Repair of Refractory Calf Soft Tissue Defects with Bridged CrossLeg Anterolateral Thigh Flap Combined with VSD and External Frame

Beibei Liu, Zhao Zhang^* , Duo Li, Zhong Liu, Jian Jiao, Yu Shi, Pin’an Xu & Yadong Zhou

Department of Traumatic Orthopedics, Weapons’ Industrial 521 Hospital, Xi ‘an, Shaanxi, China

*Correspondence to: Dr. Zhao Zhang, Department of Traumatic Orthopedics, Weapons’ Industrial 521 Hospital, Xi ‘an, Shaanxi, China.

Copyright © 2022 Dr. Zhao Zhang, et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Introduction
With the rapid development of industrial and agricultural mechanization and transportation industry, patients with refractory calf soft tissue defects with fractures caused by high-energy mechanical injuries and machine strangulation injuries are on the increase. The number of motorcycle users in large cities is increasing year by year due to the pressure of traffic congestion in China, and motorcyclists are often more severely injured in car accidents, and the number of female users is increasing rapidly, which also increase the proportion of women with such injuries accordingly. The majority of these injuries are characterized with injury to one of the main arteries of the lower leg, and the anterior medial calf has thin subcutaneous tissue and poor blood supply, making the management of soft tissue defects very difficult. Because of the poor mobility of the skin and soft tissues in the adjacent area and the rupture and injury of one main artery, neither subtraction incision nor adjacent transposition flap repair can be performed. In addition, there are no vessels available for anastomosis in the recipient area, free flap repair cannot be used directly. We preferred to avoid using local vessels for the recipient anastomosis due to high risk of flap failure and possible iatrogenic lower limb ischemia due to further vascular injury or vascular steal phenomenon [1]. Lower extremity reconstruction is complicated when high-energy mechanisms leave a large traumatic footprint. Here, the soft tissue defect and the vascular zone of injury extended from knee to ankle, making flap design and recipient vessel selection particularly Challenging [2].

Cross-leg pedicled flaps were first described in 1979 by Taylor et al. as a salvage effort to reconstruct a large defect after recipient vessels in the injured leg spasmed, precluding microvascular anastomosis [3]. The cross-leg flap is an ancient flap that still has some clinical use today [4]. With the advancement of clinical anatomy and and microsurgical techniques, it has developed into various forms. As a result of advances in microsurgery, injuries that would have previously been deemed unsalvageable and subsequently required amputation are being successfully repaired [5]. Advanced microsurgical techniques provide a great opportunity for surgeons to achieve functional and aesthetic goals in traumatized lower extremity reconstruction.

The goal of free flap transfer using microsurgical techniques is both soft tissue coverage and improvement of functional outcome [6]. Cross-leg free flaps allow for a large variety of donor sites, including latissimus dorsi, rectus abdominis, deep circumflex iliac artery, radial forearm, and anterolateral thigh flap [7]. Among them, the bridged cross-leg free anterolateral thigh flap has been widely used now. It can provide skin, fascia, muscle or any these in combination with excellent results and minimal morbidity of the donor site [8]. Haykal performed a meta-analysis of timing for microsurgical free flap reconstruction for lower limb injury and found early free flap reconstruction to have significant lower rate of free flap failure and infection compared to delayed reconstruction [9]. So our treatment arrangements were very compact. With the great use and promotion of VSD in recent years, trauma infection has been well controlled and the trauma area has been reduced accordingly. The use of external frame technology can provide strong support to prevent limb shortening in trauma with bone defects, and also significantly improve the subjective comfort of patients, avoiding the inconveniences of observation and cleaning of plaster external fixation and thus significantly reducing the risk of infection. The importance of this study is that it solves the problem of having no tissue flap for transposition at the defect site and the problem of having no suitable anastomotic vessel in the recipient area. The innovations of this study include the combined use of three techniques for soft tissue repair, and the overlay of VSD in the donor area to avoid donor-area implants, which were promptly returned after 6 weeks of “borrowing” the posterior tibial artery from the healthy side. This is also different from previous studies. The good results were achieved in 13 patients with soft tissue defects of the lower leg combined with fractures. The satisfactory effect are reported below.

