BERKELEY, CA (UroToday.com) - Implant materials are used for various reconstructive surgeries in urogynecologic practice, including laparoscopic colposuspension, cystocele, rectocele, uterine prolapse repair and for stress urinary incontinence. In the recent past, the tension-free mid urethral sling approach has gained popularity and the introduction of minimally invasive sling techniques such as TVT, intravaginal slingplasty (IVS) and the suprapubic approach to suburethral polypropylene tape (SPARC) have renewed interest in the role of polypropylene mesh sling materials for continence surgery. Based on an experimental research series, the local tissue response, biomechanical properties and sling material structure may have a role in the surgical outcome.

In a recent study by A. Yildirim and colleagues from Istanbul, Turkey, an animal model was used to explore the tissue reaction and tissue-to-material attachment strength of different synthetic sling materials. The study is published in the November 2005 issue of the Journal of Urology.

In the study, 4 different types of polypropylene prostheses were tested for mesh-to-tissue detachment strength, including a TVT device by Gynecare, the SPARC sling system by AMS, IVS by Tyco and the Galmesh surgical polypropylene hernia mesh by Gallini. Solvent dehydrated Tutoplast cadaveric fascia lata was also evaluated. While TVT, SPARC and the Galmesh meshes consist of a macroporous mesh comprising 1 or 2 monofilaments, IVS is constructed of nonstretch multifilament polypropylene mesh tape. The surgical procedure performed on 20 rabbits entailed implantation of a 0.5 by 1.0 cm piece of material sewn to the rectus muscle with direct contact. At the same time, 4 subfascial tunnels were created in the upper extremity and each material was implanted in this tunnel. On days 2, 7, 15 and 30 after implantation mechanical testing was performed to define tissue detachment strength and the strips of the 5 materials were examined by light microscopy for evidence of tissue reaction by a blinded pathologist. The intensity of tissue reaction was scored on a grading scale.

Mechanical testing was done by dissecting the distal part of the implanted material from the upper extremity and hanging increasing weight from it under gravity until the mesh moved and detached from the tissue.

Analysis of the results showed that all materials exhibited a quite uniform tissue reaction as judged by light microscopy that began soon after implantation. All meshes showed stable fibrosis and muscle infiltration on day 30. Cadaveric fascia (Tutoplast) persisted with remarkable perifascial fibrosis at day 30. Examination of the mean detachment strength test from days 2 to 30 were 291.6 to 2,390 gm for TVT, 178.4 to 2,160 gm for SPARC, 188.4 to 1,850 gm for hernia mesh and 92.8 to 1,510 gm for IVS. At all data points the TVT was significantly higher than the IVS. SPARC and hernia mesh showed statistically similar results to the TVT. Based on similar histological and biomechanical properties, the authors suggest that hernia mesh, which is usually cheaper and available as a single, free product might be more economical than the pre-packaged polypropylene mesh kits.

J Urol. 2005 Nov;174(5):2037-40