Low power CO2 laser-assisted microvascular anastomosis: an experimental study

Low power CO2 laser-assisted microvascular anastomosis (LAMA) was used for saphenous artery autotransplantation in 40 rabbits. Eighty end-to-end anastomoses were performed by three methods (conventional interrupted suture, stay suture + laser, laser without stay suture). The long term patency rate in the three types of anastomosis is 93%, 93%, and 100%, respectively. The time needed for the laser procedure is half to one-third of that required for the interrupted suture method. The tensile strength of the bonding site can withstand up to 250 mm Hg of arterial pressure. We have demonstrated that the CO2 laser can be used in microvascular anastomosis with or without stay sutures. Aneurysm formation is a potential risk of LAMA. Accurate coaptation of the transected vessel, precise control of laser energy, and minimal area exposed to the laser beam are the key points for further improving anastomotic quality.     

Comparative study of suture and laser-assisted anastomoses in rat sciatic nerves

Conventional suture repair of peripheral nerves results in a fibrotic reaction that is detrimental to nerve regeneration. As an alternative procedure known as "laser-assisted" repair, a laser can be used, along with a reduced number of sutures, to reanastomose served peripheral nerves. To explore the long-term implications of this technique, the right sciatic nerves of Sprague-Dawley rats were surgically cut and reanastomosed either by means of four epineurial sutures or two epineurial sutures and CO2 laser welds. Tensile strength, electrophysiology, histology, and functional studies were performed up to 11 months postoperatively. Tensile strength measurements indicate no long-term disadvantage with the laser-assisted technique, although the short-term tensile strength is lower than with conventional suture repair. The conduction velocities of the repaired nerves were similar for both techniques; however, laser-assisted repaired nerves were found to have lower stimulation thresholds and reduced branching compared to the suture repaired nerves. The measured functional recovery was similar for both repair techniques.     

Microvascular anastomosis using a new diode laser system with a contact probe

The aim of the present study was to demonstrate the usefulness of our newly produced diode laser device (an 830-nm output of 190 mW CW) for microvascular end-to-end anastomoses. In the device, diode laser energy is delivered to a contact ceramic tip with a 200-microns diameter output end. Its wavelength is 830 nm and its power 60 mW. This device is small (30 x 25 x 10 cm), lightweight (gross weight 3kg), and easy to manipulate. Compared with conventional microvascular suture anastomosis (CMSA), the time required for the laser-assisted vascular anastomoses (LAVA) was reduced by almost half. Anastomosed portions of both methods were examined 1, 2, 4, 12, and 24 weeks later for patency and aneurysm formation. The patency rate and incidence of aneurysmal formation were the same in both groups. Histological examination revealed that LAVA is superior to CMSA in the smoothness of the inner surface, less inflammatory reaction, and normal collagen and elastic reorientation. The tensile strength and bursting pressure measured immediately after anastomosis demonstrated no significant difference between the two groups. It was concluded that this diode laser contact method may be clinically useful for microvascular surgery.     

CO2 Laser nerve welding: Optimal laser parameters and the use of solders in vitro

To improve the welding strength, an in vitro study was performed to investigate the bonding strength of CO₂ laser nerve welding (LNW), with and without the use of human albumin solution, dried albumin solution, egg white, fibrinogen solution, fibrin glue, and red blood cells as a solder. Fifteen different combinations of laser power (50, 100, and 150 mW) and pulse duration (0.1 to 3 s) were used with a spot size of 320 μm. The results have been compared to suture, fibrin glue, and laser-assisted nerve repair (LANR). The strongest welds (associated with whitening and caramelization of tissue) were produced at 100 mW with pulses of 1.0 s and at 50 mW with pulses of 3 s. The use of a dried albumin solution as a solder at 100 mW with pulses of 1 s increased the bonding strength 9-fold as compared to LNW (bonding strength 21.0 ± 8.6 g and 2.4 ± 0.9 g, respectively). However, positioning the nerves between cottons soaked in saline for 20 minutes resulted in a decrease of the bonding strength (9.8 ± 4.5 g). The use of a 20% albumin solution and egg white, both at 50 mW with pulses of 3 s, resulted in a bonding strength of, respectively, 5.7 ± 2.1 g and 7.7 ± 2.4 g. Other solders did not increase the bonding strength in comparison to LNW. The substantial increase in bonding strength for some solders suggests that it is worthwhile to investigate the dehiscence rate and nerve regeneration of solder enhanced LNW in an in vivo study. © 1994 Wiley-Liss, Inc.     

