Avascular Necrosis Stages

What are the avascular necrosis stages and what is it?

Avascular necrosis stages, sometimes referred to as osteonecrosis or ischemic bone necrosis refers to the death of bone at a cellular level caused by an interrupted flow to the supply. Blood is vital to all cells within the body and without it, the tissue within the bone dies.

Where the condition is present within a joint, the affected joint can often display a serious destruction of the articular surfaces.

Which bones are affected?

Avascular necrosis can occur within any bone of the human body, although, the most common areas are the shoulder, knee and hip joints. Somewhere in the region of 50% of cases of the disease display multiple areas of damage to bones and joints.

The condition causes intense pain in the affected joints that will not be alleviated over time and will get worse as the disease progresses.


As the condition of avascular necrosis is prevalent in hip joints, a full hip replacement is often the most common form of treatment used to combat the disease when present within this area. There are, however, a variety of different other methods of treatment that are available, including THRs.

THRs are most effective when used as a treatment for older patients but as the recovery times are long and the life spans of the hip joints are relatively short, they are not commonly used on younger patients. Hip resurfacing (also known as metal on metal, or MOM, resurfacing) is a relatively new form of treatment for sufferers of the disease within the area of the hip.

With a MOM, the head of the femur is completely removed - as opposed to a full THR procedure which sees the entire neck of the femur be removed as part of the procedure. The MOM procedure is still in early stages within America, but is already in use across Great Britain and is seen as a good alternative to the full THR treatment.

Avascular necrosis stages

There are a variety of different staging systems in use for the diagnosis of Avascular necrosis, including an outdated developed AVN staging system from Ficat which is largely based on the findings of radiology investigations. The radiology-based staging system was later amended after the use of MRI scans became more prevalent in the staging of the AVN system.

According to the Subcommittee of Nomenclature of the International Association on Bone Circulation and Bone Necrosis, the stages go from stage 0 to stage VI, with 13 stages in total.

Stage 0

of AVN scale is assigned when the patient displays no symptoms of the disease, radiology findings indicate nothing abnormal and histology results suggest osteonecrosis.

Stage 1

Is defined by the possibility (but not the condition) that the sufferer may not be displaying symptoms, the results of radiology scans are defined as 'unremarkable', an MRI indicates the likeliness of AVN and blood results are abnormal.

Stage 2

Occurs when the patient is displaying symptoms of AVN, radiology results are abnormal, there is no Subchondral radiolucency and an MRI indicates the presence of AVN

Stage 3

Requires the patient to be displaying symptoms, subchondral lucency is seen on radiology results.

Stages 3A-3B

Are defined based on the crescent; under 15% is IIIa, IIIb is between 155-30% and IIIc is greater than 30%.

Stage 4

Includes the presence of either collapse or flattening of the head of the femur, irregular joint space and sensitive CT scans (more so than radiography). The three sub-stages of stage IV are: stage IVa with under 15% of visible collapse, IVb which indicated between 15-305 of collapse to the femoral head and IVc with a collapse of more than 30% of the head of the femur.

In stage 5

Narrowing of the joints and osteoarthritis are visible on a radiography scan, as well as acetabulum sclerosis

Stage 6

Indicates extensive damage to the joint and head of the femur.

Last Reviewed:
August 18, 2017
Last Updated:
October 19, 2017
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