Experimental study of mechanical microvascular anastomosis with new biodegradable ring device.

The commercially available mechanical vascular anastomotic device with ring-pin technique employs polyethylene rings and stainless steel pins, but even after healing of the anastomotic site, the ring remains. To resolve this disadvantage, the ring material was replaced by biodegradable material, and a ring coupling device was fabricated. This new ring was used to anastomose the femoral vein of rabbits, and morphological observations were made macroscopically and by light and scanning electron microscopy. Of the 58 anastomosed veins, 54 were patent, giving a patency rate of 92.9%. The ring was largely absorbed 15 weeks after anastomosis and completely after 30 weeks. Histologically, re-endothelialisation was observed in 1 week. Infiltration of inflammatory cells was significant around the ring at 3 weeks, but inflammation subsided within 6 weeks. There were no findings indicating adverse effects of the stainless steel pins remaining outside the vascular wall.     

Comparison of laser-assisted and conventionally sutured microvascular anastomoses by bursting pressure: a reanalysis and further studies

Methods of testing the strength of microvascular anastomoses are reviewed historically, in the light of recent applications to laser-assisted microvascular anastomosis techniques. The results of two experiments using hydrostatic distension to bursting point to determine the strengths of laser-assisted and conventionally sutured anastomoses of rat arteries and veins are presented. Considerable variation of the bursting pressures was found at any given time after anastomosis, and by the third postoperative day, the sutured vessels showed a significant fall in strength to their weakest level, with not as great a fall in the laser group. The sutured vessels were stronger than were the laser-anastomosed vessels, except at 3 days and after 6 weeks, when there were no significant differences between the two types of anastomosis. Aneurysmal vessels did not always burst at lower pressures than did nonaneurysmal vessels of comparable age.     

Comparison of indium 111 oxine-labeled platelet aggregation between sutured and argon laser-assisted vascular anastomoses

The thrombogenicity of argon laser-assisted vascular anastomoses (LAVAs) was compared with that of sutured vascular anastomoses (SVAs) by measurement of platelet aggregation at the site of repair in a canine model. Sequential 1 cm longitudinal carotid and femoral arteriotomies (n = 80) or jugular and femoral phlebotomies (n = 80) were performed, with each vessel having two tandem, randomly positioned arteriotomies or phlebotomies separated by a 4 cm length of intact vessel. One incision was repaired by SVA with continuous 6-0 polypropylene sutures and the other by argon LAVA. For the laser fusions, argon laser energy was applied to the adventitial surface of the vessel with a 300 micron fiberoptic probe with 0.5 W power, 1100 joules per square centimeter energy fluence, and 150 second exposure per 1 cm length. The arterial and venous segments of SVAs and LAVAs and an equivalent length of normal vessel were harvested at 48 hours (n = 16, 16, 16), 2 weeks (n = 12, 12, 12), and 4 weeks (n = 12, 12, 12). Autologous indium 111 oxine-labeled platelets were injected intravenously 48 hours before removal of the vascular repairs and the radioactivity of the specimens was determined on removal with a NaI (T1) well-type scintillation counter. Anastomotic platelet adherence index (APAI) was calculated as the ratio of emissions of SVA or LAVA to normal reference vessel.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of laser-assisted fibrinogen-bonded and sutured canine arteriovenous anastomoses.

