Osteonecrosis is a type of disease that can lead to bone collapse caused by an inadequate supply of blood to the bone tissue. As a living tissue, bone requires a certain amount of blood in order to function properly. Without an adequate blood supply, a serious case of osteonecrosis can develop that leads to the death of bone tissue.
Osteonecrosis is often referred to as ischemic necrosis of bone, aseptic / avascular necrosis (AVN) or simply ON. It is an irreversible bone condition that can be excruciatingly painful and disfiguring. The American Academy of Orthopaedic Surgeons estimate that between 10,000 and 20,000 Americans are diagnosed with osteonecrosis each year, most of who are in their mid-to-late thirties. Osteonecrosis typically affects either end of the epiphysis of the femur, the long bone that runs between the knee and hip joints. Osteonecrosis of the hip is diagnosed as the underlying cause in approximately 10% of all hip replacement surgeries in the United States.
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 osteonecrosis sufferers living with the disease throughout the United States.
Causes of Osteonecrosis
The causes of osteonecrosis are divided into two categories: post-traumatic osteonecrosis and non-traumatic osteonecrosis.
Post-traumatic osteonecrosis refers to the onset of the bone condition after experiencing a significant trauma. 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 condition for reasons unrelated to a physical trauma. People may be more susceptible to development of the bone condition if they have a history of diseases or activities known to disrupt blood supply, such as alcoholism, smoking, blood clotting disorders, kidney disease, connective tissue disease, lupus, or have undergone treatment with high levels of corticosteroids. Oftentimes the condition has unknown causes and is referred to as an idiopathic case of osteonecrosis.
More recently, a family of drugs called bisphosphonates has been linked with the development of non-traumatic osteonecrosis.
Osteonecrosis of the jaw & Fosamax
Fosamax is a type of oral bisphosphonate that is used for the treatment of a number of bone diseases, notably osteoporosis and osteitis deformans (Paget's disease). Recently, Fosamax has been linked with the development of non-traumatic osteonecrosis of the jaw, or "dead jaw" as it is commonly called. Whereas osteonecrosis typically affects the body's larger joints, such as the hips, shoulders, ankles and knees, osteonecrosis of the jaw affects the jawbone and accompanying maxillofacial region.
Early osteonecrosis symptoms are similar to those associated with arthritis. During activity, osteonecrosis sufferers may experience pain and aching of the joints. The discomfort is oftentimes sporadic and short-lived, holding many osteonecrosis sufferers back from consulting with a doctor in regards to the issue. As such, osteonecrosis often goes undiagnosed for a lengthy period of time until the occurrence of increasingly painful symptoms eventually elicits a sufferer's response.
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.
The earlier an osteonecrosis diagnosis can be made, the better the chances are of limiting the severe and long-term affects of the painful bone condition. If a case of osteonecrosis goes untreated, it can eventually culminate in bone collapse. The best method for early osteonecrosis diagnosis is MRI (Magnetic Resonance Imaging). An MRI can detect the onset of osteonecrosis before the condition has had ample time to cause significant damage to the affected bone(s). It is not until the bone condition has progressed to a serious stage that its effects can be viewed via x-ray, at which point it typically includes joint involvement.