DIEP (Deep Inferior Epigastric Artery Perforator) Flap is becoming one of the commonest autologous breast reconstruction operations and is considered by many as the gold standard. The procedure uses lower abdominal tissue for reconstruction to create a breast mound with excellent long term results. The ideal candidate should have enough lower abdominal tissue for the reconstruction (unilateral or bilateral) keeping in mind that this is a one off opportunity.
The main contraindications for this procedure is the lack of enough abdominal tissue and of course the general health and fitness of the patient to undergo a 4-6 hour procedure. Relative contraindication include smoking, diabetes, morbid obesity, vascular disease, hypercoagulable state and abdominal scars disrupting the vessels. Discretion should be exercised in patients with significant co-morbidities that are planned for, or likely to require adjuvant chemotherapy or radiotherapy. Experienced surgeons and team in theatre and post operative period is key.
The deep inferior epigastric artery (DIEA) 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 it. The perforators range in size from 0.3mm to 1mm. Flaps including zones one to three can be reliably harvested on a single large perforator.
In immediate reconstruction, the breast is marked with the patient standing. The midline (sternal notch to umbilicus), anterior axillary line, infra-mammary fold (IMF) and breast footprint is marked. If a smaller breast is anticipated or desired a conservative wise pattern marking is used. Markings must be more conservative than for a standard breast reduction so that there is little risk of skin shortage or tightness following flap inset and wound closure.
In unilateral delayed reconstructions, the footprint and IMF are transposed from the contralateral side, with the IMF being placed 2cm above the contralateral to accommodate downward migration following abdominal closure.The skin envelope deficiency is measured by subtracting the distance from sternal notch to new IMF on the mastectomy side from the sternal notch to IMF on the contralateral side.
The abdomen is marked with the patient supine. The presence of abdominal scars, bulges, hernia and rectal divarication should be documented. The midline marking to the umbilicus is continued to the symphysis pubis. The upper limit of our flap corresponds to the upper border of the umbilicus in the midline and the lower limit is marked at approximately 12cm below this. This will ensure maximal recruitment of perforators. We use 12cm as the flap width that can be accommodated in the majority of abdominoplasty closures without undue tension on the wound. This may be increased or decreased according to patient height and body habitus. The lateral limit to the flap is just medial to the anterior-superior iliac spine (ASIS). A gentle upward curve on the lower border and a relatively straighter line on the upper border then join the points.
Pre-operative detection of perforators: The use of CT angiography, MRA and hand held doppler are well described in aiding detection of suitable perforators. A detailed discussion of these methods is beyond the scope of this book however,we have found that the use of CT angiography, undertaken and reported by an interested and experienced radiologist can significantly reduce the operative time spent localising a suitable perforator.
The operation is considered long and tedious, the process is simplified by dividing it to multiple steps, each performed to perfection in timely manner will result in efficient use of theatre time with good outcome
Preparation and Flap Dissection
We preferentially use the contralateral flap to facilitate a two-team approach. The lower border of the hemi-abdomen is incised first. The SIEV is identified and between 2 to 3 cm distally included. We do not include a greater length as typically a vein graft is required regardless of length if used a s a lifeboat. Dissection continues straight down to the rectus sheath.
The superior incision is made down to Scarpa’s fascia and additional sub-Scarpa’s fat is recruited into the flap while preserving the fascia that gives strength and facilitates the abdominal wall closure. We recruit 2-3cm of subscarpa’s fat superiorly to increase the volume of the flap and minimize oedema and bulk of the upper abdominal flap post-operatively. When dissecting laterally, firm medial traction on the flap allows resection of a greater volume of fat around the ASIS and minimizes ‘dog-ear’ formation. The umbilicus is isolated and dissected as per standard abdominoplasty.
Once outlined in this way, dissection proceeds at the level of the rectus sheath, towards the midline, advancing the leading edge of the flap along a broad front. As dissection proceeds there may be cues to encountering a suitable perforator. These include: Tenting of the rectus sheath. A bluish hue within the advancing edge. A hole in the rectus sheath; arborizations within the deep fat of the flap. Most suitable perforators will lie within a six centimeter radius of the umbilicus.
Our choice of perforator depends on whether the procedure is bilateral or unilateral. The ideal perforator is a medial row one as this lies more centrally within the flap and provides a longer pedicle.However, if performing a bilateral procedure where perfusion of only a hemi DIEP is required, lateral row perforators may suffice. This is supported by recent perfusion studies of the abdomen which demonstrate primary zones 1 and 2 of medial row perforators comprise the entire ipsilateral hemi-abdomen and routinely cross the midline to perfuse the medial part of the contralateral hemi-abdomen, whereas primary zones 1 and 2 for lateral row perforators are more limited and do not routinely perfuse the contralateral hemi-abdomen.
It is noteworthy that selection of a lateral row perforator will entail greater dissection of the nerves. The nerves that innervate the rectus abdominis muscle have been shown to enter the posterior surface up to the midpoint of the muscle just medial to the lateral row perforators, therefore harvesting of lateral row perforators may denervate the rectus muscle.
Vessel diameter is a key factor in perforator choice. In accordance with Hagen-Poiseuille’s Law the flow in a tube is related the fourth power of the radius, therefore choosing a single perforator of greatest diameter is far more effective than multiple perforators of a smaller diameter at increasing blood flow .
