Avascular Necrosis
Avascular Necrosis is made up of two words, Avascular & Necrosis. Avascular means lack blood supply & Necrosis means ‘Cell Death’. Death of bone tissue, because of lack of blood supply, is known as Avascular Necrosis (AVN).
It is also called Osteonecrosis or Bone Infarction. The bone like any other living tissue is made up of living cells, and any living tissue needs blood supply to survive. So basically, in Avascular Necrosis the blood flow to that specific part of the bone is interrupted. In simpler terms, just like a plant dies because of lack of water supply, in the same way the bone dies because of lack of blood supply. The death of bone can eventually lead to breakdown of the bone & ultimately to joint collapse. Avascular necrosis is also known as Osteonecrosis, Aseptic Necrosis, Ischemic Bone Necrosis & Bone infarction
Osteonecrosis can happen in any bone but most often it develops in the end of long bones such as:
• Femoral Head(Thigh Bone)
• Head of Humerus (Upper Arm Bone)
• Lower end of humerus
Less often, the bones of the elbows, ankles, feet, wrists, and hands are affected.
Who gets osteonecrosis or the Risk factors for developing AVN/ Osteonecrosis?
Osteonecrosis can be seen an any age group, but it is most common in people in their 30s and 40s.There are certain risk factors that can interrupt the blood supply to the bones which in turn causes Avascular Necrosis. There are some factors that are known to increase the chances of osteonecrosis. However, it may be seen with patients even without these factors. Factors that may increase the chance of getting AVN include:
• Idiopathic means no identified reason
• Excessive alcohol use. Consuming several alcoholic drinks, a day for several years also can cause fatty deposits to form in your blood vessels.
• Trauma. Injuries, such as hip dislocation or fracture, can damage nearby blood vessels and reduce blood flow to bones.
• Regular or heavy smoking
• Steroid use. Use of high-dose corticosteroids, such as prednisone, is a common cause of avascular necrosis. The reason is unknown, but one hypothesis is that corticosteroids can increase lipid levels in your blood, reducing blood flow.
• Bisphosphonate use. Long-term use of medications to increase bone density might contribute to developing osteonecrosis of the jaw. This rare complication has occurred in some people treated with high doses of these medications for cancers, such as multiple myeloma and metastatic breast cancer.
• Certain medical treatments. Radiation therapy for cancer can weaken bone.
• Blood disorders like Sickle Cell Anemia
• Organ transplantation, especially kidney transplant, also is associated with avascular necrosis
What are the types of osteonecrosis?
There are two types of osteonecrosis:
• Traumatic, which follows an injury. The most common causes of traumatic osteonecrosis are a bone fracture (break) or dislocation.
• Nontraumatic, when there is no history of injury.
Pain can be mild or severe and usually develops gradually. Pain associated with avascular necrosis of the hip might centre on the groin, thigh or buttock. Besides the hip, the areas likely to be affected are the shoulder, knee, hand and foot. Some people develop avascular necrosis on both sides (bilaterally) — such as in both hips or in both knees.
Stage I : Patient may or may not be symptomatic.
Radiography and CT scan findings are unremarkable.
AVN is considered likely based on MRI and bone scan results (may be subclassified by extent of involvement [see below]).
Histology findings are abnormal.
Stage II : Patient is symptomatic.
Plain radiography findings are abnormal and include osteopenia, osteosclerosis, or cysts.
Subchondral radiolucency is absent.
MRI findings are diagnostic.
Stage III : Patient is symptomatic.
Radiographic findings include subchondral lucency (crescent sign) and subchondral collapse.
Shape of the femoral head is generally preserved on radiographs and CT scans.
Subclassification depends on the extent of crescent, as follows:
Stage IIIa: Crescent is less than 15% of the articular surface.
Stage IIIb: Crescent is 15–30% of the articular surface.
Stage IIIc: Crescent is more than 30% of the articular surface.
Stage IV: Flattening or collapse of femoral head is present.
Joint space may be irregular.
CT scanning is more sensitive than radiography.
Subclassification depends on the extent of crescent, as follows
Stage IVa: Less than 15% of surface is collapsed.
