Microvascular anastomosis using modified micro-stents: a pilot in vivo study

Innovative Use of an Injectable, Self-Healing Drug-Loaded Pectin-Based Hydrogel for Micro- and Supermicro-Vascular Anastomoses

Microvascular surgery plays a crucial role in reconnecting micrometer-scale vessel ends. Suturing remains the gold standard technique for small vessels; however, suturing the collapsed lumen of microvessels is challenging and time-consuming, with the risk of misplaced sutures leading to failure. Although multiple solutions have been reported, the emphasis has predominantly been on resolving challenges related to arteries rather than veins, and none has proven superior. In this study, we introduce an innovative solution to address these challenges through the development of an injectable lidocaine-loaded pectin hydrogel by using computational and experimental methods. To understand the extent of interactions between the drug and the pectin chain, molecular dynamics (MD) simulations and quantum mechanics (QM) calculations were conducted in the first step of the research. Then, a series of experimental studies were designed to prepare lidocaine-loaded injectable pectin-based hydrogels, and their characterization was performed by using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and rheological analysis. After all the results were evaluated, the drug-loaded pectin-based hydrogel exhibiting self-healing properties was selected as a potential candidate for in vivo studies to determine its performance during operation. In this context, the hydrogel was injected into the divided vessel ends and perivascular area, allowing for direct suturing through the gel matrix. While our hydrogel effectively prevented vasospasm and facilitated micro- and supermicro-vascular anastomoses, it was noted that it did not cause significant changes in late-stage imaging and histopathological analysis up to 6 months. We strongly believe that pectin-based hydrogel potentially enhanced microlevel arterial, lymphatic, and particularly venous anastomoses.

Comparison of a coupling system and the suture method in end-to-side microvascular anastomosis in head and neck reconstruction

BACKGROUND

Use of coupling devices in microvascular anastomosis continues to increase, but it is not yet actively used in end-to-side (ETS) anastomosis because there is no standard method. Therefore, we propose an easy and time-saving ETS micro-anastomosis method using coupling devices in head and neck reconstruction and compare it with the conventional suture method.

MATERIALS AND METHODS

We retrospectively reviewed 30 consecutive cases (43 anastomoses) of ETS anastomosis in head and neck reconstruction from 2018 to 2022. Patient characteristics, operative details, and anastomosis time were evaluated. When using the coupling device, a cross incision was created in the recipient vessel to form vascular flaps. By pulling the flaps out of the ring, the intact vessel lining was fixed. Other procedures were the same as for a traditional anastomosis.

RESULTS

The mean anastomosis time was 12.81 min (range, 6.7-24.87) for the suture and 4.96 min (range, 2.02-9.4) for the coupling device, a statistically significant difference (p-value <.00005). There was no venous insufficiency or flap failure with either method.

CONCLUSIONS

ETS venous anastomosis using the coupling device is an easy-to-use, safe, and timesaving procedure for head and neck reconstruction.

Evaluation of fibrin, cyanoacrylate, and polyurethane-based tissue adhesives in sutureless vascular anastomosis: a comparative mechanical ex vivo study

The stability of a microvascular anastomosis is an important prerequisite for successful tissue transfer. Advances in tissue adhesives are potentially opening new avenues for their use in sutureless microsurgical anastomosis, however they have not yet gained clinical acceptance. In this ex vivo study, a novel polyurethane-based adhesive (PA) was used in sutureless anastomoses and its stability compared with that of sutureless anastomoses performed with fibrin glue (FG) and a cyanoacrylate (CA). Stability was assessed using hydrostatic (15 per group) and mechanical tests (13 per group). A total of 84 chicken femoral arteries were used in this study. The time taken to create the PA and CA anastomoses was significantly faster when compared to the FG anastomoses (P < 0.001): 1.55 ± 0.14 min and 1.39 ± 0.06 min, respectively, compared to 2.03 ± 0.35 min. Both sustained significantly higher pressures (289.3 mmHg and 292.7 mmHg, respectively) than anastomoses using FG (137.3 mmHg) (P < 0.001). CA anastomoses (0.99 N; P < 0.001) and PA anastomoses (0.38 N; P = 0.009) could both withstand significantly higher longitudinal tensile forces compared to FG anastomoses (0.10 N). Considering the background of an in vitro study, the PA and CA anastomosis techniques were shown to be similar to each other and superior to FG, due to their stability and faster handling. These findings need to be validated and confirmed in further in vivo studies.

