This study reveals three critical new findings. First, in SILPEC procedures for male pediatric inguinal hernia, manipulation time was significantly reduced when the attending surgeon had JSPS certification as a supervisor. Second, a history of hernia incarceration in male patients undergoing SILPEC was associated with a significant increase in manipulation time. Third, in SILPEC procedures for female patients, prophylactic surgery for asymptomatic contralateral PPV was associated with a shorter manipulation time than in cases with symptomatic hernia.

Notably, studies investigating the relationship between JSPS-certified supervisory surgeons and surgical outcomes have been limited. In our previous examination of transumbilical laparoscopic-assisted appendectomy performed by young pediatric surgeons with < 10 years of post-graduate experience, we found that the absence of a JSPS-certified supervisory surgeon as attending was an independent risk factor for a prolonged operative time [7]; therefore, to our knowledge, this is the only report to date that has examined this association. In other surgical fields, a similar association has been reported, wherein procedures supervised by surgeons certified in Endoscopic Surgery Skill Qualification by the Japan Society of Endoscopic Surgery significantly reduced the operative time for laparoscopic cholecystectomy performed by young surgeons [8]. Wiseman et al. reported that in laparoscopic cholecystectomy, attending surgeons accounted for 44.5% of the variance in operative time [9]. However, resident surgeons only contributed 11.0%, underscoring the substantial impact of attending surgeon-related factors on operative time [9]. Therefore, integrating our findings with the existing literature, we can conclude that certified supervisors possess superior coaching skills compared to non-certified surgeons, enabling inexperienced surgeons to conduct procedures more efficiently. In the present study, no significant association was found between JSPS-certified supervisory surgeons and manipulation time in female patients undergoing SILPEC. This result may be due to the relative simplicity of performing SILPEC in female patients, in whom anatomical structures such as vas deferens or testicular vessels are absent, thus reducing the need for intensive guidance from the attending surgeon.

Furthermore, in male patients undergoing SILPEC, a history of hernia incarceration was significantly associated with prolonged manipulation time, likely due to inflammation induced in the peritoneum surrounding the internal ring. Miyano et al. reported that, among pediatric patients who underwent LPEC within 1 week of manual reduction of an incarcerated hernia, 61.9% exhibited edematous changes in the peritoneum surrounding the hernia ring [10]. In addition, they observed that, in early post-incarceration cases (within one week), LPEC required a significantly shorter operative time than conventional open repair; however, comparisons with non-incarcerated cases were not conducted in that study [10]. In cases of marked peritoneal edema, even experienced surgeons may encounter poorly defined tissue planes [11], necessitating particularly cautious and gentle manipulation to avoid damaging the fragile peritoneum. Furthermore, depending on the extent of edema, separating the vas deferens and testicular vessels from the peritoneum may become more challenging, potentially contributing to the extended manipulation time. In contrast, no clear association was observed between history of hernia incarceration and manipulation time in female patients undergoing SILPEC. This may be attributed to the small sample size as only one female patient had a history of incarcerated hernia in this study, which may have limited statistical power. Furthermore, the interval between manual reduction and surgery was 89 days, suggesting that any edema or inflammatory changes in the peritoneum associated with incarceration may have been resolved by the time of surgery.

In female patients, the manipulation time for prophylactic repair of an asymptomatic contralateral PPV was significantly shorter than that for symptomatic hernia repair. One contributing factor may be the smaller diameter of the opening in contralateral PPVs than on the symptomatic side. Ho et al. conducted a retrospective study of 569 pediatric patients with inguinal hernias. They found that the mean ± standard deviation diameter of the opening in contralateral PPVs, measured during laparoscopic surgery, was significantly smaller than that in symptomatic hernias (6.1 ± 2.5 mm vs. 11.2 ± 3.1 mm; P < 0.001) [12]. Therefore, the shorter manipulation time for asymptomatic PPV repair in our study may be due to the reduced needle passage distance required for the SILPEC procedure. In contrast, this correlation between asymptomatic PPV and reduced manipulation time was not observed in male patients, likely due to the technical complexity required to cross over the vas deferens and testicular vessels with the LPEC needle, which is a major determinant of manipulation time. Another reason for the shorter manipulation time in female asymptomatic PPV cases could be that prophylactic repair is generally performed after repair of a symptomatic hernia. In a related study, Moran-Atkin et al. reported that surgical residents who performed 10 min of warm-up simulation training within 1 h of laparoscopic surgery showed significant improvements in depth perception, bimanual dexterity, and efficiency of movements compared to a non-warm-up group [13]. At our institution, particularly in female patients, less-experienced young surgeons often perform SILPEC. Therefore, it is plausible that repeating the same technique during the initial symptomatic hernia repair might improve the efficiency, thereby reducing the manipulation time for subsequent asymptomatic PPV repair. In addition, among female patients, attending surgeons with post-graduate years > 18 years were associated with significantly prolonged manipulation times. This disparity may reflect the fact that attending surgeons with ≤ 18 post-graduate years had more opportunities to serve as operating surgeons during the early implementation phase of SILPEC than those with > 18 post-graduate years. Consequently, they were able to achieve a higher level of proficiency with the technique than their senior counterparts, which likely contributed to the observed differences in the manipulation times.

Several limitations associated with the present study warrant mention. First, this was a single-center retrospective study, which may have limited the generalizability of our findings to other institutions or broader patient populations. Second, the analysis was limited to cases with complete video records because some surgical videos were missing. The missing videos were randomly distributed; however, this limitation may have affected the comprehensive evaluation of the manipulation time by reducing the sample size and potentially introducing selection bias. Third, in the multivariate analysis of manipulation time, the clinical experience of surgeons and attending surgeons was primarily evaluated based on their post-graduate years. This approach may not fully capture the actual number of procedures performed, supervisory experience, or true level of proficiency. Finally, the relatively limited sample size in specific subgroups, such as patients with a history of hernia incarceration or cases involving ovarian sliding hernias, may have affected the statistical power of this study. Therefore, a larger sample size would be able to provide more precise insights and strengthen the reliability of conclusions regarding the factors influencing manipulation time in SILPEC.

However, despite these limitations, this study remains significant because the manipulation time for each side was evaluated individually, including in cases with contralateral PPV. In previous studies, most analyses relied on the total operative time, making it challenging to separately assess the impact of factors, such as asymptomatic PPV and hernia incarceration on manipulation time. However, in the present study, we demonstrated the effects of these individual factors.

In conclusion, our results revealed that the attending surgeon holding JSPS certification as the supervisor significantly reduced the manipulation time in SILPEC for male pediatric inguinal hernias. In addition, patient-specific factors, such as hernia incarceration in male patients and asymptomatic contralateral PPV in female patients, had a significant impact on manipulation times. These findings suggest that optimizing the selection of surgeons based on patient background and strengthening mentorship structures to support skill development among young surgeons could further enhance outcomes and improve procedural effectiveness in pediatric surgery.