What is the preferred choice for internal sutures for a tummy tuck, permanent or absorbable?

This question is a good one, and there are probably many answers, none of them wrong.  In short, this is typically determined by your surgeon's preference and experience, so I'd ask him/her.  My own preference has evolved over time, and I currently use a long lasting, but slowly absorbable running suture reinforced with some interrupted sutures to tighten the abdominal wall during abdominoplasty.  Over several months, these sutures dissolve and by then the muscles will have scarred together enough so that a permanent suture is not needed.  Permanent sutures may be more likely to become infected and knots may cause palpable lumps in some thin patients.  The biggest issue with permanent sutures is that they are theoretically not necessary.  Sutures will not keep tissues together over time in the absence of adequate wound healing, so I don't use them often.

Hello and thank you for your
question.  I prefer to use a combination of permanent and absorbable sutures for the diastasis repair.   If you are an appropriate candidate for a tummy tuck, this can be done
through a low and short incision, all completely below the bikini line.  The belly button can be designed to look
natural and have no scars on the exterior.  
Your muscles can also be plicated resulting in a flat abdomen.  Make sure you specifically look
at before and after pictures of real patients who have had this surgery
performed by your surgeon and evaluate their results.  The most important
aspect is to find a surgeon you are comfortable with. I recommend that you seek
consultation with a qualified board-certified plastic surgeon who can evaluate
you in person.
Best wishes and good luck.
Richard G. Reish, M.D. FACS
Harvard-trained plastic surgeon