Materials and Methods
General Information
There were 13 cases in this group, 8 males and 5 females, with a mean age of 39.2 years (range, 22-54years). There were 8 cases of car accident injury, 4 cases of machine strangulation injury, and 1 case of fall from height injury. All cases were admitted with open calf injury combined with fracture. 7 cases were sent to our hospital directly by the emergency center, and 6 cases were transferred to our hospital after a period of treatment in other hospitals(Table1). The patients sent to our hospital by the emergency center underwent VSD coverage for fracture fixation with a clear external frame, skin and soft tissue defect of lower leg with fracture exposure after debridement. Among the transferred patients, 2 cases had skin and soft tissue necrosis, osteonecrosis, and endophyte exposure after initial treatment of emergency debridement and internal fixation in other hospitals. 4 cases were treated with debridement and external frame fixation with VSD coverage, and all of them had skin and soft tissue defects after surgery, including 1 case with osteonecrosis and endophyte exposure. The area of skin defects ranged from 8 cm × 9 cm to 23 cm × 16 cm, and ultrasound or angiography before flap grafting suggested dissection or injury of one main artery of the lower leg.

Treatment Method
Preoperative Preparation for Flap Grafting
Six patients were transferred to our hospital and underwent VSD coverage within two days, including three patients with osteonecrosis who underwent partial or complete endophyte removal, necrotic bone removal, and VSD coverage with external frame fixation. 13 patients were actively treated with postoperative antiinfection therapy, including three patients who were treated with sensitive antibiotics based on the positive results of intraoperative tissue culture and the results of drug sensitivity tests. The VSDs were replaced several times before flap grafting until the culture was negative. The remaining 10 cases were treated with broad-spectrum antibiotics. Before surgery, the patients were instructed to enhance nutrition and perform relaxation training for the soft tissue of the thigh skin.

Surgical Method
After satisfactory anesthesia, the operating area of both lower extremities was routinely disinfected and sterile towels were laid. Necrotic and suspicious tissues were thoroughly removed, instruments and excipients were replaced, and the operator changed gloves. The anterolateral thigh flap was designed according to the preoperative Doppler flowmetry detection through the branch point, and the flap slightly larger than the trauma surface by 1-2 cm was routinely cut. The skin and subcutaneous tissues were incised, and the flap was lifted proximally to find the posterior tibial artery and vein. Attention should be paid to the protection of the tibial nerve and the posterior tibial artery crossing branches in the surgery. The “ ” shaped skin incision was generally up to 8 cm wide and could be widened in obese patients. The length depends on the patient’s lower extremity and could be considered longer in obese patients and patients with inversion of the knee. The free flap artery and vein were anastomosed with the posterior tibial artery and vein to reconstruct the flap blood flow. After inspecting the flap for good blood flow, the free flap was fixed in the soft tissue defect area of the lower leg, and the flap of the posterior tibial artery penetration was rolled into a skin tube, with the posterior tibial artery and vein walking in the skin tube. The exposed area of the donor area of the flap on the healthy side of the calf was covered with VSD and continuous negative pressure was applied. The distance between the two lower legs was adjusted, the Schanz pin was added on the healthy side, and the outer frame was adjusted on the affected side, keeping both lower limbs parallel. The anterolateral thigh flap donor area was advocated to be reduced by tension sutures as much as possible, and the remaining area was grafted with free skin.

Postoperative Management
Postoperatively, patients were absolutely bedridden, kept warm by baking lamps, and flap blood flow was closely observed. Treatment and care after vascular anastomosis were strictly followed, with routine antiinfection, anti-thrombotic and anti-spasm treatments. Postoperatively, the VSD dressing on the healthy side was surgically changed every 7-10 days. Flap blocking training was performed 4 weeks after surgery, and flap dissection was performed 6 weeks after surgery by removing the flap from the external frame between the two legs. The “ Π” shaped posterior tibial artery flap was replanted and the “borrowed” posterior tibial artery was anastomosed to the distal end. Postoperative ultrasound was performed to check the status of the anastomosed artery.

Results
All patients were followed up for 11~ 30 months. All flaps were viable and no vascular crisis occurred. Two cases had localized redness and necrosis at the flap edges, which healed after routine dressing changes. The flap shape, color and elasticity recovered well. At the final follow-up, 9 cases were rated as excellent, 3 cases as good, and 1 case as acceptable according to the functional evaluation of the Thermann scale. The donor area recovered well, and the muscle and skin innervated by the “borrowed” healthy posterior tibial vessels did not show any functional or sensory impairment. (This study was approved by Ethics Committee).

