The Gracilis Flap
Anatomic considerations
A long and thin muscle, the gracilis provides a reliable workhorse for reconstructive microsurgery. Both for wound coverage, and as a functional muscle transplant, the gracilis has wide reconstructive applicability. The intramuscular neural anatomy allows the muscle to be thinned segmentally, allowing excessive bulk to be trimmed as needed before functional muscle transplantation.
The muscle width varies with the size of the patient, and is generally wider in men, and physically fit patients. It can be used to cover wounds roughly up to 6 cm wide and 20 cm long. It has broad applicability in both lower and upper extremity reconstruction and in functional muscle reconstruction after paralysis or muscle loss.
Anatomy
A medial thigh muscle, the gracilis takes origin off the pubic symphysis, inferior pubic ramus and ischium then inserts distally into the medial condyle of the knee. The axis of the muscle can be outlined by drawing a line from the ischium to the knee medial condyle. Or alternatively, the adductor longus is palpated medially with the thigh abducted, and the gracilis axis is defined 2 to 3 finger breadths posterior to the adductor longus.
Vascular Anatomy
The afferent artery and efferent veins run superficial to the adductor magnus muscle, underneath the adductor longus. By retracting the adductor longus, the artery can be traced to it's origin on the medial femoral circumflex vessels, branches of the profunda femoral system. There are two secondary pedicles to the gracilis muscle, that can be found segmentally and distal to the proximal pedicle. The are both ligated and divided when the muscle is harvested. With extremely short leashes, they are not used for revascularizing the gracilis as a free flap.
Note in the figure below that the nerve branches into three segments to supply the anterior, mid and posterior segments of the muscle. This arrangement is valuable for thinning and debulking the muscle.
The gracilis vessels take origin from the medial femoral circumflex system, a branch of the profundda femoral vessels.
Flap Harvest
The patient is placed supine, with the leg prepped entirely free to the groin. The thigh is abducted and the knee slightly flexed. The axis of the muscle is marked posterior to the adductor longus by two the three finger breadths. Because the pedicle enters the muscle approximately 10 centimeters below the ischium, the incision markings need to take this into consideration. An optional distal incision is made near the muscle insertion at the knee to transect the distal tendon if the entire length of the flap is needed.
The incision is marked over the axis of the muscle, two to three finger breadths below the easily palpable adductor longus muscle.
The proximal incision is carried down through the fat and the muscular fascia to the muscle. The fascia is elevated off the muscle anteriorly and the septal junction of the gracilis and adductor longus is identified. This space is then entered by retracting the two muscles from each other and the pedicle to the gracilis is identified in this areolar plane. The pedicle can be isolated at this point or further muscle dissection may be performed now that the vascular supply has been safely located an protected.
The pedicle is identified by incising the muscular fascia over the gracilis muscle and retracting the space between the gracilis and adductor longus. The pedicle is traced back to its origin by exposing it between the planes of adductor longus and magnus.
The muscle is then freed of all soft tissue attachments except for the pedicle. The proximal tendon is cauterized to detach it from the ischiopubic ramus and the distal muscle is transected with cautery near the insertion or at the distal wound, depending on the length needed. The nerve is transected - long if a functional muscle is being transplanted, or short if length is not necessary.
After exposing the pedicle, the proximal and distal insertions need only be detached and the minor pedicles divided.
The wound is closed in layers over a suction drain. The patient is allowed to ambulate when clinically acceptable for the recipient site area.
Post-Operative Care
The ankle is splinted in neutral and the patient is allowed to ambulate in a cast shoe at about a week after surgery, usually with an ace wrap to prevent edema. At all other times the foot is kept elevated. The donor site can heal slowly if closed under tension or in the elderly patient.