In 1901, George Kelling, a surgeon from Dresden, performed the first experimental laparoscopy on a dog by creating pneumoperitoneum via “Coelioskope” [1], marking the inception of laparoscopic surgical exploration. Over the subsequent century, surgeons worldwide leveraged their expertise to pioneer advancements in laparoscopic techniques [2]. The landmark moment arrived in 1987 when Dr. Philippe Mouret of Lyons, France, performed the first laparoscopic cholecystectomy [3], igniting widespread interest among surgeons globally. Since then, numerous procedures have been adapted to a laparoscopic approach.

Certain surgeries, such as inguinal hernia repair and radical prostatectomy, pose unique anatomical challenges when approached laparoscopically. This complexity can cause difficulties for newly graduated surgeons. In the United States, data from the American Board of Surgery from 2007 to 2009 revealed higher mortality and severe complication rates among newly graduated surgeons than among their more seasoned counterparts [4]. However, technical proficiency is not necessarily correlated with experience [5].

In residency training programs, residents now have limited autonomy in performing laparoscopic procedures [6], likely reflecting a cultural shift towards emphasizing safety and meeting university standards. A survey of United States general surgery residents from 14 residency programs indicated insufficient readiness to perform surgery independently [7]. Similarly, the first nationwide Japanese survey on laparoscopic surgery training and the autonomy of young surgeons conducted in 2021 revealed that young surgeons felt less confident in performing advanced laparoscopic procedures beyond cholecystectomies or appendectomies [8]. Consequently, this disparity has prompted newly graduated surgeons to pursue additional training opportunities in minimally invasive surgery programs.

These observations have led to the belief that surgeons with seniority in open surgery may have a shorter learning curve during laparoscopic procedures [9]. Credentialing guidelines set forth by the Society of American Gastrointestinal and Endoscopic Surgeons stipulate that surgeons must demonstrate competence in open procedures before transitioning to laparoscopic surgery [2]. Similarly, the Japan Society for Endoscopic Surgery guidelines for performing endoscopic surgery, established in 1996, recommend proficiency in open surgery before performing endoscopic procedures.

Our study aimed to establish the safety and efficacy of laparoscopic inguinal hernia repair (LHR) performed by recently graduated surgeons lacking prior expertise in open approaches by comparing the noninferiority of outcomes between LHR and open inguinal hernia repair (OHR).

We conducted a retrospective cohort study focusing on inguinal hernia repair surgeries performed by a single surgeon during the learning phase at a secondary care 500-bed hospital. The participating surgeon lacked independent experience in performing LHR during the residency training program. The exposure was limited to a single cadaveric LHR workshop session and only five instances of OHR. Data were retrieved from the electronic medical database between July 2021 and November 2022. Our study population consisted of patients aged 18 years and older who had undergone inguinal hernia repair. Patients with emergency inguinal hernia conditions, such as incarceration or strangulation; recurrent inguinal hernias; bilateral inguinal hernias; and other concurrent operations were excluded from our analysis. The term “recently graduated surgeons” referred to individuals who had recently completed their residency training and begun independently performing surgical procedures at their respective hospitals. The selection of learning surgeons in the context of inguinal hernia repair was based on their experience, specifically, the number of cases they had performed independently or had just surpassed the established learning curves for this procedure. In our study, the learning curve for OHR comprised 31 to 40 cases [10,11], while for LHR, the learning curve was 13 to 33 cases [12–14]. LHR was performed using two distinct techniques, the totally extraperitoneal (TEP) and transabdominal preperitoneal (TAPP) approaches. For TEP, we used the enhanced view TEP hernia (eTEP) technique introduced by Daes in 2012 [15]. eTEP was performed according to the guidelines and recommendations [15–17]. Conversely, OHR was performed using the well-established and widely recognized Lichtenstein technique, first described in 1989 [18]. The operative procedure for OHR was conducted following the steps outlined by Sakorafas et al. [19].

