Laser tissue soldering in urinary tract reconstruction: first human experience

Comparison of effects of suture materials on wound healing in a rabbit pyeloplasty model

OBJECTIVES

To compare the effects of chromic catgut, polyglactic acid, polydioxanone (PDS), and polytrimethylene carbonate suture on urothelial healing in a rabbit model simulating pyeloplasty.

METHODS

Pyeloureterotomies were performed on 8-week-old rabbits [12 rabbits (24 renal units) and 3 control rabbits] and closed with interrupted 7-0 sutures. At 10 days, 5 weeks, and 12 weeks postoperatively, we assessed the upper tracts by examining microscopic sections of the renal pelvis and upper ureter. Acute and chronic inflammation, foreign body reaction, and fibrosis/scar formation were assessed blindly and scored from 0 to 4.

RESULTS

Histologic evidence of acute and chronic inflammation and foreign body reaction was most severe at 10 days and 5 weeks in pyeloureterotomies closed with chromic catgut. There was mild inflammation in those closed with polyglactic acid at 10 days, but it was minimal in those closed with polyglactic acid, PDS, and polytrimethylene carbonate at 5 and 12 weeks. Reabsorption of polyglactic acid was complete by 5 weeks, but was incomplete with the other three sutures at that time. By 12 weeks, there was persistent suture in 50% of the renal units closed with polydioxanone and in 100% of those closed with polytrimethylene carbonate. No animal developed a renal calculus.

CONCLUSIONS

Because of the mild inflammatory response and rapid tissue reabsorption of polyglactic acid in this animal model, this suture appears to be the best suture for pyeloplasty.

Dural Closure with Laser Tissue Welding

This study investigates the use of tissue-soldering techniques to substitute or reinforce traditional suture closure of dural incisions. Fresh human cadaveric dura was incised and subsequently closed by use of three techniques: (1) conventional interrupted suture with 4–0 silk ( n = 25), (2) laser solder reinforced suture closure ( n = 25), and (3) laser solder closure alone ( n = 25). Anastomosis tensile strength and hydrostatic leak pressures were measured. Dural repair was also performed in 15 live Lewis rats. Dural closure was accomplished with 9–0 Prolene sutures ( n = 5), laser-reinforced suture closure ( n = 5), and laser solder closure alone ( n = 5). Histologic examination of the closure immediately after soldering and 2 weeks later was performed. Suture closure alone had the lowest leak pressure, 9.4 ± 1.7 mm Hg, and an intermediate break point, 13.3 ± 2.1 Kgf/cm2. Measurements with laser solder alone revealed a mean leak pressure of 26.2 ± 3.7 mm Hg and a break point of 4.6 ± 1.4 Kgf/cm2. Solder-reinforced suture closure leak pressure measured 64.0 ± 6.7 mm Hg and 21.4 ± 2.4 Kgf/cm2. There was a statistically significant increase in leak pressure and tensile strength in the closures performed with laser weld reinforcement of traditional suture technique ( p = 0.0001). Dural closure with laser tissue welding alone provided an immediate leak-free closure, but with poor tensile strength. Histologic examination of welded dura and underlying brain tissue showed no evidence of thermal injury in four of five animals studied. Laser welding may significantly decrease the incidence of cerebrospinal fluid leak after dural closure. In addition, laser tissue welding also makes dural closure possible where space constraints make traditional suture closure difficult.

Hypospadias repair by laser tissue soldering: intraoperative results and follow-up in 30 children

OBJECTIVES

We examined the use of laser tissue soldering (LTS) as an adjunct to suturing of, as well as a primary means of, tissue closure in urethral reconstruction.

