FEMALE UROLOGY

The tensile properties of tension-free vaginal tape and cadaveric fascia lata in an in vivo rat model
Spiess PE, Rabah D, Herrera C, Singh G, Moore R, Corcos J
Department of Urology, McGill University, Montreal, Canada
BJU Int. 2004;93: 171-3

• Objective: To examine the tensile properties (break load and maximum average load), after in vivo implantation in a rat animal model, of tension-free vaginal tape (TVT) and cadaveric fascia lata (CFL), as pubovaginal slings of these materials have become popular for treating stress urinary incontinence.
• Materials and Methods: Twenty Sprague-Dawley rats (300-400 g) had 1 x 2 cm strips of commercially available TVT and CFL implanted on the right and left anterior abdominal wall, respectively. Half of the animals were then killed at 6 weeks and the remainder at 12 weeks, after which the strips of TVT and CFL were removed and their tensile properties measured using a tensiometer. The tensile strength of TVT and CFL strips maintained only in normal saline served as controls.
• Results: The TVT strips had a mean break load of 0.740 kg in the control and only 0.390 kg for CFL (P < 0.05). At 6 weeks the TVT material had a mean (sd) maximum average load of 0.634 (0.096) kg and a mean break load of 0.589 (0.249) kg, whereas the respective values for the CFL were 0.323 (0.198) and 0.167 (0.063) kg (P < 0.05). Similarly at 12 weeks, TVT had a greater mean maximum average and break load than CFL, at 0.742 (0.052) and 0.274 (0.126), and 0.737 (0.056) and 0.185 (0.128) kg, respectively.
• Conclusion: This is the first study to assess the tensile properties of the currently used sling materials, TVT and CFL, in an in vivo model. TVT has a greater break load and maximum average load than CFL; the tensile strength of these materials does not decrease with time.
  
  
• Editorial Comment
  The authors measure and compare the tensile properties of commercially available synthetic polypropylene mesh and cadaveric fascia lata after 6-12 weeks of in vivo implantation. Their description and quantification of the temporally associated comparative changes of these materials help shed light on one of the potential causes of failures of suburethral slings using cadaveric fascia lata. The implantation site was abdominal which does raise the spector of a possible different induced tissue change or alteration had the materials been placed in the suburethral area (a site oft plagued with postoperative bleeding). This study does highlight the long-term durability of the polypropylene mesh without an associated potential genetic contamination. The interested urologist looks forward to the author’s promised further long-term studies utilizing this clinical, experimental model.

Dr. Steven P. Petrou
Associate Professor of Urology
Mayo Medical School
Jacksonville, Florida, USA