Once a perforator has been selected, the anterior rectus fascia is incised. By gently pushing the deep tissue off the fascia the perforator is encircled. A small cuff of fascia around the perforator is left to minimise this risk of injury to the perforator and in addition the weight of the fascial ring is advantageous in allowing the pedicle to untwist during inset. Splitting the fascia a few centimetres longitudinally superiorly and inferiorly aids visualization of the proximal transmural course of the perforator.
Muscle superficial to the perforator is divided using bipolar cautery. Perforator dissection is aided by initially dissecting the muscle from the anterior surface of the perforator, up to the posterior rectus space. Once the perforator’s anterior surface is adequately exposed, it is released from its lateral and posterior muscle attachments. It is important to ligate branches at a distance( 1 to 2 mm) form the perforator, such that if the clip were to become displaced, a new clip could be applied without risk of damage to the perforator. For smaller branches bipolar coagulation is used. Dubakey forceps interposed between the perforator and bipolar to act as a heat sump prevents thermal injury to the perforator. Use of a small self-retaining retractor can aid dissection through very gentle traction upon the surrounding tissues.
As dissection proceeds towards the main pedicle, the motor nerves will be identified. This will occur more frequently if a lateral row perforator has been chosen, in addition the nerves are more likely to be orientated above the perforator, contrasted with medial row perforators where the nerves are deep.
Once the perforator has been completely dissected free long its’s length up to the posterior sheath, dissection can proceed with relative ease to the main pedicle. We undertake this final phase of dissection transmuscularly and choose not to do this from the lateral edge of the rectus muscle to to avoid traction upon the motor nerves.
Once sufficient pedicle length is obtained (typically 10 to 13cm), the proximal vessels are triple ligated and the pedicle divided. This is usually just proximal to the point where the DIEVs become confluent. The distal end is not ligated as this permits observation of retrograde flow from both artery and vein. The presence of retrograde flow firstly indicates that the vessels are unlikely to have been injured during harvest and secondly it indicates the presence of crossover between the hemiabdomens, albeit in the opposite direction.
Abdominal Wall Closure
Once the flap is removed flap is removed the fascia is closed with a double layered 0 Looped Nylon. The abdominoplasty flaps are approximated with a sharp towel clip and the position of the umbilicus marked on the anterior abdominal wall. An oval disc of skin is excised and a longitudinally skewed cone of fat is removed to mimic the depression surrounding a aesthetically pleasing umbilicus. Two 2/0 Vicryl sutures are places between the rectus sheath and the deep dermis of the anterior abdominal wall in the three o’clock and nine o’clock position lateral to the umbilicus. This serves to firstly to recreate the natural indent surround the umbilicus and secondly distributes some of the tension of the abdominal wall closure away from the inferior suture line. The abdominal wall is then closed in two layers; a 2/0 Vicryl to the fascia and an absorbable barbed suture to the deep dermis (V-Loc™).
Flap Design and Inset
In unilateral breast reconstruction zone 4 of the elevated flap is excised. Gentle compression of the flap reveals any open blood vessels to coagulate or clip. To create projection of the flap, one to three figure of eight sutures are used on its’ deep surface.
The flap is orientated so that the superficial vein is superomedial. By holding the flap over the defect and allowing the pedicle to hang freely, any twisting of the pedicle will correct itself, aided by the weight of the fascial cuff. Once the pedicle has stopped moving it can then carefully be delivered to the recipient vessels. The generosity of the pedicle length of the DIEP flap permits the use of varied recipient vessels. In our unit we predominately use the thoracodorsal vessels. This is particularly advantageous in immediate reconstruction as the axilla is accessed with ease.
The flap is secured onto the chest wall with four to six 2/0 Vicryl sutures. These should pass through scarpa’s fascia of the flap and not the dermis to avoid an unnatural step post-operatively. In skin sparing mastectomies where a nipple disc of skin remains, we incise through the dermis approximately 2mm from the skin edge, this minimises the ridge effect which can occur when suturing the mastectomy skin flap directly to the nipple disc. Two to three drains are used depending on the recipient vessel site.
In our unit the preferred site of anastomosis is to the thoracodorsal vessels. A lzy S or a small V shaped insision with the use of two self retaining retractors gives adequate exposure. The anastomosis is usually performed above the bifurcation of the Serratus Anterior Vessels allowing for the Latissmus Dorsi to be used as a local pedicle flap based on the Serratus Branch if needed in the future. (Further details about the anastomosis is found in the microvascular anastomosis Chapter)
Stacked flaps can be used in patients in large breasted breast, to match the contralateral side. The will allow the utilization of the whole volume of the lower abdominal flap, avoiding contralateral breast reduction or fat transfer to match the volume. Also this can be used in patients with midline abdominal scars. Another way of augmenting the volume is combining the flap with an implant.
Post operative management
Patients are nursed in a high dependency unit in accordance with our unit’s protocol. Clinical monitoring of the flap every hour day one post-op, every two hours day two post-op etc continues to a minimum of four hourly observations day four and subsequent inpatient days. Patients sit out day two or three and mobilise day four. The majority of patients are discharged day six or seven post-op.
The patient lays flat with one pillow under her head not allowed to sit pt up or roll. Knees are flexed using bed controls/pillow. Sips of water are allowed in the first 12-24 hours and IV fluid are prescribed. ½ hourly flap observations for 4 hours then 1 hourly. Arm position as indicated by surgeon, affected side not to go into a gown for 5 days and patient not to move shoulder to elbow on the surgery side.