A nomogram for preoperative prediction of microvascular invasion in ruptured hepatocellular carcinoma

BACKGROUND AND AIM

Microvascular invasion (MVI) is defined as the presence of micrometastatic cancer cell emboli in hepatic vessels, including small vessels, and at present, researchers believe that is an important factor for early postoperative recurrence and survival. Here, we developed and validated a preoperative predictive model for the presence of MVI in patients with ruptured hepatocellular carcinoma (rHCC).

METHODS

We retrospectively collected data for 210 rHCC patients who underwent staged hepatectomy at Wuhan Tongji Hospital, and 91 patients who underwent staged hepatectomy at Zhongshan People's Hospital between January 2010 and March 2021. Then, the former was used as the training cohort and the latter was used as the validation cohort. Logistic regression was used to screen for variables associated with MVI, and these variables were used to construct nomograms. We used R software to assess the discrimination, calibration ability, as well as clinical efficacy of nomograms.

RESULTS

Multivariate logistic regression analysis identified four risk factors independently associated with MVI: max tumor length [odds ratio (OR) = 1.385; 95% confidence interval (CI), 1.072-1.790], number of tumors (OR = 2.182; 95% CI, 1.129-5.546), direct bilirubin (OR = 1.515; 95% CI, 1.189-1.930), and alpha-fetoprotein (cutoff = 400 ng/mL) (OR = 2.689; 95% CI, 3.395-13.547). Nomograms were built from the four variables and they were tested for discrimination and calibration, and the results were good.

CONCLUSION

We developed and validated a preoperative predictive model for the presence of MVI in patients with ruptured HCC. This model can help clinicians identify patients at risk of MVI and make better treatment options.

Treatment of postsurgical trigeminal neuralgia with Fu's subcutaneous needling therapy resulted in prompt complete relief: Two case reports

RATIONALE

Trigeminal neuralgia is a recurrent unilateral transient electroshock-like pain. Fu's subcutaneous needling (FSN), used to treat the musculoskeletal problems, has not been reported in this field.

PATIENT CONCERNS

The pain extent of case 1 had no reduction after the previous microvascular decompression, the pain of case 2 relapsed 4 years after the microvascular decompression.

DIAGNOSES

Postsurgical trigeminal neuralgia.

INTERVENTIONS

FSN therapy was applied on the muscles around the neck and face area, which the myofascial trigger points were palpated in these muscles. The FSN needle was inserted into the subcutaneous layer and the needle tip was pointed toward the myofascial trigger point.

OUTCOMES

The following outcome measurements were observed before and after treatment, including numerical rating scale, Barrow Neurology Institute Pain Scale scores, Constant Face Pain Questionnaire scores, Brief Pain Inventory-Facial scores, Patient Global Impression of Change scores, and medication dosage. The follow-up surveys were made after 2 and 4 months respectively. The pain of Case 1 was significantly reduced after 7 times FSN treatments and the pain of Case 2 was even disappeared after 6 times FSN treatments.

LESSONS

This case report suggested that FSN can relieve postsurgical trigeminal neuralgia safely and effectively. Clinical randomized controlled studies are needed to be further conducted.

Wide surgical margins improve prognosis for HCC with microvascular invasion

OBJECTIVE

Hepatocellular carcinoma (HCC) is the sixth leading cause of malignant tumors worldwide. Liver resection is a pivotal treatment modality for HCC. Surgical margin plays an important role in decreasing recurrence and improving prognosis for HCC patients.

MATERIALS AND METHODS

This paper aimed to perform a systematic review of the literature in regard to surgical margin in HCC patients with microvascular invasion (MVI).

RESULTS

Residual MVI due to insufficient surgical margins is the main origin of postoperative recurrence and metastasis in HCC patients. A wide surgical margin (WSM) significantly improves oncological outcomes and long-term survival in HCC patients with MVI. Progress in the preoperative prediction of MVI may contribute to precise surgical decision-making in the future.

CONCLUSIONS

WSM was associated with better outcomes in HCC patients with MVI. WSM is recommended for well-preserved liver function HCC patients who are predicted to have a high risk of MVI preoperatively.

Microvascular anastomotic arterial coupling: A systematic review

INTRODUCTION

There are several reasons microsurgeons may not use a coupler device in arterial anastomosis: may be thick-walled, non-pliable due to atherosclerotic calcification or present vessel geometrical discrepancies. This review summarises the current applications, efficacy and troubleshooting of microvascular coupler devices in arterial end-to-end anastomosis.

METHODS

A systematic review of the literature was performed in November 2020 across 4 electronic databases and in accordance with the PRISMA guidelines. All studies comprised the data synthesis that reported the use of a microvascular coupler device for arterial end-to-end anastomosis. Data were extracted and collected in three groups of standardised variables: study, anastomosis-related and technical characteristics.

RESULTS

Out of the 7,690 articles identified, 20 were included in the final data synthesis. Included studies involved a total of 1639 patients, who underwent 670 arterial and 1,124 venous anastomoses. Out of all arterial anastomoses, 351 were performed in free tissue transfers in head and neck, 117 in breast, 4 in upper extremity and 5 in lower extremity reconstruction, whereas the remaining were not specified. The total arterial coupler anastomosis success rate reported was 92.1% (617/670). Fifty-three (8%) arterial anastomoses were reported to result in either troubleshooting events or intra- or post-operative failures, most being reported in extremity reconstructions.

CONCLUSIONS

Arterial coupling is not widespread with predominant use in head and neck and chest reconstructions, and total reported efficacy of 92.1%. Microsurgeons are reluctant to routinely use current widespread coupler devices as a result of inherent arterial characteristics. This study delivered collective recommendations, 'do's and don'ts' of microvascular arterial coupling.

Low molecular weight heparin for prevention of microvascular occlusion in digital replantation

BACKGROUND

The success of digital replantation is highly dependent on the patency of the repaired vessels after microvascular anastomosis. Antithrombotic agents are frequently used for preventing vascular occlusion. Low molecular weight heparin (LMWH) has been reported to be as effective as unfractionated heparin (UFH) in peripheral vascular surgery, but with fewer adverse effects. Its benefit in microvascular surgery such as digital replantation is unclear. This is an update of the review first published in 2013.