Stage IVb: Approximately 15–30% of surface is collapsed.
Stage IVc: More than 30% of surface is collapsed.
Stage V : Radiography findings include narrowing of the joint space, osteoarthritis with sclerosis of acetabulum, and marginal osteophytes.
Stage VI: Findings include extensive destruction of the femoral head and joint.
Stages of AVN femoral head (Hip)
Osteonecrosis develops in stages. Hip pain is typically the first symptom. This may lead to a dull ache or throbbing pain in the groin or buttock area. As the disease progresses, it becomes more difficult to stand and put weight on the affected hip and moving the hip joint is painful.
It may take from several months to over a year for the disease to progress. It is important to diagnose osteonecrosis early, because some studies show that early treatment is associated with better outcomes.
The stages of osteonecrosis. The staging system given in the below table is based on the consensus of the Subcommittee of Nomenclature of the International Association on Bone Circulation and Bone Necrosis (ARCO: Association of Research Circulation Osseous).The disease can progress from a normal, healthy hip (Stage I) to the collapse of the femoral head and severe osteoarthritis (Stage VI).
Diagnosis
During a physical exam your doctor will likely press around your joints, checking for tenderness. Your doctor might also move the joints through a variety of positions to see if your range of motion has been reduced.
Is there a test for osteonecrosis?
• If your doctor suspects you have osteonecrosis, may take your medical history and do a physical exam. Many disorders can cause joint pain. Imaging tests can help pinpoint the source of pain. Options include:
• X-rays- They can reveal bone changes that occur in the later stages of avascular necrosis. In the condition’s early stages, X-rays usually appear normal.
• MRI — These tests produce detailed images that can show early changes in bone that might indicate avascular necrosis. It is the recommendation for the detection of earlier stages of the disease due to its high sensitivity in detecting bone edema.
• Bone scan. A small amount of radioactive material is injected into your vein. This tracer travels to the parts of your bones that are injured or healing and shows up as bright spots on the imaging plate.
How is avascular necrosis treated?
Specific treatment for avascular necrosis is dependent on many factors like:
• Age of the patient , overall health, and medical history
• Extent of the disease
• Location and amount of bone affected
• Underlying cause of the disease
• Patient’s tolerance for specific medicines, procedures, or therapies
• Expectations for the course of the disease
The goal of treatment is to improve functionality and stop further damage to the bone or joint. Treatments are needed to keep joints from breaking down, and may include:
• Medicines- These are used mainly to control pain.
• Assistive devices- These are used to reduce weight on the bone or joint.
• Core decompression- For this surgical procedure, the inner layer of bone is removed to reduce pressure, increase blood flow, and slow or stop bone and/or joint destruction.
• Osteotomy- This procedure reshapes the bone and reduces stress on the affected area.
• Bone graft- In this procedure, healthy bone is transplanted from another part of the body into the affected area.
• Joint replacement- This surgical procedure removes and replaces an arthritic or damaged joint with an artificial joint. This may be considered only after other treatment options have failed to relieve from pain and/or disability.
Osteonecrosis of the Hip
Many patients will ultimately need a total hip arthroplasty however joint salvaging procedures such as core decompression report with varying results. Core decompression is most effective in the early stages of osteonecrosis and when the lesions only involve a small amount of the weight-bearing surface of the femoral head.
The procedure may use vascularised bone grafts or biologic agents that promote bone repair. Core decompression is typically successful for 50–90% of patients. Its success depends on the amount and location of bone death in a joint, how much weight the joint tends to bear and other factors.
Exercises that work the muscles while in standing most effectively assist with daily activities such as walking and stair climbing, however they also put the most amount of stress through the hip joint. Other exercises in sitting or lying, for this reason, may also be prescribed.
To reduce your risk of avascular necrosis and improve your general health:
• Limit alcohol.
• Heavy drinking is one of the top risk factors for developing avascular necrosis.
• Keep cholesterol levels low.
• Tiny bits of fat are the most common substance blocking blood supply to bones.
• Monitor steroid use.
• Don’t smoke.