Typical Cases
The patient, a 35-year-old male, was admitted to an other hospital with an open left calf injury with fracture caused by a car accident injury. The fracture was not fixed with an external fixator. 2 weeks later, an incision and internal fixation of the fracture was performed. He was transferred to our hospital 4 weeks after internal fixation due to wound infection and exudation with endophyseal exposure. After admission, a lower extremity arteriogram showed that the anterior tibial artery was dissected from the mid-calf. He was treated with partial endograft removal, necrotic bone removal, bone cement implantation, external frame fixation, and VSD coverage. Intraoperative bacterial culture of the suspected tissue was performed, and after two consecutive wounds were negative for tissue culture, a bridged cross-leg free anterolateral thigh flap repair was performed. The external frame was fixed to the bilateral calf and the VSD covered the donor area of the healthy calf, and the VSD dressing was changed every 7-10 surgeries. Flap block training was performed 4 weeks postoperatively, and flap disconnection was performed 6 weeks postoperatively by removing the flap from the external frame between the legs. (See Figure 1).

Discussion
Advantages and Disadvantages of the Bridged Cross-Leg Free Anterolateral Thigh Flap
Advantages: 1) These injuries often result in large skin soft tissue defects combined with dissection or injury of the main artery. The commonly used cross-leg flap and myocutaneous flap cross-leg tip graft do not require a vascular anastomosis technique, but the area of the excised flap is limited. The free anterolateral thigh flap is often not applicable due to the lack of suitable vessels in the recipient area, and it is extremely risky to use the remaining trunk vessels in the recipient area to perform Flow-through technique for repair.
2) The general condition of the periwound tissue is poor, such as edema, brittle tissue, and poor elasticity, which makes local transposition flaps and random flaps inapplicable. 3) The recipient area is the posterior tibial artery and vein of the healthy side, which are normal vessels similar caliber to the vascular tip of the flap, and the operator can adopt a comfortable position, which reduces the difficulty of microanastomosis and has a high rate of anastomotic vessel patency. After 6 weeks of “borrowing” the posterior tibial artery and vein, the vessels and soft tissues were returned, and the healing on the healthy side was linear, and there was no functional or sensory impairment to the innervated muscle and skin tissues. 4) The flap was cut from healthy tissue and the soft tissue was thick and resistant to infection, so the probability of infection was low and the success rate was high.

Disadvantages: 1) 6 weeks postoperative disconnection, multiple surgeries, long treatment period, longer hospitalization and bed rest time for patients, and high costs are a high demand for patient compliance, which sometimes causes psychological disorders and even mental anxiety. 2) The prolonged parallel immobilization of both lower limbs and bed rest can easily cause bed rest complications, such as joint stiffness, crushing pneumonia, and deep vein thrombosis of lower limbs. Therefore, the flap should be selected with caution for patients with combined pulmonary and vascular diseases. 3) The need to cut off the posterior tibial artery on the healthy side is not an option for patients with vascular variants and blocked posterior tibial artery vasculature affecting distal blood flow. 4) High requirements for the operator’s microscopic anastomosis technique, especially the mismatch of vessel caliber may lead to vascular crisis or even flap necrosis.

Advantages and Disadvantages of VSD Technology
Advantages: 1) This type of injury often requires repeated multiple debridement, aggressive debridement of necrotic and suspicious tissues, and aggressive postoperative anti-infection treatment. The use of VSD technique after debridement can cover a large area of the wound and provide adequate drainage. In addition to effective infection control, it can also promote the growth of granulation tissue on the trauma surface, reduce the original trauma surface, and prepare for soft tissue repair. 2) The donor area is covered with VSD, which is replaced on time and returned after 6 weeks of “borrowing” of the posterior tibial artery, which is better than the traditional donor area implant healing. The posterior tibial artery perforator flap was returned with nearly normal sensation, which was significantly better than the skin graft in terms of sensation and wear.

Disadvantages: 1) After the VSD technique covers the wound, daily postoperative care and flushing are required, which increases the nursing workload compared with the implant, and sometimes the patch may break and leak, resulting in negative pressure failure. 2) VSD dressing in the donor area needs to be changed every 7-10 days, which increases the number of surgeries, raises the cost, and has a higher financial requirement for patients.

