A Hybrid Technique to Treat Inguinal Wound Infection after Arterial Surgery with Lateral Femoral Bypass and Intra-Incisional Negative Pressure Wound Therapy

Background: Patients with the inguinal wound infection after arterial surgery remains clinical challenge. Sustaining lymphatic leakage have been shown as a common and potentially serious complication. However, it remains clinical challenge for surgery to deal with this tough problem. Methods: This study describes a hybrid technique of using radical debridement, lateral femoral bypass (LFB) and intra-incisional negative pressure wound therapy (iNPWT) for single-staged treatment of complex inguinal wound infection after arterial surgery (IWI-AS). Results: Between January 2017 and June 2021, 5 IWI-AS cases treated with this new method were identied. Of the patients, 3 were males and 2 were females. The average age was 49.4 years (range, 33 to 77 years). 4 cases suffered emergent operations due to the sudden bleedings. after vascular bypass reconstructions and an average of 2.2 (range:1-3) iNWPT, all cases achieved wound healing at an average duration of 4.6 weeks (range: 3-6weeks). Moreover, all cases showed no bacterial growth and grafts patency as indicated by doppler ultrasound or CT angiography postoperatively. One case did not receive bypass imaging evaluation at postoperative 12 months. Weakness of quadriceps femoris was observed in one case. Conclusion: single-staged therapy of LFB and iNPWT hybridization is a technically handy and effective method for treatment of inguinal wound infection after arterial surgery.


Introduction
Femoral artery diseases in groin, resulting from trauma, tumor resection, Iatrogenic injuries are very common. Insitu anatomic reconstruction is standard management for inguinal arterial defects. However, of these arterial intervention cases, 2% to 5% patients suffer sustaining lymphatic leakage [1][2][3] . Approximately 5% patients developed a groin wound infection 4,5 . Femoral artery defect in the setting of groin lymphatic leakage and wound infection makes vascular reconstruction and wound healing more complicated and challenge. The failure of treatment conclusively leads to limb loss and life-threatening problems.
Multiple-staged management of inguinal wound infections after arterial surgeries has been increasingly reported 6,7 . In this study, we introduced a hybrid technique, including aggressive debridement, intra-incisional negative pressure wound therapy (iNPWT) and lateral femoral vascular bypass implant with great saphenous vein, to synchronously address the limb revascularization and wound healing for IWI-AS in single stage. we reviewed our results to assess the e cacy of this single-staged treatment for inguinal wound infections after arterial surgeries.

Methods
In this study, patients with inguinal wound infection after arterial surgery who underwent radical debridement, lateral femoral vascular bypass and intra-incisional NPWT from January 2017 to June 2021 were retrospectively reviewed. Patient demographic information and therapy details and clinical outcomes, including gender, age, cause of disease, comorbidities, operations, microbiology of wound, type of vascular graft, times of NPWT, wound healing, duration from surgery to wound healing, patency of bypass, recurrence of infection and lymphatic leakage, limb salvage, major adverse events (MAEs) were recorded. Ethics board approval for retrospective study involving humans was obtained from Ethics Committee of Zhongnan Hospital of Wuhan University, Wuhan, China.
Operative procedure For bleeding cases, ligations of rupture arteries were obligatory for hemostasis. Then an aggressive debridement was performed by excision of fascia and suspect infected tissue except for femoral nerve and veins until wounds bled. Wounds were sealed with 1% povidone-iodine solution for sterilization and irrigated with at least 9L saline.
2 incisions near middle inguinal ligament or in contralateral inguinal region (in case 4) and in middle 1/3 of thigh were made as counterincision to expose the uninvolved external iliac artery (EIA) or contralateral super cial femoral artery (SFA) (in case 4) and ipsilateral SFA, deep femoral artery (DFA). The bypass was initially tunneled under the incised inguinal ligament in the proximal incision and passes through the rectus femoris muscle (in case 4, rstly passes through skin of the lower abdomen) to the distal incision. The channel needs to be fully expanded to at least 3cm width to avoid compressing grafts. The great saphenous vein in thigh were preferred as conduits in 4 patients. The great saphenous vein in shank as alternative was considered in context of the exhausted great saphenous vein in thigh in case 5. In proximal incision, the EIA or contralateral SFA (in case 4) as an in ow vessel, was anastomosed with inverted great saphenous vein in end-to-side manner. After con rming that the graft was patent without blood leakage, the autograft was delivered to distal incision via the tunnel and anastomosed to SFA and DFA in end-to-end manner ( Figure 1). After most of the debrided wound was sutured.
Vacuum drainage apparatus was inserted into the remaining 3cm unclosed wound and served as intra-incisional NPWT.