Preliminary report: a new technique of enterotomy closure using Nd:YAG laser welding compared to suture repair

This study compared the histology and tensile strength of Nd:YAG laser welded and sutured small bowel enterotomies in Sprague-Dawley rats. Enterotomies (0.5 cm long) were either welded with the Nd:YAG laser (1 W and 10.6 sec pulses) or repaired with interrupted, simple 6-O silk sutures. Group I consisted of seven animals; five with enterotomies repaired by laser welding and two repaired by suturing. Group II consisted of eight animals with each having both laser and suture repairs. Animals were killed and specimens were removed and examined at 1 day, and at 1, 2, and 3 weeks postoperatively to compare the progression of healing. On macroscopic examination the laser welded enterotomies were closed 84% of the time and only 23% had adhesion formation while 90% of sutured repairs were closed and 100% had adhesion formation. Histologic examination of both suture and laser welded enterotomies demonstrated active healing at 1 week with minimal collagen bridging the enterotomies. At 2 and 3 weeks the sutured enterotomies had granulomatous reaction around the sutures while the laser welded enterotomies had minimal inflammatory response and near normal small bowel histology. The tensile strength of the 3-week specimens from both the suture and laser welded enterotomies were 50% of normal bowel. These findings suggest that the laser welding of small bowel enterotomies is comparable in closure and tensile strength to suture repair. The time required to repair the enterotomy is significantly decreased, the procedure is easily performed, and there is a marked decrease in adhesion formation following laser repair.     

An experimental study on nerve repair using carbon dioxide laser

Although microsurgical techniques of nerve suture are now widely practiced, the prognosis is not always satisfactory. We have therefore developed a new method using CO2 laser and fibrin film to evaluate its clinical availability by determining its adhesiveness and axonal regeneration. The sciatic nerve of Wistar rats was cleanly cut. Fibrin films that are not themselves at all adhesive were placed on the suture site and were firmly anastomosed by irradiating them with 70 mW laser energy. Measurement of the tensile strength has demonstrated that effective adhesiveness may be obtained for nerve repair. According to the postoperative quantitative evaluation of the number of myelinated fibers of larger size and the mean diameter of myelinated fibers, the laser method appears to be significantly better than the conventional suture methods. In conclusion, this laser method is useful for clinical application.     

A comparison of absorbable suture and argon laser welding for lateral repair of arteries.

Conventional vascular anastomoses between autogenous vessels are performed with nonabsorbable sutures. Recently, use of absorbable sutures and laser-assisted vascular anastomoses has been advocated because of their improved healing characteristics. This study compared arterial repairs with the argon laser, absorbable suture, and nonabsorbable suture for technical characteristics including additional suture and overall success rates, burst strength, and cost. Absorbable and nonabsorbable suture closures were comparable with respect to technique, but laser-assisted vascular anastomosis was technically more demanding and required almost twice as much time for completion. The argon laser successfully closed only 58.6% of the arteriotomies, and 90% of the closures required additional sutures for complete hemostasis. All sutured arteriotomies were successfully completed by use of either absorbable or nonabsorbable suture. Burst strength was similar for all groups, but was uniformly greater than 300 mm Hg for sutured repairs, whereas two of five laser-assisted closures burst below 300 mm Hg. Finally, costs for purchasing ($35,000) and operating ($300/hr.) an argon laser make laser-assisted vascular anastomosis much more expensive than sutured repair. These data suggest argon laser-assisted vascular anastomoses are more technically demanding, less successful, and more expensive than conventional sutured anastomoses when evaluated in large caliber arteries in a canine model. Absorbable suture, however, is comparable to conventional nonabsorbable sutured arterial repairs in expense, handling characteristics, and success rates with the added advantage of eliminating permanent foreign body in the arterial wall when it is absorbed.     