OBJECTIVES

To assess if treatment with subcutaneous LMWH improves the salvage rate of the digits in patients with digital replantation after traumatic amputation.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase, AMED and CINAHL databases, and the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers, to 17 March 2020. The authors searched PubMed, China National Knowledge Infrastructure (CNKI) and Chinese Electronic Periodical Services (CEPS) on 17 March 2020 and sought additional trials from reference lists of relevant publications.

SELECTION CRITERIA

We included randomised or quasi-randomised controlled trials comparing treatment with LMWH versus any other treatment in participants who received digital replantation following traumatic digital amputation.

DATA COLLECTION AND ANALYSIS

Two review authors (PL, CC) independently extracted data and assessed the risk of bias of the included trials using Cochrane's 'Risk of bias' tool. Disagreements were resolved by discussion. We assessed the certainty of evidence using the GRADE approach.

MAIN RESULTS

We included two new randomised trials in this update, bringing the total number of included trials to four. They included a total of 258 participants, with at least 273 digits, from hospitals in China. Three studies compared LMWH versus UFH, and one compared LMWH versus no LMWH. The mean age of participants ranged from 24.5 to 37.6 years. In the studies reporting the sex of participants, there were a total of 145 men and 59 women. The certainty of the evidence was downgraded to low or very low because all studies were at high risk of performance or reporting bias (or both) and there was imprecision in the results due to the small numbers of participants. The three studies comparing LMWH versus UFH reported the success rate of replantation using different units of analysis (participant or digit), so we were unable to combine data from all three studies (one study reported results for both participants and digits). No evidence of a benefit in success of replantation was seen in the LMWH group when compared with UFH, regardless of whether the outcomes were reported by number of participants (risk ratio (RR) 0.98, 95% confidence interval (CI) 0.87 to 1.10; 130 participants, 2 studies; very low-certainty evidence); or by number of digits (RR 0.97, 95% CI 0.90 to 1.04; 200 digits, 2 studies; low-certainty evidence). No studies reported the incidence of compromised microcirculation requiring surgical or non-surgical therapy, or any systemic/other causes of microvascular insufficiency. There was no evidence of a clear difference between the LMWH and UFH groups in occurrence of arterial occlusion (RR 1.08, 95% CI 0.16 to 7.10; 54 participants, 1 study; very low-certainty evidence) or venous occlusion (RR 0.81, 95% CI 0.20 to 3.27; 54 participants, 1 study; very low-certainty evidence). Two studies reported adverse effects. The LMWH and UFH groups showed no evidence of a difference in wound bleeding (RR 0.53, 95% CI 0.23 to 1.23; 130 participants, 2 studies; low-certainty evidence), haematuria (RR 0.43, 95% CI 0.09 to 2.11; 130 participants, 2 studies; very low-certainty evidence), ecchymoses (RR 0.82, 95% CI 0.21 to 3.19; 130 participants, 2 studies; very low-certainty evidence), epistaxis (RR 0.27, 95% CI 0.03 to 2.32; 130 participants, 2 studies; very low-certainty evidence), gingival bleeding (RR 0.18, 95% CI 0.02 to 1.43; 130 participants, 2 studies; very low-certainty evidence), and faecal occult blood (RR 0.27, 95% CI 0.03 to 2.31; 130 participants, 2 studies; very low-certainty evidence). We could not pool data on coagulation abnormalities as varying definitions and tests were used in the three studies. One study compared LMWH versus no LMWH. The success rate of replantation, when analysed by digits, was reported as 91.2% success in the LMWH group and 82.1% in the control group (RR 1.11, 95% CI 0.93 to 1.33; 73 digits, 1 study; very low-certainty evidence). Compromised microcirculation requiring surgical re-exploration, analysed by digits, was 11.8% in the LMWH group and 17.9% in the control group (RR 0.86, 95% CI 0.21 to 3.58; 73 digits, 1 study; very low-certainty evidence). Compromised microcirculation requiring incision occurred in five out of 34 digits (14.7%) in the LMWH group and eight out of 39 digits (20.5%) in the control group (RR 0.72, 95% CI 0.26 to 1.98; 73 digits; very low-certainty evidence). Microvascular insufficiency due to arterial occlusion, analysed by digits, was 11.8% in the LMWH group and 17.9% in the control group (RR 0.66, 95% CI 0.21 to 2.05; 73 digits, 1 study; very low-certainty evidence), and venous occlusion was 14.7% in the LMWH group and 20.5% in the control (RR 0.72, 95% CI 0.26 to 1.98; 73 digits, 1 study; very low-certainty evidence). The study did not report complications or adverse effects.

AUTHORS' CONCLUSIONS

There is currently low to very low-certainty evidence, based on four RCTs, suggesting no evidence of a benefit from LMWH when compared to UFH on the success rates of replantation or affect microvascular insufficiency due to vessel occlusion (analysed by digit or participant). LMWH had similar success rates of replantation; and the incidence rate of venous and arterial microvascular insufficiency showed no evidence of a difference between groups when LMWH was compared to no LMWH (analysed by digit). Similar rates of complications and adverse effects were seen between UFH and LMWH. There was insufficient evidence to draw conclusions on any effect on coagulation when comparing LMWH to UFH or no LMWH. The certainty of the evidence was downgraded due to performance and reporting bias, as well as imprecision in the results. Further adequately powered studies are warranted to provide high-certainty evidence.

Assessment of chronic radiation proctopathy and radiofrequency ablation treatment follow-up with optical coherence tomography angiography: A pilot study

BACKGROUND

Chronic radiation proctopathy (CRP) occurs as a result of pelvic radiation therapy and is associated with formation of abnormal vasculature that may lead to persistent rectal bleeding. While incidence is declining due to refinement of radiation delivery techniques, CRP remains one of the major complications of pelvic radiation therapy and significantly affects patient quality of life. Radiofrequency ablation (RFA) is an emerging treatment modality for eradicating abnormal vasculature associated with CRP. However, questions remain regarding CRP pathophysiology and optimal disease management.

AIM

To study feasibility of optical coherence tomography angiography (OCTA) for investigating subsurface vascular alterations in CRP and response to RFA treatment.

