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AVN or Avascular Necrosis
is not the common thing and it occurs generally due to interruption in blood supply to specific organ.Due to lack of oxygenation to particular region it starts to become lifeless and this process depends on the level of lack of blood supply and also on the collateral blood supply which is good or deficient.
What can be done in such a case?
This is not the infection or gangrene
which can spread and should need immediate surgical intervention for replacement of the part just for pain.There are chances of revascularisation of the region and hence protecting the affected part.As you have mentioned that your husband is having pain ,but he is able to move so it means that his hip joint is not damaged upto that much level that it cannot support the bod weight.
There are certain medications in homeopathy
which can increase the blood perfusion to all over the body and also the affected part so it will help in protecting the hip joint and when sufficient blood supply is established his hip joint will become stable to bear the weight and that too without pain.
For this you must consult your nearest homeopath for further help,
Wish you speedy recovery,
dr jignesh parmar