Postoperative Management
One week postoperatively, wound secretion was subjected to bacterial culture. the wound was observed at the weekly renewal of VSD device. The wounds were completely closed until the drainage volume <50 mL every 24 hours and then treated by conventional wound dressing change or another NPWT until wound healed. Microbiology-based sensitive antibiotics were applied for a minimum of 6 weeks. CT angiography and vascular ultrasound examinations were employed to con rm the patency of bypass at postoperatively 1-2 months. Results 5 consecutive patients (3 males and 2 females) with an average age of 49.4 years (range, 33 to 77 years) were included. The case series were described in Table 1. All cases received initial in-situ femoral arterial reconstructions for different causes, including 1 cases of trauma-related femoral artery occlusion, 1 case of tumor resection-related femoral defect and 1 case of extracorporeal membrane oxygenation (ECMO) catheterrelated femoral artery rupture and 2 cases of catheter-related femoral artery pseudoaneurysm. Of these, initial vascular grafts were vascular prostheses in 3 cases, and great saphenous veins of thighs in 1 case. In particular, case 5 received another great saphenous vein implant operation due to the anastomotic bleeding after initial surgery with prosthesis. Case 2 initially received a reconstruction with damaged femoral artery resection and endto-end anastomosis. Post-operative Inguinal lymphatic leakages and infections were manifested by the unhealed wound and persistent serous and pyogenic discharge from incision. Wound infections were evidenced by microbiological test around grafts, including klebsiella pneumoniae, enterococcus faecalis, staphylococcus aureus, escherichia coli, staphylococcus epidermidis.
As the failure of previous vascular reconstruction, all cases received these salvage surgeries including radical debridement, lateral bypass with great saphenous vein and intra-incisional NPWT. 4 of 5 patients received emergent surgeries due to the unexpected bleedings on prior arterial anastomoses. 1 of 5 patients received selective operation. All cases employed EIAs as in ows (except for case 4), SFAs/DFAs as out ows and GSVs as grafts. In case 4, the contralateral SFA is selected as in ow due to the ipsilateral EIA occlusion (Table2).
As shown in table 2, after an average of 2.2 (range:1-3) intra-incisional NWPT treatments, all cases achieved wound healing at an average duration of 4.6 weeks (range: 3-6weeks) from the de nitive surgery to wound healing. Moreover, the one-week postoperative pathogen examinations showed no bacterial growth in all cases. All affected limbs were successfully revascularized which indicated by unobstructed arterial grafts via doppler ultrasound examinations or CT angiography at discharge. All cases kept primary patency at postoperative 12 months except for case 1. This patient did not participate in the visit and underwent angiography at postoperative 12 months due to tumor recurrence. All limbs were salvaged without amputation. Incomplete femoral nerve injury, manifested as weakness of quadriceps femoris, was observed in case 5 preoperatively. The quadriceps femoris force was restored after intensi ed rehabilitation.

Selected case report
A 38-year-old male was admitted with left vertebral pseudoaneurysm for endovascular therapy via inguinal percutaneous femoral arterial access (Case 5). 4 months later, the patient felt pain in the left groin area. Physical examination revealed a pulsating mass at entry site and extreme swelling in the left lower limb. CT angiography showed that there was a 5cm*6cm pseudoaneurysm in the common femoral artery, and the patient was readmitted to receive false aneurysm resection and rst revascularization procedure with in-situ arti cial blood vessel transplantation. However, the patient presented persistent lymphatic leakage with at least 150ml/day discharge. On the 14th day after the rst reconstructive operation, the patient suddenly experienced bleeding from the anastomosis of the transplanted blood vessel and underwent an in-situ revision surgery with autologous great saphenous vein transplantation (Figure 2a,b). Thereafter, the lymphatic leakage was not ceased spontaneously and a secondary wound infection with staphylococcus epidermidis was veri ed by bacteriological examination. Dressing change, debridement and NPWT treatment were employed for a certain interval, the wound yet not healed. However, sudden anastomosis bleeding occurred again on the 21st day after the second surgery. The patient was then subject to the de nitive surgery with radical debridement, simultaneous EIA-SFA lateral bypass with autologous saphenous vein transplantation and intra-incisional NPWT treatment (Figure 3a, b). 1 week later, microbiology test of wound discharge showed that there was no bacterial growth. After receiving another two intra-incisional NPWT treatments, the drainage volume of the wound was less than 50ml within 24 hours. Then the wound was sutured at 3 weeks after and healed at 6 weeks after the last operation (Figure 4a, b). 6 weeks and 12months postoperatively, CT angiography of affected limb showed that the graft was unobstructed without obvious stenosis (Figure 5a, b).

