Risks of doing a second FUT into new areas of my head only 9 months after the first FUT?

Dear navid.amini,
Thank you for posting this question. A majority of the hair from your first transplant has grown out at this point, so it’s perfectly fine to undergo a 2nd FUT at 9 months. As an aside, the International Society of Hair Restoration Surgery maintains that FUT is the Gold Standard when it comes to surgical hair restoration. FUE is a specialty method, of this the singular advantage is that it does not leave a linear scar in the donor area, which is hardly a concern to people who wear their hair longer than a military high-and-tight. Since you have already had an FUT, and have a linear scar, the logic behind undergoing an FUE isn’t there. I hope this information is helpful to you.
Kind Regards,
Ken Anderson, MD, FISHRS

You can safely have another hair transplant surgery as long as the prior results have grown and your scalp is back to normal.   There is no "absolute" time frame.  It is best to see a doctor for an examination.

The time schedule of 9 months post-op to repeat an FUE is ok -into new areas. Your surgeon will be very careful, I'm sure, not to over harvest and thin out your donor hair area too much.

I do not believe that surgeons still performing  FUT! I advice you to prefer FUE technique in hair restoration surgery to yieldmore grafts . Surgeon  harvests grafts one by one under local anesthesia with micro motor (motorised FUE) and there is no need to relaxing excersises of scalp ..

Hi, If you have sufficient laxity and have healed uneventfully, a second FUT transplant at 9 months is fine. Check with your doctor, and as long as he see adequate healing and growth after the first procedure, you are fine to procedure with the second,Dr. Robert Jones

By nine months your donor area should be sufficiently recovered.  Since it takes up to a full year for final results many surgeons waiting that long before adding more grafts, but if you're having a different area done there should be no issues.

Putting the new grafts into a new area will not be that risky -  as long as your surgeon knows what they're doing, there should be no danger of the two areas looking like they don't blend. The risk to the scar at the back of your head is minimal if you take out the old scar. If you are looking to get a second surgery done in the virgin tissue either above or below the first scar, the risk would be that you might conceivably widen the first scar, or have trouble closing the incision due to tension which would lead to a widened second scar. 
Good Luck!

A repeat strip surgery is not a problem at the 9th month if you need more density or have to address areas where you were not transplanted before.