiated mesenchymal cells from adjacent living bone tissue grow into the dead marrow spaces, as well as entry of macrophage
s that degrade dead cellular and fat debris. Second, there is cellular differentiation
of mesenchymal cells into osteoblast
s or fibroblast
s. Under favorable conditions, the remaining inorganic mineral volume forms a framework for establishment of new, fully functional bone tissue.
, knee
, and hip. The classical sites are: head of femur, neck of talus and waist of scaphoid.
Clinical avascular necrosis most commonly affects the ends (epiphysis
) of long bones such as the femur
(the bone extending from the knee joint to the hip joint). Other common sites include the humerus
(the bone of the upper arm), knees, shoulders, ankles and the jaw
. The disease may affect just one bone, more than one bone at the same time, or more than one bone at different times. Avascular necrosis usually affects people between 30 and 50 years of age; about 10,000 to 20,000 people develop avascular necrosis of the head of the femur in the US each year. When it occurs in children at the femoral head, it is known as Legg-Calvé-Perthes syndrome
.
, when it is usually diagnosed and treated by dental and maxillofacial surgeons.
In the early stages, bone scintigraphy and MRI are the diagnostic modalities of choice.
X-ray images of avascular necrosis in the early stages usually appear normal. In later stages it appears relatively more radio-opaque due to the nearby living bone becoming resorbed secondary to reactive hyperemia. The necrotic bone itself does not show increased radiographic opacity, as dead bone cannot undergo bone resorption
which is carried out by living osteoclast
s. Late radiographic signs also include a radiolucency area following the collapse of subchondral bone (crescent sign
) and ringed regions of radiodensity resulting from saponification and calcification of marrow fat following medullary infarcts.
or metal on metal (MOM) resurfacing. It is a form of a THR, however in this procedure, only the head of the femur is removed as opposed to a THR in which the entire neck is removed. MOM resurfacing is still experimental in America but has been endorsed in Great Britain as an excellent alternative to a THR. A MOM Resurfacing may not be suitable in all cases of Avascular Necrosis, its suitability depends on how much damage has occurred to the femoral head of the patient, bone is always undergoing change or remodelling. The bone is broken down by osteoclasts and rebuilt by osteoblasts. Some doctors also prescribe bisphosphonates (e.g. alendronate
) which reduces the rate of bone breakdown by osteoclasts, thus preventing collapse (specifically of the hip) due to AVN.
Other treatments include core decompression, where internal bone pressure is relieved by drilling a hole into the bone, and a living bone chip and an electrical device to stimulate new vascular growth are implanted; and the free vascular fibular graft (FVFG), in which a portion of the fibula, along with its blood supply, is removed and transplanted into the femoral head.
Progression of the disease could possibly be halted by transplanting nucleated cells from bone marrow into avascular necrosis lesions after core decompression, although much further research is needed to establish this technique.
and baseball
careers of star athlete Bo Jackson
.
In addition to the athletes listed, AVN has affected musicians including Andy Bell
of the electronica
/pop
duo Erasure
has had the condition and replaced both hips.
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
) of bone components due to interruption of the blood supply. Without blood, the bone tissue dies and the bone collapses. If avascular necrosis involves the bones of a joint
Joint
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...
, it often leads to destruction of the joint articular surfaces (see Osteochondritis dissecans
Osteochondritis dissecans
Osteochondritis dissecans , often abbreviated to OCD or OD, is a joint disorder in which cracks form in the articular cartilage and the underlying subchondral bone. OCD is caused by blood deprivation in the subchondral bone. This loss of blood flow causes the subchondral bone to die in a process...
).
