Corticosteroids Use & Avascular Necrosis of the Femoral Head

Avascular necrosis (AVN) of the femoral head occurs commonly after long term corticosteroid use. The corticosteroids such as prednisone are prescribed for a number of medical conditions. Long term use is associated with AVN of the femoral head requiring total hip replacement, particularly in younger patients.

 

Avascular necrosis is due to loss of the blood supply of the head of the femur. This results in subsequent bone death, also known as necrosis. The upper end of the thigh bone (femoral head) forms the ball of the hip joint.

The femoral head has a precarious blood supply. Any disruption may lead to bone death and the collapse of the joint.

Glucocorticoids or corticosteroids are medications used to treat a number of medical conditions. The medication is commonly used in a short duration to decrease inflammation and reduce pain. Long term use of oral corticosteroids is one of the major risk factors for avascular necrosis of the femoral head.

Glucocorticoids are prescribed as a treatment for chronic conditions. Diseases such as nephrotic syndrome, transplant recipients, systemic lupus erythematosus, and a number of skin conditions are managed with corticosteroids. The steroids suppress the immune system and provide relief from autoimmune diseases. Corticosteroids are also illicitly used by athletes and bodybuilders to rapidly build muscle mass.

The majority of the patients with these diseases happen to be young and middle-aged adults. The high incidence of avascular necrosis in these patients is linked with the effects of glucocorticoid therapy.

Corticosteroids reduce the inflammatory cell function in the body. The other effect directly linked with the avascular necrosis is lipogenesis or an increase in lipid/fat content of the blood. The increased lipid content causes blockage of the blood flow of the small vessels. The head of the femur is particularly susceptible due to precarious blood supply.

Another effect of glucocorticoids is high blood pressure in the body. Constant hypertension causes the narrowing of the small blood vessels of the body. The arteries in the head of the femur constrict leading to a reduction in the blood supply of the head.

The reduced blood supply and blockage of the venous supply causes increased pressure build-up in the head of the femur. The bone cells deprived of their nutrition and oxygen supply die. The head of the femur collapses leading to small fractures in the ball.

The osteoblasts are cells in the bone required for laying down new bone. The osteoblasts also are responsible for releasing factors required for the function of the osteoclasts. The osteoclasts are the cells responsible for the absorption of the bone normally.

In a healthy bone, there is a fine balance between the action of these two types of cells. The balance is lost under the effect of long term glucocorticoid use. The result is cell death in the bone.

The spherical contour of the head of the femur is lost. The incongruity causes grinding of the joint surface leading to arthritic changes. In the end stages, the bone collapses and the joint becomes severely arthritic and loses the function.

The symptoms of AVN hip is joint pain and stiffness. The patients may walk with a limp. Some of the patients may experience a restriction of movements in one direction. The restriction gradually becomes global leading to fixation of the hip in one position.

The diagnosis of avascular necrosis of the hip is made by a physician after a thorough physical examination and radiological evidence. The physician looks for tender points and moves the hip through a range of motion. The restriction of motion of the hip in various planes is examined.

Both the hips are usually involved in the case of high dose steroid-induced avascular necrosis. The imaging tests are done in the form of an X-ray and MRI. The X-ray might show the areas of the collapse of the head of the femur. An X-ray also provides information about the arthritic changes in the ball and the cup of the joint.

By the time the changes of avascular necrosis are evident on an X-ray, the AVN is in advanced stages. An MRI and bone scan are able to detect changes in the early stages of the disease. The necrosis of bone in the early stages is evident as signal changes in an MRI.

The Management of avascular necrosis usually depends upon the stage of the disease. A vast majority of the avascular necrosis patients usually present in the late stages. A total hip joint replacement offers an excellent treatment in such cases.

Other management options include the use of core decompression and stem cell therapy. The core decompression technique involves the use of small drills made in the head of the femur. The pressure inside the head of the femur is reduced allowing revascularization and repair.

Stem cell therapies involve the use of stem cells cultured to be inserted in the necrotic parts. The stem cells have the potential to turn into bone cells and allow repair of the necrotic segments.

Some of the other techniques used are surgical dislocation of the hip joint and removal of the necrotic segment and graft insertion. Various bone cutting and rotational surgeries known as rotational osteotomies may be used in the early stages.
Currently, there is limited evidence of the effectiveness of these techniques in the treatment of avascular necrosis of the hip. Total hip replacement remains the best surgical treatment option for these patients.

 

The image shows a femoral component used in primary hip replacement. The metallic implant has a plasma porous coated layer in the upper part. The plasma coated layer aids in bone ingrowth on the implant for a steadier fixation. The lower part is smooth for aiding insertion and has grooved slit to allow blood and debris to come out while insertion in the canal.

Total hip replacement of the hip joint offers early relief from pain and return to previous activity. With the advancement of surgical techniques and instruments, a successful total hip replacement may last for 15-20 years or even more.