This is a gradual process of destruction of the bone that arises secondary to the decreased blood supply. The underlying causes are varied ranging from certain diseases and drug intake, to trauma and damage to the blood supply arising during procedures. Alternate names of this condition are avascular necrosis, aseptic necrosis or ischemic necrosis.
Risk Factors and Causes of Osteonecrosis
- Steroid use over long term
- Alcohol intake
- Sickle Cell Disease
- Systemic Lupus Erythematosus (SLE)
- Antiphospholipid Antibody Syndrome (APLA)
- Gaucher Disease (a genetic disease with accumulation of certain metabolites)
- Decompression sickness (a condition arising secondary to high pressures experienced with deep-sea diving)
- Post transplantation
This condition can affect any bone and very commonly affects the femur (thigh bone) at the hip joint and it the underlying cause for about 10% of total hip replacements in the United States.
Symptoms of Osteonecrosis
As the disease process is gradual, symptoms don’t often manifest till later stages. Early clinical diagnosis is necessary for effective treatment and prevention of disability. The common symptoms are as follows
- Pain: This is the most common symptom. The location depends on the bony site involved. Most commonly the pain is noted at the groin, buttocks and thighs is the case of Osteonecrosis of the femoral head (at the hip joint)
- Night pains preventing sleep
- Limping and abnormal gait: this develops in late stages due to severe pain and difficulty bearing weight on the affecting limb
Diagnosis of Osteonecrosis
The history of bone pain in typical sites and the presence of an underlying cause or risk factor suggest the diagnosis. This is confirmed through physical examination of the involved site and imaging
- Physical examination: a complete examination of the painful area and surrounding bones and joints will be done to look for any deformity and limitation of range of movement.
- X-Ray: Images are obtained from various angles to facilitate diagnosis. Often, the X-ray may remain normal for months after the symptoms appear.
- Nuclear imaging using Technetium 99m radionuclide bone scanning: These are better than X rays to identify lesions at an earlier stage, but are expensive and not routinely recommended
- Magnetic Resonance Imaging (MRI): MRI is the best imaging tool to identify lesions at earlier stages. A non-contrast MRI with typical findings on imaging is considered diagnostic.
Treatment of Osteonecrosis
The treatment options differ based on the patient’s age, the underlying cause and stage of the disease process. The general options are as below:
- Management of the underlying cause: Stop intake of steroids or alcohol if present, and treat the underlying disease.
- Medications and nonoperative treatment
- Bisphosphonates: These are drugs that prevent the loss of bone mineral density. These may offer benefit in some patients although it increases the risk of osteonecrosis of the jaw.
- Anticoagulants: These are useful in patients with underlying pro-clotting diseases like SLE or APLA syndrome
- Statins: These help by lowering fat cell production, and their deposition in vessels
- Pain killers: NSAIDs are useful for symptomatic relief of pain
- Reduced weight bearing and rest of the affected area
- Electrical stimulation of the affected area
- Operative procedures
- Core decompression surgery: By decreasing pressure inside the bone, the blood supply is restored
- Osteotomy: this is a procedure which involves partially cutting away a piece of the bone to help weight-bearing on a deformed bone or joint
- Bon graft: This involves replacing a piece of diseases bone with a healthy bone from elsewhere in the body
- Total joint replacement: This is the final option to relieve symptoms and restore joint function.
Complications of Osteonecrosis
These patients are at an increased risk for developing arthritis in the affected joints with increased pain, stiffness and deformity, requiring specialist treatment.
Prognosis of Osteonecrosis
This condition is generally managed with operative procedures however, complete return to normal functioning is rare as some deformity persists. Avoidance of steroid use and alcohol and management of any underlying risk factors generally are effective at preventing recurrence of the disease.