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PubMed1995

Laser tissue welding: a comprehensive review of current and future clinical applications.

Laser techniques for joining tissue, in combination with other surgical technologies, will be a hallmark of surgery in the next century. At present, there are many clinical applications of tissue welding and soldering which are beginning to achieve wide spread acceptance. These exciting clinical developments are the result of many advances which have been made in the past few years in our understanding of the mechanism of laser tissue welding. Also contributing to this progress are many important technical refinements such as tissue solders and feedback control of the laser device. In this article, we describe in depth the history and development of laser tissue welding including key theoretical concepts as well as crucial experiments which have added to our insight into this phenomenon. We also review the evolving concepts of its clinical application and indicate clinical applications which are likely to become more important in the future.

Equipment Design↗
PubMed1994

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 microns. 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.

Anastomosis, Surgical↗
PubMed1992

Low-voltage coagulation for welding sutures watertight: an experimental study.

A rat model was developed to test the watertightness of sutures. In this model it was proved that welding by use of low-voltage coagulation current did not improve on the watertightness obtained with conventional skin suturing. The mean leak pressure after welding was about 4.2 cm H2O, i.e. statistically significantly lower than the mean leak pressure of the conventional suture, which is 14.1 cm H2O. Neither addition of protein solder nor an additional conventional suture improved these results. It is therefore concluded that low-voltage coagulation is unsuitable for welding tissues.

Animals↗
PubMed1987

Conventional reanastomosis versus laser welding of rat uterine horns.

In this study we compared conventional surgical techniques with those of low-power CO2 lasers (output 140 mW; spot size 0.4 mm) used to weld transected rat uterine horns. On one side a microanastomosis was made by standard surgical technique of 8-0 nylon; the other side was "welded" either after doing the anastomosis with 8-0 sutures or without any anastomotic sutures. Histologic sections obtained from rats' uteri treated with conventional and laser surgery showed that on the laser-treated sutured side there was less necrosis and inflammatory and giant cells. The animals that underwent laser welding without suturing had no necrosis, suppuration, or granulation; giant cells were not present. We conclude that in the tissue from the laser-treated animals, when compared with conventional and laser-with-suture surgery, histologic features indicate healing process by primary intention via an aseptic noninflammatory reaction.

Animals↗
PubMed1985

Heat welding for surgical sutures.

The purpose of this experimental study was to test the potential value of heat welding to cut the ends of knotted surgical sutures. This heat process resulted in knot security in a coated polyglactin suture with fewer throws than those needed for the same suture with knotted ends cut by scissors. Results of mechanical performance testing of the knotted sutures cut either by scissors or welding did not differ significantly. With refinements in the technical design of the heat source, suture welding may have important applications in surgery.

Hot Temperature↗
PubMed2006

Comparison of suture welding and hand-tied knots in mini-open rotator cuff repair.

PURPOSE: This study was undertaken to compare the results of mini-open rotator cuff repair with outcomes attained with hand-tied knots and suture welds. METHODS: A total of 50 consecutive patients treated by a single surgeon with mini-open cuff repair and suture welding were retrospectively evaluated and compared with 55 consecutive patients treated with mini-open cuff repair and hand-tied knots. The groups were similar in terms of age, sex, hand dominance, and preoperative duration of symptoms. All procedures were performed in a hospital outpatient surgery center with patients in a lateral decubitus position under general anesthetic. Glenohumeral arthroscopy and arthroscopic acromioplasty were performed in all cases. Rotator cuff tears were repaired through enlargement of the lateral portal. All patients were evaluated before and after surgery with the University of California Los Angeles (UCLA) Shoulder Scale. RESULTS: In all, 47 of 50 patients treated with suture weld were available for evaluation, with an average follow-up of 26 months. Preoperative UCLA scores averaged 12.5, and postoperative scores averaged 29.6. Of 55 patients treated with hand-tied knots, 40 were available, with an average follow-up of 28 months. Preoperative UCLA scores averaged 13.2, and postoperative scores averaged 31.5. CONCLUSIONS: No statistical difference in postoperative UCLA scores was noted between the 2 groups (P = .297). LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Adolescent↗
PubMed2005

Coupling an ultrasonic propagation code with a model of the heterogeneity of multipass welds to simulate ultrasonic testing.

