Severe lower limb trauma with large-sized soft tissue defects and tibia bone exposure is frequently encountered at emergency department, and further reconstruction remains a big challenge for surgeons [20]. In this situation, flap procedures were necessary for defect coverage and limb salvage. However, local flap technique or ipsilateral free flap transplantation are often impossible due to extensive tissue defect and potential vascular damage. In this study, we introduced a modified recipient blood flow-preserved cross-leg anterolateral thigh flap procedure for reconstruction of complex lower limb injuries. This method is an effective and safe alternative for patients with different sizes of tissue defect in unilateral lower limb.
The cross-leg flap technique has been applied to patients with lower limb injuries a long time ago. Since it was first introduced by Stark in 1952, various cross-leg flap procedures were reported, including pedicled flap procedures and free flap procedures [1, 21]. For small-sized tissue defect, cross-leg pedicled flap procedure was preferred for the reason that it is relatively easy and safe to perform [22]. However, for large-sized defect, cross-leg free flap procedure was the optimal strategy [23, 24]. The cross-leg free flap surgery has been applied to lower limb reconstruction since 1979 [25]. In this procedure, the free flap was temporarily nourished by vessels of uninjured lower limb, and was divided from the intact leg after flap revascularization. Skilled microsurgical technique is requisite for this procedure. With the popularity of microsurgical techniques, free flap transplantation has gradually become the standard method for salvaging severely traumatized lower limb [23, 26, 27]. A favorable lower extremity salvage rate of 93% was reported in free flap transplantation [27]. In free flap procedure, compared with end-to-side fashion, an end-to-end anastomosis between recipient vessels and donor vessels is preferred, which obviates the potential thrombosis caused by changes of blood flow at the anastomosis site. However, the major drawback of end-to-end anastomosis is sacrificing the recipient artery, which results in a considerable reduction of blood supply to distal leg. In early-stage clinical studies of cross-lag free flap technique, recipient arterial sacrifice was considered inevitable [28]. Nevertheless, in recent years, several innovative techniques were reported to preserve the integrity of the recipient artery. In 2000, Topalan et al. introduced a latissimus dorsi free flap with Y-shaped arterial pedicle in lower limb construction. This strategy not only provided blood supply to the flap, but also preserved the blood flow of the recipient artery, which was called the flow-through technique [13, 29]. For the case without arterial bifurcation, Akyurek et al. introduced a two-stage method to restore the continuity of the recipient artery in 2002 [30]. In the first stage, an end-to-end anastomosis was performed between the thoracodorsal artery of latissimus dorsi free flap and the uninjured recipient posterior tibial artery. After flap revascularization, the thoracodorsal artery was transected and rerouted to the distal end of the posterior tibial artery in the second stage. In 2016, Gencel et al. performed the cross-leg flow-through pedicled latissimus dorsi free flap procedure on 6 patients with high voltage electrical injuries [11]. In this small sample clinical study, the thoracodorsal artery and circumflex scapular artery (or serratus branch) were prepared as T-shaped pedicle, and further anastomosed to the contralateral posterior tibial artery. Adequate diameter and blood flow of the posterior tibial vascular system contribute to the survival of the flap. In 2020, Bali et al. conducted a study of 12 patients who underwent recipient blood flow-preserved cross-leg free flap procedures [12]. In Bali’s study, an anterolateral thigh fasciocutaneous flap was used in 8 patients for reconstruction of small or medium defects, while a latissimus dorsi flap was used in 4 patients with large defects. Besides, the arterial pedicle was designed as T-shaped fashion in anterolateral thigh flap but not in latissimus dorsi flap. Thus, the blood flow of recipient posterior tibial artery was reestablished in the first stage of anterolateral thigh flap procedure (flow-through technique), while in the second stage of latissimus dorsi flap procedure (rerouting technique). To our knowledge, there are only a few studies of flow-through pedicled cross-leg free flap procedures for lower limb reconstruction in previous literature, all of which involve fewer cases [11, 12, 29, 31–34]. Among these studies, the flaps are chosen based on the size and shape of the tissue defect. Generally, the anterolateral thigh flap is preferred in relative small-sized defect, while the latissimus dorsi flap is suitable in relative large-sized defect. Compared with the anterolateral thigh flap, the latissimus dorsi flap is relatively traumatic to harvest and difficult to prepare a Y-shaped arterial pedicle. Besides, the surgical position needs to be changed during the cross-leg latissimus dorsi flap transplantation. Therefore, the anterolateral thigh flap is more ideal for complex lower limb reconstruction, but it is hindered in popularity due to limited defect coverage. Traditionally, the proximal part of the free flap is used to cover the vascular pedicle, which will lower the effective flap area for defect coverage. In present study, we performed a modified flow-through pedicled cross-leg free flap procedure on patients with different size of unilateral lower limb tissue defect. Compared to previous techniques, our method has several advantages.
First, a meshed split-thickness skin was used to wrap the vascular pedicle. For anterolateral thigh flap, a sufficient length of vascular pedicle can be harvested. Instead of flap coverage, we performed free skin wrapping technique to protect the vascular pedicle. On the one hand, the obtained flap can be fully used for defect coverage, which means that the anterolateral thigh flap procedure is also suitable for patients with large-sized tissue defects. Our study suggests that various defects ranging from 72 to 378 cm2 could be effectively covered by relevant-sized anterolateral thigh flaps. On the other hand, compared with flap coverage, skin wrapping is more convenient for postoperative blood flow observation and dressing change, and is much easier for pedicle division in the second-stage procedure [12]. The free skin wrapping technique has been reported previously [35]. Serel et al. reported a case who had unhealed wound on the right foot and underwent cross-leg anterolateral thigh perforator flap procedure, in which a split-thickness skin was used to wrap the vascular pedicle [35]. Together with our results, a meshed split-thickness skin grafting is an effective and convenient method for vascular pedicle coverage.
Second, the lateral circumflex femoral arterial system is employed for design of the Y-shaped arterial pedicle. The lateral circumflex femoral artery consistently gives off transverse branch and descending branch. This arterial bifurcation is not difficult to dissect and prepare as a Y-shaped fashion. The anterolateral thigh free flap is widely used in post-traumatic reconstruction, including upper limb, lower limb and body trunk [15, 36, 37]. For reconstruction of different injury types, the anterolateral thigh flap can be harvested as fasciocutaneous or musculocutaneous flap. Generally, satisfactory survival rate and aesthetic outcome can be achieved by the anterolateral thigh flap procedure [36]. In addition, the anterolateral thigh flap is rich in its arterial perforator system, which is beneficial to flap survival on the one hand, and can be designed as single or bilobed style on the other hand. A bilobed flap is an optimal and practical choice to cover irregular tissue defects. In particular, when the defect width is large, a large-length single anterolateral thigh flap can be redesigned as a large-width bilobed flap. In our case series, both single and bilobed flap procedures produces good clinical results.
Third, the anterolateral thigh flap harvest and cross-leg flap transplantation are performed in the same surgical position, which can shorten the first-stage operation time. Furthermore, the vascular pedicle is easily divided after the flap revascularization, which greatly shortens the second-stage operation time. After flap transplantation, the parallel external fixation between two legs is relatively comfortable.
There are some limitations of our study. Postoperative parallel fixation of two lower limbs are necessary, and the fixation time is relatively long (4 weeks). Pressure ulcer prevention and physical therapy intervention should be carried out during the fixation period. In our procedure, the incision of flap donor site is relatively large, which requires further skin grafting in partial cases (27% in our study). This study is a retrospective design and its sample size is relatively small, which calls for a large-sample prospective study in the future.