Evaluation of the long-term results of vascular anastomosis using polyurethane adhesive and shape-memory stent in the rat carotid artery model

INTRODUCTION

In free flaps, 5%-10% of complications are related to failure of sutured vascular anastomoses. Adhesive-based microvascular anastomoses are potential alternatives but are associated with failure rates of 70% in research studies. VIVO is a new adhesive with slow biodegradation within 6 months that has shown a 100% patency rate in research studies over 2 h observation time but long-term patency has not been evaluated. The authors hypothesize that VIVO will enable a reliable microvascular procedure comparable to sutured anastomoses over a 28-day period.

MATERIALS AND METHODS

The right common carotid artery of 60 male Sprague Dawley rats, ~450 g, were used for microvascular end-to-end anastomosis. VIVO was applied with reduced sutures with a temporary catheter in one group and in the other with a custom-shaped memory stent. Anastomoses with eight interrupted sutures served as control. All groups were n = 20. Anastomosis time and bleeding were recorded for each procedure. Doppler flowmetry was performed 20 min, 1, 10, and 28 days postoperatively. Postmortem toluidine staining was used for semi-quantitative analysis of stenosis, thrombosis, necrosis, and aneurysm formation by histologic evaluation.

RESULTS

No occlusion was detected 20 min and 1 day postoperative, and after 28 days of observation in all anastomoses. The anastomosis time of the VIVO with catheter group was about 32% significantly faster than the VIVO with stent group. In the VIVO group with stent, the bleeding time was ~80% shorter than in the control group with 2.1 ± 0.3 and VIVO with catheter 2.0 ± 0.5 (p ≤ .001 each). Minor and nonsignificant stent-associated thrombus formation and stent-typical intraluminal stenosis were detected exclusively in the VIVO with stent group.

CONCLUSION

Within the limitations of a rat study, the use of VIVO in anastomosis showed promising results. VIVO with catheter was found to be advantageous.

A Novel Method of End-to-Side Microvascular Anastomosis Using T-Shaped Metal Stents: A Porcine Study

ABSTRACT

End-to-side anastomosis requires highly specialized techniques. An easy end-to-side anastomosis technique enables anastomosis of vessels with different diameters and under various situations. We invented T-shaped metal stents and evaluated novel methods of end-to-side sutureless anastomosis, confirming their safety, effectiveness, and operability. We performed 8 end-to-side sutureless anastomoses in 4 7- to 11-month-old, male Mexican hairless piglets. After induction of anesthesia, the left femoral artery was resected by approximately 8 cm, and the superior and posterior stumps of the resected femoral artery underwent an end-to-side anastomosis with the right femoral artery by the placement of the metal stents with subsequent use of adhesive for the circumferential area. The patency of blood vessels and the presence of thrombosis were evaluated by ultrasonography or contrast-enhanced computed tomography and histology 4 weeks postoperatively. All the animals survived the procedure; no thrombosis was identified in any of the 8 anastomosis sites according to imaging studies performed 4 weeks postoperatively. Histological examination confirmed the probe patency of blood vessels and neointimal cell proliferation around stent branches. End-to-side anastomosis is possible with T-shaped metal stents. In the future, we aim for the practical application of these stents by improving their operability.