The knowledge of the anisotropic and heterogeneous behaviour of the material is the key point for understanding ultrasonic testing. In the case of austenitic stainless steel multipass welds, there was no exact knowledge. The succession of passes and complex solidification processes makes the modelling of the resulting grain orientation difficult. The MINA model allows such a description. Coupling this model with the new propagation code ATHENA permits a very good understanding of the propagation of elastic waves in this kind of complex media. After discussing the existing models of grains orientations for multipass welds, we show how the new MINA model allows to simulate the anisotropic heterogeneous structure in a more realistic manner. We introduce the simulated grains structure and the real one, obtained by macrographs, into the ATHENA propagation code. We obtain a very good correlation between the two simulated propagations. A first experimental application is also successful. We show in a quantitative and qualitative way that the modelling results are close to the experimental measurements on a thick austenitic weld.

Journal Article↗
PubMed1994

Preliminary results of laser tissue welding in extravesical reimplantation of the ureters.

One exciting potential use of laparoscopic technology is the extravesical reimplantation of the ureters. We have assessed the efficacy of laser-activated fibrinogen solder to close vesical muscle flaps over submucosal ureters (Lich-Gregoir technique) in a canine model. Four dogs were subjected to unilateral flap closures via a protein solder (indocyanine green and fibrinogen) applied to the bladder serosa and exposed to 808 nm. continuous wave diode laser energy. Contralateral reimplantation was performed using 4-zero vicryl muscle flap closures (controls). At 7, 14 and 28 days postoperatively, intravenous pyelograms confirmed bilateral ureteral patency. At intravesical pressures above 100 cm. H2O, there was no evidence of wound disruption in either group. Nondisrupted wound closures were sectioned and strained until ultimate breakage to determine tensile strength. At each study interval the laser-welded closures withstood greater stress than the controls. Although these data represent single tissue samples and are not amenable to statistical analysis, laser-welded closures appeared to be stronger at each study interval. In conclusion, laser-welded vesical wound closures appear at least as strong as suture closures in the canine model.

Animals↗
PubMed2004

Interactions of fibroblasts with soldered and laser-welded joints.

Relatively little is known about the biocompatibility of the soldered or laser-welded joints of dental appliances. We investigated the reaction of human gingival fibroblasts cultured in vitro in direct contact with samples of soldered and laser-welded joints from orthodontic lingual arches. Contrast phase light microscopy was used to evaluate cell adhesion, morphology and proliferation after 6 and 24h and after 7 and 16 days. Scanning electron microscopy (SEM) was performed at 16 days. Our in vitro findings provide evidence that laser-welded orthodontic appliances have superior fibroblast biocompatibility.

Adult↗
PubMed1986

Skin closure by Nd:YAG laser welding.

Skin incisions 6 mm in length were made on the backs of hairless mice. Control wounds were closed with interrupted 5-0 Prolene sutures, and experimental wounds were approximated and closed by laser welding using a Nd:YAG laser. The wounds were examined daily, and specimens were excised at weekly intervals for histopathologic study, transmission electron microscopy, tensile strength determination, and type I collagen-specific messenger ribonucleic acid measurements. The laser-welded wounds demonstrated rapid healing. Histologic study showed a functional scar tissue at day 7 and a minimal residue of the original wound at day 14. Tensile strength of the control and experimental wounds was similar at all time points. The levels of collagen-specific messenger ribonucleic acid were significantly higher in the sutured group in comparison with the laser group or with normal control skin. This study suggests that laser welding might have advantages over suturing, since the former is sterile and nontactile, does not require introduction of foreign material into the wound, and provides subjectively improved cosmetic results.

