Osteonecrosis (Avascular Necrosis)
What Is Osteonecrosis?
Osteonecrosis, also known as avascular necrosis, occurs when the normal supply of blood flow to a bone is reduced or completely cut off, causing that part of the bone to die. Without adequate blood supply, bone tissue cannot survive, and the affected area begins to deteriorate. Over time, this can lead to collapse of the bone structure and severe arthritis in the affected joint. While osteonecrosis can occur in any bone, it most commonly affects the hip and knee joints, where the consequences of bone death can significantly impact mobility and quality of life.
Traumatic injuries to bones are common causes of osteonecrosis. Hip fractures or joint dislocations can damage or sever the blood vessels that supply the femoral head (the ball of the hip joint), leading to bone death. Even after the fracture or dislocation is treated, osteonecrosis may develop weeks or months later as a complication. The severity and location of the initial injury significantly affect the likelihood of developing osteonecrosis.
Several medical conditions can also lead to osteonecrosis. Sickle cell anemia and Gaucher's disease make it difficult for blood to move through bone because they increase pressure inside the bone or cause blockages in blood vessels. HIV, lupus, and diabetes all increase a person's chances of developing osteonecrosis through various mechanisms that affect blood flow or bone health. People who take high doses of corticosteroids for long periods of time are also at a higher risk—these medications can affect fat metabolism and blood vessel health, potentially leading to decreased bone blood supply. Cancer treatments, particularly radiation therapy, can damage blood vessels supplying bone. Organ transplant recipients are at increased risk due to both the transplant itself and the immunosuppressive medications required afterward. Dialysis patients may develop osteonecrosis as a complication of kidney disease. Heavy, long-term alcohol use can also cause this painful condition by interfering with the body's ability to maintain adequate bone blood supply.
In many cases, osteonecrosis is not detected until the disease is quite advanced because there may be no discernible symptoms in the early stages. Pain is typically the first symptom to appear. In the hip, this may manifest as a dull ache or throbbing pain in the groin or buttock area. In the knee, pain on the inside of the knee is typically the first symptom, which may occur suddenly and be triggered by a specific activity or minor injury. As the condition worsens, pain occurs during weight-bearing activities. Eventually, pain develops even during simple movement and sometimes occurs even when at rest. The progression from early asymptomatic disease to advanced painful arthritis can vary from months to years.
Nonsurgical Treatments
Treatment options for osteonecrosis depend on the stage of disease, the amount of bone affected, which bone is involved, and the underlying cause. If caught in its early stages before bone collapse occurs, osteonecrosis may be treated without surgery. Our doctors offer comprehensive nonsurgical treatments to slow disease progression and manage symptoms.
Lifestyle Modifications
For hip osteonecrosis, it may be necessary to use crutches for several months to avoid further damage by reducing weight-bearing on the affected joint. Restricting physical activity and limiting the amount of weight placed on the hip or knee joint can help slow the development of further damage. Activity modifications include avoiding high-impact exercises and heavy lifting. For knee osteonecrosis, reduced weight-bearing using crutches temporarily relieves pressure on the joint and allows healing processes to work. Your doctor may recommend avoiding activities that aggravate symptoms.
Medications
Over-the-counter or prescription anti-inflammatory drugs may help relieve pain and reduce inflammation. Be sure to talk with your doctor before taking any new medications. Drugs commonly used to treat osteoporosis, such as bisphosphonates, may help slow the progression of osteonecrosis by strengthening bone and potentially preventing collapse. Cholesterol-lowering medications can help keep blood vessels that flow into bones from becoming blocked. Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen can help reduce pain and swelling, though they should be used carefully and under medical supervision.
Physical & Occupational Therapy
Physical therapy exercises may help maintain range of motion in the affected joint while protecting it from excessive stress. For the hip, gentle exercises can preserve mobility without placing harmful loads on the damaged bone. For the knee, a prescribed program of physical therapy can help strengthen thigh muscles and maintain range of motion. Water exercise may be recommended to further reduce stress on the joint while maintaining fitness. The therapist designs exercises that balance the need for movement with protection of vulnerable bone.
Supportive & Assistive Devices
Electrical stimulation is a newer treatment approach where electrical currents delivered through electrodes attached to the skin encourage bone growth to replace damaged bone. This noninvasive therapy may help stimulate healing processes in early stage osteonecrosis. Crutches or other assistive devices reduce the load on affected joints during the healing period.
Surgical Treatments
Surgery is a common treatment for osteonecrosis because in many cases the condition is far advanced by the time it has been detected. The right surgical approach depends on the stage of disease, the joint involved, and the extent of bone damage.
Core Decompression & Grafting
For hip osteonecrosis caught early, core decompression combined with bone grafting is sometimes successful in preventing collapse of the femoral head and development of arthritis. Core decompression involves drilling one or more holes into the femoral head to relieve pressure in the bone and create channels for new blood vessels to nourish affected areas. This procedure is often combined with bone and cartilage grafting (osteochondral grafting) to help regenerate healthy tissue. An allograft uses healthy bone tissue from a donor, while an autograft uses healthy tissue taken from another bone in your body. Synthetic bone grafts are also available, sometimes mixed with the patient's own bone marrow cells to enhance the bone regeneration process. For knee osteonecrosis, core decompression and osteochondral grafting may also be used to treat affected areas.
Vascularized Fibula Graft
This advanced procedure for hip osteonecrosis involves taking a small segment of bone from the fibula (the smaller bone in the leg) along with its blood supply (an artery and vein). This living graft is transplanted into a prepared channel in the femoral neck and head. The artery and vein are then microsurgically reattached to blood vessels in the hip region to maintain blood flow to the graft. This technique brings living bone with its own blood supply directly to the area of necrosis, promoting healing and preventing collapse.
Osteotomy
For knee osteonecrosis, an osteotomy may be performed on either the tibia or femur. The surgeon cuts and reshapes damaged bone or inserts a wedge of bone graft or synthetic bone to shift weight off the damaged area of the knee. This redistributes forces across the joint, relieving pressure and pain while improving function. This procedure is most effective when the necrotic area is relatively small and well-localized.
Arthroscopic Debridement & Microfracture
For knee osteonecrosis with cartilage involvement, arthroscopic surgery uses a tiny camera and miniature surgical instruments to remove loose bits of bone and damaged cartilage from inside the joint. The surgeon may also drill multiple tiny holes (microfractures) in the bone underlying a small lesion to encourage blood flow and stimulate a healing response. This promotes the formation of repair cartilage to cover exposed bone.
Autologous Chondrocyte Implantation
For knee osteonecrosis with significant cartilage loss, cartilage-producing cells can be collected from the patient and cultured in a laboratory for up to six weeks to multiply. These cells are then implanted into the area of cartilage loss during a second surgery. The cells grow in the joint, replacing damaged cartilage with healthy cartilage over time.
Joint Replacement
When the bone has already collapsed and advanced arthritis has developed, joint replacement surgery may be necessary. This procedure involves removing the damaged bone ends and replacing them with artificial components made of metal and plastic. Joint replacement can provide dramatic pain relief and restore function, allowing patients to return to many daily activities. The hip and knee are the joints most commonly requiring replacement due to osteonecrosis. Modern joint replacement techniques and implants offer excellent long-term outcomes for patients with end-stage osteonecrosis.