History of Avascular Necrosis/Osteonecrosis 

250 plus years and still no one can explain how we exactly get Osteonecrosis 

1st described in 1738 by Alexander Munro 

https://archive.org/details/anatomyofhumanbo1741monr

James Russell first described osteonecrosis in 1794, between 1829 and 1842 Jean Cruveilhier, the noted French anatomist, recorded gross deformation of the femoral head as a late complication of trauma, presumably as a result of vascular damage.Kragelund in 1886 and Konig in 1888 published more comprehensive reports on this subject.
Freund, however, is generally credited with the first detailed description of bilateral idiopathic aseptic necrosis of the femoral heads.The more recent works by Phemister and his associates have become classics on the etiology, pathogenesis, and treatment of this condition.
And a full description of the entity followed in 1930 by Phemister. 

Since then many researchers have been trying to determine the pathogenesis of osteonecrosis, but this seems only to have succeeded in creating more questions. 
Why does a disease with so many diverse etiologies seem to end in one common pathological entity? 
Why do some patients enter this pathway to destruction while others remain unaffected? Is there some genetic predisposition we are yet to discover? 
There is no animal model that is suitable for the study of the human form of osteonecrosis. 
Many experiments conducted in steroid treated rabbits and rats have produced severe lipidemia, fatty livers, loss of body weight, severe malnutrition, decreased blood flow in the femoral head, fat embolism of multiple organs including bone, but no bone necrosis.
The treatment of osteonecrosis is considerably more successful at early stages of the disease. The early diagnosis of osteonecrosis depends upon the identification of individuals at risk. 
Understanding the pathogenic factors leading to osteonecrosis enables the early investigation of at-risk individuals and facilitates prompt diagnosis

A number of hypotheses concerning the pathogenesis of osteonecrosis exist with the most commonly accepted hypothesis by Jones
Osteonecrosis is defined as cell death of bony tissue (marrow and mineralized tissue) due to ischaemia. It represents the final common pathway of several disease entities, which result in impaired blood supply to the bone tissue, causing necrosis of the bone. 
Jones has demonstrated the final common pathway for non-traumatic osteonecrosis to be a coagulopathy within the intraosseous microcirculation leading to both intraosseous venous thrombosis and retrograde arterial occlusion. In contrast, a sick cell syndrome hypothesis has been proposed3 suggesting that there is little evidence to support the hypothesis that an interruption of the blood supply to bone is involved directly, rather, the pathologic features may result from a direct metabolic effect on the cells.
Bone as a tissue has a remarkable biological capacity to repair and reconstitute itself. Necrosis of the bony portions of a joint should not in any way affect the normal metabolism and functioning of the articular cartilage. The chondrocytes should initiate a series of cellular responses that ultimately “heal” the dead portion of the bone replacing it with new living bone. Therefore there is no reason to expect that the development of osteonecrosis should result in any discernible biological sequelae or clinical, but it does.
Etiology
    Idiopathic (40% of all reported cases) • Alcoholism (20% of all reported cases)

    Antiphospholipid antibody syndrome

    Dysbaric disorders
Photo of Alexander Munro

    Endotoxic (Schwartzman) reactions secondary to systemic bacteraemia

    Gaucher’s disease

    Haemoglobinopathies including sickle cell disease

    Hypercoagulable states

        Protein C and Protein S deficiency

        Antiphospholipid antibodies

        Lupus anticoagulant 

 Hypercortisolism
    Endogenous

    (Cushing’s syndrome)

