Reconstruction of Gustilo type IIIC tibial open fracture caused by shotgun injury using combination Masquelet technique and cross-leg pedicle flap

Highlights • The treatment of open fracture combined with artery injury is challenging.• In case a free flap is contraindicated, the cross-leg flap is a good optein.• Masquelet technique is a promising treatment for bone defect with artery injury.


Introduction
The shotgun injury may cause large-scale bone and soft tissue destruction especially when people get shot from a very close range [1,2]. Traditionally, open fracture with large bone and soft tissue defect can be treated via serial debridement, external fixation and vascularized bone graft. However, when vascularized bone graft is not available or contraindicated, alternative treatment option is necessary. * Corresponding author at: Department of Orthopedics, Taichung Veterans Gen-

Case report
The case report has been written according to the SCARE 2018 guidelines [4].
A 34-year-old man suffered a shotgun attack from 2 m away on his right proximal tibia. Clinical examination revealed a Gustilo type IIIC open fracture. The pellets entered from the posterior calf and came out the anterior side of the tibia, creating a 15 × 20 cm 2 open wound. Radiographs indicated comminuted fracture with bone loss about 7 cm and multiple shotgun pellets (Fig. 1). Computed tomography angiography revealed poor contrast enhancement in the right anterior tibial artery (Fig. 2).   Initial wound debridement with fixation by external fixator were done 2 h after the trauma (Fig. 3). The shrapnel fragments and dead bone were removed thoroughly. Subsequent wound exploration revealed segmental loss of anterior tibial artery. On day 3, day 6, day 9 and 14 after trauma, four times of debridement were performed sequentially and clean and well-perfused wound bed was noted.
On post-trauma day 16, we fixed the tibial fracture with two locking plates (lateral: NCB Proximal Tibia System, Zimmer Biomet; medial: 3.5-mm Locking Compression Plate, DePuy Synthes). We filled the bone defect with vancomycin and gentamicin loaded cement spacer (Fig. 4). The skin defect was covered with a cross-leg pedicle flap. The flap is nourished by the posterior tibial artery and three perforator vessels (Fig. 5). We immobilized the two legs with cross-leg external fixators (Fig. 6). The pedicle of the cross-leg flap was divided and the cross-leg external fixator was removed 3 weeks after the flap transplantation. Partial weight bearing was allowed after the flap dividing surgery.
We replaced the cement spacer with mixed autogenous and synthetic bone graft at 12 weeks after trauma [5,6]. At 12 months, bone healing was observed on the radiograph (Fig. 7). The range of motion of right knee was achieved to 0-120 degree. The patient referred no pain during the daily activities.

Discussion
The treatment of open fracture involves segmental bone loss and large soft tissue defect along with major vessel injury caused by shotgun injury is challenging. Free vascularized osteocutaneous flap such as fibula and iliac crest flap have been reported as reliable flap with satisfactory results [7]. However, the integrity of lower leg vessels is mandatory for the success of this treatment. The injured anterior tibial artery with large trauma zone was an obvious contraindication for free flap reconstruction.
Bone transport is also an effective technique for long bone defects. However, the prolonged external fixator use may cause stiffness of ankle and knee, low quality of life and potential pin tract infection are also the drawbacks.
Generally, nonvascularized bone graft is not advocated for reconstruction in bone defects over 5 cm. Masquelet et al. introduced a technique to treat bone defects of more than 5 cm with non-vascularised bone graft in 2000 [5]. This technique comprises two stages of operation. The first stage of the Masquelet technique includes radical debridement, soft tissue repair, and implantation of a cement spacer into the bone defect. The second stage is performed 6-8 weeks later. The cement spacer is replaced by the nonvascularized bone graft. Soft tissue repair is often performed with flap coverage in the first stage. However, free flap surgeries are relatively contraindicated in patients with vascular insufficiency. As an alternative, cross-leg pedicle flap is a promising bailout for soft tissue repair. Its advantages include high flap survival rate, short operation time, and irrelevant to vessel condition in trauma limb [8]. The incidence of joint stiffness was reported less commonly in young individuals [9].
Masquelet introduced a technique to treat segmental bone loss [5]. Proponents advocated that the biological membrane induced by the cement spacers enhance thevascularity and corticalization of bone graft and facilitate bone union. The Masquelet technique offers several advantages. 1. The early application of antibioticimpregnated cement spacers expedites local delivery of antibiotics. 2. The limb length and rotation are maintained by using internal fixation devices as early as possible. The Masquelet technique combined with flap coverage has also been studied. Li et al. retrospectively evaluated 18 cases of diaphyseal bone defect treated with bone reconstruction and flap coverage. All patients in these cases achieved good bone union [10]. Alassaf et al. reported a child with a 10-cm bone defect open fracture who was successfully treated using the Masquelet technique and a radial forearm flap coverage [3]. In our case, we performed adequate debridement in the first place. Subsequently, we restored the length and rotation of the proximal tibia through double plating and used antibiotic cement as a spacer, followed by soft tissue coverage with cross-leg pedicle flap. The cement spacer was replaced by mixed autogenous and synthetic bone graft after 12 weeks according to the principle of Masquelet technique.
The cross-leg pedicle flap is a historical flap for treating lower extremity trauma [11]. When free flap surgeries are relatively contraindicated, the cross-leg flap can be a worthy alternative to reconstruct lower extremity defects [9]. Though complications as pin tract infection, joint stiffness, deep vein thrombosis and pressure sore may occur [12], our experience showed that adequate local hygiene and vigorous ankle pumping exercise effectively prevent these complications. Our outcome demonstrates that the Masquelet technique in combination with cross-leg pedicle flap is an effective and safe method to treat Gustilo type IIIC open fracture caused by type III shotgun injury with large-scale bone and soft tissue defects.

Conclusion
This case report highlights the value of treating segmental bone loss, large soft tissue defect and vascular injury caused by shotgun injury using the Masquelet technique in combination with crossleg pedicle flap coverage. We recommend this effective and safe method to restore bone and soft tissue defect simultaneously without the need for microsurgery while ensuring an excellent outcome.

Conflicts of interest
All the three authors disclose any financial and personal relationships with other people or organisations that could inappropriately influence of our work.

Sources of funding
We have no source of funding for our research.

Ethical approval
We have the IRB approve letter attached as supplement data.

Consent
We have consents from the patient and authors.

Author contribution
Chun-Yen Chen's work was Data collection, and original draft. Yung-Cheng Chiu's work was study design and methodology providing.
Cheng-En Hsu's work was data analysis or interpretation and writing the paper.

Research studies
Out was not a human study.

Provenance and peer review
Not commissioned, externally peer-reviewed.