Tuesday, November 18, 2008

Avoiding Denervation of Abdominal Muscles during DIEP Flap Breast Reconstruction Surgery

The following interesting article was published in the "Plastic and Reconstructive Surgery" journal this month.....

Avoiding Denervation of Rectus Abdominis in DIEP Flap Harvest II: An Intraoperative Assessment of the Nerves to Rectus
by Rozen W, Ashton M, Kiil B, et al.
Plastic and Reconstructive Surgery:Volume 122(5) November 2008 pp 1321-1325.

Background: The deep inferior epigastric artery perforator (DIEP) flap aims to reduce donor-site morbidity by minimizing rectus muscle damage; however, damage to motor nerves during perforator dissection may denervate rectus muscle. Although cadaveric research has demonstrated that individual nerves do not arise from single spinal cord segments and are not distributed segmentally, the functional distribution of individual nerves remains unknown. Using intraoperative nerve stimulation, the current study describes the motor distribution of individual nerves supplying the rectus abdominis, providing a guide to nerve dissection during DIEP flap harvest.

Methods: Twenty rectus abdominis muscles in 17 patients undergoing reconstructive surgery involving rectus abdominis (DIEP, transverse rectus abdominis musculocutaneous, or vertical rectus abdominis musculocutaneous flaps) underwent intraoperative stimulation of nerves innervating the infraumbilical segment of the rectus. Nerve course and extent of rectus muscle contraction were recorded.

Results: In each case, three to seven nerves entered the infraumbilical segment of the rectus abdominis. Small nerves (type 1) innervated small longitudinal strips of rectus muscle, rather than transverse strips as previously described. There was significant overlap between adjacent type 1 nerves. In 18 of 20 cases, a single large nerve (type 2) at the level of the arcuate line supplied the entire width and length of rectus muscle.

Conclusions: Nerves innervating the rectus abdominis are at risk during DIEP flap harvest. Small, type 1 nerves have overlapping innervation from adjacent nerves and may be sacrificed without functional detriment. However, large type 2 nerves at the level of the arcuate line innervate the entire width of rectus muscle without adjacent overlap and may contribute to donor-site morbidity if sacrificed.

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Here's my take....

The long and the short of it is that for DIEP flap surgery to be considered successful several things need to happen (in my opinion):

1) the tissue (flap) transferred to the chest to create the new breast must survive. ie the new breast must live. Obvious.
2) the patient must not suffer any ill-effects from removal of the tissue ("flap") from the abdomen. This is what we call in the trade "donor-site morbidity". Abdominal bulging, hernia and significant loss of muscle strength fall in this category.
3) the patient must be happy.

Number 1 is obvious.

This article addresses number 2. Ideally, other than the scar, the patient's abdomen must recover completely from the surgery and suffer no long-term problems for the surgery to be deemed a full success.

Preserving all the patient's muscle is not enough if the nerves supplying it have all been cut. A muscle without a healthy nerve supply will lose it's tone, strength and function. If the DIEP surgeon does not take great care to identify and preserve the muscle's nerve supply, the risk of abdominal bulging will increase significantly and the muscle-preserving benefits of the procedure will essentially be lost.

The importance of choosing an experienced DIEP flap surgeon cannot be understated. I have heard of some patients (indeed some of mine too) entering the consultation with their DIEP flap surgeon having already decided they will be getting a DIEP flap and nothing else.

This can be a dangerous game to play. Here's why: in rare instances, patients may not have the appropriate anatomy for a DIEP flap. The most likely reason for this in our experience is prior abdominal surgery. Though this happens rarely in experienced hands, we do see it on occasion. Trying to "force" a DIEP flap out of a patient who does not have favorable anatomy requires more muscle dissection and can actually increase the risk of nerve damage. This can increase the risk of abdominal complications: loss of muscle tone, decreased muscle strength long term and abdominal bulging. In these situations,  some patients may be better served by a muscle-sparing type 2 free TRAM flap which removes a very small, postage-stamp sized piece of muscle but still preserves overall muscle function.

As long as you have chosen an experienced microsurgeon specializing in these procedures, chances are extremely high you will indeed get a DIEP flap. However, your anatomy and previous history are the deciding factors. Your surgeon didn't give that to you, he just has to work with it.

Dr C

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Dr Chrysopoulo is a board certified breast reconstruction surgeon specializing in DIEP flap breast reconstruction surgery. He and his partners perform over 350 DIEP flap procedures each year with a success rate of over 99%. PRMA Plastic Surgery, San Antonio, Texas. Toll Free: (800) 692-5565.

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