Animals↗
PubMed2002

Intracardiac ultrasonic suture welding for knotless mitral valve replacement.

OBJECTIVE: The difficulty in tying multiple knots with endoscopic instruments constitutes a technical obstacle to the development of closed-chest valve surgery. The following set of experiments was undertaken to ascertain the in-vivo feasibility of using an intracardiac ultrasonic welding device for knotless suture fixation during mitral valve replacement (MVR). METHODS: Five adult sheep weighing 48-52 kg underwent MVR with a commercially available mechanical prosthesis, using pledgetted interrupted polypropylene sutures. An ultrasonic suture welder designed for intracardiac use was used to adjust suture tension and fuse strands together without knots. Echocardiographic assessment of the mitral prosthesis was carried out at baseline and after maintenance of supraphysiologic arterial pressures for 60 min. Subsequently, the animals' explanted hearts were assessed under sustained left ventricular (LV) pressurization to 180 mmHg in an ex-vivo pressure-loop system. RESULTS: MVR was successfully performed in all animals and welds reliably completed in less than 1 s. One sheep could not successfully be weaned off cardiopulmonary bypass; however, a normal prosthetic valve implant was confirmed at post-mortem examination. Echocardiographic assessment prior to and during LV pressurization revealed normal seating and function of the prosthesis in all cases. At post-mortem examination all valves were adequately implanted, suture tails laid flat on the surface of the prosthesis' sewing ring, welded suture strands were intact and accurately point-fused together, and no evidence of perivalvular leak was found around any of the prostheses despite sustained LV pressurization. CONCLUSIONS: This new modality proved reliable in an acute sheep model of MVR and could constitute a promising avenue towards facilitation of total endoscopic valve procedures in humans.

Animals↗
PubMed2007

Nanorobotic spot welding: controlled metal deposition with attogram precision from copper-filled carbon nanotubes.

With the continuing development of bottom-up nanotechnology fabrication processes, spot welding can play a role similar to its macro counterpart for the interconnection of nano building blocks for the assembly of nanoelectronics and nanoelectromechanical systems (NEMS). Spot welding using single-crystalline copper-filled carbon nanotubes (CNTs) is investigated experimentally using nanorobotic manipulation inside a transmission electron microscope (TEM). Controlled melting and flowing of copper inside nanotube shells are realized by applying bias voltages between 1.5 and 2.5 V. The average mass flow rate of the copper was found to be 120 ag/s according to TEM video imaging (measured visually at approximately 11.6 nm/s through the CNT). Successful soldering of a copper-filled CNT onto another CNT shows promise for nano spot welding and thermal dip-pen lithography.

Copper↗
PubMed1993

Sutureless laser-welded anastomosis of the femoral artery and vein in rats using CO2 and Nd:YAG lasers.

In a comparative study, it was demonstrated that sutureless, laser-welded, end-to-end anastomoses in the rat femoral artery and vein are feasible, using either CO2 or Nd:YAG laser. Conventional microsurgical suture anastomoses served as the controls. Patency rates in experimental animals and controls were equal (96 to 100 percent). No aneurysms were observed. For successful laser welding, the anastomosis must be completely tension-free. In arteries, this was accomplished only by interposition of a graft from the contralateral artery. The absence of any foreign-body reaction and the saving in operative time support the use of sutureless laser welding.

Anastomosis, Surgical↗
PubMed1994

Laser welding--suitable for vascular anastomosis?

Carotid arteries of 21 piglets were transsected and reanastomosed either by laser welding (Neodym:YAG laser) or by conventional suture anastomosis. Histological specimens of the anastomoses obtained 2 to 32 days after the operation showed less foreign body reaction and intimal hyperplasia after laser welding than after suturing. There was, however, no significant difference when comparing occurrence of thrombosis, patency rate, or growth of the anastomosis in growing animals. Neither our study nor a review of the literature of laser-assisted vascular anastomosis in microvessels and large arteries up to 5 mm diameter could establish a definite clinical application for laser welding in vascular anastomosis.