METHODS

Two patients with normal rectum and 8 patients referred for, or undergoing endoscopic RFA treatment for CRP were imaged with a prototype ultrahigh-speed optical coherence tomography (OCT) system over 15 OCT/colonoscopy visits (2 normal patients, 5 RFA-naïve patients, 8 RFA-follow-up visits). OCT and OCTA was performed by placing the OCT catheter onto the dentate line and rectum without endoscopic guidance. OCTA enabled depth-resolved microvasculature imaging using motion contrast from flowing blood, without requiring injected dyes. OCTA features of normal and abnormal microvasculature were assessed in the mucosa and submucosa. Blinded reading of OCTA images was performed to assess the association of abnormal rectal microvasculature with CRP and RFA treatment, and rectal telangiectasia density endoscopic scoring.

RESULTS

OCTA/OCT images are intrinsically co-registered and enabled depth-resolved visualization of microvasculature in the mucosa and submucosa. OCTA visualized normal vascular patterns with regular honeycomb patterns vs abnormal vasculature with distorted honeycomb patterns and ectatic/tortuous microvasculature in the rectal mucosa. Normal arterioles and venules < 200 μm in diameter versus abnormal heterogenous enlarged arterioles and venules > 200 μm in diameter were visualized in the rectal submucosa. Abnormal mucosal vasculature occurred in 0 of 2 normal patients and 3 of 5 RFA-naïve patients, while abnormal submucosal vasculature occurred more often, in 1 of 2 normal patients and 5 of 5 RFA-naïve patients. After RFA treatment, vascular abnormalities decreased, with abnormal mucosal vasculature observed in 0 of 8 RFA-follow-up visits and abnormal submucosal vasculature observed in only and 2 of 8 RFA-follow-up visits.

CONCLUSION

OCTA visualizes depth-resolved microvascular abnormalities in CRP, allowing assessment of superficial features which are endoscopically visible as well as deeper vasculature which cannot be seen endoscopically. OCTA/OCT of the rectum can be performed in conjunction with, or independently from endoscopy. Further studies are warranted to investigate if OCTA/OCT can elucidate pathophysiology of CRP or improve management.

Robot-assisted microvascular anastomosis in head and neck free flap reconstruction: Preliminary experiences and results

BACKGROUND

The da Vinci Surgical System has facilitated considerable advancements in surgery. The process and results of robot-assisted microvascular anastomosis in real clinical situations have rarely been reported. This study presents our experience of performing robot-assisted microvascular anastomosis in free flap reconstruction in patients with oropharyngeal cancer.

PATIENTS AND METHODS

This was a retrospective study of reconstructive operations using a free radial forearm flap for oropharyngeal defects after tumor extirpation in 15 consecutive adult patients (12 men and 3 women). In total, 17 robot-assisted microvascular vessel anastomoses (2 arteries and 15 veins) were performed; moreover, 13 arteries and 13 veins were anastomosed using the standard operating microscope and hand-sewing technique.

RESULTS

The recipient and donor vessel diameters were 2.5 ± 0.7 and 2.1 ± 0.8 mm, respectively. The donor blood vessel diameter selected for anastomosis using da Vinci Surgical System was significantly smaller (2.1 ± 0.8 vs. 2.5 ± 0.6 mm) than that for a standard operating microscope and hand-sewing technique (p = .021), the operating time spent (38.4 ± 10.4 vs. 28.0 ± 7.7 min) was significantly longer (p < .001). The vascular patency rate was 100%, and all flaps survived without requiring additional operation for revision.

CONCLUSION

Robotic surgical systems can facilitate vascular microanastomosis and provide a blood vessel patency rate comparable to that of a standard operating microscope and hand-sewing technique.

Hyperspectral imaging for monitoring of perfusion failure upon microvascular anastomosis in the rat hind limb

BACKGROUND/PURPOSE

Objective, reliable and easy monitoring of microvascular tissue perfusion is a goal that was achieved for many years with limited success. Therefore, a new non-invasive hyperspectral camera system (TIVITA™) was tested for this purpose in an in vivo animal model.

METHODS

Evaluation of tissue oxygenation during ischemia and upon reperfusion was performed in left hind limb in a rat model (n=20). Ischemia was induced by clamping and dissection of the superficial femoral artery. Reperfusion of the limb was achieved by microsurgical anastomosis of the dissected artery. Oxygenation parameters of the hind limb were assessed via TIVITA™ before and immediately after clamping and dissection of the artery, 3 and 30min after reperfusion as well as on postoperative days 1 and 2. Thereby, the non-operated hind limb served as control. As clinical parameters, the refill of the anastomosis as well as the progress of the affected leg were assessed.

RESULTS

In 12 from 20 cases, TIVITA™ recorded a sufficient reperfusion with oxygenation parameters comparable to baseline or control condition. However, in 8 from 20 cases oxygenation was found impaired after reperfusion causing a re-assessment of the microvascular anastomosis. Thereby, technical problems like stenosis or local thrombosis were found in all cases and were surgically treated leading to an increased tissue oxygenation.

CONCLUSIONS

The TIVITA™ camera system is a valid non-invasive tool to assess tissue perfusion after microvascular anastomosis. As it safely shows problems in oxygenation, it allows the clinician a determined revision of the site in time in order to prevent prolonged ischemia.

Occipital Microarteriovenous Malformation Resection, Strategy, and Nuances

We describe a patient who presented with superior quadrianopsia due to an occipital micro AVM that bled into the optic radiation. Onyx embolization was attempted. However, early follow-up angiogram revealed recanalization and recurrence of the AVM. He was then taken to the hybrid operative room, where a complete resection was achieved confirmed by intraoperative angiogram. He made a complete recovery with no new neurologic deficit and stable visual field deficit. This case demonstrates treatment strategy, surgical planning, and technical nuances in microsurgical resection of micro AVMs located in an eloquent area. Management of a ruptured microarteriovenous malformation (microAVM) localized in an eloquent brain region is challenging. The major difficulties are those related to localizing and defining the micronidus in order to achieve complete resection and definitive cure while preserving function. The best and definitive treatment for AVMs is either surgical resection or radiosurgery. However, in our institute a small subset of microAVMs might be cured by endovascular embolization in a single session. In the case presented here, a single feeder was demonstrated and microcatheter navigation toward a good working position seemed feasible; thus we decided to try first an endovascular approach.

