Background and purpose: Bladder-neck suspension has been used widely for the management of female stress incontinence. Despite high early success rates, the long-term results are poor. This in-vitro model was designed to simulate the tear forces affecting the sutures under standardized laboratory conditions.
Materials and methods: First, we determined the ultimate strength of various tissues (porcine vagina [PV], human vagina [HV], porcine colon, and chicken skin) in resisting standardized traction force and expansion. Subsequently, different types of suture fixation (U stitch, Z stitch, patch suspension) and button techniques (titanium 2 mm and buttons with various diameters) on PV were exposed to standardized stress impulses generated by the horizontal movement of a metal sledge and the traction force of a 0.5-kg weight pulling on the suture. Amplitude, frequency of the sine movement, traction force on the suture, and tissue thickness were modified; and the tear-out time of the fixation (suture, button) was measured.
Results: The PV and HV revealed similar ultimate strengths (49.04 N and 32.08 N, respectively, for traction force; 58.25% and 58.20%, respectively, for expansion). Increasing the frequency (110-160/min), amplitude (8-24 cm), or traction force (0.3-1.2 N) shortened the tear-out time. Tissue thickness had a nearly linear correlation with the tear-out time. The conventional suture technique was almost equal to the smaller buttons (8 and 12 mm) in tear-out resistance, but the 20-mm button was superior (2.6-fold increase in tear-out time). Further improvement of the button technique could be achieved by use of round silicone-coated buttons with medium hardness (shore 40).
Conclusion: A button-like support is promising, being superior to conventional suturing. Compared with tension-free vaginal tape, it provides the advantage that paraurethral suspension prevents erosion of a foreign body through the urethra. Further technical improvements may include adjustment devices for postoperative fine-tuning of the bladder-neck suspension.