Anastomosis, Surgical↗
PubMed1995

Measurements of air concentrations of thorium during grinding and welding operations using thoriated tungsten electrodes.

An evaluation was performed to determine whether thorium was present in concentrations above the derived air concentration during grinding and welding operations using thoriated tungsten electrodes. A few of the advantages of using thoriated tungsten electrodes in industry include easier are starting, greater stability, and reduced weld metal contamination. The electrodes used in this evaluation contained 2% thoria (thorium oxide) and were either 2.4 mm or 3.9 mm in diameter. Personal breathing zone and area air samples were collected for the experienced welders participating in this evaluation during grinding operations. The results during the grinding operations for personal and area air samples were generally below the derived air concentration (DAC) for 232Th for solubility class Y of 0.04 Bq m-3 (1 x 10(-12) microCi mL-1) as per 10 CFR 20. The area samples collected during welding operations were below the DAC.

Air Pollutants, Occupational↗
PubMed1991

Skin closure with dye-enhanced laser welding and fibrinogen.

The topical application of wavelength-specific dye and fibrinogen has been used to enhance laser closure of vascular anastomoses. We compared the closure of skin incisions by two different dye-enhanced, fibrinogen-based laser welding systems [argon laser (power density 4.78 W/cm2) with fluorescein isothiocyanate dye (n = 32) and diode laser (power density 9.55 W/cm2) with indocyanine green dye (n = 32)] with closure by interrupted 5-0 nylon suture (n = 64) and examined tensile strength, hydroxyproline production, histology, and cosmesis. Two 3-cm full-thickness incisions were made on the shaved backs of 64 rats. One incision was closed with suture, whereas the other, after treatment with the appropriate dye, was welded with either argon- or diode-lasered fibrinogen. At postoperative days 5, 10, 15, and 28, the closure sites were harvested and sectioned for analysis. Initially, wounds closed with argon-lasered fibrinogen showed less inflammatory response, greater collagen production (34.61 +/- 0.74 mg/gm), and greater mean peak stress at rupture (64.85 lbs/in2) than those closed with suture (16.42 +/- 3.20 mg/gm, 26.68 lbs/in2) (p less than 0.05). By 15 days, both argon and diode laser closures are superior in strength and collagen production to suture closure (p less than 0.05). At 28 days, diode laser closures (1315.60 lbs/in2) are stronger than suture closures (998.09 lbs/in2), whereas both are stronger than argon laser closures (813.16 lbs/in2) (p less than 0.05). Cosmetically, argon-welded wounds consistently appeared finer and lacked cross-hatched suture scars.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1994

Healing of incisions in the tongue: a comparison of results with milliwatt carbon dioxide laser tissue welding versus suture repair.

The healing of carbon dioxide laser weld closures produced by two commercial instruments of differing design were compared. Healing after laser welding was also compared to healing following conventional suture closure. Healing was evaluated histologically and by measurement of tensile strength over time. No histologic differences were found between closures produced by different lasers; however, in all cases suture closure resulted in slower healing times consistent with a foreign body reaction prolonging the healing process. Tensile strength measurements were performed at intervals over the first 21 days after the operation. Laser repair was found to be equivalent to or stronger than suture repair at every interval measured. The clinical use of the carbon dioxide laser for tissue welding of oral injuries should be investigated further, since it appears to be a good alternative to suture repair.

Analysis of Variance↗
PubMed1990

"Tissue welding" with the argon laser in middle ear surgery.

Over the past 10 years the argon laser has been recognized as a valuable adjunct to middle ear surgery. It has been used to vaporize and cut tissue and to coagulate microbleeding. It has been used by many other surgical specialties to "weld" adjacent tissues together. This welding process appears to have a limited but helpful role in middle ear surgery. A pilot study of 30 surgical cases in which argon laser "tissue welding" has been used are reported. The benefits, limitations, and possible future implications are discussed.

Adolescent↗