Modeling of blood flow through sutured micro-vascular anastomoses

Microanastomosis is a surgical procedure used to reconnect two blood vessels using sutures. The optimal microanastomosis may be predicted by assessing the factors that influence this invasive procedure. Blood flow and hemodynamics following microanastomosis are important factors for the successful longevity of this operation. How is the blood flow affected by the presence of sutures? Computational Fluid Dynamics (CFD) is a powerful tool that permits the estimation of specific quantities, such as fluid stresses, that are hardly measurable in vivo. In this study, we propose a methodology which evaluates the alterations in the hemodynamic status due to microanastomosis. A CFD model of a reconstructed artery has been developed, based on anatomical information provided by intravascular ultrasound and angiography, and was used to simulate blood flow after microanastomosis. The 3D reconstructed arterial segments are modeled as non-compliant 1.24 - 1.47 mm diameter ducts, with approximately 0.1 mm arterial thickness. The blood flow is considered laminar and the no-slip condition is imposed on the boundary wall, which is assumed to be rigid. In analyzing the results, the distribution of the wall shear stress (WSS) is presented in the region of interest, near the sutures. The results indicate that high values of WSS appear in the vicinity of sutures. Such regions may promote thrombus formation and subsequently anastomotic failure, therefore their meticulous study is of high importance.

Liposuction Preserves the Morphological Integrity of the Microvascular Network: Flow Cytometry and Confocal Microscopy Evidence in a Controlled Study

BACKGROUND

Liposuction is a very popular technique in plastic surgery that allows for the taking adipose tissue (AT) on large surfaces with little risk of morbidity. Although liposuction was previously shown to preserve large perforator vessels, little is known about the effects of liposuction on the microvasculature network.

OBJECTIVES

The aim of this study was to analyze the effect of liposuction on the preservation of microvessels at tissue and cellular levels by flow cytometry and confocal microscopy following abdominoplasty procedure.

METHODS

Percentage of endothelial cells in AT from liposuction and en bloc AT was determined by multicolor flow cytometry. Moreover, vessel density and adipocyte content were analyzed in situ in 3 different types of AT (en bloc, from liposuction, and residual AT after liposuction) by confocal microscopy.

RESULTS

Flow cytometric analysis showed that en bloc AT contained 30.6% ± 12.9% and AT from liposuction 21.6% ± 9.9% of endothelial cells (CD31(pos)/CD45(neg)/CD235a(neg)/CD11b(neg)) (P = .009). Moreover, analysis of paired AT from the same patients (n = 5) confirmed a lower percentage of endothelial cells in AT from liposuction compared to en bloc AT (17.7% ± 4.5% vs 21.9% ± 3.3%, P = .031). Likewise, confocal microscopy showed that en bloc AT contained 8.2% ± 6.3%, AT from liposuction only 1.6% ± 1.0% (P < .0001), and AT after liposuction 8.9% ± 4.1% (P = .111) of CD31(pos) vessels. Conversely, adipocyte content was 39.5% ± 14.5% in the en bloc AT, 45% ± 18.4% in AT from liposuction (P = .390), and 18.8 ± 14.8% in AT after liposuction (P = .011).

CONCLUSIONS

For the first time, we demonstrate that liposuction preserves the microvascular network. Indeed, a low percentage of endothelial cells was found in AT from liposuction and we confirm the persistence of microvessels in the tissue after liposuction.

Intrahepatic Vascular Anatomy in Rats and Mice--Variations and Surgical Implications

INTRODUCTION

The intra-hepatic vascular anatomy in rodents, its variations and corresponding supplying and draining territories in respect to the lobar structure of the liver have not been described. We performed a detailed anatomical imaging study in rats and mice to allow for further refinement of experimental surgical approaches.

METHODS

LEWIS-Rats and C57Bl/6N-Mice were subjected to ex-vivo imaging using μCT. The image data were used for semi-automated segmentation to extract the hepatic vascular tree as prerequisite for 3D visualization. The underlying vascular anatomy was reconstructed, analysed and used for determining hepatic vascular territories.

RESULTS

The four major liver lobes have their own lobar portal supply and hepatic drainage territories. In contrast, the paracaval liver is supplied by various small branches from right and caudate portal veins and drains directly into the vena cava. Variations in hepatic vascular anatomy were observed in terms of branching pattern and distance of branches to each other. The portal vein anatomy is more variable than the hepatic vein anatomy. Surgically relevant variations were primarily observed in portal venous supply.

CONCLUSIONS

For the first time the key variations of intrahepatic vascular anatomy in mice and rats and their surgical implications were described. We showed that lobar borders of the liver do not always match vascular territorial borders. These findings are of importance for the design of new surgical procedures and for understanding eventual complications following hepatic surgery.

Applications of three-dimensional printing technology in the cardiovascular field

Three-dimensional (3-D) printing technology has rapidly developed in the last few decades. Meanwhile, the application of this technology has reached beyond the engineering field and expanded to almost all disciplines, including medicine. There has been much research on the medical applications of 3-D printing in neurosurgery, orthopedics, maxillofacial surgery, plastic surgery, tissue engineering, as well as other fields. Because of the complexity of the cardiovascular system, the application of this technology is limited and difficult, as compared to other disciplines, and thus there is much room for future development. Many of the difficulties associated with this technology must be overcome. Nonetheless, there is no doubt that 3-D printing technology will benefit patients with cardiovascular diseases in the near future.

Long-term functional outcomes and quality of life after oncologic surgery and microvascular reconstruction in patients with oral or oropharyngeal cancer

CONCLUSIONS

Surgery for oral or oropharyngeal cancer with free-flap reconstruction is associated with moderate but persistent functional and quality of life (QoL) problems. Patient age, tumor stage, tumor site, and radiotherapy were the main predictors of functional outcome.

OBJECTIVES

To evaluate long-term functional outcomes and QoL, and to determine their predictive factors in patients with oral or oropharyngeal cancer after oncologic surgery and free-flap reconstruction.

METHODS

Patients who underwent surgery with free-flap reconstruction for oral or oropharyngeal cancer between 2000 and 2009 who were alive at least 1 year after therapy were included in this study. Patients completed the Voice Handicap Index (VHI-10) questionnaire and the European Organization for Research and Treatment of Cancer (EORTC) QoL questionnaires QLQ-C30 and H&N35. Swallowing was evaluated using the Dysphagia Outcome and Severity Scale (DOSS) and by flexible fiberoptic laryngoscopy.

RESULTS

Sixty-four patients were included in the study. VHI-10 mean score was 11.2 ± 9 and its predictive factors were T stage (p = 0.005) and tumor involvement of the tongue base (p = 0.01). The mean DOSS score was 4 ± 0.8. Age (p = 0.008), gender (p = 0.04), and radiotherapy (p = 0.001) were the main predictive factors of the DOSS score.

