Avascular necrosis is especially common in the hip joint. A variety of methods are now used to treat avascular necrosis[19], 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 metal on metal 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. Metal on metal resurfacing is still experimental in America but has been endorsed in Great Britain as an excellent alternative to a THR. Bone is always undergoing change or remodelling[23]. The bone is broken down by osteoclasts and rebuilt by osteoblasts[23]. 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[24].
Other treatments include Core Decompression, where internal bone pressure is relieved by drilling a hole into the bone, and living bone chip and 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[25].
Progression of the disease could be halted by transplanting nucleated cells from bone marrow into avascular necrosis lesions after core decompression, although more 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[23]. 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[23]. 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[1], and the joint surface breaks down[12], leading to pain and arthritis[12].
Diagnosis
Orthopaedic doctors most often diagnose the disease except when it affects the jaws, when it is usually diagnosed and treated by dental and maxillofacial surgeons.
Because early x-rays are usually normal in the early stage of the disease , bone scintigraphy [21]and MRI [22] are the diagnostic modalities of choice since both can detect minimal changes at early stages of the disease. Late radiographic signs 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