How long does it take for abdominis rectus muscle tear to heal?

Thank you for your question. Unfortunately you seem to have a complicated past surgical history with your abdomen and hernia history. It is difficult to really answer your question without knowing exactly what is taking place, and that requires a thorough review of your MRI and a physical exam.  The reason is that without knowing the extent and location of the "chronic abdominis muscle tear" it is difficult to make a treatment recommendation. I am not sure what type of physician that you saw, but you may want to have second opinions with a general surgeon and/or plastic surgeon.  Best wishes