Muscle conserving free gracilis transfer (mini-gracilis free flap)

Abstract

Gracilis is a commonly used muscle for free tissue transfer. It is also split into two based on its pedicles and used as two units. Use of distal part as a free flap in isolation has never been described in literature. We describe a technique of harvesting a small unit of gracilis based on its minor pedicle and maintaining the continuity and conserving the major bulk of muscle. Thus, the function of the muscle is preserved and the same is also available for transfer on its major pedicle later, if required.

INTRODUCTION

Trauma to lower extremities is very common, resulting in soft tissue loss. Gracilis is a commonly used muscle for free tissue transfer for small- to medium-sized soft tissue defects.[1,2] Linear defects of tibia, defects around ankle and dorsum of foot, and exposed bone with osteomyelitis can be covered with gracilis free flap. Since gracilis does not result in much functional deficit, closure to the defect and can be harvested under regional block, it is more frequently used for free tissue transfer of lower extremities. It has been split longitudinally based on its neurovascular anatomy for functional reconstruction. Because of its type II nature of blood supply, it has been transversely split and used as multiple free flaps based on its major as well as minor pedicles.[3,4]

The idea and technique of harvest

A portion of gracilis centred over the minor pedicle can be harvested and transferred safely as a free flap to cover small- to moderate-sized defects, leaving behind the major part of gracilis with its major neurovascular pedicle. Preoperative Doppler is helpful in locating the minor pedicle along the lateral border of gracilis. A 5–7 cm exploring incision is centred over the junction of middle and lower-third of thigh along the line of gracilis harvest. The harvest can be done under tourniquet as the minor pedicle is usually present 10–15 cm further down, which is effectively 20 cm below the pubic tubercle. However, one may operate without tourniquet since the field is quite clean and bloodless. It is deepened until gracilis is reached. Then, the muscle is dissected gently from its bed on the lateral border to locate the minor pedicle. The size of muscle required can then be harvested by cutting both superiorly, inferiorly and longitudinally, keeping the entry point of minor pedicle safe [Figures 4 and 5]. The minor pedicle is dissected till the femoral artery in the subsartorial canal. The mini-gracilis can now be transferred as a free flap.

Figure 4.

Gracilis conserving mini-gracilis flap based on the minor pedicle. Showing the preservation of continuity of the muscle (approximately 50% width at the site of harvest)

Figure 5.

Schematic mini-gracilis raised on minor pedicle, showing conservation of the major neurovascular pedicle and major bulk and continuity of muscle

CASE REPORT

A 23-year-old male worker sustained accidental penetrating injury to his left foot with an iron rod while working in a factory. He was initially managed by an orthopaedician for 2 weeks. When the patient presented to us, he had granulating wound on the dorsum of left foot, measuring 11 cm × 9 cm on the medial side and 7 cm × 5 cm on the lateral aspect, with a bony tunnel through the cuneiform communicating both these wounds [Figures 1 and 2]. The extensors to the great and little toes were intact, but extensor digitorum communis of second, third and fourth toes were injured. The leg was on external fixator. Lateral X-ray showed a tunnel through the tarsals [Figure 3]. Routine investigations were within normal limits. The patient was eager to return to his home state at the earliest and was not interested in undergoing any major reconstructive procedure. So, our plan was to do basic minimum reconstruction so as to allow the wound to heal.

Figure 1.

Medial side of foot showing granulating wound 11 cm × 9 cm with a bony tunnel communicating with the wound on the lateral side of the foot

Figure 2.

A granulating wound, 7 cm × 5 cm on the lateral aspect, with a bony tunnel connecting the wound on the medial side

Figure 3.

X-ray showing the bony tunnel through the tarsal bones

The bony tunnel required filling of the defect with vascularised tissue to convert the complex defect into two separate simple wounds. External fixator was removed in consultation with the orthopaedician to simplify execution of anastomosis. We harvested a small cylindrical segment of gracilis, measuring 5 cm in length and 2.5 cm in breadth, based on its minor pedicle, preserving the continuity of the muscle [Figures 4 and 5]. This mini-gracilis flap was used to fill the bony tunnel and the artery of the minor pedicle was anastomosed end side to the dorsalis pedis artery and the veins to the dorsalis pedis venacomitantes. Thus, the complex defect was converted into two simple wounds with granulating wound in the periphery and vascularised muscle in the centre, which was skin grafted [Figure 6]. The patient had an uneventful postoperative recovery. The patient has a well-settled skin graft on the foot and a well-settled small donor scar in the right thigh [Figures 7 and 8]. He is able to walk with minimal limp after 2 months.

Figure 6.

Complex wound converted to simple wound after filling the bony tunnel with mini-gracilis free tissue transfer

Figure 7.

Well-settled skin graft on dorsolateral side with noticeable muscle bulge at the site of bony tunnel

Figure 8.

Well-settled skin graft on the medial side with noticeable muscle bulge at the site of bony tunnel

DISCUSSION

Gracilis arises from the ischiopubic ramus adjacent to the body of the pubis. It is widest and thickest superiorly (6 cm × 2 cm approx) and narrows to end as a rounded tendon to be inserted into the upper medial tibia. It is supplied by the anterior division of obturator nerve. Its vascular anatomy conforms to the type II pattern.[5] The major pedicle is a branch of medial circumflex femoral artery and enters the muscle 6–12 cm inferior to the pubic tubercle. The minor pedicle or pedicles arise from superficial femoral artery or the profunda femoris artery and enter the muscle 10–15 cm more distally. The muscle flexes the leg and rotates it medially and also is an adductor of thigh. It is preferred as free muscle transfer for coverage of small- to medium-sized defects, functional muscle transfer for facial palsy[6] and brachial palsies.[7] It has been longitudinally or transversely split and used for free tissue transfer.[3,5] Our technique utilises a small chunk of gracilis based on its minor pedicle, preserving the continuity of the muscle and its major pedicle. The length of the minor pedicle is 5–7 cm, and the diameter of the artery in the minor pedicle is 1.2–1.8 mm and that of venacomitantes is 1–1.2 mm[8] (which is not very difficult for anastomosis). In an anatomical study, single minor pedicle was present in 100% cases, but multiple minor pedicles were present in 90% cases.[9] If there is a single minor pedicle, most of the muscle can survive, especially the lower half. However, if more muscle is required, one may base the flap on its major pedicle.

Even though this muscle is expendable, since the nerve supply, blood supply, muscle bulk and continuity are preserved, theoretically there should be minimal functional impairment if any. The flap is ideal for covering small defects around the malleoli, ankle and foot, tendoachilis, metacarpophalangeal, metatarsophalangeal joints, exposed screw and mesh. In situations where the size of the defect is little larger, when the whole width of the muscle is required, the inferior half of gracilis can be taken in isolation, leaving behind the superior half with its pedicle. The other advantages of this procedure are a smaller donor site scar (however, scar at the upper thigh is cosmetically better located) and availability of the muscle on its major pedicle, if required at a later date.

CONCLUSION

Muscle conserving mini-gracilis can be a useful option in the armamentarium of microvascular surgeons for covering small defects with the advantages of minimal morbidity and a smaller donor site scar. Also, whenever required, the distal half of gracilis can be used in isolation, sparing the proximal half.