What is Avascular Necrosis of the hip?
Avascular Necrosis (AVN) is a disease where there is cellular death (necrosis) of bone components due to interruption of the blood supply. Without blood, the bone tissue dies and the bone collapses. When avascular necrosis involves the bones of the hip joint, it often leads to destruction of the joint articular surfaces resulting in deformity of the femoral head and separation of the overlying cartilage. In the late stages of AVN, progressive damage to the hip joint results in early osteoarthritis.
What causes AVN to develop?
Often no cause is identified. This is ‘Idiopathic AVN’. Known risk factors include the use of corticosteroid medications, high alcohol consumption and hip joint trauma (dislocations and fractures).
What is the natural course of hip AVN?
This depends on a number of factors. In the early stages of AVN, good medium term results can be obtained with the use of the medication bisphosphonate . Once collapse of the femoral head has occured, the outcome for the hip joint is less favourable. Surgical intervention may offer some improvement. Hip joints with significant collapse and deformity of the femoral head due to AVN reliably develop early onset osteoarthritis.
What is the treatment for hip AVN?
In the early stages of AVN, bisphosphonate medications (which can improve bone density) may prevent or slow progression of the disease Pain associated with AVN can often be significantly improved with a minimally invasive drilling procedure (Forage). Once the disease has progressed and the femoral head has collapsed, the outcome for the hip joint is less favourable. Femoral osteotomy may be recommended to protect the softened area of the femoral head by reshaping the upper thigh bone. Ultimately, hip joints with end stage AVN and associated osteoarthritis are best treated with an artificial joint replacement. In these situations, both hip replacement and hip resurfacing have been shown to be effective.