Causes
There are many theories about what causes avascular necrosis. Proposed risk factors include, chemotherapy, alcoholismAlcoholism
Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
, excessive steroid
Glucocorticoid
Glucocorticoids are a class of steroid hormones that bind to the glucocorticoid receptor , which is present in almost every vertebrate animal cell...
use, post trauma, caisson disease (decompression sickness), vascular compression, hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
, vasculitis
Vasculitis
Vasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
, arterial embolism
Arterial embolism
Arterial embolism is a sudden interruption of blood flow to an organ or body part due to an embolus adhering to the wall of an artery and blocks the flow of blood, the major type of embolus being a blood clot...
and thrombosis
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
, damage from radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
, bisphosphonates (particularly the mandible), sickle cell anaemia, Gaucher's Disease
Gaucher's disease
Gaucher's disease is a genetic disease in which a fatty substance accumulates in cells and certain organs.Gaucher's disease is the most common of the lysosomal storage diseases. It is caused by a hereditary deficiency of the enzyme glucosylceramidase. The enzyme acts on the fatty acid...
, and deep diving
Deep diving
The meaning of the term deep diving is a form of technical diving. It is defined by the level of the diver's diver training, diving equipment, breathing gas, and surface support:...
. In some cases it is idiopathic
Idiopathic
Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...
(no cause is found). Rheumatoid arthritis
Rheumatoid arthritis
Rheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development...
and lupus
Lupus
Lupus most commonly refers to the disease systemic lupus erythematosus.Lupus may also refer to:-Medicine:* Lupus erythematosus, a chronic autoimmune disease with several different forms...
are also common causes of AVN. Prolonged, repeated exposure to high pressures (as experienced by commercial and military diver
Diver
Diver or divers can refer to:*Diving, the sport of performing acrobatics while jumping or falling into water**:Category:Divers*Underwater diving**:Category:Underwater divers**Scuba diving, in which a diver uses a scuba set to breathe underwater...
s) has been linked to AVN, though the relationship is not well-understood.
Cell death and repair
The hematopoietic cells are most sensitive to anoxiaAnoxia
The term anoxia means a total decrease in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts:* Anoxic waters* Anoxic event* Dead zone or hypoxic zones...
and are the first to die after reduction or removal of the blood supply, usually within 12 hours. Experimental evidence suggests that bone cell
Bone cell
There are five types of bone cells.*Osteoblasts - These are commonly called bone-forming cells. They secrete osteoid, which forms the bone matrix. They also begin mieralization, and are unable to divide....
s (osteocytes, osteoclasts, osteoblasts etc.) die within 12–48 hours, and that bone marrow fat cells die within 5 days.
Upon reperfusion, repair of ischemic bone occurs in 2 phases; First, there is angiogenesis
Angiogenesis
Angiogenesis is the physiological process involving the growth of new blood vessels from pre-existing vessels. Though there has been some debate over terminology, vasculogenesis is the term used for spontaneous blood-vessel formation, and intussusception is the term for the formation of new blood...
and movement of undifferentiated mesenchymal cells from adjacent living bone tissue grow into the dead marrow spaces, as well as entry of macrophage
Macrophage
Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
s that degrade dead cellular and fat debris. Second, there is cellular differentiation
Cellular differentiation
In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a simple zygote to a complex system of...
of mesenchymal cells into osteoblast
Osteoblast
Osteoblasts are mononucleate cells that are responsible for bone formation; in essence, osteoblasts are specialized fibroblasts that in addition to fibroblastic products, express bone sialoprotein and osteocalcin.Osteoblasts produce a matrix of osteoid, which is composed mainly of Type I collagen...
s or fibroblast
Fibroblast
A fibroblast is a type of cell that synthesizes the extracellular matrix and collagen, the structural framework for animal tissues, and plays a critical role in wound healing...
s. Under favorable conditions, the remaining inorganic mineral volume forms a framework for establishment of new, fully functional bone tissue.
Presentation
While it can affect any bone, and half of cases show multiple sites of damage, avascular necrosis primarily affects the joints at the shoulderShoulder
The human shoulder is made up of three bones: the clavicle , the scapula , and the humerus as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The major joint of the shoulder is the glenohumeral joint, which...