Comprehensive data collection encompassed patient characteristics, intraoperative details, and postoperative data. Patient characteristics included age, sex, body mass index (BMI), comorbidities, history of abdominal surgery, current use of antiplatelets/anticoagulants, and the specific side of the inguinal hernia. Intraoperative data encompassed critical aspects of the surgical procedure, specifically the choice between OHR and LHR. For LHR, distinctions were made between the eTEP and TAPP techniques, the utilization of tacker devices, balloon space maker devices, three-dimensional (3D) meshes, and instances of conversion to OHR. Information on the mesh used was also documented. Inguinal hernias were classified into direct, indirect, or pantaloon types, and the largest sac size was determined intraoperatively.

Other intraoperative metrics included the operative time (OT), defined as the interval (in minutes) from the initial skin incision to skin closure, and estimated blood loss (EBL; mL), which was extracted from records maintained by the anesthesiologists. In addition, the occurrence of intraoperative complications was documented. Intraoperative complications were defined as organ injury during the surgical procedure, including injury to the spermatic cord and major blood vessels. Postoperative data analysis involved assessing the length of stay (LOS), monitoring for postoperative complications, quantifying postoperative opioid utilization, and tracking instances of recurrence within 3 months following the surgical procedure. Opioid use was ascertained by quantifying the frequency of administration required by patients during the postoperative period. Our standard analgesic regimen primarily entailed the administration of morphine for pain management, unless contraindications or adverse reactions necessitated substituting fentanyl. Morphine was administered at a dose of 0.05–0.1 mg per kg of body weight per dose, whereas fentanyl was administered at a dose of 0.5–1 µg per kg of body weight per dose. The postoperative complications were categorized as follows: formation of seroma or hematoma formation at the surgical site, surgical site infection (SSI), spermatic cord edema (SCE), acute urinary retention (AUR), and hernia recurrence. SSI was operationally defined as a localized infection that manifested within 30 days following the surgical procedure, with or without concurrent systemic inflammatory responses. Complications were classified using the Clavien-Dindo classification system, which provides a structured and standardized approach to categorizing and evaluating the severity of postoperative complications. Instances of revisit to the emergency or outpatient department before the scheduled follow-up appointments were documented. Additionally, data on the need for readmission and subsequent surgical intervention were collected. To monitor recurrence, a postoperative follow-up protocol was implemented wherein patients were contacted telephonically 1 year after surgery. During this communication, patients were queried about the presence of recurrent masses or symptoms at the site of the prior repair. Patients who reported the absence of symptoms or masses were categorized as having experienced no recurrence.

The main objective of this study was to assess and compare the occurrence of complications between OHR and LHR performed by a surgeon during the learning phase. As the primary analysis, noninferiority testing with a predetermined noninferiority margin of 15% was employed. In addition, we evaluated various secondary outcomes, including OT, EBL, LOS, recurrence rates, revisit rates, readmission rates, and reoperation rates, to comprehensively compare the two surgical approaches.

Sample size calculation

The sample size in our study was determined using n4Studies (version 2.2) [20], to assess two population proportions within a noninferiority trial. Our study aimed to investigate whether the complication rate associated with the LHR procedure was noninferior to that associated with the OHR procedure, particularly within the context of a learning surgeon’s practice. The sample size calculation was predicated upon a 15% noninferiority margin (δ), utilizing proportions of P1 (LHR) at 0.036 and P2 (OHR) at 0.019 [21] and considering a significance level of 0.05 for a type I error (α) and a power of 0.2 for a type II error (β). Additionally, the sample size ratio between groups was 0.5. Consequently, the calculated sample size comprised 15 LHR procedures and 31 OHR procedures, thereby ensuring the study possessed an 80% statistical power to discern and affirm the noninferiority of outcomes between the examined groups.

Statistical analysis

We applied descriptive statistical methods to juxtapose continuous variables. These methods encompassed the computation of means, medians, and standard deviations (SDs) or interquartile ranges (IQRs), as well as the determination of minimum and maximum values. Frequency distributions were generated for categorical variables. Subsequently, 95% confidence intervals (95% CIs) were calculated to ascertain the precision of the findings. We employed a paired t-test for continuous variables that exhibited a normal distribution to evaluate the statistical significance of the observed variances. Conversely, the Wilcoxon rank-sum test was used as an alternative hypothesis test for nonparametric data. In instances involving categorical variables, the chi-square test was used, and where appropriate, the Fisher exact test was employed to scrutinize the hypotheses. Our analytical approach was structured to discern disparities between diverse factors and their corresponding 95% CIs.

