AVN (Avascular Necrosis) or ON (Osteonecrosis. What is AVN, what causes it and how to repair AVN damage.
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 :
fibula (autologon or homologonpaft)
Treatment with tantalium implants
small arthroscopic prothesis
AVN is also known as:
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
Major Trauma: Fractures
Caisson Disease (Deep Sea Divers)
Sickle Cell Disease
Causes of Osteonecrosis- Probable
Corticosteroids: High Dosages
Connective Tissue Disease
Blood Clotting Disorders
Progression of AVN
Medical Treatments for AVNCore 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 GraftingWhen 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 GraftingRegular 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. Additional References about ON and AVN: About AVNAVN and Hip Resurfacing ON at About Joints AVN at Wikipedia The ON/AVN Support Group Int’l Association