Patency of different arterial and venous end-to-side microanastomosis techniques in a rat model

Microvascular anastomotic patency is the most important factor in determining a successful outcome in free-flap transfers. End-to-end and end-to-side techniques have been shown to provide equivalent arterial patency rates in clinical and basic science studies, and end-to-side anastomoses have been used extensively in microsurgical reconstruction. Nevertheless, the effect of venotomy shape on the patency of venous end-to-side anastomoses has not been previously reported. The purpose of this study was to compare the patency rates of end-to-side anastomoses using different techniques in both arteries and veins. In total, 104 Sprague-Dawley rats were subdivided into four groups. The rats were anesthetized, and anastomosis was performed on either the femoral artery or vein on the right with the left used as control. Vesselotomy was varied between an end-to-side hole and an end-to-side slit with patency measured immediately following surgery and at 2 weeks. No significant difference in patency or histology between these techniques was demonstrated in any group. We conclude there is no difference in patency rate between the two techniques in arterial or venous vesselotomies; however, in small vessels < 1.5 mm, the slit technique is technically easier, and clinical recommendations are given.     

Continuous sutures for microarterial end-to-side anastomoses

A continuous suture technique for end-to-side microarterial anastomoses has been developed and tested in an experimental model on rat common carotid arteries.     

Rotational in vitro compliance measurement of diverse anastomotic configurations: a tool for anastomotic engineering

Anastomotic configurations with a small internal diameter are prone to intimal hyperplasia which can cause occlusion within weeks or months. A link between intimal hyperplasia and inhomogenities of the elastic profile of the anastomosis has been established, making anastomotic engineering directed towards smoothing the compliance profile at the anastomotic site essential. Methods to date restrict the anastomotic compliance measurement to one plane. We present a method by which the anastomotic configurations are rotated, thereby allowing an anastomotic elastic profile assessment in multiple planes. Eight end-to-end anastomoses (ovine common carotid artery) and three end-to-side anastomoses (e-PTFE graft to ovine common carotid artery) were prepared and mounted in an artificial circulation system. Anastomotic circumferential compliance (maximal-minimal diameter/(maximal-minimal pressure.minimal diameter)) was measured by means of a laser-scan-micrometer and a Statham pressure transducer. By rotating end-to-end anastomoses, the compliance was measured in three, and in end-to-side anastomoses in four different planes. Multiplanar compliance variability in areas remote to both end-to-end and end-to-side anastomoses was approximately 9%. At the suture line the variability was approximately 22% in end-to-end anastomoses and 78% in end-to-side anastomoses. These results show that local factors result in different compliance profiles when utilizing a multiplanar technique, particularly in end-to-side anastomoses. The rotational apparatus is a tool which can be used to more accurately engineer a homogeneously compliant anastomosis, with the ultimate goal of prolonging anastomotic patency.     

Microvascular anastomosis in an optical cavity: is it possible?

Microsurgery is one of the highly interesting surgical procedures that can be performed using different applications and in different specialties, including plastic surgery. The endoscope is a popular instrument used in many fields, including plastic surgery. Although the operating microscope is still a must for microsurgical performance, microsurgery could be performed, depending on the experiences and facilities, by using other visual-assisting equipment. From this point of view, the authors tried to find less costly and more widespread equipment suitable for performing microsurgery that can, furthermore, be applied in special situations and indications, such as operating in an optical cavity. The authors investigated this issue with the endoscope. In this experimental project, the authors performed vascular microsurgical anastomoses of the rats' femoral vessels to create an optical cavity in a prefabricated skin retraction model in the groin area of 10 Sprague-Dawley male rats. The microsurgical anastomoses of the femoral vessels and nerves were performed easily in a reasonable time, without recorded difficulties, and with maximum physical and visual comfort for the surgeon. The authors spent a mean time of 28.1, 27.3, and 19.2 minutes for the arterial, venous, and neural anastomoses, respectively. In this group of animals, 90 percent vascular patency and 100 percent accurate neural anastomoses were recorded. The advantage the authors noted was that this new technique of operating in the field of microsurgery, with its feasibility and difficulties, would be a point of research and application for the young generations of microsurgeons.     