To assess noninferiority, a 15% noninferiority margin was adopted as the critical threshold. Binary variables, including complication, recurrence, revisit, readmission, and reoperation rates, were parameters for evaluating noninferiority, applying a 15% noninferiority margin. No previous study had specifically compared the outcomes of the learning curve for inguinal hernia repair surgery. Consequently, the selection of a 15% noninferiority margin was based on a comprehensive systematic review conducted by Afify and Khaled [21]. The authors highlighted that a highly regarded randomized controlled trial by Neumayer et al. [22] found a significant difference in recurrence rates at 2 years between LHR and OHR (10.1% vs. 4.9%). Based on this, we decided to use a 5% significant difference between groups to detect noninferiority. To further enhance the robustness of this margin, an additional 10% was incorporated, accounting for the differences in complication rates observed between OHR and LHR within the context of a learning surgeon environment. Furthermore, Kaplan-Meier curves were generated to delineate the cumulative incidence trends between OHR and LHR concerning the recurrence, revisit, readmission, and reoperation rates.

To compare continuous variables, namely OT, EBL, and LOS, our analysis identified these variables as nonparametric. To enhance the graphical representation, a moving average was employed to smooth the plotted curves. Furthermore, to discern stable points in these variables during the learning curve, a slope threshold of 0.5 was established. This threshold was instrumental in detecting the points of variable stability throughout the temporal progression of the learning curve, thereby elucidating the trends associated with OT, EBL, and LOS.

All statistical analyses were performed using R Studio (version 2023.06.0+421, R Foundation for Statistical Computing) with the dplyr, ggplot2, survival, survminer, lubridate, and epiDisplay packages. The significance level was set at p-values of ≤0.05. No efforts were made to impute missing data in the analysis.

Patient characteristics

Between July 2021 and November 2022, 91 hernia surgeries performed by a single surgeon during the learning phase were considered. From this dataset, we excluded 19 patients who presented with emergency inguinal hernias, three patients with recurrent inguinal hernias, and one patient with bilateral inguinal hernias. Additionally, two patients who underwent concurrent operations (Tenckhoff catheter insertion and vasectomy) were excluded from the analysis. Subsequently, 66 patients formed the basis for data analysis, including 45 and 21 patients in the OHR and LHR groups, respectively. The comparative analysis between the OHR and LHR cohorts revealed no significant differences concerning age, BMI, underlying diseases, history of prior abdominal surgery, or the characteristics of hernia disease (Table 1).

Table 1 . Patient characteristics.

Characteristic	Open	Laparoscopic	p-value
No. of patients	45	21
Age (yr)	63 (58–68)	61 (51–73)	0.64
Male sex	43 (95.6)	21 (100)	>0.99
Body mass index (kg/m2)	22.9 ± 3.6	21.2 ± 2.8	0.05
Underlying disease	24 (53.3)	14 (66.7)	0.31
Comorbidity
Hypertension	20 (44.4)	6 (28.6)	0.22
Dyslipidemia	10 (22.2)	5 (23.8)	>0.99
Diabetes mellitus	5 (11.1)	2 (9.5)	>0.99
Others	14 (31.1)	10 (47.6)	0.19
Previous abdominal surgery	11 (24.4)	4 (19)	0.76
Antiplatelet use	7 (15.6)	0 (0)	0.09
Anticoagulant use	0 (0)	1 (4.8)	0.32
Inguinal hernia type			0.14
Direct	4 (8.9)	2 (9.5)
Indirect	38 (84.4)	14 (66.7)
Pantaloon	3 (6.7)	5 (23.8)
Side			0.67
Right	24 (53.3)	10 (47.6)
Left	21 (46.7)	11 (52.4)

Values are presented as number only, median (interquartile range), number (%), or mean ± standard deviation..

Intraoperative characteristics

Regarding the intraoperative disparities between the OHR and LHR groups, the median sac size was not significantly different (p = 0.55) between the two cohorts. Specifically, the median sac size within the OHR group was 3 cm (IQR, 3–4 cm), while the LHR group had a size of 4 cm (IQR, 3–5 cm). In the LHR group, the utilization of 3D mesh accounts for 38.1%.