Mechanical strength and hydrostatic testing of VIVO adhesive in sutureless microsurgical anastomoses: an ex vivo study

Conventional anastomoses with interrupted sutures are challenging and inevitably associated with trauma to the vessel walls. The goal of this study was to evaluate a novel alternative adhesive-based suture-free anastomosis technique that uses an intraluminal stent. Overall, 120 porcine coronary vessels were analyzed in an ex vivo model and were examined for their mechanical (n = 20 per cohort) and hydrostatic strength (n = 20 per cohort). Anastomoses were made using the novel VIVO adhesive with an additional intraluminal nitinol stent and was compared to interrupted suture anastomosis and to native vessels. Sutureless anastomoses withstood pressures 299 ± 4.47 [mmHg] comparable to native vessels. They were performed significantly faster 553.8 ± 82.44 [sec] (p ≤ 0.001) and withstood significantly higher pressures (p ≤ 0.001) than sutured anastomoses. We demonstrate that the adhesive-based anastomosis can also resist unphysiologically high longitudinal tensile forces with a mean of 1.33 [N]. Within the limitations of an in vitro study adhesive-based suture-free anastomosis technique has the biomechanical potential to offer a seamless alternative to sutured anastomosis because of its stability, and faster handling. In vivo animal studies are needed to validate outcomes and confirm safety.

Microvascular anastomosis techniques using the medical adhesive VIVO and expandable micro-stents in a rat carotid artery model

BACKGROUND

Sutured anastomosis remains the gold standard in microvascular surgery. The procedure is not free of complications and is a time-consuming operation requiring a high level of experience. The aim of this study was to develop new methods for a stable, faster, and safer anastomosis using a novel biodegradable adhesive, VIVO, and a custom-made microvascular stent.

METHODS

The VIVO medical adhesive was used for a total of 30 anastomoses in rats in the right carotid artery: 15 anastomoses were performed with a temporary intraluminal catheter, VIVO, and reduced sutures (VIVO + TC). A further 15 anastomoses were performed with nitinol stents, VIVO, and reduced sutures (VIVO + SM). Sutured anastomoses served as controls (C) and were performed on the left carotid arteries of the 30 rats. Operation and bleeding times were assessed, and patency was evaluated by Doppler flowmetry and indocyanine green (ICG) angiography. Subsequently, the anastomoses were evaluated histopathological.

RESULTS

The overall patency was recorded as 100% in all groups. No thrombosis or circulatory disturbance was found. Compared to C and VIVO + SM, VIVO + TC proved to be significantly less traumatic, less demanding, and time-saving. The sealing properties of VIVO lead to shorter bleeding times and less oozing. In contrast, VIVO + SM proved to be the most technically demanding and time-consuming procedure.

CONCLUSION

The success of a microvascular sutured anastomosis is determined by a short ischemic interval. Compared to sutured anastomosis, VIVO + TC showed ease of use as well as shorter time taken for anastomosis, less trauma, and lower blood loss. More long-term studies on the functions, biological interactions, and survival rates of glue-based anastomoses need to be initiated.

Endothelial inflammatory and thrombogenic expression changes in microvascular anastomoses - An immunohistochemical analysis

The aim of this study was to investigate intraluminal vessel diameters and endothelial expression levels of pro-inflammatory and -thrombotic mediators in patent and non-patent microvascular anastomoses. Endothelial expression of CD31, VCAM-1, E- and P-Selectin, eNOS, iNOS and PAI-1 was evaluated by immunohistochemistry and compared to non-anastomosed arteries as controls. Intraluminal diameters were determined via H.E.-staining. In 20 human anastomoses (8 patent, 12 non-patent) neither the analysis of endoluminal de-endothelialization (p = 0.966) nor luminal narrowing (p = 0.750) revealed any significant differences between patent and non-patent microanastomoses. Expressions of pro-inflammatory mediators were significantly higher in patent anastomoses compared to controls but did not show any difference compared to non-patent anastomoses (p > 0.050). iNOS was higher in non-patent compared to patent anastomoses (p = 0.030) and controls (p = 0.001), whereas eNOS did not reveal any differences between these groups (p = 0.611 and p = 0.130). In non-patent anastomoses PAI-1 was expressed higher compared to patent anastomoses and controls (p = 0.021 and p < 0.001). Irrespective of their patency, anastomoses are characterized by endothelial dysfunction with a pro-inflammatory and pro-thrombotic milieu. Avoiding endothelial trauma during suturing is essential in order not to aggravate existing endothelial dysfunction in microanastomoses. Additionally, the influence of medication-related changes on anastomoses should be investigated as this is still an indistinctive topic.