Preferential use of end-to-side arterial anastomoses in free flap transfers.

In our early clinical experience with free flaps, we used end-to-end arterial anastomoses and in 9 our of 24 we had complete failures--7 of which were due to early arterial thrombosis. Contrarily, in 41 consecutive free flaps with end-to-side anastomoses we have not had a single failure. At the same time that we began using the end-to-side anastomoses, we also began using the latissimus dorsi free flap as our flap of first choice, and we agree that this was probably an additional reason for our improved success rate. The use of end-to-side anastomoses has the following advantages: (1) a high success rate; (2) preservation of all existing vessels in an injured extremity; (3) greater freedom of operative planning; and (4) technical simplicity in terms of access to the vessels. For us, these advantages have made end-to-side anastomosis the technique of choice in the transfer of free flaps.     

Bipolar anastomosis technique with removable instruments: an easy, fast, and reliable technique for vascular anastomosis

The interrupted suture technique is most commonly used for microsurgical vascular anastomosis. For several reasons (e.g., exposure of suture material to blood, time needed), many attempts have been made to find other solutions. This article describes a new means of performing a microsurgical vascular anastomosis. The aim of this study was to show the feasibility and possible advantages of this new technique. The basic components at work here are a modified cuff and electrically generated heat used to unite the vessel walls. In this way, both endothelial layers are adapted without manipulating the inside of the vessel or leaving behind foreign matter. Various energy/coagulation time settings were used to perform arterial anastomoses (n = 42) in an isogeneic abdominal aorta interposition model in the rat. The quality of anastomosis was evaluated at days 1, 10, 21, and 120. Immediately after the welding process all anastomoses (n = 42) were patent. No stenosis was found at any observation time. Anastomosis time ranged from 3 to 18 minutes (average, 11 minutes). This new technique permits a vascular anastomosis to be performed easily and reliably with a high patency rate. With this technique, the authors are convinced that a skilled surgeon can create a high-quality anastomosis in a fraction of the time needed to sew an anastomosis.     

The laser-assisted end-to-side microvascular anastomosis

A simple method of performing the laser-assisted end-to-side microvascular anastomosis was devised. This technique was tested on 150 Sprague-Dawley rats in two separate series of experiments. In the first, end-to-side anastomoses were performed on the iliac artery under the normal tension due to the elastic recoil of severed vessels. Four stay sutures were placed 90 degrees apart, and the intervals were "spot welded" with a low-wattage CO2 microsurgical laser unit. The patency rate (96 percent) was equivalent to that found in a control group utilizing the conventional all-suture method (92 percent), but there was a significantly higher aneurysm rate (44 versus 11 percent). In a second model, an arterial bypass with very low anastomotic tension was performed around an obstruction created in the carotid artery. This model resulted in turbulent flow but low anastomotic tension. Here the laser-anastomosis patency rate was 98 percent, versus 42 percent for the conventional all-suture method. The placement of fewer sutures in association with turbulent flow in this model may account for the improved patency rate. The avoidance of excessive tension at the anastomotic site reduced the incidence of aneurysms to a negligible level.     

Morphological evaluation of reconstructive operations on the bronchi using a microsurgical technic in an experiment

Morphological study of bronchial anastomoses repair made with or without microsurgical techniques has been performed in 30 mongrel dogs. Comparative analysis of bronchoscopy, microscopy and scanning electronic microscopy data shows earlier epithelialization, more regular conjunction of bronchial tube and less marked inflammation in anastomosis made with microsurgical techniques. The fact may be explained by a less pronounced traumatization of bronchial tissues with microinstruments and also by tight suture of mucosal layer which creates favourable conditions for repair of anastomosis per primam.     