Among the techniques employed within the LHR group, 20 patients (95.2%) underwent the eTEP technique, whereas one patient (4.8%) underwent the TAPP technique. In the eTEP cohort, the predominant method for creating the preperitoneal space involved the use of a balloon space maker (18 patients, 90%). Moreover, a tacker was used to fix the mesh in the eTEP technique in 66.7% of cases (14 patients). Regarding conversion to open surgery within the LHR group, only one of 21 patients required conversion to OHR, constituting a 4.8% conversion rate (Table 2).

Table 2 . Intraoperative characteristics.

Variable	Open (n = 45)	Laparoscopic (n = 21)	p-value
Laparoscopic approach
TAPP	1 (4.8)
eTEP	20 (95.2)
Utilization of balloon space maker in eTEP
Yes	18 (90)
No	2 (10)
Utilization of tacker in eTEP
Yes	14 (66.7)
No	7 (33.3)
Presence of conversion
Yes	1 (4.8)
No	20 (95.2)
Sac size (cm)	3 (3–4)	4 (3–5)	0.55
Use of 3D mesh			<0.001
Yes	0 (0)	8 (38.1)
No	45 (100)	13 (61.9)

Values are presented as number (%) or median (interquartile range)..

3D, three-dimensional; TAPP, transabdominal preperitoneal; eTEP, enhanced view totally extraperitoneal..

Primary outcome

The primary outcome of our investigation, specifically the complication rate, was not significantly different between the OHR and LHR groups (p = 0.50). The complication rate in the OHR cohort was 26.7%, which was slightly higher than that in the LHR cohort (19.0%). Assessment of complications based on the Clavien-Dindo classification system revealed no discernible disparity between the cohorts (p > 0.999). Notably, one patient in the OHR group experienced an intraoperative complication, specifically transection of the spermatic cord, whereas no such complications were observed during LHR procedures. In terms of postoperative complications, no significant difference was observed between the OHR and LHR cohorts (p = 0.76) (Table 3). Postoperative complications observed in the OHR group included seroma (36.4%), hematoma (18.2%), SSI (18.2%), SCE (9.1%), AUR (9.1%), and recurrence (9.1%). Conversely, the LHR group did not present with hematomas, SSI, SCE, or AUR. However, seroma and recurrence occurred in 75% and 25% of the LHR group, respectively.

Table 3 . Postoperative outcomes.

Variable	Open (n = 45)	Laparoscopic (n = 21)	p-value
Complication rate	12 (26.7)	4 (19)	0.5
Clavien-Dindo classification
Class I	2 (16.7)	1 (25)	>0.99
Class II	4 (33.3)	1 (25)
Class IIIA	3 (25)	1 (25)
Class IIIB	3 (25)	1 (25)
Intraoperative complication	1 (2.2)	0 (0)	>0.99
Postoperative complication	11 (24.4)	4 (19)	0.76
Seroma	4 (36.4)	3 (75)
Hematoma	2 (18.2)	0
SSI	2 (18.2)	0
SCE	1 (9.1)	0
AUR	1 (9.1)	0
Recurrence	1 (9.1)	1 (25)
Recurrence rate	1 (2.2)	1 (4.8)	0.54
Revisit rate	7 (15.6)	4 (19)	0.73
Readmission rate	4 (8.9)	1 (4.8)	>0.99
Reoperation rate	3 (6.7)	1 (4.8)	>0.99
No. of opioid doses	0 (0–1)	0 (0–1)	0.17
Length of stay (day)	2 (2–3)	3 (2–3)	0.11
Operative time (min)	35 (30–45)	75 (55–80)	<0.001
Estimated blood loss (mL)	5 (2–5)	5 (5–5)	0.14

Values are presented as number (%) or median (interquartile range)..

SSI, surgical site infection; SCE, spermatic cord edema; AUR, acute urinary retention..

