Introduction
Bone is a living hard tissue that makes up the body's skeleton. The bones have blood vessels of various cells, proteins, minerals, and vitamins. They can grow, reform, and repair themselves. Bones have their metabolism, and it is a lifelong process where the old bone tissues are removed, and new bone tissues are added. The coordinated cellular and molecular events within the bone help maintain the state of internal physical and chemical conditions of the living bone.
What Is Avascular Necrosis?
Necrosis means the death of body tissue, and this condition is irreversible. It is caused by a lack of blood and oxygen supply to the tissue. It affects many areas in the body, like bone, skin, organs, and other tissues.
Avascular necrosis is the death of bone tissue due to an interruption in blood supply. It generally affects the extremities of the long bones; the most common site is the hip joint. Other common sites are the shoulder, knees, ankles, and wrists. It usually affects people between the ages of 30 and 50. Avascular necrosis is called osteonecrosis, aseptic necrosis, ischemic necrosis, or bone infarction.
What Is Meant by Avascular Necrosis of the Hip?
The avascular necrosis which occurs in the hip is also called osteonecrosis of the hip. The hip joint is known as the hip and socket joint. The ball is considered to be the head of the thighbone, known as the femur bone. This is round and ball-shaped. The socket is cup-shaped which is part of the pelvis. This socket is the acetabulum. The head-shaped bone fits into the cup-shaped space in the acetabulum. When there is movement of the hip, the head of the femoral bone rotates within the cup-shaped space of the acetabulum. But, avascular necrosis affects the femoral head by disrupting the blood supply and destroying the bone tissue.
In many conditions, avascular necrosis of the hip or osteonecrosis of the hip is progressive. In the long run, the affected hip bone tissue degenerates. Without proper treatment, there are chances for the femoral head to collapse due to avascular necrosis of the hip. When this condition occurs, the shape of the femoral head alters, and it does not move smoothly within the acetabulum. This can result in a form of arthritis called osteoarthritis. Avascular necrosis of the hip, when it reaches the extreme stage of damage, needs to be corrected by hip replacement surgery. In the initial stages, there may not be any symptoms, but as the condition worsens, the person can experience pain in the hip, thigh, knee, groin, and buttock.
What Causes Avascular Necrosis?
The abnormal process associated with avascular necrosis is blood vessel occlusion, altered lipid metabolism, clots inside blood vessels, premature cell death, and mechanical stress. They are caused by:
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Trauma:
Acute injury leading to bone fracture and joint dislocations are the important and main reasons for avascular necrosis.
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Block in the Blood Vessel:
Sometimes, calcium and fatty deposits in the blood vessels reduce the blood flow to the bone, which results in necrosis.
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High Dose Steroids:
Most cases of avascular necrosis occur secondary to high doses of daily administration of corticosteroids. The reason is attributed to an increased level of fat in the blood.
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Chronic Alcoholism:
Chronic use of alcohol results in fat deposits in the blood vessels.
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Chemotherapy and Radiotherapy:
Cancer treatments like chemotherapy and radiation therapy directed to kill fast-growing cancer cells can also kill the normal bone cells.
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Drugs:
Long-term use of NSAIDs (non-steroidal anti-inflammatory drugs) and bisphosphonates might contribute to developing avascular necrosis.
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Organ Transplantation:
Avascular necrosis is a disabling complication that often occurs after kidney transplantation. Immunosuppressive therapy after solid organ transplant has a strong connection to avascular necrosis.
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Other Diseases:
Avascular necrosis is associated with sickle cell anemia, systemic lupus erythematosus, Gaucher’s disease, and Caisson's disease.
What Are the Symptoms of Avascular Necrosis?
Initially, avascular necrosis remains asymptomatic. The symptoms begin slowly and increase over time. The manifestations are,
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Pain and tenderness around the bone.
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Stiffness and decreased range of motion.
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Loss of muscle tissue.
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Joint deformity.
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Inflammation develops as the condition worsens.
How to Diagnose Avascular Necrosis?
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Patient History and Physical Examination:
A focused history of recent trauma, long-term steroid, alcohol, or associated drug usage, and other systemic diseases will help in outlining avascular necrosis. Physical examination checks for tenderness and decreased movements in and around the bone.
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Imaging Modalities:
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X-rays: A dead bone appears more radiopaque (dense structures that resist the passage of X-rays that appear white in the radiographic image) compared with the neighboring live bone.
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Computed Tomography Scan (CT) and Magnetic Resonance Imaging (MRI): These tests are the preferred choices as they produce detailed images and help diagnose avascular necrosis early.
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Bone Scintigraphy (Bone Scan): A small amount of radiopaque material is injected into the patient's vein and then scanned with the camera. The images obtained show bright spots in the area of injury.
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What Are the Stages of Avascular Necrosis?
Based on the clinical and radiological findings, avascular necrosis can be classified into various stages. This classification system is named ARCO (association research circulation osseous) classification and was used to assess avascular necrosis. The ARCO staging is as follows:
How to Treat Avascular Necrosis?
The goal of treatment for avascular necrosis is to improve the functions of the affected joint and stop the progression of further bone damage. The treatment modality depends on the age of the patient, stage of the disease, cause of the disease, location, and extent of bone damage.
1. Conservative Management:
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Rest: The disease progression can be halted by giving complete rest to the affected bone.
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Supporting Device: Reducing stress by offloading the affected joints using crutches, braces, and slings.
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Medications: Painkillers to reduce pain, cholesterol-lowering drugs, and blood thinners are used to delay the disease progression.
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Exercises: Mild and regular exercises are advised to improve the movements of the joints.
2. Surgical:
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Core Decompression: The bone's inner layer is removed and indicated in ARCO stages I and II.
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Realignment Osteotomy: The necrotic area is relocated from the weight-bearing site and is indicated in ARCO stages III and IV.
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Arthroplasty: The damaged part of the joint is replaced with a metal or plastic alternative. It is indicated in advanced cases.
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Bone Transplant: It is also called bone grafting, which involves replacing the dead bone with a healthy bone from other body sites.
Conclusion:
Avascular necrosis is a degenerative disease. The amount of disability depends on the location of the dead bone. Treating this disease in the early stages shows better results. Eating a healthy diet, limiting alcohol, quitting tobacco, and maintaining an appropriate weight can minimize the risk of avascular necrosis. Patients are sometimes unaware of the condition since the symptoms of avascular necrosis show up late. Therefore, periodic screening is essential in high-risk patients.
