Necrosis or Osteonecrosis)
What is aseptic
Aseptic necrosis (also
referred to as avascular 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 collapse.
What causes aseptic
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).
What conditions are
associated with aseptic necrosis?
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.
How is aseptic necrosis
The diagnosis of aseptic
necrosis can be made with x-rays, but this is a later stage finding.
Earlier signs of avascular necrosis can be detected with MRI scanning or
suggested by nuclear bone scanning.
What is the treatment
for aseptic necrosis?
The treatment of aseptic
necrosis is critically dependent on the stage of the condition. Early
aseptic necrosis (before x-ray changes are evident) can be treated with
a surgical operation called a core decompression. This procedure
involves removing a core of bone from the involved area and sometimes
grafting new bone into the area. This allows new blood supply to form,
preserving the bone. Weight bearing should be restricted.
Later stages of aseptic
necrosis (when x-ray changes have occurred) inevitably lead to seriously
damaged bone and joints requiring joint replacement surgery.
Certain particular bony
areas are prone to development of osteonecrosis because of their
relatively precarious blood suply
Avascular necrosis occurs
in other bones, particulary:
-Infarction causes marrow
edema and venous outflow obstruction, increasing pressure and widening
the area of infarction.
-Hiperemia of the
sorrounding bones causes osteoporosis of living bone,while infarcted
bone retains its density and thus appears whiter or denser on
-The bone is gradually
revascularized. But bone reabsortion can lead to mecanical failure, with
subcondral fractures (crescent sign).
-the result is flattening
of femoral head, whith incongruity of joint and rapidy progression of
-Hip pain, particulary
with weigth bearing and rotation.
-limitation of wiegth
bearing and motion.
-Can be normal
initially,but frequently shows increased density of necrotic bone.
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.
-Often shows increased
uptake around the necrotic bone.This represents acumulation of
radionuclide in the area of increased bone turnover, at the junction
beetwen dead and reactive bone.
-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.
-Femoral neck stress
(Enneking`s stages of osteonecrosis):
||step of flatening
Treatment: Stages I, II,
-Core decompression -
Wherin a channel is drilled throught the femoral neck.This procedure
does give good relief. But this procedure is very controversial, because
subsequent series have had failed.
Free vacularized fibular
Treatment: Stages IV and
-Total hip arthroplasty -
Ongoing concern over cement disease, particulate matter, and stress
shield changes in the femur inthe cemented or non cemented protheses
makes a total hip arthroplasty a less desirably option. Can, also be
tried for stage VI.
-Bipolar arthroplasty -
Worst results are found, probably because of use of thin polyethylene in
young heathy patients.
-Arthrodesis - Poor choice
for bilateral necrosis (50 - 80%)
Mankin HJ: Non traumatic
necrosis of bone (osteonecrosis). N Engl J Med 1992;326:1473
For related information,
please visit the Total
Hip Replacement and Total
Knee Replacement forums.
For further information,
please visit the following site:
Necrosis of the Hip