Hypothesis / aims of study
Until the introduction of the AdVance™ sling (AMS Men’s Health/Boston Scientific, MA, USA) in 2006 the obturator region did not play a major role in male incontinence surgery. Therefore little is known about the characteristics and stability of the obturator membrane in men.
As a further development of suburethral slings in women the single incision sling (SIS) technique with inside-out transobturator anchors have become increasingly popular. The known data of pull-out forces of existing female anchoring systems come from animal models. No such informations are available for men. We only know from abdominal hernia repair that the tensile strength of mesh material should exceed 32 N/cm to withstand the intraabdominal pressure in this area .
With the experience of male sling surgery and transobturator anchoring techniques in female continence surgery we developed a novel male anchoring system. The aim is to facilitate the insertion process of the male sling and to reduce the risks of the procedure by avoiding large needles or trocars. As a first step the novel anchoring technique is presented.
Study design, materials and methods
As a fundamental part of the developing process of a new sling system we extensively studied and measured the obturator region in male cadavers. The neuro-vascular anatomy was meticulously dissected and the thickness of the obturator membrane was measured at different points with a micrometer caliper. With particular respect to safety and stability of the new sling system the optimal area for anchor insertion was determined. We then performed pull-out tests with the PelFix anchor (FEG, Aachen, Germany) that we previously described in an in-vitro and an animal model . This very small anchor has demonstrated superior stability in comparison to three different approved devices in particular in the porcine rectus fascia. For the utilization in men also a new applicator was developed (Fig. 1). The test anchors were made of aluminium, the pull-out forces were measured on a Newton scale.
In four male cadavers all aspects of the obturator region were extensively dissected, colored, measured, and photo documented. The thickness of the obturator membrane was measured with a micrometer caliper (110 - 360 µm). Despite considerable inter-individual variations there was a consistent increase in membrane thickness from the cranial-lateral aspect (110 - 250 µm) to the caudal-medial area (210 - 360 µm). The obturator nerve and vessel branches are usually located lateral of this caudal-medial ‘safety zone’. Accordingly, the test anchors were placed in this area with the newly designed applicator. The pull-out forces in nine fresh male cadavers were consistently measured between 30 and 50 Newton (mean 41.1 N, Fig. 2). These values are far beyond the physiological forces that can be expected in the male pelvic floor, although no data from in vivo tests exist.
Interpretation of results
For the first time a new technique of male sling insertion and fixation is presented. Instead of transobturator trocar usage sling fixation is secured by an intraobturator anchor on either side. Like in previous studies in porcine rectus fascia the PelFix anchor demonstrates excellent stability through its transverse position after perforating the obturator membrane. In our study we were able to identify the optimal area of anchor insertion that is in the caudal-medial aspect of the obturator foramen. Here we find the thickest tissue to secure stability and the least chance to compromise obturator vessel or nerve branches. The degree of immediate anchor stability as measured in Newton by pull-out tests is very high, the pull-out forces are well beyond the expected maximum intraabdominal pressure.