Secondary outcomes

The secondary outcomes, including recurrence rates, revisit rates, readmission rates, reoperation rates, opioid utilization, LOS, OT, and EBL, were not significantly different between the groups, except for OT (p < 0.001). The median OT in the OHR group (35 minutes; IQR, 30–45 minutes) was considerably shorter than that in the LHR group (75 minutes; IQR, 55–80 minutes). The reoperation rate was observed to be three cases in the OHR (6.7%) and one case in the LHR (4.8%). Among these cases, one instance of reoperation in both the OHR and LHR groups was attributed to recurrence. Additionally, the remaining two cases in the OHR group required reoperation due to postoperative expanding hematomas.

Noninferiority graph

We established the noninferiority of various binary outcomes, encompassing complication, recurrence, revisit, readmission, and reoperation rates, between the LHR and OHR groups. Notably, the LHR group demonstrated noninferior outcomes compared with the OHR group across complication, recurrence, readmission, and reoperation rates, considering a predefined 15% noninferiority margin. However, we could not confidently assert noninferiority regarding revisit rates between the LHR and OHR groups, because the horizontal line representing revisit rates crossed the threshold of the noninferiority margin (Fig. 1).

Figure 1. Forest plot comparing laparoscopic inguinal hernia repair (LHR) and open inguinal hernia repair (OHR).

Moving average graphs

Continuous variable data, encompassing OT, EBL, and LOS, were systematically charted according to the sequential order of the surgeries performed to ascertain the stabilization points for each variable, signifying the optimal learning curve phase. OHR reached a stabilization point earlier than LHR, enabling the identification of optimal operation phases based on the parameters. The shaded regions in the plots represent 95%CIs for each surgical group. Across the variables, our findings indicated a significant difference between the LHR and OHR for OT (Fig. 2).

Figure 2. Moving average plot of operative time between the laparoscopic inguinal hernia repair (LHR) and open inguinal hernia repair (OHR) groups.

Cumulative incidence

We analyzed cumulative incidences by comparing recurrence, revisit, readmission, and reoperation rates between the OHR and LHR cohorts. Across all parameters, the cumulative incidence of individuals at risk for recurrence was higher in the OHR group (Fig. 3). However, no significant differences were detected between the two cohorts.

Figure 3. Kaplan-Meier curve and number at risk of recurrence between the laparoscopic inguinal hernia repair (LHR) and open inguinal hernia repair (OHR) groups.

The ratio of open inguinal hernia repair to laparoscopic inguinal hernia repair during the study period

We conducted a comparison of the ratio between LHR and OHR at 3-month intervals during the study period. Our analysis revealed no significant differences between the ratios observed in each 3-month interval (Fig. 4).

Figure 4. Ratio of open inguinal hernia repair (OHR) to laparoscopic inguinal hernia repair (LHR) performing in 3-month interval.

Our analysis revealed no significant differences in the patient characteristics between the OHR and LHR cohorts. Postoperative outcomes also demonstrated no significant differences between the two groups, except for the longer OT required for LHR procedures. The noninferiority chart based on postoperative binary outcomes revealed no inferiorities in complications, recurrence rates, readmissions, or reoperations between the groups.

Our study reported a higher complication rate compared with reports from a high-volume center in Europe. Specifically, our study documented a 19.0% postoperative complication rate (4 of 21), whereas the high-volume center reported a significantly lower rate (0.41%) [23]. Notably, the complications in our study were predominantly minor, with only one of four cases requiring intervention under general anesthesia. This discrepancy may be attributed to the focus of our study on data from recently graduated surgeons, suggesting that the observed higher complication rates may reflect an early trend in their learning curve.

Regarding the recurrence rates, our findings align closely with those of previous studies that examined the learning curves of LHR. Our study reported a recurrence rate of 4.8%, consistent with the recurrence rate of 4.3% reported by Gao et al. [13]. Additionally, Goksoy et al. [24] reported recurrence rates among learning surgeons of 3.1% to 4.9%.

Given the potential for selection bias influencing the ratio of OHR to LHR during the study period, we sought to address this concern through our analysis (Fig. 4). Our findings indicate no significant difference between the OHR and LHR performances within each 3-month interval. We cautiously assert that the observed ratios across different intervals in our study likely did not introduce bias during the investigation.

