Avascular necrosis (AVN), better known as osteonecrosis, of the femoral head, is a disease that causes death of bone.
In the earliest stages of osteonecrosis plain x-rays are often normal. A magnetic resonance image (MRI) is the key that allows us to detect AVN at its earliest stages.
Will it get Worse?
The natural history of osteonecrosis is linked to the size of the necrotic segment. Very small lesions (involvement of less than 15% of the femoral head) may resolve without any further treatment. On the other hand, lesions involving greater than 50% of the femoral head progress to collapse, and ultimately require in total hip arthroplasty.
Does Avascular Necrosis Cause Pain?
AVN may be present without any pain whatsoever. There may be early hip pain but unfortunately, pain often develops only once the osteonecrosis has progressed quite far. At that time the pain is caused by fragmentation and collapse of the femoral head.
How often is the other hip affected?
Verification of the status of the opposite hip is very important as part of the evaluation of osteonecrosis, because studies have shown that often the contralateral hip is asymptomatic and has a normal x-ray, and even more importantly in cases of non-traumatic osteonecrosis, the incidence of bilaterality is up to 80%.
No one really understands the cause of AVN, but it appears to be related to a disruption of the blood flow to the femoral head. Four basic mechanisms are implicated: mechanical disruption (e.g., broken hip), external pressure on or damage to a vessel wall (e.g., vasculitis, radiation therapy), arterial thrombosis or embolism (e.g., sickle cell diseases, prednisone, alcohol), and venous or blood outflow occlusion (e.g., infection). Although the relationship between the inciting event and the onset of osteonecrosis is clear in some cases, such as vascular disruption from a femoral neck fracture or arterial thrombosis from sickled blood cells, the inciting event in most cases is poorly understood. There is an increased incidence of osteonecrosis seen in people who chronically use corticosteroids, as well as people who consume more than 3 glasses of wine or 5 beers per week.
Frequently Asked Questions
Do I need an operation to correct Osteonecrosis?
There are several treatment choices, determined by the extent of involvement of the femoral head.
Are there other choices?
Besides non-operative management and core decompression, there are several other treatment modalities, which include osteotomies, bone grafting, and total hip arthroplasty.