The mechanics of urethral closure, incontinence and midurethral sling repair. Part 2 further experimental validation (1993‐2003)

In Part 1, The original 1990 science behind the MUS, the hypothesized closure mechanisms, and the prototype MUS itself were presented. The next phase of MUS development began in 1990 in collaboration with the late Ulf Ulmsten. It had two arms Further development of the prototype MUS. Further anatomical, imaging, urodynamic studies to validate the role of PUL in the closure mechanisms. A second series of prototype MUS operations performed under LA/sedation resulted in a permanently implanted polypropylene sling and the MUS as is known today. The tape was elevated until no urine leaked on coughing. This demonstrated that the artificial PUL neoligament needed to be at a specific length to work. Anatomical, EMG and video ultrasound, and X‐ray studies confirmed three directional muscles contracted pubourethral (PUL) and uterosacral (USL) ligaments. The contribution of the horseshoe shaped rhabdosphincter (RS) to continence was directly tested with pressure measurements under live surgery conditions. It was concluded that the RS was responsible for pressure generation but not continence. Continence was a consequence of intraurethral resistance to flow created by the distal and proximal urethral closure mechanisms, both governed ultimately by the Law of Poiseuille. Conclusions The key element in curing USI is creation of a competent PUL using the collagenous neoligament surgical principle described in Part 1. This creates a firm insertion point for the three directional muscle forces, restoring their contractile strength and closure.