大鼠颈总动脉端-侧吻合模型的建立

目的建立大鼠颈总动脉端-侧吻合模型,以期对欲进行显微血管吻合训练或相关实验的同道提供帮助。方法成年SD大鼠10只,将左侧颈总动脉远端穿过颈前肌肉群和气管之间的隧道,与右侧颈总动脉行端-侧吻合。结果成功建立大鼠颈总动脉端-侧血管吻合动物模型,手术成功率约为100%,平均吻合所需8针,平均血管吻合所需时间(35±5)min。吻合3个月后观察通畅率100%,HE染色示吻合口愈合良好。结论吻合成功的关键是提高显微操作技术水平,同时注意保护术野中小的血管和神经。此模型可以较好的应用于显微血管缝合训练。     

Microsurgery in the clinic and laboratory

Laboratory animals have been crucial to the development of modern microsurgical techniques which are now routinely used in many clinical departments worldwide. In return, microsurgical techniques are important in biomedical research as they allow many surgical procedures to be performed on rodents instead of dogs, pigs or primates. This has obvious advantages in terms of low cost, the use statistically valid numbers for comparison and the availability of genetically defined animals which are more likely to give valid answers to immunological questions. Microsurgical reconstruction is important in plastic, orthopaedic, urogenital, vascular and peripheral nerve surgery in man and it is likely that it will become part of every surgeon's training in the near future. In this review, the instrumentation essential to any microsurgical enterprise and the sutures available are described. Basic microsurgical techniques for end-to-end and end-to-side anastomosis of small vessels and for joining peripheral nerves, oviducts and other tubular structures are given in outline. Techniques for transplanting kidney, heart, heart and lung, liver, spleen, pancreas, small bowel, stomach, testicle, ovary and whole joint are only outlined but key references are given. Finally, some of the clinical indications for microsurgical reconstruction are reviewed.     

Pilzanastomosen im Phasenkontrastmikroskop

Summary The value of anastomosis-formation between two fungous culture mounts has been examined on several occasions sinceDavidson and co-workers. Fungous anastomoses have been observed and compared systematically in the phase contrast microscope and in the ordinary microscopic field for further clarification of this biological phenomenon of fungi. The Agar-double-block-method (developed from the Agar-block-method ofRiddell andKaden) proved itself suitable for the observation of anastomoses. The phase contrast microscope facilitated an improved observation of the anastomoses, and the results confirm the fungous anastomoses by evidence of their plasma continuity. Therefore suggestion is made, to utilise this additional value of anastomosis formation in the diagnosis of non identified fungous culture mounts.     

Pharyngoesophageal reconstruction using a fabricated forearm free flap

A new microsurgical alternative in reconstruction of the pharynx and cervical esophagus is reported. A trapezoidal forearm flap is fabricated into an inverted skin tube and placed in the pharyngoesophageal defect. Although microvascular anastomoses are required to revascularize the transferred forearm flap, the long and large nutrient vessels of the flap make anastomoses easy and reliable. None of our 12 patients demonstrated any necrosis of the transferred flap. This one-stage, less invasive operation for pharyngoesophageal reconstruction greatly benefits older persons, who are the more likely to be involved with pharyngoesophageal carcinomas.     

Clinical review: irradiation for lower extremity arterial occlusive disease

Lower extremity atherosclerosis, a disease of aging, is both widespread and increasing in prevalence-it is estimated that almost 100,000 patients per year in the United States require operative bypass for lower extremity ischemia. It is an axiom of vascular surgery that essentially every bypass graft will eventually fail. Many if not most such failures are due to the process of intimal hyperplasia at one or both anastomoses. The search for a "cure" for intimal hyperplasia has been long, but thus far unrewarding. Recent advances in therapeutic irradiation, however, offer a potential solution to this problem. This review is designed to acquaint the radiation oncologist with the basic concepts behind lower extremity atherosclerosis and its treatment, and to introduce briefly the special problems inherent in considering irradiation of an end-to-side anastomosis.     

Elevation of deeply located vascular structures in order to facilitate end-to-side anastomosis

This paper presents a simple method of carrying deeply located recipient vascular structures to the surface in order to facilitate end-to-side anastomoses in free-flap transplantations.     

