Osteonecrosis Sudhir Babhulkar
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INTRODUCTION1

Osteonecrosis is a disease, which can lead to the collapse of bone and is caused by an inadequate supply of blood to the specific bone tissue involved. As a living tissue, bone is continuously remodeling and requires a certain amount of blood in order to function properly. Without an adequate blood supply, in the stage of insufficiency, serious cases of avascular necrosis can develop that leads to the death of bone tissue. Commonly, it affects young patients between the age of 30 to 60 years. Osteonecrosis is often referred to as an ischemic necrosis of bone, aseptic or avascular necrosis (AVN) or idiopathic avascular necrosis. It is an irreversible state of bone disorder that can be excruciatingly painful, disfiguring and disabling. Although osteonecrosis can be an extremely painful and debilitating disease, it is not considered to be fatal. In fact, there are hundreds of thousands of patients suffering from osteonecrosis, living with the disease throughout the world.
Osteonecrosis is divided into two categories: post-traumatic osteonecrosis and non-traumatic osteonecrosis.
Post-traumatic osteonecrosis refers to the onset of the bone disorder after experiencing a significant trauma. This is associated with mechanical interruption of the circulation to the femoral head. A severely broken bone or dislocated joint is typically the underlying cause behind the development of osteonecrosis.
Non-traumatic osteonecrosis refers to the onset of the bone disorder for reasons unrelated to a physical trauma. Several pathologies have been reported to be associated with this type of osteonecrosis. People may be more susceptible to development of bone disorder, if they have a history of diseases or activities known to disrupt blood supply, such as alcoholism, smoking, blood clotting disorders, hepato-renal disease, connective tissue disease, lupus erythromatosis, or have undergone treatment with high levels of corticosteroids and organ transplantation. More recently, a family of drugs called bisphosphonates has been linked with the development of non-traumatic osteonecrosis.
The signs and symptoms in early stages of osteonecrosis are similar to those associated with arthritis. During activity, osteonecrosis patients may experience pain and aching of the limbs and joints affected. The discomfort is often sporadic and short-lived, holding many osteonecrosis sufferers back from consulting physician with regards to the issue. As such, osteonecrosis often goes undiagnosed for a period of time until the occurrence of increasingly disabling painful symptoms causing severe arthritic changes, restricting the activities of daily living. The earlier an osteonecrosis diagnosis can be made, the better the chances are of limiting the severe and long-term effects of the painful bone disorder. If a case of osteonecrosis goes untreated, it can eventually culminate in bone collapse and arthritic changes (Figs 1.1A and B).
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Figs 1.1A and B: X-ray of pelvis showing changes of osteonecrosis of both femoral heads with deformation of right femoral head in a young 20 years, sickle cell disease patient
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Fig. 1.2: X-ray pelvis showing classical radiological changes of osteonecrosis of right femoral head in a young female 24 years with lupus erythematosus
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Figs 1.3A and B: MRI scan of the same patient showing advanced changes in right hip
The best method for early osteonecrosis is radioisotope bone scan or magnetic resonance imaging. An MRI can detect the onset of osteonecrosis before the condition has had ample time to cause further damage to the affected bones. It is not until the bone condition has progressed to a serious stage that its effects can be viewed on X-ray, at which point it typically includes joint involvement and is too late (Figs 1.2 and 1.3).
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Figs 1.4A and B: X-ray of shoulder of two patients showing multiple dense sclerotic spots fused to each other showing segmental involvement
Osteonecrosis is known to affect multiple locations in the axial and appendicular skeleton and is associated with diverse medical conditions and injury. Since the femoral head of the hip is the most common bone to be affected by osteonecrosis, symptoms often include limping and a great deal of pain in the groin. This topic of osteonecrosis of femoral head will be dealt in this monograph in detail, though other regions will also be discussed. Similar changes of osteonecrosis are noticed in humeral head (Figs 1.4A and B), vertebral end plates, distal femur, proximal tibia, talus, scaphoid, lunate, metatarsal heads, etc.