Gracilis Tissue Transfer

Anatomy and Physiology

The gracilis muscle is the most superficial of the adductor muscles; it originates on the symphysis pubis and pubic arch. It inserts distally onto the medial surface of the tibia within the pes anserinus. The muscle belly is broad and flat at its origin but tapers to its insertion. It functions to adduct, flex the knee and hip, and medially rotate the hip.[4] As described by Mathes and Nahai, the gracilis has a Type 2 blood supply, one dominant pedicle with several minor pedicles.[5]

The dominant pedicle for this flap is from the descending branch of the medial femoral circumflex artery, although a direct branch from the profunda femoral artery has been described. In most adults, the perforating vessel may be found approximately 10 cm inferior to the pubic tubercle. Arising from the common femoral artery, the medial circumflex artery branches run deep to the adductor longus and superficial to adductor magnus. Usually, two vena comitantes accompany the dominant pedicle.

The gracilis can also be harvested with a skin paddle at the base of the muscle thanks to fasciocutaneous and musculocutaneous perforators. The anterior branch of the obturator nerve provides innervation to the muscle and the surrounding skin. Arising from the obturator foramen, the nerve then divides into anterior and posterior branches beneath the pectineus muscle. The anterior branch then passes in between the adductor longus and brevis to eventually innervate the deep aspect of the gracilis muscle. Both the vascular and nerve pedicles can be harvested with about 7 cm of length, making the gracilis muscle ideal for free tissue transfer.

Indications

The indications for the use of the free gracilis are numerous and can subdivide into two broad categories: functional and non-functional. Functional tissue transfer refers to the harvest of a muscle with its respective intact nerve, which allows the muscle to contract, providing the patient a dynamic repair. Since this article is specifically about free gracilis transfer, it will focus on those indications. 

Functional free gracilis tissue transfer has been used in brachial plexus injuries to restore elbow flexion, Volkmann's contracture to restore wrist flexion, facial reanimation, and finger extension or flexion after tumor resection.[6][7]

Non-functional free gracilis transfer is mainly used for soft tissue coverage after lower extremity trauma. The TUG flap has also been described as a second-line choice for microsurgical breast reconstruction.

Contraindications

There are no absolute contraindications for free tissue transfer. Age is not a risk factor for these procedures. ASA class III, increased operative times, smoking status, and obesity are all risk factors for complications such as flap failure, but no single risk factor has shown to be an absolute contraindication to free tissue transfer.[8]

Equipment

The required equipment is the same as for any standard operation with the addition of microsurgical instruments. Most importantly is the magnification by either loupes or microscope. A microsurgical tray includes jeweler’s forceps, micro scissors, microneedle holders, microvascular clamps, vessel dilators, micro suture (8-0, 9-0). Topical and intraluminal medications such as papaverine, heparinized saline, and TPA should be available on the field. Depending on the institution, there may be different flap monitoring techniques such as internal Doppler devices, transcutaneous Sp02 monitors, or a Doppler probe.

Personnel

Ideally, a microsurgical scrub team should receive training at the hospital where these procedures are performed. Microsurgical instruments are delicate and different than the vast majority of other surgical equipment. While in the ICU, nursing staff familiar with flap monitoring should be utilized. Appropriate training for staff is imperative for optimal outcomes.

Preparation

As for all surgeries, a thorough history and physical are required. Risks and comorbidities are reviewed and optimized when appropriate. An in-depth discussion with anesthesia and nursing to avoid the use of pressors and vasoactive drugs during the case and the need to have anticoagulants available. Appropriate pads are placed on bony prominences to decrease the risk of pressure sores. The patient is prepped and draped in the usual sterile fashion.

Technique or Treatment

The elevation of the gracilis muscle is relatively straight forward. The skin incision will vary depending on whether or not a myocutaneous flap is raised. 

Standard surgical prep is used from the pubis to below the knee. With the patient under general anesthesia, the leg is abducted and externally rotated. While in this position, the adductor longus becomes taught and easily palpated at its origin from the pubis. The gracilis muscle originates posterior to the origin of the adductor longus. Next, a line is drawn from the gracilis origin to the medial femoral condyle. The incision is placed 2 to 3 cm posterior to this line in the proximal aspect of the thigh. 

The gracilis muscle is the most superficial of the adductors, located in between the adductor longus anteriorly and adductor magnus posteriorly. If questions arise, the microsurgeon may flex or extend the knee as the gracilis is the only one of the three muscles to cross the knee joint. After the muscle is isolated, meticulous dissection around the muscle belly takes place to identify the vascular pedicle from the deep surface. The pedicle is consistently 10 cm from the pubic tubercle between the adductor longus and magnus. Dissection of the pedicle occurs from distal to proximal ligating branches to the adductor longus and magnus until traced back to the origin. If the flap is for functional free tissue transfer, the microsurgeon will need to locate the anterior branch of the obturator nerve and follow it back as far as necessary. 

The muscle is then divided from its origin through the same incision, and distally at the pes anserinus through a separate incision. The insertion of the gracilis tendon lies in-between the sartorius superficially and semitendinosus deep. 

After harvesting the flap, it is flushed with heparinized saline, placed at the site of the defect, temporarily fixated to a position that will allow for safe microsurgical anastomosis. Many different techniques exist for vessel anastomosis; most incorporate hand sewn arteries and venous coupler. After ischemia time ends, the flap is then inset into the defect. If a muscle flap is harvested and inset depending on preference, the microsurgeon may skin graft immediately or wait several days. For myocutaneous flaps, the skin is inset into the defect, and a perforator is identified for Doppler probe monitoring.[9]

Complications

As with any surgery, free tissue transfer is not without complications. These complications may be minor such as skin necrosis or partial flap loss to major such as flap failure. One study of extremity trauma and reconstruction with free gracilis muscle only transfer showed higher generalized complications with increasing age >70 and ASA score. Higher ASA score also correlated with increased major flap complications.[10]

Clinical Significance

The free gracilis is a procedure all microsurgeons should have in their armamentarium. It is one of the “workhorse” flaps for reconstruction. It can be used all over the body for a variety of soft tissue defects, functional deficits, and extremity salvage. 

Enhancing Healthcare Team Outcomes

In a busy reconstructive practice, the plastic surgeon is involved with a vast number of different specialties and subspecialties to heal wounds and provide solutions to complicated problems. These include head and neck reconstruction, limb salvage, breast reconstruction, and traumatic soft tissue defects. These patients frequently are topics of discussion during interdisciplinary rounds. This interprofessional approach to manage complex injuries or wounds provides the patient with the optimal outcome.