Objective analysis of mechanical resistance of tension-free devices

The "tension-free" procedures are widely used by surgeons for the treatment of urinary incontinence and prolapse. The clinical results are largely in favour of these procedures. The aim of our study is to determine objectively the mechanical tissue resistance when using these techniques, before healing begins.

We measured the mechanical resistance using four different routes: the retro-pubic space, the transobturator, the translevator ani muscle and the trans-sacrospinous ligament. We compared five different meshes, TVT, IVS, Lift, Prolene and Prolene Soft. In order to study the effect of increasing dimensions, we tested Prolene tapes measuring 1, 1.5 and 2 cm in width. We performed traction tests on meshes implanted in cadavers. Measurements were made with a dynamometer and the results expressed in Newtons.

This study shows that TVT offers a better resistance to traction via the retro-pubic space route. There was no significant difference among the four routes when the same type of mesh measuring 1cm was used. However, an increase in the dimensions of Prolene tapes improves their resistance in the tissues, thereby facilitating fixation before healing begins. Also, these increasing dimensions (in width) show that there is better resistance with the trans-sacrospinous ligament compared with the transmuscular one.

The increasing size of prosthetic meshes does not show the superiority of certain routes with commercial meshes of 1cm in width. The higher resistance obtained with wider tapes is probably due to an increased surface area between the tissues and meshes. This increase in resistance does not seem to be important for the treatment of urinary incontinence. However, it should be of interest for the treatment of prolapse where traction and surface are more important.

Two different recommendations can be deduced from our study. On one hand, the arms of prosthetic meshes for pelvic floor repair should measure more than 1cm in width in order to improve their maintenance in the tissues in the immediate post-operative period. On the other hand to improve fixation, the posterior arms of the transperineal mesh should be passed through the sacrospinous ligament rather than via the transmuscular route. The resistance of tissues is also influenced by the armature of the prosthetic mesh. They must therefore be developed commercially specifically for "tension-free" fixation. Our results need to be confirmed by further studies including more cadavers and younger patients.