    Exogenous (37% of all reported cases)
Hyperlipidemia

Hypersensitivity reactions
    Allograft organ rejection

    Anaphylactic reactions
Inflammatory conditions
    Systemic Lupus Ertythematosus

    Inflammatory bowel disease
Malignancy
    Metastatic carcinoma

    Acute promylelocytic or lymphoid leukaemia
Pregnancy

Radiation therapy

Traumatic
    Femoral head dislocation

    Intracapsular neck of femur fracture
    Viral infections

        HIV

        Hepatitis

        Cytomegalovirus

        Rubella

        Varicella

        Measles Vascular Anatomy
The circulation and arrangement of blood vessels in long bones have been disputed for many years. The most widely accepted patterns of intraosseous circulation are those proposed by Brooks9 in 1971. Bones have multiple arterial inlets and venous outlets, with long bones having four arterial inputs. The nutrient artery supplies blood to the diaphyseal cortex and marrow, the metaphyseal artery supplies to the metaphyseal cortex and marrow and the epiphyseal artery supplies the epiphysis. The periosteal arteries probably do not provide significant arterial input. Nutrient, metaphyseal and epiphyseal vessels enter the bone through foramina in the cortex and anastamose to supply marrow, cancellous bone, and cortex in a centrifugal direction. The epiphyses of long bones are covered with avascular joint cartilage, as a result, the dual blood supply (periosteal system and the nutrient, metaphyseal and epiphyseal system) does not exist in these areas. Instead, the functional end arteries comprise those ascending in the epiphyseal cancellous bone toward the articular surface. As a result, the epiphysis and the articular surfaces are particularly susceptible to circulatory insufficiency.
Although the role of an impaired blood supply to the femoral head in the pathogenesis of osteonecrosis has not been confirmed, Atsumi and Kuroki10 have found an abnormal blood supply in patients with corticosteroid induced osteonecrosis. 

They found that in most cases the blood supply of the superior retinacular arteries from the extraosseous site was impaired


What is OsteonecrosisOsteonecrosis comes from the Greek words for bone (osteo) and death (necrosis), a concept first put forward by Hippocrates in antiquity. Osteonecrosis term is used to describe cellular death in bone tissue most commonly related to an interruption of its blood supply and the subsequent destruction of its architectural structure. Many different terms have been coined to describe Osteonecrosis, such as avascular necrosis, aseptic necrosis, ischemic necrosis , and osteochondritis dissecans , all of which are commonly used in the medical literature.
In 1794, the first modern-day description of Osteonecrosis disorder was made by James Russell. At that time, infectious etiologies were the primary pathogenic agent. It was only in 1888 that the term aseptic necrosis of the bone was first used to describe what we now know as osteonecrosis.
Most osteonecrosis cases are related to traumatic interruption of the blood supply to the bone; however, nontraumatic cases related to systemic disorders remain a diagnostic challenge, especially in defining the precise cause of bone death.
Different Forms of Osteonecrosis

There seem to be two distinct forms of this condition:
(a) a secondary form, caused by a number of well-recognized risk factors, working alone or in concert, and
(b) an idiopathic, or primary form, for which no identifiable risk factors have been identified
Cause of Osteonecrosis
When osteonecrosis of the femoral head follows a fracture or a dislocation of the hip, there is a clear association between the mechanical interruption of the blood supply and the subsequent development of osteonecrosis.
Vascular Occlusion – Trauma is the most common cause of vascular occlusion with subsequent osteonecrosis, and the likelihood of developing this is directly proportional to the following:
Extent of fracture displacement

Impingement on the vascular supply of the bone

Available collateral circulation of the affected site

Intravascular Coagulation – The intraosseous microcirculation is as susceptible to a prothrombotic state as any other part of the circulation. Taking Virchow’s triad as an example, this may be the result of one or a combination of factors, including endothelial damage, circulatory stasis, or a hypercoagulable state. Endothelial damage may be related to trauma, atherosclerotic lesions, or autoimmune inflammatory connective tissue disorders that may affect the endothelial lining.
Pregnancy and

Pregnancy and Osteonecrosis

Osteonecrosis of the femoral head is a rare manifestation of pregnancy, especially in healthy women who have no known risk factors for the development of this disorder. The cause of osteonecrosis in these patients is unknown, but different hypotheses have postulated the possibility of amniotic fluid emboli, a relative hypercoagulable state, excessive mechanical strain, and an increase in endogenous steroid production. To date, the largest case series was described by Montell and associates. In this case series, 13 women developed hip pain late in the second or in the third trimester of their pregnancy. In general, these women tended to have a small body habitus, and during their pregnancy, they had gained excessive weight, indicating that this may have a pathogenic role in the development of osteonecrosis. All the affected women had involvement of their left hip, and 4 of them had bilateral involvement. As a rule, a high index of suspicion is required by the clinician to prevent the misdiagnosis or the delayed diagnosis of osteonecrosis in these patients.
Diagnosis of Osteonecrosis

Osteonecrosis following a hip fracture is described as prolonged pain even after the successful surgical treatment of the orthopedic injury. The pain is described as a deep aching or boring pain localized to the groin and at times radiating down the thigh and into the knee region. Radiographs often are normal early, and a high suspicion is required to make the diagnosis by the use of a bone scan or MRI. In patients with atraumatic osteonecrosis of the hip, the earliest stages of the disease process are often asymptomatic.
Treatment and Medical Therapy for osteonecrosis

Therapy for osteonecrosis is based on the stage of the disease as well as the age of the patient. In patients who have, according to the Steinberg classification system, stage I lesions, conservative measures may be undertaken early, such as pain control and limited weight bearing, although the disease itself continues to progress if the lesion is in the weight-bearing portion of the femoral head.

#Osteonecrosis 

#AvascularNecrosis 

#WEGOHealth

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