Identification of a learning curve for surgical procedures provides important information for surgeons wishing to implement new procedures in their practice. Furthermore, knowledge about learning curves is essential for the establishment of minimum requirements for surgical training. The learning curve required for endoscopic pelvic organ prolapse (POP) surgery has been extensively studied (1–3), while scant evidence is available on vaginal POP surgery, especially on native-tissue repair (NTR). 
The aim of the study was to identify the learning curve for vaginal POP NTR using sacrospinous ligament fixation (SSLF), with and without hysterectomy, and to assess the impact of introduction of a fellowship program on surgery outcome.

Following IRB approval, we collected data using the hospital's electronic medical records of all patients who underwent POP surgery with SSLF for apical suspension between January 2012 and December 2023. Data collected included comorbidities, body mass index (BMI), smoking status, menopausal status, parity, previous pelvic floor surgery, and pelvic floor symptom history. Prolapse staging was carried out using the pelvic organ prolapse quantification system (POP-Q). The surgeries were performed by a single fellowship-trained pelvic floor surgeon during January 2012- December 2018 (“Period 1”), by 2 fellowship-trained pelvic floor surgeons during January 2019-December 2020 (“Period 2”), and by the two senior surgeons and 3 fellows during January 2021- December 2023 (“Period 3”). Right SSLF was performed using either the Capio® device (Boston Scientific, Marlborough, MA, United States) with either 2 polyglactin-910 or 2 polypropylene sutures or the Digitex™ (Coloplast, Minneapolis, MN, United States) with 2 polydioxanone sutures. Concomitant procedures included vaginal hysterectomy, amputation of the uterine cervix, anterior and/or posterior colporrhaphy by native tissue repair. A trans-obturator mid-urethral sling (MUS) was carried out for overt or occult stress urinary incontinence (SUI). Data on duration of surgery, intraoperative estimated blood loss (EBL), visual analogue scale (VAS) pain levels on post-operative day 1 (POD-1) and at the 3-weeks follow-up, duration of hospital stay and perioperative complications were collected. For patients who returned for follow-up 6-18 months following surgery, data on subjective and objective outcome of surgery was collected. 
Categorical variables were summarized as frequency and percentage. Continuous variables distribution was evaluated using histogram. Since all variables were not normally distributed, they were reported as median and IQR. Spearman’s correlation coefficient was used to evaluate the association between op time and years of experience. Chi-square test and Fisher exact test were applied to compare categorical variables between periods and Kruscal-Wallis test was used for continuous and ordinal variables. Multivariable logistic regression was used to study the association between period and postoperative pain, while controlling for potential confounders. The regression included 2 blocks. In the first block the period was forced into the regression. In the second block age, BMI, diabetes mellitus, asthma, anemia, smoking, constipation, sexual activity, previous POP surgery were considered for inclusion, using a forward stepwise method (p<0.05 was used as criteria for inclusion). All statistical tests were two-sided and p< 0.05 was considered significant. SPSS software was used for statistical analyses. (IBM SPSS statistics for Windows, Version 28, IBM corporation, Armonk, NY, USA, 2021).

From January 2013 to December 2023, 340 women underwent SSLF, combined with additional pelvic reconstructive surgery procedures. Eighteen patients were excluded from analysis: 2 patients had SSLF following conversion of robotic surgery to the vaginal route; 1 patients planned for high uterosacral suspension was converted to SSLF following intraoperative ureteral obstruction and stent insertion; 1 patient had total laparoscopic hysterectomy for uterine fibromas combined with vaginal reconstructive surgery; 14 women had mesh-augmented cystocele repair in combination with SSLF. Three-hundred and twenty-two women were included in final analyses:126 had surgery in period 1, 71 in period 2 and 125 in period 3. Median age was 66 (61-72), body mass index (BMI)=26.3 (23.9-29.4), 84 (26.1%) women had diabetes mellitus, 306 (95%) women were post-menopausal, median parity was 3 (0-13). Eighteen (5.6%) patients had previous POP surgery. 
During period 1, we identified a negative correlation between duration of surgery and years of experience, both in cases with hysterectomy (r=-03, p<0.001) and in those without (r=-0.4, p=0.015) (Figure 1). We did not observe this association during period 2 (r=-0.096, p=0.55; r=0.02, p=0.89), nor during period 3 (r=0.07, p=0.48; r=0.2, p=0.12).
Surgery duration was significantly longer in period 3 as compared to either period 1 (p<0.001), or period 2 (p=0.002), while no difference was observed between period 1 and period 2 (p=1.0) (Figure 2). 
We observed a significant lower rate of pain at POD-1 during period 1 as compared to period 2 and 3, as 56 (44.8%) women reported significant pain during period 1, 50 (72.5%) in period 2, and 97 (82.9%) during period 3 (p<0.001). We observed no difference in pain on POD-1 between period 2 and period 3 (p=0.24). Upon multivariable logistic regression, which included 2 blocks, we observed that after controlling for diabetes and suture type patients in period 2 tended to have higher probability for pain at POD-1 (OR: 2.03, 95%CI 0.96-4.32, p=0.066) and patients operated in period 3 had significantly higher probability of pain at POD-1 (OR: 3.32, 95%CI 1.53-7.22; p=0.002), both when compared to period 1.

During the 6 initial years since implementation of the SSLF technique, when a single fellowship-trained surgeon carried out all procedures, we have identified a gradual decrease in surgery duration. Surgery duration stayed similar after an additional fellowship-trained surgeon joined the first surgeon. After initiation of a fellowship program, operative time significantly increased, as compared to the previous periods. Moreover, we observed a significantly higher rate of immediate postoperative pain in patients operated during the fellowship program, in comparison with the first two periods. This difference remained significant after controlling for suture type and for diabetes.

Despite SSLF being a minimally invasive and relatively short procedure, a significant gradual decrease in duration of surgery is expected during up to 6 years from implementation of the technique. Training of new surgeons has a significant impact on both operative time and immediate postoperative pain.

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