METHODS

Since June 1994, 26 boys ranging in age from 3 months to 14 years (mean 3.0 years) underwent hypospadias repair using LTS techniques. The classification of hypospadias was subcoronal in 13, midpenile in 5, penoscrotal in 7, and scrotal in 1. Laser tissue soldering was used in an additional 4 patients: tunica vaginalis patch graft corporoplasty in 2 (scrotal hypospadias), epispadias fistulae in 1, and urethral diverticulum in 1. Of these cases, 3 hypospadias repairs were completely sutureless. An intraoperative comparision was made between suturing and LTS with respect to operative time and degree of difficulty in performing LTS. Postoperatively, patients were examined to determine complications, including stricture, fistula, or impaired wound healing. An unselected group of 25 consecutive boys undergoing hypospadias repair between 1991 and 1992 served as a historical control group.

RESULTS

No intraoperative complications resulted from laser activation. In 5 of the 30 procedures (16.6%), suture disruption was noted to occur, with a higher incidence seen with finer, dyed suture material. For hypospadias repair, the average time to suture was 6.7 min/cm (n = 23), whereas it was 3.1 min/cm for adjunctive LTS (n = 23) and 1.4 min/cm for sutureless urethroplasty (n = 3). Follow-up ranged from 3 to 22 months (average 9.6). Four fistulae were noted (1 onlay, 2 skin tube grafts, 1 Thiersch tube) each following penoscrotal or scrotal hypospadias repair; a fifth fistula developed following a traumatic catheterization in a sutureless repair. The overall complication rate in the LTS group was 19% (5 of 26) versus 24% (6 of 25) for controls, whereas that for the distal forms of hypospadias was 11% (2 of 18) and 13.6% (3 of 22), respectively.

CONCLUSIONS

Tissue soldering with laser and chromophore-doped solder is feasible, safe, and easy to perform. Laser tissue soldering may be an alternative to standard microsuture technique for hypospadias repair.

Human albumin solder supplemented with TGF-beta 1 accelerates healing following laser welded wound closure

BACKGROUND AND OBJECTIVE

We examined the possibility that human albumin solder can be used as a vehicle for site specific delivery of growth factors for the purpose of accelerating tissue repair following laser welded wound closure. Certain human recombinant growth factors have been shown to accelerate wound healing in model systems. Pilot in vitro studies have established that several growth factors, including TGF-beta 1, maintain bioactivity following exposure to temperatures achieved during laser tissue welding. Using a temperature controlled laser delivery system (TCL) to precisely maintain welding temperatures, it is now possible to avoid thermal denaturation of exogenous bioactive molecules such as growth factors.

STUDY DESIGN/MATERIALS AND METHODS

HB-EGF, bFGF, and TGF-beta 1 were tested in vitro for maintenance of bioactivity after exposure to 80 degrees C. In vivo experiments using porcine skin determined the efficacy of solders augmented with growth factors. Incisions were repaired using human albumin alone or supplemented with HB-EGF (2 micrograms), bFGF (10 micrograms), or TGF-beta 1 (1 microgram). Wounds were excised at 3, 5, and 7 days post-operatively. Tensile strength, total collagen content, and histology were performed.

RESULTS

At 3 days, tensile strength (TS) of TGF-beta 1 wounds were 36% (P < 0.05) and 20% (n.s.) stronger than laser alone and suture closures, respectively. By 5 days the TS of the TGF-beta 1 group increased by 50% (P < 0.05) and 59% (P < 0.02) over laser alone and suture groups, respectively. At 7 days the TGF-beta 1 group was 50% (P < 0.05) and 79% (P < 0.01) stronger than laser solder alone or suture, respectively. The HB-EGF and bFGF groups were equivalent to the laser solder group at all time points. Total collagen TGF-beta 1 Accelerates Healing Following Laser Welding content at 7 days increased in the TGF-beta 1 group by 7% (n.s.) over the suture group and 21% (P < 0.05) in the laser group.

CONCLUSION

Human albumin solder supplemented with TGF-beta 1 increases the early post-operative strength of laser welded wounds. This novel application of laser tissue soldering augmented with a growth factor has the potential to bring about immediate fluid tight seals while providing site specific delivery of biological modifiers. This may lead to an overall improvement in post-operative convalescence, wound infections, and hospital costs.