Non-suturing microvascular anastomosis in maxillofacial reconstruction- a comparative study

AIM

The aim of the study is to compare the advantages and disadvantages of non-suturing anastomotic methods over conventional microsuturing for microvascular venous anastomosis.

MATERIALS AND METHODS

All patients reporting to the institute for hard and soft tissue reconstruction (Primary/secondary) were enrolled in the study. Patients with systemic comorbidities, peripheral vascular diseases, or anatomical aberration of the indicated donor site were excluded from the study. The patients selected for the study were randomly allocated to five groups of different techniques of venous anastomosis, namely Group I (conventional microsuturing), II (fibrin sealant reinforced microsuturing), III (couplers), IV (staplers), V (Laser Assisted Vascular Anastomosis (LAVA)). Intraoperative anastomotic time, flap ischaemic time, patency and leakage were the parameters that were assessed for all five groups.

RESULTS

80 Patients were randomly allocated to five groups and each group comprised 16 patients. The mean ischaemic time and standard deviation of Group I and Group II were 256.19 ± 10.622 min and 255.19 ± 11.083 min, and for groups III, IV, and V were 193.38 ± 9.972 min, 139.06 ± 6.413 min, and 139.31 ± 6.364 min respectively (p < 0.001). Mean anastomotic time and standard deviation were 19.813 ± 1.5366 min in Group I and 20.281 ± 1.6514 min in Group II. The non-sutured anastomosis groups III, IV, and V showed a mean anastomotic time of 5.375 ± 0.9876 min, 4.175 ± 0.7664 min, and 3.856 ± 0.867 min respectively (p value < 0.001). In Groups I and II, 18.8% of patients had delayed patency and in Groups III, IV and V, immediate patency was observed in all subjects (p value 0.030). In Groups I and II, 18.8% and 6.3 % of patients respectively had leakage, whereas all patients in Groups III, IV, V had no leakage from the anastomotic site (p value 0.119).

CONCLUSION

Based on the results of the study, non-suturing techniques should be preferred over microsuturing technique whenever appropriate for venous anastomosis.

Sutureless microvascular anastomosis assisted by an expandable shape-memory alloy stent

Vascular anastomosis is the highlight of cardiovascular, transplant, and reconstructive surgery, which has long been performed by hand using a needle and suture. However, anastomotic thrombosis occurs in approximately 0.5-10% of cases, which can cause serious complications. To improve the surgical outcomes, attempts to develop devices for vascular anastomosis have been made, but they have had limitations in handling, cost, patency rate, and strength at the anastomotic site. Recently, indwelling metal stents have been greatly improved with precise laser metalwork through programming technology. In the present study, we designed a bare metal stent, Microstent, that was constructed by laser machining of a shape-memory alloy, NiTi. An end-to-end microvascular anastomosis was performed in SD rats by placing the Microstent at the anastomotic site and gluing the junction. The operation time for the anastomosis was significantly shortened using Microstent. Thrombus formation, patency rate, and blood vessel strength in the Microstent anastomosis were superior or comparable to hand-sewn anastomosis. The results demonstrated the safety and effectiveness, as well as the operability, of the new method, suggesting its great benefit for surgeons by simplifying the technique for microvascular anastomosis.