Bursting strength in CO2 laser-assisted microvascular anastomoses

Iliac artery end-to-end anastomoses were performed in 42 Sprague-Dawley rats, divided into seven groups, to determine the welding effects of CO2 laser radiation in microvascular anastomoses. Conventional suture techniques were performed on right iliac arteries, and left iliac arteries were anastomosed with a laser-assisted technique. Bursting strength and diameters of the anastomotic sites were measured at different intervals (from one day to five weeks) post surgery. The anastomotic patency rate was 100 percent in both groups, and the aneurysm rate was only 2 percent in the laser group. Bursting strength was low at one and three days post surgery in both groups; then, it increased gradually until both groups could withstand higher than physiologic pressures. Results of high patency rates, low aneurysm formation, and the ability to withstand pressures higher than physiologic, suggest that the laser-assisted anastomotic technique can play an important role in microvascular surgery.     

Laser assisted vessel anastomosis of coronary arteries in vitro: Optimization of bonding conditions

Laser-assisted anastomosis of pigs' coronary arteries has been investigated using an Argon laser and a technique of applying an appropriate chromophore to the site of anastomosis. Remote infrared temperature measurements have shown that bonding was achieved at temperatures between 65 and 80°C corresponding to the collagen denaturation temperature and visual changes in the appearance of the tissue. Further laser irradiation produced carbonization and extensive tissue damage. Application of a chromophore at the site of anastomosis allowed a large reduction in the incident laser energy density. In end-to-end anastomosis, with only one supportive stay suture, bursting pressures of 90 to 310 mmHg (mean 203 mmHg) were achieved within a power range of 0.3 to 0.5 W with an exposure time of 50 to 210 s. Histological sections showed limited tissue damage but some variation in the vessel wall alignment which may explain variability in the mechanical strength. The laboratory studies have allowed us to optimize bonding conditions before embarking on animal tests.     

Experimental study of tensile strength at arterioprosthetic anastomosis

An experimental study was conducted to investigate the possible role of the suture materials in occurrence of false aneurysms at the suture line. Mature mongrel dogs were used in the experiment. A segment of abdominal aorta was replaced by woven Teflon graft. Braided silk was used as the suture material on one side, and polyglycolic acid suture on the other. The dogs were sacrificed one to 16 weeks after the operation, and the implanted prostheses were excised along with the abdominal aorta. The tensile strengths of the anastomosis on both ends of the graft were calculated. The tensile strength of the braided silk consisted about 8% of the total tensile strength at 16 weeks after surgery. The degree of sliding of the synthetic graft at the anastomotic site and the outer layer of the graft were analyzed at each measurement of tensile strength. In the 1st Department of Surgery, Yokohama City University Hospital 125 arterial synthetic prostheses have been implanted in patients during 1964 to 1982. False aneurysms occurred in 9 cases. The incidence was 19.2% in the cases where silk suture material was used but was 4.0% when synthetic suture material was used. It was concluded that the use of synthetic grafts was preferable, since it conjoined well with the outer layer. Furthermore, the plastic suture material did not degenerate and seemed to prevent the occurrence of false aneurysm.     

膝十字韧带移植重建术中韧带末端缝合固定的生物力学研究及临床应用

目的研究膝十字韧带移植重建术中韧带末端缝合固定的方法及固定强度。方法将24条带髌骨的髌韧带标本分为3组,对其末端分别采用Krackow双锁边缝合法缝合2针、3针,缝合材料为Ethilon缝线及直径0.4mm钢丝,对样本分别进行拉伸力学检测以比较强度,探讨最佳的缝合针数和方法并应用于临床。结果Krackow双锁边缝合法缝合2针,缝合点固定强度超过钢丝材料的破坏强度;用缝线缝合2针的强度达到80N以上,超过缝线材料的破坏强度;将第一针贯穿韧带缝合,不降低固定强度。根据实验结果,将改良的Krackow双锁边缝合法临床应用17例,加速了术后早期康复,取得良好效果。结论Krackow双锁边缝合法缝合2针或3针的固定强度差别不大,差异无显著性意义,第一针贯穿韧带,可减少缝线裸露但不降低固定强度,均超过缝合材料破坏强度。若想增加固定强度,应从改进缝合材料强度和增加缝线数目着手,此缝合法临床应用可加速康复,固定可靠。     