The effect of laser-assisted fibrinogen bonding (LAFB) on the development of intimal hyperplasia was studied with stress-strain profiles and histologic evaluation of canine arteriovenous fistulas (AVFs). In 19 animals femoral AVFs were created with an 808 nm diode laser after topical application of fibrinogen mixed with indocyanine green dye; in the contralateral limb a sutured AVF was created. The animals were divided into three groups. Group 1 dogs (n = 6) were killed serially up to 4 weeks after surgery to examine the healing of the anastomoses created with LAFB. Group 2 dogs (n = 6) were killed 1 month after surgery, and the fresh specimens were strained axially to produce a stress-strain profile graph. Group 3 dogs (n = 7) were killed 7 months after surgery, and the AVFs were infused with formalin under pressure and histologically prepared to allow comparison of the ratio of maximum to minimum intimal hypertrophy. Fibrinogen used for LAFB was resorbed during the first month after operation without evidence of foreign body reaction or inflammation. Tensile break force was not significantly different in the laser-bonded group (4.6 +/- 2.4 pounds) and the sutured group (4.3 +/- 1.7 pounds). The modulus (tensile break force per square inch), a measure of elasticity, identified the laser-bonded AVF (149 +/- 44 pounds per square inch) to be less rigid than the sutured AVF (203 +/- 35 pounds per square inch) (p less than 0.05). No significant differences in the degree of intimal hyperplasia were noted in any area of the anastomoses. Use of LAFB neither accelerates nor prevents intimal hyperplasia in a canine AVF model.(ABSTRACT TRUNCATED AT 250 WORDS)     

Venous anastomoses with a microvascular anastomotic device in head and neck reconstruction

The Microvascular Anastomotic System (3M coupler) uses a friction-fit union of implant rings composed of high-density polyethylene and stainless-steel pins. Several reports have described equal or greater patency rates, as well as more rapid performance, using the device, compared to conventional suturing techniques. Eighty-nine patients, who underwent head and neck surgery with free-tissue transfers, using the Microvascular Anastomotic System, were evaluated. A hundred and twenty-one venous anastomoses were done using the device. All but one was done in an end-to-end manner Arteries were anastomosed with a conventional suture technique. The flap survival rate was 100 percent. The authors conclude that the device is reliable and time-sparing for end-to-end venous anastomoses in head and neck reconstruction.     

肌腱周边缝合距断端不同距离的缝合对抗张力的比较

目的研究缝针出入点距对合口距离对肌腱修复抗张强度的影响。方法采用新鲜猪后肢跖深屈肌腱,将40根肌腱分为4组,每组10根,横行切断,以改良Kessler法缝合,周边加强,缝针出入点距断端距离分别为4、7、10、12mm,检测缝合后肌腱2mm间隙形成的负荷,最大抗张强度,采用ANOVA进行统计分析。结果对肌腱的横断伤,以改良Kessler法缝合修复时缝针出入点距断端的距离越大,肌腱的抗张强度越强,其中4mm间距抗张强度明显低于其它三组(P<0.05),而其它三组无明显统计学差异。结论肌腱横形损伤修复时,随着缝针出入点距断端的距离增大,其抗张强度有递增趋势。     

Use of a novel penetrating, sutureless anastomotic device in arterial microvascular anastomoses

The advent of microsurgery and microvascular anastomosis has helped to alter the treatment of many traumatic defects as well as revolutionize the reconstructive options after extirpative surgery. These procedures, however, continue to be technically demanding and intensive. In addition, increased ischemia and operative times are known to raise complications in microsurgery, particularly in older patients. The nitinol U-clip (Medtronic, Inc., Minneapolis, MN) is a new penetrating clip applied in an interrupted fashion that eliminates knot tying and decreases operative time. This technology holds the potential for rapid, reproducible sutureless microvascular anastomoses. In addition, the surgical technique is very similar to conventional suture microanastomosis, lending itself to comparatively decreased learning curves and suitability for training programs. We present three consecutive cases of successful microsurgical anastomoses using this technology.     

Protection of stapled colorectal anastomoses with a biodegradable device: the C-Seal feasibility study

Background

A colorectal anastomotic leak can be life-threatening. We have assessed the feasibility of a new intraluminal biodegradable bypass device that we designed to avoid anastomotic leakage and the necessity of a temporary stoma.

Methods

Fifteen patients underwent colorectal surgery. Before performing the anastomosis in a standard way, the C-Seal (Polyganics BV, Groningen, The Netherlands) was glued to the anvil of the circular stapler. Consequently, the bypass was fixated in the staple row just proximal of the simultaneously made anastomosis. A water-soluble contrast enema was performed after 1 week.

