Mini or Retropubic Sling in Women with Intrinsic Sphincter Deficiency at 12 Months- A RCT (Mini RISD).

Abstract

Introduction: Retropubic midurethral slings have been shown to be safe and effective. Single incision slings (SIS) can potentially improve patient experience with less pain, and faster return to normal activity. SIS have been shown to be noninferior to standard midurethral slings at 36months. Intrinsic sphincter deficiency (ISD) defined as MUCP<20 cm water or VLPP <60 cm water is associated with a higher risk of sling failure. Comparison of the efficacy and safety of the retropubic and the mini single incision sling (SIS) in an ISD population has not yet been determined. Objective(s): To assess if the SIS is as efficacious as the RP sling for women with urodynamic stress incontinence (USI) and ISD and compare clinical outcomes. Method(s): Multicentre randomized controlled trial involving women with SUI/ISD. Demographic data of eligible women and POPQ examination was collected. Randomization to SIS or RP occurred in equal probability. Concomitant prolapse operation was performed as required and concomitant OAB was treated. Post-operative interview and examination including uroflow, cough stress test and POPQ assessment were performed at 6 weeks, 6 and 12 months. Standardized questionnaires were performed at 6 and 12 months. The primary outcome was the objective cure rate (negative clinical cough stress test) at 6 and 12 months. Secondary outcomes included immediate and short term complications and patient reported outcomes. Based on an objective cure rate of 79% in the retropubic arm, a sample size of 132 participants was calculated to detect a difference of 20% in the SIS arm (alpha=0.05, power80%). Categorical outcomes were compared using chi-squared test and continuous outcomes using the independent samples t-test for normally distributed data. Results were analyzed by ITT analysis. Result(s): 112 women were randomized from February 2016 to September 2022 and had 6 month follow up; 104 completed 12 month follow up. Table 1 shows numbers randomized and allocated and baseline comparison. The sample size of 132 was not reached due to withdrawal of the SIS by the national regulatory body in 2018 and subsequent need for ethics reapplication, Covid restrictions in 2020 to 2022 and womens reluctance to have mesh. At 12 months, the objective and subjective cure rates were no different; greater than 80 % and 70 % respectively. 68% in the RP group and 75% in the SIS group reported improvement as very much better or much better (RR 0.91 (95% CI 0.71-1.18), p=0.48). There was no difference in post-operative complications between the 2 groups however, one SIS was removed for groin pain; 2 patients in the RP group and 1 in the SIS group had sling loosening. In the RP group, 2 had repeat retropubic sling, 1 had mesh erosion requiring excision In the SIS group, 5 had repeat surgery (4 RP - 1 still wet and had bulkamid, 1 fascial sling). Conclusion(s): After 12 months, there was no difference in subjective or objective cure rate between the RP sling and SIS for ISD. Mesh complications were uncommon in both groups. Further follow up is occurring at 2 years.