Discussion
The groin wound infection after arterial surgery remains a signi cant clinical challenge. Multiple factors, including rich lymphatic tissue and fascia tissue, the proximity to the perineum, predispose inguinal femoral arterial reconstruction to complicated with infections 8, 9 . In particular, persistent lymphatic leakage after arterial reconstruction in the groin has subsequently emerged as a common and potentially serious complication.
Persistent epithelial breach poses the wound and graft at high risk of secondary infection, these serious complications were presented in all of our cases series. The complex conditions imply that it is notoriously di cult to treat and do not succumb to the remedy for simple vascular reconstruction surgery. The goal of treatment for IWI-AS should be to salvage the limbs and their functions. In our case series, all patients achieved well-vascularized lower limb, elimination of infection and wound healing in 6 weeks after intra-incisional NPWT surgeries.
For complicated femoral arterial injury, ligation is the simplest approach, collateral branches around the hip avoid limb loss in most healthy populations in case of ligation, but it is inevitable to cause critical ischemia and disability in lower limb, especially in patients with pre-existing arterial disease 8, 10 . Therefore, ligation is not rstly recommended. The optimal strategy is supposed to rebuild the trunk of artery to maximize blood supply for limb salvage. In situ arterial reconstruction often failed to restore aortic blood ow in the setting of infected groin, which was attribute to uncontrolled infection and erosion-related bleeding 11,12 . In this regard, the bypass strategy was proposed. For bypass technique, the graft is tunneled through uninfected tissue, it protects the graft from erosion of infection. LFB and OCB are the frequently-used extra-anatomical techniques and have comparable effect in graft latency and limb salvage 8, [13][14][15] . Nonetheless, OCB is more technically-challenging than LBP due to the di cult traverse of obturator foramen. It also has a risk of obturator vessel and nerve injury and potentially damages the collateral circulation of affected limb, whereas LBP is close to anatomic site and less invasive to surrounding tissues 8 . Additionally, given LBP is operatively convenient and time-saving, it is quite suitable for emergent bleeding cases 15 . Notably, 25% patients suffered acute bleeding 6 . In our study, all cases suffered sudden bleedings and received emergent LFB operations. All affected lower limbs were succeeded to be well revascularized without graft re-perforation that indicated by the distal pulses of dorsalis pedis arteries and vascular ultrasound at nal follow-ups.
As ready-to-use grafts, prosthetic conduits are extensively used in vascular surgeries. Indeed, our cases also received prosthesis reconstructions in previous surgeries. Prosthesis-related bacteria colonization often leads to recurrence of wound infection, thus once infecting, the prosthetic graft would inevitably be completely removed. Although harvest of autograft, such as great saphenous vein, maybe bring donor site damage and the graft needs massive further process, including dilation and branch ligations, autograft was still the rst choice in term of its long-lasting durability and resistance to infection, especially in young populations and infected setting 16 . Cryopreserved human cadaveric allografts present comparable performance with autografts but take relative higher cost and serve as alternative substitute for vascular graft in the absence of autografts 8 .
Sustaining inguinal lymphatic leakage and secondary infection are another challenge for wound healing. Unsurprisingly, debridement, especially radical debridement, is obligate and primary to infected wound. The debridement may be not enough for wound healing. Vascularized muscle aps and NPWT therapy were welldocumented methods for treating lymphatic leakage and infection, in particular for graft-preserved cases 1,9,[16][17][18] . However, the use of aps is often restricted to the already compromised blood supply of muscle and surgeon's skills. NPWT, as another reliable method for infected wound, was prophylactically and therapeutically applied alone in groin wound following vascular surgery and showed good results 18 . However, there were 6.4% reinfections and 7.1% bleeding events in previous report 19 . In addition to debridement, the times and manners of NPWT application also play a role in recurrence of infection. Our previous study indicated that NPWT in intraincisional manner was much more effective for drainage and compressing lymphatic tubes than that in closed-incisional manner 20 . Therefore, we enveloped the NPWT device in incision on basis of aggressive debridement and performed periodic replacement of intra-incisional NPWT until the volume of drainage was less than 50ml every day. All cases showed negative wound bacteria result after the rst NPWT and achieved wound closure after 1-3 times of NPWTs. Providing reinfection was occurred, muscle ap could serve as a remedy. Nevertheless, bypass graft was away from NPWT, the NPWT caused bleeding was not observed in our study.
Major adverse event was quadriceps femoris weak in case 5. Although we had carefully protected the femoral nerve, quadriceps femoris weak still appeared. We did not know the situation of muscle before the surgery. We also had no electromyographic evidence to a rm the incomplete nerve injury-related muscle weak. In fact, it cannot exclude disuse-atrophy cause. Finally, strength of quadriceps femoris was restored via rehabilitation.
As a fact, there are several limitations in this study. Firstly, CT angiographies were not routinely performed in all patients at last visit, as the patients concerned about the radiation hazard, thus long-term durability were not well evaluated postoperatively. Secondly, this is a retrospective study. Recall bias probably existed. Thirdly, the study had only 5 patients. Thereby, the power of conclusions is limited. In all, the reliable outcomes need to be further validated in well-designed study with larger populations.

Conclusion
In conclusion, the hybrid technique of lateral femoral bypass combining with intra-incisional NPWT is a technically handy and effective method for single-staged treatment of inguinal wound infection after arterial surgery, in particular with emergent bleeding from erosive graft. The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.     a Wound view before the third femoral artery reconstruction surgery. The previous vein graft was ligated immediately due to the anastomotic bleeding. b Wound view after radical debridement and proximal and distal anastomoses of bypass (blue arrows).
Page 12/13 Figure 4 a Wound view after 3 times intra-incisional negative pressure wound therapies, the unclosed wound (blue arrow) was for vacuum drainage apparatus insertion. b Wound healing view at 6 weeks postoperatively. The two incisions in right leg were used for great saphenous vein harvest and healed (blue arrows).