Results

The sheath was well compatible with the standard stapler device and easy to use. All donuts remained intact. No radiologic or clinical leaks were observed after surgery.

Conclusions

This pilot study shows that the C-Seal can be applied successfully in colorectal surgery. Further investigation with large numbers of patients is now necessary to assess the efficacy of the C-Seal as a protective device.     

An experimental study of the strength in arterial prosthetic anastomoses: relationship between anastomotic tensile strength and its organization]

Five types of 6-mm diameter arterial prostheses, i.e.m woven Teflon, woven Dacron, velour woven Dacron, velour knitted Dacron and expanded polytetrafluoroethylene (E-PTFE), were studied in the dog to assess anastomotic tensile strength and its organization. Five types of composite grafts, about 3.0cm in length, were implanted in the abdominal aorta of fifty-two adult mongrel dogs using absorbable polyglycolic acid suture. At 16 weeks after the implantation, if the composite graft was patent, tensile strength of the bilateral anastomoses were measured and its organizations were examined microscopically. The mean forces required to disrupt the anastomoses of velour woven Dacron, velour knitted Dacron and E-PTFE were greater than those of woven Teflon and woven Dacron. At the disrupted sites of woven Teflon and woven Dacron, which were non-velour grafts, fibrous outer sheath were remarkably separated from the grafts. This results indicate that organization and fixation of fibrous outer sheath are the most important factors in the strength of arterial prosthetic anastomoses and velour grafts have superiority over non-velour grafts. The organization of E-PTFE was poor, but its tensile strength was equal to velour grafts. It is considered E-PTFE has an advantage due to non-crimped structure and requires further evaluation over longer period.     

Evaluation of the mechanical strength and patency of functional end-to-end anastomoses

Background Although many mechanical devices are being developed for functional end-to-end anastomosis (FETEA), the best choice remains to be determined. The mechanical strength of each device is an important factor associated with anastomotic leakage. In turn, anastomotic patency is related to postoperative stenosis. This study examined the bursting pressure and circumference of several FETEAs. Methods Young domestic pigs were used in this study. In experiment 1, a 10-cm segment of intestine was transected using an EndoGIA 60 blue, EndoGIA 60 green, or GIA 60 blue stapler, and the bursting pressure of each instrument’s mechanical staple line was examined. In experiment 2, after FETEA had been created with EndoGIA 60 blue, the bursting sites were examined, and the bursting pressures of buttressed and nonbuttressed FETEA were measured and compared. In experiment 3, the circumference of FETEA was compared between the closed technique and reinforcement. Results The bursting pressure of EndoGIA 60 blue was significantly higher than that of the other devices. When an anastomotic crotch was buttressed, the bursting pressure (44 ± 13 mmHg) was significantly increased over that of the nonbuttressed FETEA (27.5 ± 5.8 mmHg; p < 0.05). The circumference of FETEA using the wide technique (92.7 ± 2.3 mm) was larger than that using the offset technique (55.7 ± 5.8 mm). Conclusions The bursting pressure of the mechanical staple line using the EndoGIA 60 stapler was the strongest. Functional end-to-end anastomosis was stronger when created with buttress of an anastomotic crotch, and larger circumferences were created with the wide technique.     

Comparison of arcuate-legged clipped versus sutured hepatic artery, portal vein, and bile duct anastomoses