Mussel inspired coating of a biocompatible cyclodextrin based polymer onto CoCr vascular stents

During the past decade, drug-eluting stents (DES) have been widely used for the treatment of occlusive coronary artery diseases. They are supposed to reduce the incidence of early in-stent restenosis by the elution of highly hydrophobic antiproliferative drugs. Nevertheless, the absence of long-term activity of these devices is responsible for late acute thrombosis probably due to the delayed re-endothelialization of the arterial wall over the bare metallic stent struts. Thus, a new generation of DES with a sustained release of therapeutic agents is required to improve long-term results of these devices. In this article, we report an original functionalization of CoCr vascular devices with a hydrophilic, biocompatible and biodegradable cyclodextrins based polymer which acts as a reservoir for lipophilic drugs allowing the sustained release of antiproliferative drugs. In this setting, polydopamine (PDA), a strong adhesive biopolymer, was applied as a first coating layer onto the surface of the metallic CoCr device in order to promote the strong anchorage of a cyclodextrin polymer. This polymer was generated "in situ" from the methylated cyclodextrins and citric acid as a cross-linking agent through a polycondensation reaction. After optimization of the grafting process, the amount of cyclodextrin polymer coated onto the CoCr device was quantified by colorimetric titrations and the resulting film was characterized by scanning electron microscopy (SEM) investigations. The cytocompatibility of the resulting coated film was assessed by cell proliferation and vitality tests. Finally, the ability of this coated device to act as a drug-eluting system was evaluated with paclitaxel, a strong hydrophobic antiproliferative drug, a reference drug used in current vascular drug-eluting stents.

Introduction of a microsurgical in-vivo embolization-model in rats: the aorta-filter model

Vascular thrombosis with subsequent distal embolization remains a critical event for patients. Prevention of this life-threatening event can be achieved pharmacologically or mechanically with intravascular filter systems. The ability to evaluate the risk of embolization of certain techniques and procedures in vascular and microvascular surgery, such as, tissue glue or fibrin based haemostatic agents lacks convincing models. We performed 64 microvascular anastomoses in 44 rats, including 44 micro-pore polyurethane filter-anastomoses and 20 non-filter anastomoses. The rats were re-anesthetized and the aorta was re-exposed and removed four hours, three, seven, fourteen, thirty-one days, and six months postoperatively. The specimens were examined macro- and microscopically with regard to the appearance of the vessel wall, condition of the filter and the amount of thrombembolic material. Typical postoperative histopathological changes in vessel architecture were observed. Media necrosis was the first significant change three days postoperatively. Localized intimal hyperplasia, media necrosis, increase of media fibromyocytes and adventitial hypercellularity were seen to a significant extent at day seven postoperatively. Significant neovascularization of adventitia adjacent to the filter was seen after 14 days. A significant amount of thrombotic material was seen after four hours, three and 14 days interval. Only three intravascular filters became completely occluded (6.82%). The aorta-filter-anastomosis model appeared to be a valid in-vivo model in situations at risk for thrombembolic events, for microsurgical research and allowed sensitive analysis of surgical procedures and protection of the vascularized tissue. It may be suitable for a wide range of in-vivo microvascular experiments particularly in the rat model.

Identification of technique variations among microvascular surgeons and cases using hierarchical task analysis

A hierarchical taxonomy was developed for identifying differences among microvascular surgeons and cases and for investigating the impact of those differences on case outcome. Hierarchical task analysis was performed on eight microvascular anastomosis cases. The analysis was simplified by redefining subtasks and elements to only describe actions and adding attributes to describe the work object, method, tool, material, conditions and ergonomics factors. The resulting taxonomy was applied to 64 cases. Differences were found among cases for the frequency and duration of subtask, elements, attributes and element sequences. Observed variations were used to formulate hypotheses about the relationship between different methods and outcomes that can be tested in future studies. The taxonomy provides a framework for comparing alternative methods, determining the best methods for given conditions and for surgical training and retraining.

PRACTITIONER SUMMARY

A hierarchical taxonomy, created from a hierarchical task analysis and work attributes, was applied to describe technique variations among microsurgery cases. Variations in time, frequency and sequence were used to form hypotheses on best methods for standardising procedures.

Microvascular anastomosis guidance and evaluation using real-time three-dimensional Fourier-domain Doppler optical coherence tomography

Vascular and microvascular anastomoses are critical components of reconstructive microsurgery, vascular surgery, and transplant surgery. Intraoperative surgical guidance using a surgical imaging modality that provides an in-depth view and three-dimensional (3-D) imaging can potentially improve outcome following both conventional and innovative anastomosis techniques. Objective postoperative imaging of the anastomosed vessel can potentially improve the salvage rate when combined with other clinical assessment tools, such as capillary refill, temperature, blanching, and skin turgor. Compared to other contemporary postoperative monitoring modalities--computed tomography angiograms, magnetic resonance (MR) angiograms, and ultrasound Doppler--optical coherence tomography (OCT) is a noninvasive high-resolution (micron-level), high-speed, 3-D imaging modality that has been adopted widely in biomedical and clinical applications. For the first time, to the best of our knowledge, the feasibility of real-time 3-D phase-resolved Doppler OCT (PRDOCT) as an assisted intra- and postoperative imaging modality for microvascular anastomosis of rodent femoral vessels is demonstrated, which will provide new insights and a potential breakthrough to microvascular and supermicrovascular surgery.

[Application of intraoperative microvascular dopplerography in surgical treatment of arterial aneurysm of the brain]

The possibilities and results of the intraoperative microvascular dopplerography application in microsurgical exclusion of the brain arterial aneurysm (BAA) were estimated. The investigation was conducted during operative intervention in 30 patients, suffering hemorrhagic type of the brain acute blood flow disorder as a consequence of the BAA rupture. In an acute period (the first-14th day) 23 patients were operated, in the early restoration period (after 30th day)--7. Intraoperative express estimation of the blood flow have permitted to diagnose and to correct timely some typical technical complications, in particular, noncomplete BAA exclusion from the blood flow, the arterial lumen, containing the clipped aneurysm, stenosing; to reveal the arterial segments vasospasm objectively in the patients, operated on in an acute period of hemorrhage, and to diagnose a reactive spasm during manipulations on the arteries. All the patients, operated on in the early restoration period and 82.6% of patients, operated on in an acute period of subarachnoidal hemorrhage, have had reconvalesced. Application of the microvascular dopplerography secures objectivization, simplifies intraoperative estimation of the BAA radicality and the according arterial segments passability in the operative intervention zone, what promotes reduction of the ischemic complications rate and positively impacts the results of treatment.

