Cross-Leg Microvascular Free Anterolateral Thigh Flap as a Safe, Viable, and Reserve Option for Reconstruction in a Vessel-Depleted Limb

Abstract

We present the case of a 36-year-old male patient with a posttraumatic composite defect of the lower two-thirds of the anterior aspect of the left leg with exposed necrotic tibia in an old, neglected type 3b fracture of the tibia of 9-month duration. The options for definitive soft-tissue cover include microvascular free tissue transfer and cross-leg flaps. In trauma cases, the surrounding tissue is usually damaged, and the recipient vessels are frequently implicated, ruling out the use of a microvascular free flap. Cross-leg flaps are unachievable due to large defect sizes and lack of appropriate donor tissue. In this case report, we highlight the use of cross-leg microvascular free anterolateral thigh (ALT) flap cover for the composite leg defect. By presenting our case, we aim to advocate the clinical application of cross-leg free flap surgery in vessel-depleted limbs as a safe and viable option.

Keywords

leg defects - cross-leg free ALT - turnover flap

Introduction

There has been a rise in the cases of leg defects due to the increasing number of traumatic injuries over the past few decades. Free flaps/free tissue transfers are a popular option to resurface the leg defects in traumatic injuries. When there are no acceptable recipient vessels in the injured limb, cross-leg free flaps can be utilized. Here, the free flap is anastomosed with the contralateral limb vessels (unaffected limb), which perfuse the flap, while it covers/drapes the defect of the affected limb. Both limbs are held in the final appropriate position with the help of external fixators.

In situations where local and microsurgical flap options are not available, which could be due to extensive trauma resulting in vascular injury or certain patient factors, the last resort in the form of a salvage procedure is the cross-leg flap. In this case report, we wish to highlight the application of a hybrid “cross-leg free anterolateral thigh (ALT) flap” procedure for soft-tissue coverage of the defect and early recovery of the patient. There needs to be more literature available on this approach to the management of leg defects.

Case Report

A 39-year-old male patient presented with a posttraumatic grade 3b composite defect over the lower two-thirds of the anterior aspect of the left leg with an exposed necrotic tibia, measuring 20 cm × 8 cm ([Fig. 1]). Debridement of the exposed bone and free ALT flap cover was planned ([Figs. 2] [3] [4]). Following debridement, the recipient vessels were explored and found to be inflamed and fragile with poor blood flow. A decision was made to use the opposite leg's posterior tibial vessels as recipient vessels.

Fig. 1 Left: Posttraumatic composite defect over the lower two-thirds of the anterior aspect of the left leg with exposed, necrotic tibia. Center: Preoperative X-ray. Right: X-ray post bone debridement.

Fig. 2 Defect postdebridement.

Fig. 3 Cord-like structure of the posterior tibial neurovascular bundle and severe gross inflammation in the wound bed. (The anterior tibial vessel status found to be similar.)

Fig. 4 Left: Free anterolateral thigh (ALT) flap marking. Right: Free ALT flap harvested from the right thigh.

Posteriorly based turnover flaps were marked to create a bridge between the lower limbs, over which the vascular pedicle would lie. The left leg turnover flap was marked in continuity with the defect, and in the right leg, it was marked at the site of posterior tibial vessel exploration. Turnover flaps of dimension 5 × 4 cm were raised in both legs ([Fig. 5]).

Fig. 5 Inset of turnover flaps.

The posterior tibial vessels of the unaffected limb were explored and prepared for microvascular anastomosis. Both legs were brought in proximity and posteromedially-based turnover flaps were sutured together so that the skin surface would face posteriorly, and the raw surface would face anteriorly on which the eventual vascular pedicle would lie ([Fig. 5]). Then the legs were immobilized using a multiplanar external fixator. An ALT flap of 25 × 8 cm dimension was harvested and brought to the recipient site where the end-to-end method of vascular anastomosis was done and flap inset was done ([Fig. 6]).

Fig. 6 Left and center: Pictorial depiction of the end-to-end microvascular anastomosis. Right: Final suture line and flap inset. Multiplanar external fixators are used to immobilize the limbs in the final desired position.

