TISSUE :Skin and fat from the mid and upper buttock over the gluteus maximus muscle.
Innervation:Not harvested as a sensory flap.
Blood supply:The superior gluteal artery and venae via perforators through the gluteus
maximus muscle. The vessels at their exit from the pelvis are 3 to 4 millimeters in size.
Artery:Large caliber artery from 3 to 4 millimeters.
VEIN:The larger of the accompanying veins can become quite large, with a diameter
exceeding that of the artery.
PEDICLE LENGTH:From the point just between the gluteus medius and piriformis
muscles, the pedicle can be up to 7 centimeters in length
The SGAP flap has been primarily used as an alternate for breast reconstruction,
and requires significant microsurgical experience to harvest. The thickness of fat
available provides volume for unilateral reconstruction, but positioning and the donor
scar deformity have made this a less popular choice even among very experienced
microsurgeons.
The superior gluteal artery exits between the gluteus medius and piriformis muscles.
The superior gluteal artery and it's venae perforate the gluteus maximus to enter the
subcutaneous fat of the flap.
The superior gluteal artery and venae arise from the internal iliac system deep
in the pelvis. They exit posteriorly through the greater sciatic foramen, superior to the
piriformis muscle and inferior to the gluteus medius. The vessels perforate the gluteus
maximus muscle on their way to the fat and skin that overlies them. The exit from the
sandwich formed by the piriformis and the gluteus medius corresponds roughly
anatomically to 6 centimeters below the posterior superior iliac spine and 4.5
centimeters lateral to the midline of the sacrum.
The exact position of the perforators is found by using the pencil Doppler to
identify their course lateral to the exit of the artery from the pelvis.
The inferior gluteal artery and the sciatic nerve emerge inferior to the piriformis
muscle, supplying the territory of the inferior gluteal flap.
The inferior gluteal artery and the sciatic nerve emerge inferior to the piriformis
muscle, supplying the territory of the inferior gluteal flap.
OPERATIVE PROCEDURE
The lateral decubitus position is used for a unilateral flap. The patient is placed
prone for bilateral flap harvests.
The skin island of the flap is drawn overlying the superior gluteal artery
perforators marked out by pencil Doppler exam. The flap is elliptical, an at roughly a
45 degree slant upwards from medial to lateral. The apex of the axis of the flap is
marked beginning two to three finger breadths below the gluteal crease in the midline
and extending laterally and superiorly to incorporate the perforator vessels. This
allows for placement of the scar below many clothing variations. The flap can be
designed from 6 to 13 centimeters wide and from 20 to 25 centimeters long. Surgical
judgement must be used to ensure too much width is not taken a a defect is left
behind that requires excessive tension for closure.
The orientation and position of the flap is marked. It begins medial two or three finger
breadths below the upper aspect of the gluteal crease. It then angles superiorly and laterally
as depicted
The flap is elevated from superior and lateral to medial, deep to the muscular fascia. The
exit of the dominant perforator from the gluteus must be identified.
When the dominant perforator(s) is found, it is traced through the muscle and between the
piriformis and gluteus medius.
The flap is elevated from lateral and superior toward the medial aspect, deep to
the muscular fascia and above the gluteus maximus muscle. When the larger
perforator(s) are identified as one proceeds medially, they are traced into the muscle
with bipolar dissection and dissected to their exit from between the piriformis and
gluteus medius muscles.
The medial and inferior incisions can be made and the pedicle traced more
proximally by placing retraction between the exit of the artery and it's venae between
the muscular space by separating the muscles from the vascular system. The artery
and venae enlarge significantly in size at this point and there are multiple small
branches emanating in all directions. They require careful ligation with bipolar
electrocautery and/or hemoclips. Loss of proximal control of the vessels can be lead to
significant bleeding and retraction of the vein into the pelvis.
The donor area is closed in layers over a suction drain. The patient is placed
post-operatively supine, and can have slight hip flexion. Ambulation is allowed in 3 to 4
days as the donor tension relaxes.