Laser-assisted microsurgical anastomosis

A low power carbon dioxide laser was used to perform 212 end-to-end laser-assisted microvascular anastomoses (LAMA) of femoral arteries (mean diameter, 1.2 mm) in Sprague-Dawley rats. Eighty-two conventional microvascular suture anastomoses (CMSA) utilizing 10-0 monofilament interrupted sutures were done for comparison of techniques and wound healing. The mean duration of each anastomosis procedure was 16 minutes for the LAMA repairs, compared to an average of 27 minutes for the CMSA repairs (P less than 0.05). All anastomoses were patent at the completion of the procedure. Each laser-assisted anastomosis required an average of seven intermittent laser exposures of 0.1 to 0.3 seconds each with approximately 80 mW of CO2 (wavelength = 10.6 micron) radiation at a spot size of 150 micron. A patency rate of 95% was obtained on the LAMA vessels (202 of 212) compared to 96% for the CMSA repairs (79 of 82). A total of 14 aneurysms were noted in the LAMA group (7%) compared to 11 in the CMSA (13%). All aneurysms were in patent vessels. Histological analysis indicates that the progression of wound healing of LAMA and CMSA anastomoses follows similar paths chronologically and morphologically with increased scar tissue formation around the suture. Scanning electron microscopy confirms the comparable luminal healing of the LAMA and CMSA vessels, with complete reendothelialization occurring by 3 weeks postoperatively. The tensile strength of the LAMA repair, although low immediately after operation, is comparable to that of the intact artery at 21 days. These findings suggest that a low energy carbon dioxide microsurgical laser has potential beneficial clinical application for anastomosis of small vessels.     

Vascular anastomoses in growing vessels: the use of absorbable sutures

Primary end-to-end infrarenal aortic anastomoses were performed in 36 piglets using two synthetic absorbable suture materials: polydioxanone and coated polyglactin. Animals were killed at 1, 4, and 11 weeks and 6 months following operation. Each aorta was removed, burst-tested to 300 mm Hg, radiographed, and examined histologically. All anastomoses were patent, and no burst-test failures occurred. Stenosis occurred in 14 of 17 animals at 1 and 4 weeks, respectively. One of 5 animals exhibited stenosis at 11 weeks, and none of the 14 animals had stenosis 6 months postoperatively. Histological examination revealed fibrosis replacing areas of disrupted elastica at 6 months in both suture groups. This study suggests that absorbable suture material, in particular polydioxanone, because of its excellent handling characteristics and prolonged tensile strength retention, will be useful for the repair of vascular and cardiac anomalies where growth of the suture line is required.     

Laser-assisted vasal anastomosis in the rat and man

In order to study the efficacy of laser-assisted vasal anastomosis (LAVA), a microscopic carbon dioxide surgical laser (Xanar) was utilized in the anastomoses of human vas deferens in vitro and the Sprague-Dawley rat vas deferens in vivo. The longitudinal tensile and internal hydrostatic pressure strengths of laser-assisted vasal anastomoses were compared to conventional microsurgical suture anastomoses in the human vas deferens. The LAVA group had a greater mean internal hydrostatic pressure strength (p less than 0.001) and a lesser mean longitudinal tensile strength (p less than 0.001) than the conventional microsurgical group. Further evaluation was performed in the Sprague-Dawley rat model, comparing post-operative fertility, patency, healing and sperm granuloma occurrence among four surgically treated groups and a control group: LAVA, conventional suture anastomosis, sham operated, and vasectomized. Light and scanning electron microscopic examination revealed equivalent healing in both the LAVA and conventional groups. Fertility was not statistically different in the LAVA, conventional, control, and sham operated groups. However, the incidence of gross sperm granulomas observed in the LAVA group (80%) was much higher than in the conventional suture anastomosis group (0%). In conclusion, laser-assisted vasal anastomosis is a fast and simple technique for vasal reanastomosis and was as successful (in pregnancies) as conventional suture anastomosis in producing fertility in rats undergoing vasal reanastomosis, but the incidence of sperm granuloma is higher.     