Flow and wall shear stress in end-to-side and side-to-side anastomosis of venous coronary artery bypass grafts

Purpose  

Coronary artery bypass graft (CABG) surgery represents the standard treatment of advanced coronary artery disease. Two major types of anastomosis exist to connect the graft to the coronary artery, i.e., by using an end-to-side or a side-to-side anastomosis. There is still controversy because of the differences in the patency rates of the two types of anastomosis. The purpose of this paper is to non-invasively quantify hemodynamic parameters, such as mass flow and wall shear stress (WSS), in end-to-side and side-to-side anastomoses of patients with CABG using computational fluid dynamics (CFD).     

End-to-end versus end-to-side microvascular anastomosis patency in experimental venous repairs

In this experimental study, venous end-to-end and end-to-side microvascular anastomoses in similar and diameter-discrepant vessels were compared. In 50 rats, end-to-end microvascular repair of the divided epigastric vein and end-to-side repair of the epigastric vein into the femoral vein showed 5-day patency rates of 75 and 88 percent, respectively. These data are not statistically different. In 20 rats, microvascular repair of end epigastric to end femoral veins (size discrepant) and end epigastric to side femoral veins showed 5-day patency rates of 50 and 85 percent, respectively. These data are statistically different (p less than 0.05). We conclude from these experimental data that end-to-side venous repairs may be useful in lowering the anastomosis thrombosis rate seen when size-discrepant veins are repaired.     

Nonlinear finite element simulation to elucidate the efficacy of slit arteriotomy for end-to-side arterial anastomosis in microsurgery

The slit arteriotomy for end-to-side arterial microanastomosis is a technique used to revascularize free flaps in reconstructive surgery. Does a slit open to a width sufficient for blood supply? How is the slit opening affected by factors, such as arterial wall thickness and material stiffness? To answer these questions we propose a nonlinear finite element procedure to simulate the operation. Through modeling the arteries using hyperelastic shell elements, our simulation reveals that the slit opens up to a width even larger than the original diameter of the donor artery, allowing sufficient blood supply. It also identifies two factors that explain the opening of the slit: blood pressure which is predominant in most cases, and the forces applied to the slit by the donor artery. During simulation, when we increase the donor artery thickness and stiffness, it is found that the contribution of blood pressure to the slit opening decreases while that of the forces applied by the donor artery increases. This result indicates that sometimes the forces applied by the donor artery can play an even more significant role than the blood pressure factor.Our simulation elucidates the efficacy of the slit arteriotomy. It improves our understanding of the interplay between blood pressure and donor vessel factors in keeping the slit open.     

Local and global geometric influence on steady flow in distal anastomoses of peripheral bypass grafts

We consider the effect of geometrical configuration on the steady flow field of representative geometries from an in vivo anatomical data set of end-to-side distal anastomoses constructed as part of a peripheral bypass graft. Using a geometrical classification technique, we select the anastomoses of three representative patients according to the angle between the graft and proximal host vessels (GPA) and the planarity of the anastomotic configuration. The geometries considered include two surgically tunneled grafts with shallow GPAs which are relatively planar but have different lumen characteristics, one case exhibiting a local restriction at the perianastomotic graft and proximal host whilst the other case has a relatively uniform cross section. The third case is nonplanar and characterized by a wide GPA resulting from the graft being constructed superficially from an in situ vein. In all three models the same peripheral resistance was imposed at the computational outflows of the distal and proximal host vessels and this condition, combined with the effect of the anastomotic geometry, has been observed to reasonably reproduce the in vivo flow split. By analyzing the flow fields we demonstrate how the local and global geometric characteristics influences the distribution of wall shear stress and the steady transport of fluid particles. Specifically, in vessels that have a global geometric characteristic we observe that the wall shear stress depends on large scale geometrical factors, e.g., the curvature and planarity of blood vessels. In contrast, the wall shear stress distribution and local mixing is significantly influenced by morphology and location of restrictions, particular when there is a shallow GPA. A combination of local and global effects are also possible as demonstrated in our third study of an anastomosis with a larger GPA. These relatively simple observations highlight the need to distinguish between local and global geometric influences for a given reconstruction. We further present the geometrical evolution of the anastomoses over a series of follow-up studies and observe how the lumen progresses towards the faster bulk flow of the velocity in the original geometry. This mechanism is consistent with the luminal changes in recirculation regions that experience low wall shear stress. In the shallow GPA anastomoses the proximal part of the native host vessel occludes or stenoses earlier than in the case with wide GPA. A potential contribution to this behavior is suggested by the stronger mixing that characterizes anastomoses with large GPA.     