Attempts at improving anastomoses have included the development of stapling techniques. Our purpose was to evaluate arcuate-legged clipped versus standard sutured anastomoses of the hepatic artery (HA), portal vein (PV), and bile duct in a porcine liver transplantation model. Two groups of pigs were studied intraoperatively and 1 day after liver transplantation. A control group underwent sutured anastomosis of PV and HA with polypropylene and of bile duct with polydioxanone (n = 8). An experimental group underwent anastomoses with arcuate-legged clips (n = 8). We analyzed the time to perform anastomosis and flows before and at various time points after anastomosis. In addition, patency and histology of the anastomoses were evaluated 1 day after operation, including a fibrin-thrombosis score, medial injury, and inflammation score. Times to complete HA and PV anastomoses were not different between clipped and sutured groups. However, the time was shorter to complete bile duct anastomosis with clips than with sutures (6.3 +/- 1.1 minutes and 13.3 +/- 2.0 minutes, respectively). Flows through HA anastomoses were not different between groups, but flow through the PV was higher in clipped compared with sutured anastomosis (P = 0.06). Patency was 100 per cent with no leaks for all three anastomoses in both groups. Histologic data were similar between vascular anastomotic groups. Sutured bile duct anastomoses revealed mild smooth muscle injury in 75 per cent whereas clipped bile duct anastomoses displayed no smooth muscle injury. We conclude that arcuate-legged clipped anastomosis represents a viable option to sutured anastomoses of the PV, HA, and bile duct anastomoses. Bile duct anastomoses were completed in less than half the time and with less tissue damage documented histologically.     

Strength of microvascular anastomoses: comparison between the unilink anastomotic system and sutures

The Unilink system, a mechanical anastomotic device, was compared with standard suture techniques in terms of anastomotic strength under conditions of uniaxial loading. Twenty-five rabbits underwent Unilink and suture anastomosis of both carotid arteries and facial veins. Animals were sacrificed at 1 hour (five animals), 2 weeks (10 animals), and 16 weeks (10 animals), and all vessels were tested by constant loading in a material testing machine. The maximum load required to disrupt the anastomosis as well as the site of vessel failure were recorded. All 100 anastomoses were fully patent as evaluated by clinical testing. At 1 hour and 2 weeks, the Unilink arterial anastomoses were consistently and significantly stronger than the sutured anastomoses. At 16 weeks the sutured arterial anastomoses were significantly stronger than Unilink. The Unilink anastomoses, however, remained approximately 50% stronger than unoperated normal vessels. No statistical differences were observed in the strength of venous anastomoses at any of the intervals tested. There were no statistical differences in the sites of failure of the vessels under loading (i.e., at the anastomosis or proximal or distal to it) between the two techniques.     

Participation of the intestinal layers in supplying of the mechanical strength of the intact and sutured gut

The tensile properties of the intact and sutured human intestine were examined using Instron 1122 tensimeter on 471 cadaveric and 98 surgically removed specimens. By a constant strain rate method two maxima curves were received, which permit examination of the intestinal wall as a multi-layered structure. Repeatable results were generated for cadaveric and surgically removed intestines, whose mechanical properties were similar under certain storage conditions. The mechanical properties of intact intestine in axial and transversal directions were different. The mechanical strength of the intact intestinal wall was conditioned by the submucosa and muscularis, while the serosa and mucosa showed no significant strength. Comparison of axial specimens' mechanical properties of the intact intestinal wall and intestinal wall with all layers sutured through determined that only the submucosa supplies mechanical strength to anastomosis. Other layers contribute no significant force to anastomotic strength. The strength applied to thread during knot tying does not change the participation of the intestinal layers in supplying suture-holding capacity for 8 and 12 mm stitch depth. It was shown graphically why sutures that don't stitch onto the submucosa are unreliable.     

In vivo analysis of antithrombotic effectiveness of recombinant hirudin on microvascular thrombus formation and recanalization