Comparison of laser vascular welding,interrupted sutures,and continuous sutures in growing vascular anastomoses

Background and Objectives: The argon laser-assisted vascular anastomosis may solve the problems of conventional sutured anastomosis, such as vascular stenosis and arrest of growth owing to a foreign-body reaction to suture material. Study Design/Materials and Methods: Twelve argon laser-assisted vascular anastomoses, seven conventional anastomoses with interrupted sutures, and five conventional anastomoses with continuous sutures were performed in 12 young mongrel dogs. Results: Five months later, the external diameter at the anastomosis had increased 70.5% in the laser group, 67.0% in the interrupted suture group, and 22.9% in the continuous suture group. Histological examination of the laser-assisted anastomoses showed almost complete healing, with no granulomatous response around the anastomotic site. In the interrupted suture group, marked scaring and foreign body reactions were observed on the vessel wall at the site of the anastomosis. The continuous suture group showed more remarkable disorientation of the vascular layer and intimal hyperplasia than the interrupted suture group. Conclusion: Vascular anastomosis using the argon laser offers advantages over the conventional procedure in growing vessels.     

Optimum surgical suture material and methods to obtain high tensile strength at knots: problems of conventional knots and the reinforcement effect of adhesive agent

Background Strong suture material and a firmly tight knot that never loosens are necessary for tendon suture, but the appropriate combination of suture materials and the methods to make a knot are matters of uncertainty. Methods The tensile strength of four conventional tendon suture materials (Surgilon, Ethibond, Ethilon, PDS II) and newly developed FiberWire were examined. An experienced orthopedic surgeon formed surgical knots with USP2 wire (0.5–0.599 mm in diameter) by making loops and then pulled them at 20 mm/min using Instron. Results With the conventional surgical suture method (the addition of one throw on a surgeon's knot), Surgilon proved to have the highest tensile strength (163.6 ± 6.5 N). Other suture materials, when tied under the same conditions, slipped and did not reach the ultimate tensile strength. When four additional throws were made, FiberWire provided the highest tensile strength (316.6 ± 12.2 N) among the five suture materials tested (others were 140–200 N). When an adhesive agent, cyanoacrylate, was applied to a knot, PDS II provided the highest tensile strength (182.0 ± 10.1 N). Conclusions Our study suggests three suitable combinations of suture materials and methods for suture knot formation, depending on the site of surgery, that provide optimum treatment outcomes. Surgilon provides the most stable strength for general suture techniques. FiberWire is the strongest suture material for a site where a large number of throws is clinically possible. PDS II provides a strong suture when combined with cyanoacrylate reinforcement.     

Tensile strength of cadaveric fascia lata compared to small intestinal submucosa using suture pull through analysis

PURPOSE: The modified pubovaginal sling has become popular as first line treatment for stress urinary incontinence. With the increasing use of cadaveric fascia as a sling material, widespread shortages are prevalent, hence limiting its availability. The increased morbidity with the use of synthetic sling materials and autologous fascia has stimulated investigation of other sling materials. We evaluated the tensile strength of 4 suture types, and compared tensile strength of cadaveric fascia lata to porcine small intestinal submucosa using suture pull through analysis to assess their efficacy and durability for use in anti-incontinence procedures. MATERIALS AND METHODS: Suture breaking load was determined using 2 and 1-zero polypropylene suture, and 2 and 1-zero polyglactin suture. Freeze dried gamma irradiated human fascia lata and freeze-dried small intestinal submucosa were evaluated. Suture was fixed to sling material using the cross fold technique. Mean suture breakage and suture pull through were determined using a tensionometer by measuring the load applied to the sling/suture system. Statistical analysis was performed. RESULTS: Mean suture breakage load was greatest with 1-zero polyglactin (8.10 pounds) and least with 2-zero polypropylene (3.68 pounds). Mean suture breakage strength was similar for 1-zero polypropylene and 2-zero polyglactin at 5.26 and 5.40 pounds, respectively. Mean suture pull through load using 1-zero polypropylene suture and the cross fold technique was 5.64 pounds for cadaveric fascia and 2.74 pounds for small intestinal submucosa (p <0.0001). Maximum load was limited by the suture strength when using cadaveric fascia, whereas, maximum load was limited in small intestinal submucosa by its inherent tensile strength. However, using a new technique for suture fixation to the small intestinal submucosa, we were able to increase significantly mean suture pull through load to 3.36 pounds (p = 0.008). Additionally, with this new technique small intestinal submucosa allowed gross stretching before suture pull through that was not seen with cadaveric fascia. CONCLUSIONS: Despite the current standard use of 1-zero polypropylene suture for pubovaginal sling fixation, our data suggest that 1-zero polyglactin suture is the strongest, and its use with pubovaginal sling fixation warrants further investigation. Using the cross fold technique and 1-zero polypropylene suture, tensile strength was greatest with cadaveric fascia compared to small intestinal submucosa. Although small intestinal submucosa was not as strong as cadaveric fascia, our persuasive preliminary data suggest that further investigation is warranted in the use of small intestinal submucosa and other suture fixation techniques, and its observed stretch capacity. Hence, with further studies small intestinal submucosa may remain a viable option for pubovaginal sling material.     

