Stages of Avascular Necrosis AVN
Avascular necrosis AVN can be classified into five different stages. From this, some rectifying surgery can only be done in Stage 1, 2 or 3. For stages 4 and 5, joint replacement looks to be the only solution.
- Stage 1: Radiographic (x-ray) changes are absent or show minor osteopenia (condition where bone mineral density is lower than normal). An MRI scan is required for identification (MRI scan shows oedema). The onset of AVN is asymptomatic (clinically silent).
- Stage 2: First stage where radiographic (x-ray) changes are evident. This stage is characterised by sclerosis of the superior central portion of the joint head and/or osteopenia and/or subchondral cysts.
- Stage 3: In this stage, the articular surface is depressed so that the round contour is compromised, without being significantly deformed. This leads to a joint space narrowing. A plain x-ray shows a crescent sign.
- Stage 4: This stage is characterized by a wide collapse of the subchondral bone and destruction of the underlying trabecular pattern. This can lead to secondary arthritis.
- Stage 5: The final stage where both articular surfaces are affected, which leads to a disfunctional joint.
For example, if a case presents itself where the patient has avascular necrosis of the femoral head (hip), avascular necrosis most commonly affects the hip joint. The patient will have mild chronic pain in the hip, the groin, around the buttocks and at the anteromedial, towards the front and the middle of the thigh, with a normal x-ray, they should undergo observation for osteonecrosis of the femoral head and a Hip joints MRI. This pain is most commonly aggravated by activity and internal rotation in flexion. As the disease progresses, the pain may also become present at rest. Without treatment, 85% will progress to the collapse of the articular surface and will eventually require total joint arthroplasty or joint replacement.