Cog Threads for Transvaginal Prolapse Repair: Ex-Vivo Studies of a Novel Concept

The diagnosis and treatment of pelvic organ prolapse (POP) remain a relevant and scientifically challenging topic. The number of cases of genital prolapse increases each year, one in ten women need at least one surgical procedure and one in four women in midlife have asymptomatic prolapse. Using mesh implants to correct POP presents unsatisfactory clinical outcomes, requiring hospital readmission and further surgery. We hypothesize using an alternative surgical intervention technique, applying injectable biodegradable cog threads, currently used for face lifting procedures, to reinforce and correct vaginal wall defects. The threads used in this investigation are commercially available 360 degrees 4D barb threads (PCL-19G-100), made of polycaprolactone (PCL), supplied in sterile packs (Yastrid, Shanghai, China). Eleven sows' vaginal walls were used to analyze the immediate reinforcement effect of the threads. Uniaxial tensile testing and scanning electron microscopy (SEM) was performed for the initial characterization of the threads. Threads were inserted into the vaginal wall (control n = 5, cog n = 5) and were characterized by ball burst testing; a pull-out test was performed (n = 6). With SEM images, dimensions, such as thread diameter (approximate to 630 mu m), cut angle (approximate to 135 degrees), cut depth (approximate to 200 mu m) and cog distance (approximate to 1600 mu m) were measured. The mechanical behavior during uniaxial tensile testing was nonlinear. Threads could sustain 17-18 N at 18-22% of deformation. During the ball burst test, vaginal tissue reinforced with threads could support 68 N more load than normal tissue (p < 0.05), indicating its strengthening effect. Comfort and stress zones were significantly stiffer in the tissues reinforced with threads (p < 0.05; p < 0.05). Both groups showed identical deformation (elongation); no significant differences in the comfort zone length were observed, showing that threads do not affect tissue compliance. The pull-out test showed that the threads could sustain 3.827 +/- 0.1891 N force when the first cog slip occurs, at 11.93 +/- 0.8291 mm. This preliminary research on using PCL cog threads for POP treatment showed promising results in increased vaginal wall resistance to pressure load and, at the same time, not affecting its compliance. Nevertheless, to obtain long term host response in vivo, further investigation will be carried out.