Large vessel sealing with the argon laser

This study compared the histology, biochemistry, and tensile strength of laser-welded and sutured canine venotomies, arteriotomies, and arteriovenous fistulas. Twelve animals had bilateral femoral vessels studied, with one repair (control) closed with interrupted 6-0 polypropylene sutures, and the contralateral repair (experimental) welded with the argon laser. Specimens were examined at weekly intervals from 1 to 4 weeks (four animals for each type of repair), and were evaluated histologically by hematoxylin and eosin, elastin, and trichrome stains; biochemically by the formation of [3H]hydroxyproline as an index of collagen synthesis; and mechanically by tensile strength determinations. At removal, all experimental closures were patent without hematomas, aneurysms, or luminal dilatation. Histologic and biochemical examination and tensile strength determinations suggest that laser welding may be an alternative to sutures for repair of large-diameter venotomies, arteriotomies, and arteriovenous fistulas, as healing is comparable to that seen with suture repairs up to 4 weeks postoperatively.     

Significance of synthetic sutures in urological operations of the cavity system

The authors report on their experiences on synthetic nonabsorbable and absorbable suture materials in a 12-year material of urological operations of the pelvic cavity. The synthetic suture materials are compared concerning the basic requirements, the surface properties, knotting safety, tensile strength, manageability, fluid absorption, tissue compatibility, allergizing effect, absorbability and sterilizability. The experiences of animal experiments are reviewed, primarily on the basis of reaction index studies in noninfected and infected urine. It is stated that in urological operations of the pelvic cavity, a safe haemostasis and prevention of prolonged complications (e.g. pyuria, scarring, stone-formation) can be ensured mainly by the use of synthetic suture materials.     

Which Suture Material is Optimal for Pancreaticojejunostomy Anastomosis? An In Vitro Study

Background: Which suture material is optimal for pancreaticojejunostomy (PJ) anastomosis is a matter of debate with contradictory results. The aim of the present in vitro study was to determine the effects of pancreatic juice, bile, and their mixture on different suture materials in terms of breaking strength and disintegration. Material and Methods: Four suture materials, silk, polyglactin 910, polydioxanone, and polypropylene, were tested in pancreatic juice, bile, and their mixture. Determination of breaking strength and disintegration under electron microscope for each suture material was done on days 0, 3, 6, and 10. Results: The breaking strength of polyglactin 910 and silk was significantly higher than polypropylene and polydioxanone (p < .05). Polyglactin 910 significantly lost its breaking strength with time in pancreatic juice, bile, and their mixture (p < .001). The breaking strength of each type of suture did not significantly alter in pancreatic juice, bile, and their mixture at the baseline measurement and at the end of the experiment (p > .05). No obvious disintegration has been observed under electron microscope in the architecture and appearance of suture materials after days of exposure to pancreatic juice, bile, and their mixture. Conclusions: None of the suture materials was disintegrated on exposure to pancreatic juice, bile, and their mixture. Polyglactin 910 has the highest breaking strength and significantly loses its strength throughout the experiment but still remains higher than other suture materials. Polypropylene, polydioxanone, and silk showed less variation across the incubation period.