Novel biomarkers of arterial and venous ischemia in microvascular flaps

The field of reconstructive microsurgery is experiencing tremendous growth, as evidenced by recent advances in face and hand transplantation, lower limb salvage after trauma, and breast reconstruction. Common to all of these procedures is the creation of a nutrient vascular supply by microsurgical anastomosis between a single artery and vein. Complications related to occluded arterial inflow and obstructed venous outflow are not uncommon, and can result in irreversible tissue injury, necrosis, and flap loss. At times, these complications are challenging to clinically determine. Since early intervention with return to the operating room to re-establish arterial inflow or venous outflow is key to flap salvage, the accurate diagnosis of early stage complications is essential. To date, there are no biochemical markers or serum assays that can predict these complications. In this study, we utilized a rat model of flap ischemia in order to identify the transcriptional signatures of venous congestion and arterial ischemia. We found that the critical ischemia time for the superficial inferior epigastric fasciocutaneus flap was four hours and therefore performed detailed analyses at this time point. Histolgical analysis confirmed significant differences between arterial and venous ischemia. The transcriptome of ischemic, congested, and control flap tissues was deciphered by performing Affymetrix microarray analysis and verified by qRT-PCR. Principal component analysis revealed that arterial ischemia and venous congestion were characterized by distinct transcriptomes. Arterial ischemia and venous congestion was characterized by 408 and 1536>2-fold differentially expressed genes, respectively. qRT-PCR was used to identify five candidate genes Prol1, Muc1, Fcnb, Il1b, and Vcsa1 to serve as biomarkers for flap failure in both arterial ischemia and venous congestion. Our data suggests that Prol1 and Vcsa1 may be specific indicators of venous congestion and allow clinicians to both diagnose and successfully treat microvascular complications before irreversible tissue damage and flap loss occurs.

Low molecular weight heparin for prevention of microvascular occlusion in digital replantation

BACKGROUND

The success of digital replantation is highly dependent on the patency of the repaired vessels after microvascular anastomosis. Antithrombotic agents are frequently used for preventing vascular occlusion. Low molecular weight heparin (LMWH) has been reported to be as effective as unfractionated heparin (UFH) in peripheral vascular surgery, but with fewer adverse effects. Its benefit in microvascular surgery such as digital replantation is unclear.

OBJECTIVES

To assess whether subcutaneous LMWH treatment improves the salvage rate of the digits in patients with digital replantation after traumatic amputation.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator (TSC) searched the Specialised Register (October 2012), CENTRAL (2012, Issue 10) and trials databases. In addition, the authors searched PubMed, CNKI (China National Knowledge Infrastructure) and CEPS (Chinese Electronic Periodical Services), and sought additional trials from reference lists of relevant publications.

SELECTION CRITERIA

We selected randomised or quasi-randomised controlled trials of LMWH in patients who received digital replantation.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias of the included trials. Disagreements were resolved by discussion.

MAIN RESULTS

Two randomised trials involving 114 patients with at least 122 replanted digits met the inclusion criteria and were included. Both trials compared the efficacy and safety of LMWH with UFH. We found no trials comparing LMWH with placebo or other anticoagulants. The data from the two included studies were insufficient for meta-analysis. The overall success rate of replantation did not differ between the LMWH and UFH groups, 92.3% versus 89.2% in one trial (risk ratio (RR) 1.03; 95% confidence interval (CI) 0.87 to 1.22) and 94.3% versus 94.15% in the other trial (RR 1.00; 95% CI 0.89 to 1.13). The incidence of both postoperative arterial and venous insufficiency were reported in one trial and did not significantly differ between the LMWH and UFH groups (RR 1.08; 95% CI 0.16 to 7.10 and RR 0.81; 95% CI 0.20 to 3.27, respectively). Direct and indirect causes of microvascular insufficiency were not reported in the trials. Different methods were used to monitor the adverse effects related to anticoagulation in the two trials. Bleeding tendency was monitored for the LMWH and UFH groups in one trial and was reported by the incidence of wound haemorrhage (11.5% versus 17.9%; RR 0.65; 95% CI 0.17 to 2.44), ecchymoses (3.8% versus 10.7%; RR 0.36; 95% CI 0.04 to 3.24), haematuria (3.8% versus 7.1%; RR 0.54; 95% CI 0.05 to 5.59), nasal bleeding (0% versus 7.1%; RR 0.21; 95% CI 0.01 to 4.28), gingival bleeding (0% versus 10.7%; RR 0.15, 95% CI 0.01 to 2.83) and faecal occult blood (0% versus 3.6%; RR 0.36; 95% CI 0.02 to 8.42). The bleeding tendency was increased in the UFH group but this was not statistically significant. This trial also monitored coagulability changes using parameters such as antithrombin activity, factor Xa activity, bleeding time, clotting time and activated partial thromboplastin time (aPTT). No comparison was made between the LMWH and UFH groups but all data consistently showed that coagulability was reduced more in the UFH group than in the LMWH group. The other trial reported a postoperative decrease in platelet count in the UFH group (preoperative 278.4 ± 18.7 x 10(9)/L, postoperative 194.3 ± 26.5 x 10(9)/L; P < 0.05) but not in the LMWH group (preoperative 260.8 ± 32.5 x 10(9)/L, postoperative 252.4 ± 29.1 x 10(9)/L; P > 0.05).

AUTHORS' CONCLUSIONS

Current limited evidence based on two small-scaled low-to-medium quality randomised trials found no differences in the success rate of replantation between LMWH and UFH, but a lower risk of postoperative bleeding and hypocoagulability after the use of LMWH. Further well-designed and adequately powered clinical trials are warranted.

[Intraoperative decisions and surgical efficacies of trigeminal neuralgia responsible vessels]

OBJECTIVE

To explore the types of primary trigeminal neuralgia (TN) responsible vessels and curative efficacies of microscopic vascular decompression (MVD).