, knee
Knee
The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...
, and hip. The classical sites are: head of femur, neck of talus and waist of scaphoid.
Clinical avascular necrosis most commonly affects the ends (epiphysis
Epiphysis
The epiphysis is the rounded end of a long bone, at its joint with adjacent bone. Between the epiphysis and diaphysis lies the metaphysis, including the epiphyseal plate...
) of long bones such as the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
(the bone extending from the knee joint to the hip joint). Other common sites include the humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
(the bone of the upper arm), knees, shoulders, ankles and the jaw
Osteonecrosis of the jaw
Osteonecrosis of the jaw is a severe bone disease that affects the maxilla and the mandible. Various forms of ONJ have been described over the last 160 years, and a number of causes have been suggested in the literature...
. The disease may affect just one bone, more than one bone at the same time, or more than one bone at different times. Avascular necrosis usually affects people between 30 and 50 years of age; about 10,000 to 20,000 people develop avascular necrosis of the head of the femur in the US each year. When it occurs in children at the femoral head, it is known as Legg-Calvé-Perthes syndrome
Legg-Calvé-Perthes syndrome
Legg–Calvé–Perthes syndrome is a degenerative disease of the hip joint, where growth/loss of bone mass leads to some degree of collapse of the hip joint and to deformity of the ball of the femur and the surface of the hip socket...
.
Diagnosis
Orthopaedic doctors most often diagnose the disease except when it affects the jawsOsteonecrosis of the jaw
Osteonecrosis of the jaw is a severe bone disease that affects the maxilla and the mandible. Various forms of ONJ have been described over the last 160 years, and a number of causes have been suggested in the literature...
, when it is usually diagnosed and treated by dental and maxillofacial surgeons.
In the early stages, bone scintigraphy and MRI are the diagnostic modalities of choice.
X-ray images of avascular necrosis in the early stages usually appear normal. In later stages it appears relatively more radio-opaque due to the nearby living bone becoming resorbed secondary to reactive hyperemia. The necrotic bone itself does not show increased radiographic opacity, as dead bone cannot undergo bone resorption
Bone resorption
Bone resorption is the process by which osteoclasts break down bone and release the minerals, resulting in a transfer of calcium from bone fluid to the blood....
which is carried out by living osteoclast
Osteoclast
An osteoclast is a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone . This process is known as bone resorption. Osteoclasts were discovered by Kolliker in 1873...
s. Late radiographic signs also include a radiolucency area following the collapse of subchondral bone (crescent sign
Crescent sign
Crescent sign in radiology refers to a thin, curvilinear lucent line parallel and inverted to the cortical margin of a bone. It represents the margin of a disk of articular cartilage and underlying subchondral bone, that has fractured...
) and ringed regions of radiodensity resulting from saponification and calcification of marrow fat following medullary infarcts.
Treatment
Avascular necrosis is especially common in the hip joint. A variety of methods are now used to treat avascular necrosis, the most common being the total hip replacement, or THR. However, THRs have a number of downsides including long recovery times and short life spans. THRs are an effective means of treatment in the geriatric population, however doctors shy away from using them in younger patients due to the reasons above. A new, more promising treatment is hip resurfacingHip resurfacing
Hip resurfacing has been developed as a surgical alternative to total hip replacement . The procedure consists of placing a cobalt-chrome metal cap, which is hollow and shaped like a mushroom, over the head of the femur while a matching metal cup is placed in the acetabulum , replacing the...
or metal on metal (MOM) resurfacing. It is a form of a THR, however in this procedure, only the head of the femur is removed as opposed to a THR in which the entire neck is removed. MOM resurfacing is still experimental in America but has been endorsed in Great Britain as an excellent alternative to a THR. A MOM Resurfacing may not be suitable in all cases of Avascular Necrosis, its suitability depends on how much damage has occurred to the femoral head of the patient, bone is always undergoing change or remodelling. The bone is broken down by osteoclasts and rebuilt by osteoblasts. Some doctors also prescribe bisphosphonates (e.g. alendronate
Alendronate
Alendronic acid or alendronate sodium — sold as Fosamax by Merck — is a bisphosphonate drug used for osteoporosis and several other bone diseases. It is marketed alone as well as in combination with vitamin D . Merck's U.S...
