Osteonecrosis or avascular necrosis of the hip is death of a segment of bone in the femoral head due to disruption of the blood supply. The etiology of this condition is not fully understood. There are several risk factors associated with osteonecrosis of the hip.
The condition is bilateral in about 80% of the patients. Check the other hip even if it is asymptomatic.
Early diagnosis is important. In early stages of osteonecrosis, a femoral head preserving procedure may be done. In late stages of osteonecrosis, the femoral head collapses and cannot be saved. The femoral head may need to be replaced.
Obtain AP frog leg lateral views of the hip. The frog leg lateral view will show the crescent sign. MRI is the study of choice especially when the patient has persistent hip pain, radiographs are negative and the diagnosis of osteonecrosis is suspected.
The Ficat classification is a commonly used system to stage osteonecrosis of the hip.
- Stage I: normal appearing X-ray. MRI will detect the lesion (changes in the marrow).
- Stage II: sclerosis and cyst formation
- Stage III: subchondral fracture. Crescent sign and flattening of the femoral head.
Stage IV: advanced lesions with arthritis, osteophyte formation and loss of the joint space.
For early stages of osteonecrosis of the hip, initial trial of non surgical treatment is usually done. Surgery may be needed if non surgical methods are not successful.
Non-operative treatment includes:
- Bisphosphonates: may also be used before the femoral head collapses. Still experimental.
Traditional surgical treatment: when the lesion is small, a head preserving procedure can be done.
- Core decompression for stages I and II: can make a single large hole or multiple holes in the femoral head. It decompresses the head and stimulates a healing response. The lesion is anteriorly and superiorly.
- Core decompression with bone graft: debride the necrotic area and place the bone graft. Some lace this much bone graft.
- Traditional fibular graft: is done in younger patients.
- Donor site pain and leg dysfunction
- Tibial stress fracture form side the graft is taken.
- Total hip arthroplasty (cementless cup and stem) or total hip resurfacing. Resurfacing is not commonly used.
- Total hip replacement (predictable): is considered to be the traditional procedure for advanced stages of osteonecrosis of the hip.
- Total hip resurfacing (controversial): need adequate bone stock to support the femoral component. The result is not as good when compared with a patient with osteoarthritis (older group).