METHODS

A total of 162 primary TN patients underwent MVD from August 2004 to the present at our hospital.Their clinical data were collected and analyzed. There were 69 males and 93 females with an age range of 22-88 years.

RESULTS

The most common responsible vessels were superior cerebellar artery (n = 65, 40.12%), anteroinferior cerebellar artery (n = 45, 27.78%), multiple vessels (n = 26, 16.05%), posteroinferior cerebellar artery (n = 16, 9.88%), veins (n = 6, 3.70%) and vertebral artery (n = 4, 2.47%). And the pressure points were at the root of trigeminal nerve (n = 139, 85.80%), distal part (n = 16, 9.88%) and root and distal part (n = 7, 4.32%). Postoperatively pain disappeared in all patients (including one case on second surgery). Postoperative follow-ups were conducted for 132 cases.Two cases recurred over 8 years and the recurrence rate was 1.52%.

CONCLUSION

MVD is preferred method for primary TN non-responsive to pharmacotherapy. Identification and treatment of responsible vessels remain a key. Venous and distal pressure points should be taken care.

Nanotechnology and vascular neurosurgery: an in vivo experimental study on microvessels repair using laser photoactivation of a nanostructured hyaluronan solder

Sealing tissues by laser in neurosurgical procedures may overcome problems related to the use of conventional suturing methods which can be associated with various degrees of vascular wall damage. Despite the significant experimental and clinical achievements of the past, a standardized clinical application of laser-welding technology has not yet been implemented. The main problem is related to the use of common organic chromophores. A substantial breakthrough in the laser welding of biological tissues may come from the advent of nanotechnologies. In this paper we describe an experimental study, to confirm the feasibility of an innovative laser-assisted vascular repair (LAVR) technique based on diode laser irradiation and subsequent photoactivation of a hyaluronan solder embedded with near infrared (NIR) absorbing gold nanorods (GNRs), and to analyze the induced closuring effect in a follow-up study performed in animal model. Twenty New Zealand rabbits underwent closure of a 3-mm longitudinal incision performed on the common carotid artery (CCA) by means of 810 nm diode laser irradiation, in conjunction with the topical application of an optimized GNR composite. Effective closure of the arterial wound was accomplished by using very low laser intensity (30 W/cm2). The average CCA occlusion time was as low as 50 sec. Animals underwent different follow-up periods (2, 8, 30 days). After follow-up, they were re-anesthetized, the patency of the treated vessels was tested (Doppler analysis) and then the irradiated vessels were excised and subjected to histological evaluations. Morphological examinations of the samples documented the integrity of the vascular wall. No host reaction to nanoparticles occurred. Collagen and elastic fibers returned to their normal architecture 30 days after treatment. A Scanning Electron Microscopy (SEM) examination and immuno-histochemical analysis demonstrated a full re-endothelization of the vessel walls. We thus confirmed that a laser-based approach is technically easy to perform, and provides several advantages, such as a simplification of the surgical procedure, a reduction in the operative time, and the suppression of bleeding. The use of GNRs improves the selectivity of welding and minimizes the surgical trauma to vessels, resulting in an optimal healing process.

Reconstruction of the nose with a new double flap technique: microvascular osteocutaneous femur and microvascular chondrocutaneous ear flap--first clinical results

This study describes a new microvascular flap combination from the medial femur and ear to reconstruct the nose after subtotal resection and presents the first clinical results. In four patients a squamous cell carcinoma of the nose was registered. In three patients this was diagnosed for the first time while in the fourth patient it was the second relapse after two resections and local flap surgery. In every case, tumour resection ended up in an extended defect of the nose, cheek and upper lip region. For skeletal reconstruction and the inner lining of the nose, a microvascular osteocutaneous femur flap was used. After reconstructing the nasal skeleton, the remaining defect was covered by a microvascular composite flap from the left ear and preauricular region. Both flap pedicles were anastomosed to the facial vein and artery. In every case, the flaps healed without complications. There was no tumour relapse. 12 months after reconstruction, minor surgical corrections were made. The patients showed a satisfying functional and aesthetic result. The combination of a microvascular osteocutaneous femur flap and a microvascular ear flap can be used successfully for reconstructing the nose after subtotal resection.

[Primary reconstruction in a case of total eyelid avulsion]

Authors took clinical case of primary surgical reconstruction in total eyelid avulsion as an example to discuss possible mistakes of surgical technique and implant choice. Besides, prognosis for different eyelid tissues retention in total eyelid avulsion and subsequent reconstruction are analyzed. Laser Doppler flowmetry is a method for dynamic evaluation of retention and prognosis of autotissue rejection, it clearly demonstrates decrease of microcirculation in the sites of worse tissue retention.

[Hepatic tissue regeneration after electrothermocoagulation in experimental pathology of local blood circulation]

The regeneration processes course in the liver, occurring after its wedge resection performance using electrothermoadhesion method, were studied on two simulating models: the stress model of atherosclerosis and experimental hyperglycemia. The dynamics of morphological changes in the liver observed have had witnessed a tendency preservation towards formation of elastic linear cicatrix of collagen and a full-fledged morphofunctional restoration of liver after the operation. Peculiarities of the restoration processes course were connected with the disorder severity.

[Cryosurgery in diffuse hepatic diseases]

Comparative studying, using histological and biomicroscopic methods, of the dosed cryohepatodestruction (CHD), periarterial cryodenervation of hepatic artery (CDHA) and their concomitant application influence on the dynamics of hepatic restoration processes in experimental cirrhosis was performed. The investigations were done on 215 male rats owing body mass 200-280 g in a not changed and pathologically changed liver. There was shown, that CDHA promotes changes in hepatic tissue microhemocirculation, as well as the enhancement of the sinusoidal vessels diameter and relative square of vascular bed. CHD stimulates the reparative processes course in a pathologically changed organ. There was established, that while simultaneous application of two cryosurgical methods, the velocity and grade of restoration processes in cirrhotically-changed liver are enhanced in comparison with such indices changes while separate usage of these two methods.

