Avascular Necrosis of Femoral Head:
- What is avascular necrosis?
Avascular necrosis (also referred to as aseptic necrosis
or osteonecrosis) is a condition that results from poor blood supply to
an area of bone causing bone death. This is a serious condition because
the dead areas of bone do not function normally, are weakened, and can
- Pathogenesis and Risk Factors:
Aseptic necrosis can be caused by trauma and damage to
the blood vessels that supply bone its oxygen. Other causes of poor blood
circulation to the bone include an embolism of air or fat that blocks the
blood flow through the blood vessels, abnormally thick blood (hypercoaguable
state), and inflammation of the blood vessel walls (vasculitis). Conditions
that are associated with aseptic necrosis include alcoholism, steroid usage,
Cushing's syndrome, radiation exposure, sickle cell disease, pancreatitis,
Gaucher's disease, and systemic lupus erythematosus.
Avascular necrosis of bone:
a common serious complication of
allogeneic bone marrow transplantation.
- Clinical manifestations:
-Hip pain, particulary with weigth bearing and rotation.
-Limitation of wiegth bearing and motion.
- Radiographic Evaluation
-Can be normal initially,but frequently shows increased
density of necrotic bone.
-Conbination of osteoclastic and new bone formation in
revascularized areas creates x-ray appearance of mottled density.
-When collapse of segment of necrotic bone occurs, the
compression more bone into smaller area also produces increased x-ray density.
-Evaluation includes and AP view and frog-leg lateral
x-rays of hip.
- Magnetic Resonance Imaging:
-Prefered method for differential diagnosis and for radiollogically
occult necrosis, since its more sensitive than bone scans or plain films.
-also used to outline the area of involvement.
- note that there is a high incidence of bilateral AVN,
and that MRI may pick up AVN in the contralateral asymptomatic hip.
- Treatment: Stages IV and V:
- total hip arthroplasty:
- ongoing concern over cement disease, particulate matter, and stress
shielding changes in the femur in cemented or non-cemented prostheses
makes a total hip arthroplasty a less desirable option;
- bipolar arthroplasty:
- worst results of treatment are found after bipolar hemiarthroplasties
probably becuase of use of thin polyethylene in young healthy pts;
- arthrodesis of the hip has been used in some series, but becuase of
50-80 % prevalence of bilaterality of AVN, this may be poor choice;