Purpose: This study was undertaken to evaluate in vivo the effect of recombinant hirudin (r-hirudin [HBW 023]), a potent thrombin inhibitor, on the process of microvascular thrombus formation and recanalization. Methods: Thrombosis was induced photochemically in distinct arterioles (n = 25) and venules (n = 30) of the ear of 16 hairless hr/hr mice (8 to 10 weeks old, 25 to 30 g of body weight). r-Hirudin (1 mg/kg of body weight) was administered intravenously directly before thrombus induction; saline-treated animals served as controls. Thrombus formation (i.e., first platelet deposition at the endothelial lining [FPD]; inner luminal diameter reduction to 50% [D/2]; complete vessel occlusion [CVO]), vessel recanalization, microcirculatory parameters, and leukocyte-endothelial cell interaction were analyzed by means of intravital fluorescence microscopy. Results: Hirudin significantly delayed the process of thrombus formation compared with saline-treated controls in both arterioles (FPD: 381 ± 80 vs 137 ± 25 seconds, P < 0.05; D/2: 627 ± 49 vs 501 ± 71 seconds; CVO: 925 ± 78 vs 854 ± 60 seconds) and venules (FPD: 173 ± 11 vs 59 ± 4 seconds; D/2: 342 ± 54 vs 228 ± 27 seconds; CVO: 541 ± 85 vs 344 ± 43 seconds; P < 0.05). In addition, r-hirudin-treated animals showed an increased rate of vessel recanalization at 24 hours after thrombus induction (arterioles: 54% [7 of 13] vs 0% [0 of 12], P < 0.05; venules: 77% [10 of 13] vs 53% [9 of 17]), whereas microcirculatory parameters and leukocyte-endothelial cell interaction were not affected. Conclusion: Our data indicate that r-hirudin not only counteracts the process of thrombus formation but also promotes vessel recanalization, thus supporting its use in clinical microvascular surgery. (J Vasc Surg 1998;28:498-505.)     

Experimental replacement of the cervical oesophagus with a free transverse colon autograft using microvascular anastomoses.

Microsurgical revascularization in the neck has improved the survival rate of free small-bowel grafts used to replace the cervical oesophagus. Colon vessels are larger than those in the jejunum, and even with naked-eye technique good results have been reported following free colon grafting of the oesophagus. The authors thought it might be possible to achieve even better results using microvascular anastomoses in the neck, and in this way replaced the cervical oesophagus in each of 15 dogs with a free transverse colon autotransplant. Four dogs died during operation and four within three days, two of the latter with graft necrosis. The next seven dogs survived eight days or more, and all their colon grafts were viable. Where patent arteries were demonstrated (three cases) the mucosa and myenteric plexuses of the graft survived. In all four dogs where the arteries were thrombosed or not demonstrated, the mucosa was absent, myenteric plexuses were absent in three, and one graft was grossly stenosed. Among these seven dogs there were three fistulae, one where graft arteries were patent and two where they were not; immediate anastomotic healing was not guaranteed by graft survival or arterial patency.     

Correlation between flexural and indirect tensile strength of resin composite cements

Background

To evaluate a potential correlation between flexural strength and indirect tensile strength in assessing the mechanical strength of resin composite cements.

Methods

Flexural strength (n?=?5) and indirect tensile strength (n?=?5) of 7 resin composite cements (RelyX Unicem 2 Automix [RXU], Panavia SA [PSA], Clearfil SA [CSA], Panavia F2.0 [PF2], Multilink Implant [MLI], DuoCem [DCM], Panavia 21 [P21]) were determined. Specimens were either auto-polymerized or dual-cured (except P21) and stored in water at 37 °C for 1 day prior to measurement. Flexural and indirect tensile strength of 4 cements (RXU, PSA, PF2, MLI) was additionally measured directly after curing and after 96 h water storage at 37 °C.

Results

Except for PF2, dual-cured specimens achieved higher flexural strength than auto-polymerized specimens. In the indirect tensile strength test differences in auto-polymerized and dual-cured specimens were only detected for RXU and DCM. A general non-linear correlation was found between flexural and indirect tensile strength values. However, strength values of auto-polymerized and dual-cured specimens did not generally correlate.

Conclusions

Flexural strength and indirect tensile strength of resin composite cements are correlated. At high strength values the indirect tensile test is less sensitive than the flexural test. The results suggest that the indirect tensile test may only be recommended as a screening test especially for low or medium strength resin composite cements.