Use of the vascular closure staple clip applier for microvascular anastomosis in free-flap surgery

We report our initial experience using the vascular closure staple clip applier (a nonpenetrating titanium clip applied in an interrupted, everting fashion) for microvascular anastomosis in free-flap surgery. In total, 153 anastomoses were performed in 87 free flaps (174 potential anastomoses) using the vascular closure stapler between October of 1997 and June of 1999. In 66 flaps, both the arterial and venous anastomosis were performed with the clip applier, whereas in 21 flaps only the venous anastomosis was performed using the clips. A total of 146 anastomoses were performed in an end-to-end fashion, and seven were performed end-to-side. Of the 87 flaps there were 53 TRAM flaps, seven bilateral TRAM, five latissimus dorsi, four gastrocnemius, three rectus abdominis, two radial forearm fibula, and four Rubens fat-pad flaps. Seventy flaps were used for breast reconstruction, seven flaps for lower limb reconstruction, four flaps for head and neck reconstruction, and six flaps for chest wall/trunk reconstruction. There were no postoperative anastomotic complications of bleeding, thrombosis, or need for revision (100 percent patency rate), with a significantly reduced time for completion of anastomoses. The clip applier is a safe, reliable method for performing microvascular anastomoses, allowing reduced operating time and possible cost savings in free-flap surgery.     

The effect of graft caliber upon wall shear within in vivo distal vascular anastomoses

Wall shear has been widely implicated as a contributing factor in the development of intimal hyperplasia in the anastomoses of chronic arterial bypass grafts. Earlier studies have been restricted to either: (1) in vitro or computer simulation models detailing the complex hemodynamics within an anastomosis without corresponding biological responses, or (2) in vivo models that document biological effects with only approximate wall shear information. Recently, a specially designed pulse ultrasonic Doppler wall shear rate (PUDWSR) measuring device has made it possible to obtain three near-wall velocity measurements nonintrusively within 1.05 mm of the vessel luminal surface from which wall shear rates (WSRs) were derived. It was the purpose of this study to evaluate the effect of graft caliber, a surgically controllable variable, upon local hemodynamics, which, in turn, play an important role in the eventual development of anastomotic hyperplasia. Tapered (4-7 mm I.D.) 6-cm-long grafts were implanted bilaterally in an end-to-side fashion with 30 deg proximal and distal anastomoses to bypass occluded common carotid arteries of 16 canines. The bypass grafts were randomly paired in contralateral vessels and placed such that the graft-to-artery diameter ratio, DR, at the distal anastomosis was either 1.0 or 1.5. For all grafts, the average Re was 432 +/- 112 and the average Womersley parameter, alpha, was 3.59 +/- 0.39 based on artery diameter. There was a sharp skewing of flow toward the artery floor with the development of a stagnation point whose position varied with time (up to two artery diameters) and DR (generally more downstream for DR = 1.0). Mean WSRs along the artery floor for DR = 1.0 and 1.5 were found to range sharply from moderate to high retrograde values (589 s-1 and 1558 s-1, respectively) upstream to high antegrade values (2704 s-1 and 2302 s-1, respectively) immediately downstream of the stagnation point. Although there were no overall differences in mean and peak WSRs between groups, there were significant differences (p < 0.05) in oscillatory WSRs as well as in the absolute normalized mean and peak WSRs between groups. There were also significant differences (p < 0.05) in mean and peak WSRs with respect to axial position along the artery floor for both DR cases. In conclusion, WSR varies widely (1558 s-1 retrograde to 2704 s-1 antegrade) within end-to-side distal graft anastomoses, particularly along the artery floor, and may play a role in the development of intimal hyperplasia through local alteration of mass transport and mechano-signal transduction within the endothelium.