Investigating Perineal Gap as a Novel Measurement of Level III Support

INTRODUCTION: Genital hiatus (GH) is quantified by the Pelvic Organ Prolapse–Quantification (POP-Q) system using an anterior-posterior measure which describes the vertical length of the hiatus. However, GH fails to capture the horizontal width of the hiatus, leaving the overall characterization of the hiatus incomplete. The perineal gap (PG) is a novel intraoperative measure proposed by Haylen et al. (IUJ 2014) at the time of posterior repair to better quantify Level III support. Conceptually, PG is the horizontal distance between the separated ends of the perineal membrane (Figure 1). At our institution, PG is measured as part of the standard intraoperative measurements; yet the utility of PG as a clinical parameter or surgical decision aid remains incomplete. OBJECTIVE: The primary aim of this study is to determine the correlation between PG and GH measures. Our secondary aim is to explore the relationship between PG and preoperative maximum vaginal descent (MVD). METHODS: We performed a retrospective cohort study of urogynecology patients who underwent an apical suspension procedure for pelvic organ prolapse between March 2023 and March 2024. We included patients both with and without posterior repair. Standard POP-Q measures were collected preoperatively and 6 weeks postoperatively. Intraoperative measurements included PG, GH, perineal body (PB), and total vaginal length (TVL). If posterior repair was performed, these measurements were obtained before and after the posterior repair. The approach to measuring PG is described in Figure 1. PG was measured to the nearest 0.5 cm. There was no standardized criteria for when to perform a posterior repair nor the surgical technique. We report the Pearson correlation coefficients with 95% confidence intervals (CI) for PG with GH and MVD. In cases with a posterior repair, we determined the correlation between the change in PG (deltaPG) with the change in GH (deltaGH). Linear regression was used to determine the effect of posterior repair and deltaPG on deltaGH. RESULTS: Of the 126 patients in the analysis, 83% (n=105) underwent a posterior repair as part of their procedure. Mean PG was 3.12 ± 1.5 cm compared to 1.62 ± 1.3 cm in those with, versus without, a posterior repair (p<.001). The average reduction in PG was 3.0 ± 1.5 cm compared to −0.1 ± 0.3 cm for those with, versus, without posterior repair (p<.001). In those who had a posterior repair, a weak correlation was seen between pre-posterior repair GH and pre-posterior repair PG (0.28, 95% CI 0.08 – 0.45), and a weak correlation was seen between pre-posterior repair PG and preoperative MVD (0.19, 95% CI 0.01–0.36). Of those who underwent posterior repair, deltaPG and deltaGH were moderately correlated (0.38, 95% CI 0.20 – 0.54). With a posterior repair, a reduction in deltaPG by 1cm was associated with a 0.18-cm (95% CI 0.09–0.27) reduction in deltaGH. CONCLUSIONS: Perineal gap is a novel measure of Level III support. We found a 5:1 ratio between deltaPG and deltaGH at the time of posterior repair, meaning that reducing a 5-cm PG to 0 cm will result in a 1-cm decrease in GH.