The deep inferior epigastric artery perforator flap
The DIEP flap can be used for a variety of reconstructive procedures when a large segment of soft tissue, including fat and skin is necessary. It has become more popular for breast reconstruction, but requires significant microsurgical experience to harvest.
The diep Flap
Skin and fat from the lower abdominal wall. The reliable area crosses the midline. Zones 1, 2 and 3 are generally well perfused.
Innervation: Intercostal T11 and T12 dermatome via intercostal nerves. Not usually harvested as a sensory flap. There are some who encourage this, but the benefit and outcome are unclear.
Blood supply: The deep inferior epigastric artery and venae via perforators through the rectus muscle. The perforators range in size from from 0.3 mm to 1 mm. Flaps can be harvested reliably on a single large perforator system.
Artery: Large caliber artery from 2 to 4 millimeters.
Vein(s): The venae are typically paired, common to a common vessel at their draining point on the external iliac. One vein is usually larger and comparable in caliber to the artery.
Pedicle length: From the perforator point to the origin on the external iliacs. Very long with significant freedom to position.
Anatomy
The deep inferior epigastric artery arises from the external iliac artery and runs from lateral to medial under the rectus muscle. It can enter the substance of the muscle or run deep to it, while sending branches into the muscle and through the muscle. Perforators often course through the tendinous inscriptions of the rectus muscle, making their dissection somewhat more difficult. In most patients the DIEP and its venae can supply adequate circulation for zones 1-3, making the territory of perfusion larger than that of the SIEA flap.
Anatomy of the abdominal fat and skin
The perforating branches pierce the rectus fascia to supply the abdominal fat and skin. The DIEA and the accompanying veins are pictured here central and deep to the muscle. The can run lateral, central or medial as they ascend superiorly. However, there tends to be symmetry with the contralateral vessels in most people.
Cross Section of the abdominal wall demonstrating diea perforators
flap design
The abdominal skin island is designed with the lower aspect of the incision transversely placed above the pubic bone, in line with the typical transverse Cesarean section incision. It extends laterally with a gentle curve superior to the inguinal ligament finishing adjacent to the anterior superior iliac spines. The upper incision is placed above the umbilicus and gently curves laterally to meet the lower transverse incision marking. With the patient in the supine position and the knees slightly flexed
After flap harvesting, the abdominal skin and fat above the flap is elevated to the costal margin (green arrows). The tissue plane is just superior to the rectus sheath, where laterally this plane is quite mobile. Medially, the plane is quite fixed. By beginning the elevation laterally and then focusing medially, the elevation is simpler.
The green arrows show the extent of undermining after flap harvest to close the abdomen
Operative Procedure
The patient is prepped and draped supine with the arms stretched out on an armboard. The abdominal tissue can be pinched to determine the tightness of postoperative closure and markings can be adjusted accordingly. Peforators can optionally be assessed with the pencil Doppler. If bilateral flaps are to be harvested, the Doppler signals can be marked on the contralateral side as well. This is a good practice even in unilateral flaps to finds the largest and loudest perforators.
The flap is marked and the loudest doppler signals are marked with an "x"
The flap is usually elevated from lateral to medial and the search for peforators is begun when the territory of the rectus sheath over the lateral rectus muscle is reached. This dissection can be performed with a the electrocautery on a low setting, or with bipolar forceps and scissors. If bilateral flaps are being prepared, the midline incision can be made and the flap traced from medial to lateral at some point during the harvest, in order to help define perforators. Note that the attachment of the flap to the rectus fascia in the midline is much more adherent and the plane is more difficult to dissect at this level.
The major perforator to the skin is identified
As larger perforators are identified, smaller ones may be ligated. Usually the single flap can be supported on one major perforator. Occasionally, if the perforators are small, a second perforator may be used as well, as long is it is in a similar longitudinal plane with its counterpart. Two different longitudinal planes would result in excess muscle transection. The whole point of the DIEP flap is to preserve abdominal muscles.
The umbilicus is separated from the flap with a peri-umbilical incision (marked in blue above), leaving the stalk attached to the abdominal wall. When the abdomen is re draped, the umbilicus is brought through an new incision.
The flap is elevated from medial to lateral to identify perforators
When a large dominant perforator is isolated, the rectus fascia is incised longitudinally, around the perforator. Great care is required so as to not injure the vessels, especially the vein, which can be quite delicate. The fascia is opened for 10 to 15 centimeters and the perforator is traced through the muscle, using gentle retraction of the muscle and the bipolar electrocautery. Small branches of the perforator are coagulated or clipped as they sprout into the muscle and the perforator is traced to the DIEA and the venae commitans.
The peforator(s) is/are approached from medial and lateral and isolated to the diea and veins.
The DIEA vessels are then traced back to near their origin while retracting the muscle away from the deep abdominal contents. When the entire flap is isolated on the perforator, and the recipient area is ready, the DIEA and the venae can be ligated and divided. The rectus sheath is closed with a running large caliber non-braided suture.
The flap is isolated on the diep vessels
The abdominal wall is undermined to the costal margin and the abdominal incision is closed in layers over suction drains with the hips flexed in a semi-Fowler position. The umbilicus is brought through the abdominal wall after it is stretched to near closure. The patient is allowed to mobilize when clinically indicated for th recipient area. The patient ambulates with the hips flexed until the tension of the closure slowly resolves.