Postoperatively, the patient was given 5,000 units of heparin intravenously in 500 mL of normal saline over 24 hours for 5 days. On post-op day, 17 areas of superficial epidermal necrosis were noticed over the flap, and the patient was put on higher antibiotic cover. The flap settled over a week, and after 4 weeks, partial division was done by putting an incision over the ALT flap and normal leg skin junction. The vascular pedicle was clamped, and the flap was monitored for 24 hours before complete division and inset was done ([Fig. 7]). The patient is now being planned for restoration of bone length using Ilizarov's procedure ([Fig. 8]).

Fig. 7 Healed and settled flap.

Fig. 8 The patient ambulating 1 month postoperatively (the video of the same can be seen in [Supplementary Video 1],).

Discussion

A vessel-depleted condition owing to extensive trauma in the lower limbs is a common scenario. Perivascular physiologic changes make the zone of injury thrombogenic and friable.[1] The free ALT flap is the most preferred option for soft-tissue reconstruction in the lower limbs.[2] It has rightly become the workhorse flap for soft-tissue reconstruction of the lower extremity due to its versatile nature owing to the consistent anatomy of the vessels and reliable supply to a large skin area.

In situations where complex microsurgical anastomosis is not possible or in cases of failed free flaps, a popular and safe option for management is a cross-leg flap.[3] [4] Hamilton in 1854 performed the cross-leg flap to resurface a chronic nonhealing ulcer. Since the advancement of microsurgery, free tissue transfers have replaced the traditional cross-leg flaps.

Our case had a very huge soft-tissue defect measuring almost 25 × 8 cm in size, precluding a conventional cross-leg flap due to its enormous donor site morbidity.[5] The first successful use of the cross-leg free ALT perforator flap for covering a defect over the dorsum of the foot was demonstrated and published by Serel et al in 2006.[6] They used the end-to-side anastomosis of the flap's vessel to the posterior tibial artery of the other leg.

In cases of extensive trauma, postradiation or chronic infection, healthy vessels may not be present close to the defect to be reconstructed.[7] In these not uncommon situations, lengthening of the vascular pedicles is imperative. Classically, this has been accomplished using vein grafts or arteriovenous loops with a reported increase in complication rates up to fourfold.[8] A temporary arteriovenous loop is created using a vein graft, creating new recipient vessels in the first stage, followed by bisecting the loop and anastomosing the donor vessels.[9] Vessel gaps less than 10 cm can be reconstructed with interposition or transposition vein grafts. For longer gaps, arteriovenous loops or flow-through flaps must be considered.[10] Chuong et al illustrated the use of vein grafts in the head and neck microsurgical reconstruction, where the mean length of the vein graft was up to 37 cm. Although the sample size is limited, the study provides data regarding the long segment vein grafting in complex reconstructive cases.[11] An alternative option would be a cross-leg free muscle flap (latissimus dorsi or gracilis) followed by a split-thickness skin graft (STSG) cover.[12]

In our technique, the vessels are sandwiched between the turnover flap inferiorly and the free ALT flap superiorly, making it safe and countering the tension at the donor site anastomosis region. Previous studies on cross-leg free ALT flap did not describe how the vessels can be safeguarded, so this turnover flap method is safe and reliable although it needs a long series. Since the recipient limb was infected and inflamed, an infection might be the reason for de-epithelialization of the flap noted on postoperative day 17, but a good blood supply and sturdy vascular network of the ALT flap was able to counter the infection and re-epithelialization occurred by postoperative day 28.

If there is no tissue for the turnover flap in a limb having trauma, it can be planned on a normal limb; however, a longer transposition flap can also act as a bridge segment over which the recipient vessel will rest.

Conclusion

The cross-leg-free ALT flap offers functional restoration and cosmetic improvement in cases of extensive trauma and vascular injury, where traditional microvascular flaps or cross-leg flaps cannot be done. The cross-leg microvascular free ALT flap is a more effective method for covering large defects compared with cross-leg flaps, in terms of less donor site morbidity, hidden scar, axial vascularity, and better limb positioning in post operative period.

Supplementary Video 1 Video depicting patient walking with support of walker with ALT flap and external fixator in-situ.

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Conflict of Interest

None declared.

• References

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Publication History

Article published online:
03 October 2024