How long does it take for an open wound like this to close? (Photo)

The foto is difficult to assess with regard to scale, but this looks like a clean but significant wound.  Did your skin just open up, or did some of the skin necroes and die?   I would say you need a trip back to the operating room to clean the wound and reclose it.  If too much skin is missing, a latissimus flap can help bring in healthy soft skin paddle.  Wound care for a wound this size is usually just temporary until you can surgically address the wound once it is clean.  Best wishes!

It is difficult to answer your question with out an in person examination and your full medical history. There is no scale to the photograph making it difficult to judge the dimensions of the wound, additional photographs would help. However, most importantly you should be under the care of a suitably qualified and experienced plastic surgeon to help you optimise healing. Ideally this would be the surgeon that carried out your surgery but you could always ask for a second opinion from another surgeon.There are many factors that have a bearing on wound healing. Age, obesity, other medical conditions like diabetes, drugs like steroids, infection, nutrition, good wound care, amongst others!In healthy individuals clean wounds will usually heal with dressings but can take several months, depending on size. A split skin graft can be used to speed up healing of a slow healing wound once it is clean and granulating.Sorry you are having this problem, best wishes