i need advice for wound dehiscence. (photo)

I am so sorry that you have experienced this.  It seems like a rather large dehiscence and the treatment can be a bit different.  I would prefer to wash it out and try to close it because it will take a rather long time to close and it will give a rather unappealing result.  Consult with a board certified plastic surgeon for proper recommendations.

The photograph demonstrates some nonviable fat in the base of the wound. All of the nonviable tissue needs to be removed in the remaining tissue needs to be healthy and a vascular sense. Secondary closure will hasten convalescence.