Our laparoscopic technique primarily involved using the eTEP approach pioneered by Daes in 2012 [15]. This technique was developed to enhance the visualization of the operative field. Our participating surgeon found that eTEP was more comfortable to perform during the learning curve phase than the traditional TEP approach. This preference stems from the extended field of view afforded by eTEP.

The traditional belief that proficiency in open surgical techniques is a prerequisite for mastering laparoscopic procedures has sparked controversy in recent years [25]. While it has been argued that prior open surgical experience aids in transitioning to laparoscopic approaches, the evidence suggests otherwise. The psychomotor skills required for laparoscopic procedures differ substantially from those required for open surgery [26], particularly in operations such as inguinal hernia repair, where the views and anatomies vary significantly between approaches.

Experimental studies have shown no significant differences between experienced and new surgeons performing laparoscopic suturing tasks [27,28]. Only one comparative study indicated that experience improves laparoscopic suturing skills in simulated training [29]. A United Kingdom study assessing surgical skills in medical students with no prior surgical experience found no significant differences in the overall scores between open and laparoscopic techniques (p = 0.057). However, the survey responses regarding the perception of learning indicated that laparoscopic surgery was perceived as more challenging, even after training. Thus, the learning curves for open and laparoscopic surgery may be similar, even for inexperienced individuals [9,30].

In clinical practice, the postgraduate years have been shown to not significantly influence the OT or complication rates in supervised laparoscopic cholecystectomy [31,32]. However, a study from Europe and North America investigating the learning curve of laparoscopic versus open radical prostatectomy revealed that surgeons with prior experience in open radical prostatectomy exhibited significantly poorer outcomes than those whose initial procedure was laparoscopic [33]. This discrepancy highlights the ongoing controversy surrounding the influence of open surgical experiences on the adoption and outcomes of laparoscopic techniques.

To the best of our knowledge, no comparative study has examined the outcomes of OHR versus LHR, specifically among newly graduated surgeons. Our study addresses this knowledge gap by comparing the outcomes of open and laparoscopic approaches in recently graduated surgeons who had undergone only a single cadaveric LHR workshop session and five supervised OHR cases before independently performing both procedures in a rural hospital setting. We believe that our study is the first attempt to compare outcomes among newly graduated surgeons performing LHR.

Based on the noninferior outcomes observed in complication rates, recurrence rates, readmission rates, reoperation rates, EBL, and LOS between OHR and LHR, we conclude that LHR can be safely performed even by newly graduated surgeons without extensive OHR experience.

Conducting clinical trials in actual clinical practice settings, specifically those performed by newly graduated surgeons, can pose significant challenges. An obvious limitation of our study was the small sample size. Our study primarily focused on assessing the outcomes within the learning curve for LHR performed by one recently graduated surgeon, which resulted in a small sample size. This may have affected the external validity. However, future research efforts should prioritize expanding the sample sizes using multicenter study data, encompassing a broader range of surgical procedures, and comparing outcomes between open and laparoscopic approaches. By doing so, we can further dispel the notion that initiating laparoscopic surgery requires prior expertise in open surgical techniques. A comprehensive and robust body of evidence from larger studies across various procedures will help strengthen the confidence in the safety and efficacy of laparoscopic approaches, even among surgeons without extensive open surgery experience.

Ethical statements

This study was approved by the Internal Ethics Committee of Phatthalung Hospital (No. 44-2566), and the requirement for informed consent was waived because it was based on a retrospective design involving the analysis of anonymous clinical data. This study involving human participants adhered to the ethical standards set forth by the institutional and national research committee, as well as the principles outlined in the 1964 Helsinki Declaration and its subsequent revisions or equivalent ethical guidelines.

Authors’ contributions

Conceptualization: Tantinam T

Data curation: Tantinam T, Treeratanawikran T

Formal analysis: Tantinam T, ES, MS

Project administration: TP

Investigation: All authors

Methodology: Tantinam T, PK

Visualization: Tantinam T, MS

Writing–original draft: Tantinam T

Writing–review & editing: All authors

All authors read and approved the final manuscript.

Conflict of interest

All authors have no conflicts of interest to declare.

Funding/support

None.

Data availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.