) which reduces the rate of bone breakdown by osteoclasts, thus preventing collapse (specifically of the hip) due to AVN.
Other treatments include core decompression, where internal bone pressure is relieved by drilling a hole into the bone, and a living bone chip and an electrical device to stimulate new vascular growth are implanted; and the free vascular fibular graft (FVFG), in which a portion of the fibula, along with its blood supply, is removed and transplanted into the femoral head.
Progression of the disease could possibly be halted by transplanting nucleated cells from bone marrow into avascular necrosis lesions after core decompression, although much further research is needed to establish this technique.
Prognosis
The amount of disability that results from avascular necrosis depends on what part of the bone is affected, how large an area is involved, and how effectively the bone rebuilds itself. The process of bone rebuilding takes place after an injury as well as during normal growth. Normally, bone continuously breaks down and rebuilds—old bone is reabsorbed and replaced with new bone. The process keeps the skeleton strong and helps it to maintain a balance of minerals. In the course of avascular necrosis, however, the healing process is usually ineffective and the bone tissues break down faster than the body can repair them. If left untreated, the disease progresses, the bone collapses, and the joint surface breaks down, leading to pain and arthritis.Notable cases
Avascular necrosis cut short the footballNational Football League
The National Football League is the highest level of professional American football in the United States, and is considered the top professional American football league in the world. It was formed by eleven teams in 1920 as the American Professional Football Association, with the league changing...
and baseball
Major League Baseball
Major League Baseball is the highest level of professional baseball in the United States and Canada, consisting of teams that play in the National League and the American League...
careers of star athlete Bo Jackson
Bo Jackson
Vincent Edward "Bo" Jackson is a former American baseball and football player. He was the first athlete to be named an All-Star in two major American sports, and also won the Heisman Trophy in 1985....
.
In addition to the athletes listed, AVN has affected musicians including Andy Bell
Andy Bell (singer)
Andrew Ivan "Andy" Bell is the lead singer of the English synthpop duo Erasure. He also has a solo career, with the albums Non-Stop and Electric Blue.-Early life:Andy Bell originates from the Dogsthorpe area in Peterborough...
of the electronica
Electronica
Electronica includes a wide range of contemporary electronic music designed for a wide range of uses, including foreground listening, some forms of dancing, and background music for other activities; however, unlike electronic dance music, it is not specifically made for dancing...
/pop
Pop music
Pop music is usually understood to be commercially recorded music, often oriented toward a youth market, usually consisting of relatively short, simple songs utilizing technological innovations to produce new variations on existing themes.- Definitions :David Hatch and Stephen Millward define pop...
duo Erasure
Erasure
Erasure are an English synthpop duo, consisting of songwriter and keyboardist Vince Clarke and singer Andy Bell. Erasure entered the music scene in 1985 with their debut single "Who Needs Love Like That"...
has had the condition and replaced both hips.
External links
- Osteonecrosis / Avascular Necrosis at the National Institute of Health
- Osteonecrosis / Avascular necrosis at Merck Manual for patients
- Osteonecrosis / Avascular necrosis at Merck Manual for medical professionals
- Femoral head avascular necrosis at eMedicineEMedicineeMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely, two medical doctors. The website is searchable by keyword and consists of approximately 6,800 articles, each of which is associated with one of 62 clinical subspecialty textbooks...
- Center for Osteonecrosis Research
- National Osteonecrosis Foundation
- Avascular Necrosis Resources
- Coping with Osteonecosis A real life experience with good links in the comments.