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What is AVN? AVN is a hip joint problem where the blood supply to the
femoral head (ball portion) of the joint is reduced or obliterated. This
causes this portion of the bone to die, which leads to the collapse of
the effected bone and femoral head surface. There are many causes of AVN such as use of corticosteroids, over consumption
of alcohol, fat disorders, nitrogen (divers !) embolism, and other
conditions. If the condition does not heal and does not have prosthetic
surgery, the joint will normally wear out and become osteoarthritis. Not all preventive surgery for AVN is proven to be effective.
Some possible, but not proven treatments :
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decompression
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electrical therapy
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fibula (autologon or homologonpaft)
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Treatment with tantalium implants
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small arthroscopic prothesis
AVN is also known as:
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osteonecrosis
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aseptic necrosis
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ischemic bone necrosis
Legg-Calve-Perthes Disease is a form of OstenonecrosisChildren, ranging in age from 2 to early teenage
years, get a form of osteonecrosis called
Legg-Calve-Perthes disease (Perthes for short) after
the three doctors who first described it. Treatment
for Perthes is completely different for children than
treatment for adult
ON.
Causes of Ostenonecrosis - Definite
Causes of Osteonecrosis- Probable
Progression of AVN
Medical Treatments for AVN
Core Decompression
This is a simple surgical procedure, which involves
taking a plug of bone out of the involved area. It is
applicable for mild to moderate degree of involvement
that has not yet progressed to collapse. Because this
involves creating a hole in the bone, six weeks of
protected weight bearing is necessary to avoid fracture
through the hole, one of the complications of the
procedure.
Pain relief from this procedure has been excellent, but
it has not been as effective at delaying the progression
of the disease in the long term. In centers that do this
procedure frequently most studies have reported good
results in appropriate cases. However, there is some
controversy about this procedure with a few studies that
have been reported showing generally poor results.
Bone Grafting
When a section of the bone has
died, as is the case in ON, for some reason it doesn't
seem to heal. One approach to this problem is to
surgically remove the dead bone and fill the empty space
with bone graft that is either taken from the patient or
from the bone bank. The success of this approach depends
upon the quantity of bone that has died.
Vascularized Bone Grafting
Regular bone graft,
whether from the bone bank or from the patient is itself
dead bone. It serves as a scaffold for the body to build
new bone around, but the body also has to grow a new
blood supply. For this procedure, a bone along with its
blood vessels is taken from the patient and hooked up to
blood vessels near the hip. The dead bone is removed
from the femoral head and replaced with the grafted bone
that carries with it it's own blood supply.
The advantage of this technique is that the body doesn't
have to rebuild a new blood supply, and the bone graft
retains its physical and mechanical properties. This is
most appropriate prior to the collapse of the joint, but
sometimes it is used in cases with early (limited)
collapse. Healing and complete filling of the defect
still have to take place, during which time crutches or
a walker have to be used. The disadvantage of this procedure is that a substantial
piece of bone has to be taken from the patient's lower
leg (the fibula, the smaller bone of the lower leg below
the knee). Some patients may develop pain in the area
from which the bone graft is taken. The operation also
takes several hours and requires a team experienced in
these techniques. The patient is also required to be on
crutches for several months. If both hips are involved,
it may be necessary to delay treating one hip for quite
some time during which time the femoral head may undergo
collapse.
Osteotomy
(Cutting the Bone) Usually the location of
the ON is in the area of the bone that bears weight. In
some cases the bone can be cut below the area of
involvement, and rotated or turned so that another
portion of the bone that is not involved in the ON can
become the new weight-bearing area. These operations are
not very common anymore, but may apply to special cases
with smaller lesions.
Hip Resurfacing with Metal on Metal hip
prosthesis.
Total Hip Replacement (THR)
When the ON is advanced to the point that there is
involvement of the socket as well, then the only thing
that will be effective is either a hip fusion (making
the hip completely stiff) or a total hip replacement.
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