Authored by Matthew M. McRae, MD, FRCS(C), Mark H. McRae, MD, FRCS(C) and Rudy Buntic, MD
The PAP flap is an alternative to abdominal based donor sites for autologous breast reconstruction in patients where the abdomen is undesirable or contraindicated. It has been championed as an alternative to the TUG flap. The profunda femoris artery supplies the tissue of the posterior thigh through musculo and septocutaneous perforators. Claudio Angrigiani is credited with first describing and utilizing this flap in lower extremity and burn contracture reconstruction. It can be a source of autogenous tissue in small to medium sized breast reconstructions. Drawbacks include an inconsistent dominant perforator location (need for preoperative studies) and a narrow flap width limiting donor tissue volume.
As described by Cormack and Lamberty and confirmed by Angrigiani et. al, a perforator from the medial branch of the profunda femoris artery emerges 2 cm posterior to the gracilis and 8 cm inferior to the groin crease. The vessel then travels through the adductor magnus muscle and supplies the skin. The location of the dominant perforator as it pierces the fascia is variable. Perforators may also emerge through the semitendinosis and semimembranosus muscles and from the intervening septa between the gracilis and the semimembranosis as one moves down the leg. However, in the upper third of the leg, the adductor magnus perforators predominate.
Furthermore, in the posterior medial thigh there are overlapping angiosomes. The superior posterior thigh tissue can also be elevated on the inferior gluteal artery system as well as the medial circumflex femoral artery. Pre-operative imaging with MRA or CTA is used routinely to clarify perforator anatomy to the posterior thigh region.
The perforator for the PAP flap travels through the adductor magnus muscle. The muscle is large, and runs parallel, posteror and deep to the gracilis muscle.
The PAP and accompanying veins arise from deep within the thigh and run postero-medially, providing blood flow to the upper medial and posterior thigh.
Cross Section of the upper thigh. The gracilis, adductor longus and adductor magnus are indicated by the arrows. The perforator from the profunda femoral vessels in this case travels though the adductor magnus before it pierces the deep fascia of the inner thigh to enter the subcutaneous fat.
Landmarks for the PAP flap include the gluteal fold and groin crease, the posterior limit of the iliotibial band postero-laterally, and the gracilis muscle medially. The tissue is harvested from the upper third of the posterior thigh between the gluteal crease and the popliteal fossa.
Anatomy of the skin nourished with the PAP flap. A narrow strip of skin (7 centimeters or less) is obtained. The upper border of the flap is approximately 1 cm below the groin crease anterior and centrally and then travels just befow the gluteal fold posteriorly.
The patient can be marked upright to assess the gluteal folds and the extent of the posteror and anterior flap. The peforator is marked intraoperatively with a Doppler and the skin paddle can then be adjusted accordingly.
The patient is prepped and draped supine with the arms stretched out on an arm board. The lithotomy stirrups are well padded and care is taken not to place pressure on the peroneal nerves as they travel over the neck of the fibula. The thigh can be pinched to determine the tightness of postoperative closure and markings can be adjusted if necessary.
Lithotomy positioning enables the surgeon to dissect the posterior aspect of the flap under direct vision. Alternatively, the patient can be positioned prone, prolonging the surgical procedure for the necessary repositioning.
The flap is drawn as an ellipse that captures the dominant perforator (approximately 2-4 cm posterior to the gracilis muscle). The superior line is marked 1 cm below the inferior gluteal fold and extends medially below the groin crease as far as the anterior gracilis muscle. Posteriorly the incision should not extend much beyond the midline of the gluteal crease where the scar becomes more visible as the gluteal fold becomes less distinct. The further posterior-lateral the incision is made, the more difficult the dissection, flap elevation and closure become when positioned supine. The inferior incision is marked based on pinch with the patient in the standing position, 6-7 cm inferior to the superior line.
The legs are abducted and knees are bent and placed in stirrups. The perforator location may be confirmed with MRA or CT angiography pre operatively and can be confirmed with a pencil Doppler after the patient is positioned.
The skin incision are made and the dissection proceeds deep to the muscular fascia anteriorly but at the layer of Scarpa's fascia posteriorly and lateral to the adductor magnus. Elevation proceeds from anterior to posterior or inferior to superior. By dissecting at Scarpa's fascia level, damage to the posterior femoral cutaneous nerve of the thigh is prevented.
The dominant perforator is identified (a second additional perforator may be selected). The dominant perforator is approximately 3 cm posterior to the gracilis muscle as it exits the substance of the adductor magnus. Perforator dissection follows an intra-muscular or septal course prior to entering an areolar plane between the adductor magnus and flexors of the leg. Pedicle dissection continues until the vessels are of adequate diameter and of adequate length to reach the internal mammary vessels of the chest. This does not require dissection to the take off from the profunda femoris artery. Rarely is more than 7 cm of vessel needed assuming the internal mammary system is used to nourish the flap. Although the flap has been described as best suited for reconstruction of the ipsi-lateral breast, contralateral reconstruction is also adequately achieved.
The perforator is traced through the adductor magnus toward its origin. The length of the pedicle isolated need not extend to the origin of the system at the profunda femoral vessels.