Hypothesis That Urethral Bulb (Corpus Spongiosum) Plays an Active Role in Male Urinary Continence

Figure 4

Correct placement of helical needle trocar from “outside-in.” The tip of the helical needle trocar enters the perineal wound underneath the lumen of the urethra in a distal position and underneath the membranous (sphincteric) urethra. The entrance of the introducer needle tip into the perineal wound should be in the uppermost corner between inferior pubic ramus and urethral bulb. The corpora cavernosa (not shown) lie “on top” of the inferior pubic rami and are not in the line of the needle trocar passage-measured safety margin of sling to dorsal penile nerve 5 mm. Note that the level of the tip of the trocar is and should be below the lumen of the membranous urethra. When the sling is tensioned, it is pulled into a straight line well underneath the level of the caudal membranous urethral wall. Only the distalmost portion of the membranous urethra is thus supported from the dorsal side. Correct sling placement should therefore have a very low risk of urethral erosion. The main risk for urethral damage is intraoperative perforation of the urethra during trocar passage. It is imperative to protect the urethra, noticed by a transurethral catheter in situ, with the surgeons’ index finger, during needle trocar passage.