[Ultrastructural changes of vascular endothelium in patients with chronic ischemia of the extremities after conduction of multipotent stromal cells from adipose tissue transplantation]

Taking into account the impossibility of performance in some situations of reconstructive operative interventions on arteries, it is necessary to look for new methods of indirect revascularization for the extremities ischemia. Adipose tissue constitutes an accessible and sufficient source of multipotent stromal cells (MSC). Experimental investigations were made in a frame of preclinical trial on laboratory animals with the extremity ischemia simulation, and there was proved the essential stimulation of angiogenesis processes after transplantation performance of stromal-vascular fraction of adipose tissue. The work objective was to study the influence of own adipose tissue MSC transplantation on vascular endothelium changes in patients, suffering chronic ischemia of the extremities. Using electron microscopy method there was proved on microstructural level, that in clinical environment the patients, suffering chronic ischemia of the extremities of various etiology, gain undoubted effect of MSC autotransplantation performed with the objective to stimulate the processes of angiogenesis in the ischemic affection region.

New stereoscopic virtual reality system application to cranial nerve microvascular decompression

PURPOSE

Cranial nerve microvascular decompression is a habitual neurosurgical procedure. Authors describe a new application of the Dextroscope (Volume Interactions, Ltd.), a virtual reality environment, to plan and properly simulate this kind of procedures.

METHODS

In three cases of hemifacial spasm refractory to drugs and botulinum toxin treatment, the authors used a virtual reality workstation (Dextroscope) to develop an interactive simulation of craniotomy, approach, and Gore-Tex implant optimal size and position in order to reach vascular decompression of facial nerve.

RESULTS

Three-dimensional interactive environment allowed the authors to virtually carry out craniotomy, to visualize vascular and nerve relationship, and finally, to select and to simulate best Gore-Tex graft positioning in each case. During surgical procedures, facial nerve vascular compressions were exposed and Gore-Tex grafts were successfully placed as it was virtually planned. Patient outcomes were excellent, with an average improvement of two units (0-4 grades of severity scale).

CONCLUSION

Virtual reality environment can help the neurosurgeon to plan and train vascular decompression procedures. Use of appropriate craniotomy, knowledge of vascular and nerve relationship, and selection of optimum paddy size and position are the main useful applications of the Dextroscope in these procedures.

Minimally occlusive laser vascular anastomosis (MOLVA): experimental study

BACKGROUND

Temporary occlusion of an intracranial artery during microvascular anastomosis is a major risk factor in cerebrovascular surgery. A new laser vascular welding technique that minimizes the occlusion time of the recipient vessel has been developed and is described in this report.

METHOD

A new minimally occlusive technique of end-to-side microvascular anastomosis was developed employing a diode laser in association with the application of a chromophore in our experimental model of double end-to-side anastomosis. The implantation of a vein graft on the patent carotid artery was obtained through the application of three interrupted sutures at each anastomotic site; the carotid was then clamped, two arteriotomies were performed, followed by the application of a fourth suture and of the laser welding procedure on each anastomosis. Monitoring of the temperature at the site of the anastomosis was introduced in order to control the welding technique.

FINDINGS

The time of the clamping of the carotid artery was 12 min to perform two end-to-side anastomoses (i.e., 6 min for each anastomosis). All bypasses were patent after a follow-up of 90 days and histological study confirmed good preservation of the vascular wall.

CONCLUSIONS

Our laser-assisted technique of vascular anastomosis reduces the duration of the clamping of the recipient artery down to 6 min. This technique can minimize the risk of cerebral ischemia associated with occlusion of a recipient artery in intracranial bypass procedures, promoting an improved vascular healing process with a lower risk of thrombosis and occlusion.

Plasma-mediated ablation: an optical tool for submicrometer surgery on neuronal and vascular systems

Plasma-mediated ablation makes use of high energy laser pulses to ionize molecules within the first few femtoseconds of the pulse. This process leads to a submicrometer-sized bubble of plasma that can ablate tissue with negligible heat transfer and collateral damage to neighboring tissue. We review the physics of plasma-mediated ablation and its use as a tool to generate targeted insults at the subcellular level to neurons and blood vessels deep within nervous tissue. Illustrative examples from axon regeneration and microvascular research highlight the utility of this tool. We further discuss the use of ablation as an integral part of automated histology.

Free flap transfer in cranio-maxillofacial surgery: a review of the current data

BACKGROUND

The advances of cranio-maxillofacilal surgery are considerably driven by the evolution of microsurgical techniques. At present, these methods continue to provide new therapeutic options to the field. Especially, free flap transfer has evolved to become an integral part of current treatment protocols for head and neck malignancies. It ensures uneventful wound healing even after previous radiotherapy and can often preserve form and function. For many patients, this may lead to a significant improvement in their quality of life.

OBJECTIVES

This review summarizes aspects of tumor therapy, the impact of radiation, and discusses different techniques of microvascular tissue transfer.

DISCUSSION

Specific advantages in different anatomical sites of the head and neck region are highlighted in contrast to existing alternatives. Selected cases exemplify the use of popular transplants.

SUMMARY

While planning reconstructions, it is important to consider both the functional and aesthetic aspects. The best individual outcome is based on a thoughtful match of available methods to a given defect and the patient's condition.

[Replantation of the ear without microvascular anastomosis: a case report]

A 42-year-old man presented with a left-sided supralobular total ear amputation resulting from an occupational accident. Initial dissection of the amputated ear revealed no suitable vessel for anastomosis. The fenestrated cartilage with its posterior skin excised was attached as a composite graft. Four days postoperatively, it was observed that 90% of the graft was viable. Three weeks later, subtotal separation of the ear (80%) was performed combined with skin grafting for surfacing the postauricular defect. At one-year follow-up, there was partial cartilage resorption with pigmentation and minimal hyperemia of the overlying skin.

[Replantation of amputated ear with microtechnique]

OBJECTIVE

To report replantation of amputated ear with microtechnique in 5 cases.

METHODS

From 2002 to 2005, 5 totally amputated ears were replanted and 4 obediently, 1 retrogressively. In every case, 1-2 arteries and 1-3 veins were anastomosed. Seven vessels were detective and 1-6 cm vessels were transplanted from forearm or dorsal side of hand. Amputated ears obtained blood supply again in about 6-10 hours after injury and exploration was enforced for venous crisis in 2 cases, and bloodletting in 1 case.

RESULTS

All 5 cases survived. Auricles possess perfect shape, no pigmentation, slight atrophy and perfect sensation.

CONCLUSIONS

Amputated ear should be replanted as long as no obvious contusion occurred, and the keys to prevent vascular crisis are cutting off unhealthy vessels, grafting superficial veins for bridging, and the high quality of vascular anastomosis.