Fixation of Cross-leg and Fractures
We recommend the use of external fixation frame mainly for the following reasons: 1) Traditional plaster fixation requires fixation of the patient’s knee joint, which strictly limits the patient’s mobility and affects the function of the lower limb joints. The cast is heavy, several times the weight of the external brace, which makes it difficult for the patient to move and change position, and makes the experience worse. The external fixation frame does not require fixation of the knee joint, and the patient’s lower extremities are fixed parallel to each other, allowing simultaneous flexion of the hip and knee joints bilaterally and preventing joint stiffness [10]. In particular, only one additional set of devices is needed when an external fixation frame has been placed due to a fracture. 2) This type of injury is often combined with complex fractures of the lower leg, and early internal fixation of the fracture is not recommended. In 6 transferred patients, 2 of them who underwent emergency debridement and internal fixation in other hospitals developed skin soft tissue necrosis, osteonecrosis, and endophytic exposure after surgery. In the case of uncertain control of infection factors, external fixation can reduce the occurrence of infection or facilitate the control of infection that has occurred. 3) It reduces the occupancy of the cementum without disturbing the already damaged soft tissues early on, for the endograft may cause soft tissue necrosis due to increased tension. 4) It provides relatively firm fixation of the fracture, reduce the possibility of malunion and nonunion, and also provide convenience for later replacement of internal fixation, some of which may make external fixator the final fixation method. 5) It provides stable fixation for the fracture and cross-leg flap while also providing great convenience for postoperative medication changes and care. Intraoperative fixation allows the selection of a suitable position to ensure the tension of the skin tube, and the external frame can be adjusted at any time during the treatment.

Conclusion
The free anterolateral femoral flap provides good soft tissue coverage for refractory wounds, the external frame technique provides strong fixation of the fracture, and the VSD technique facilitates the entire treatment process by avoiding the need for skin grafting. Therefore, it is believed that for refractory calf soft tissue defects, a bridged cross-leg free anterolateral thigh flap combined with VSD and external frame is an effective repair method.

Bibliography

1. Ross, P. E. & Deleyiannis, F. W. B. (2015). Head loss as an explanation of the steal phenomenon in microvascular surgery. Eplasty., 15, e45.
2. Lu, J., Chavanon, V., Margulies, I., et al. (2019). Cross-leg latissimus dorsi free flap with chimeric serratus anterior bridge for lower extremity trauma: Case report and reconstructive algorithm. Journal of Clinical Orthopaedics and Trauma, 10(5), 867-872.
3. Philandrianos, C., Moullot, P., Gay, A. M., et al. (2018). Soft tissue coverage in distal lower extremity open fractures: comparison of free anterolateral thigh and free latissimus dorsi flaps. J Reconstr Microsurg., 34(2), 121e129.
4. Atiyeh, B. S., Al-Amm, C. A., El-Musa, K. A., et al. (2003). Distally Based Sural Fasciocutaneous Cross-Leg Flap: A New Application of an Old Procedure[J]. Plastic & Reconstructive Surgery, 111(4), 1470-1474.
5. Kim, S. W., Youn, S., Kim, J. D., Kim, J. T., Hwang, K. T. & Kim, Y. H. (2013). Reconstruction of extensive lower limb defects with thoracodorsal axis chimeric flflaps. Plast Reconstr Surg., 132(2), 470-479.
6. Korompilias, A. V., Lykissas, M. G., Vekris, M. D., Beris, A. E. & Soucacos, P. N. (2008). Microsurgery for lower extremity injuries. Injury, 39(Suppl 3), S103-8.
7. Manrique, O., Bishop, S., Ciudad, P., et al. (2018). Lower extremity limb salvage with cross leg pedicle flap, cross leg free flap, and cross leg vascular cable bridge flap. J Reconstr Microsurg., 34(07), 522e529.
8. Wei, F. C., Jain, V., Celik, N., Chen, H. C., Chuang, D. C. & Lin, C. H. (2002). Have we found an ideal soft-tissue flap? an experience with 672 anterolateral thigh flflaps. Plast Reconstr Surg., 109(7), 2219-2226 discussion 2227-2230.
9. Haykal, S., Roy, M. & Patel, A. (2018). Meta-analysis of timing for microsurgical free-flap reconstruction for lower limb injury: evaluation of the godina principles. J Reconstr Microsurg., 34(4), 277-292.
10. Sa Hyeok, Hong, et al. (2016). Cross-Leg Flap-Sharing Technique Using an Anterolateral Thigh Perforator Flap. Archives of Plastic Surgery., 43(4), 384-387.