Comparison of different suture techniques for laparoscopic vaginal cuff closure

Laparoscopic hysterectomy is a commonly performed procedure. However, one high-risk complication is vaginal cuff dehiscence. Currently, there is no standardization regarding thread material or suturing technique for vaginal cuff closure. Therefore, this study aimed to compare extracorporeal and intracorporeal suturing techniques for vaginal cuff closure using a pelvic trainer model. Eighteen experts in laparoscopic surgery performed vaginal cuff closures with interrupted sutures using intracorporeal knotting, extracorporeal knotting and continuous, unidirectional barbed sutures. While using an artificial tissue suturing pad in a pelvic trainer, experts performed vaginal cuff closure using each technique according to block randomization. Task completion time, tension resistance, and the number of errors were recorded. After completing the exercises, participants answered a questionnaire concerning the suturing techniques and their performance. Experts completed suturing more quickly (p < 0.001, p < 0.001, respectively) and with improved tension resistance (p < 0.001, p < 0.001) when using barbed suturing compared to intracorporeal and extracorporeal knotting. Furthermore, the intracorporeal knotting technique was performed faster (p = 0.04) and achieved greater tension resistance (p = 0.023) compared to extracorporeal knotting. The number of laparoscopic surgeries performed per year was positively correlated with vaginal cuff closure duration (p = 0.007). Barbed suturing was a time-saving technique with improved tension resistance for vaginal cuff closure.

meta-analysis by Bogliolo et al. 16 showed that barbed sutures are safe, as well tolerated as traditional sutures, and associated with reduced durations of laparoscopic vaginal vault closures.A number of studies compared it to other traditional techniques, mostly continuous cuff closures and to closure devices such as the Endo Stich [17][18][19][20] .However, to our knowledge, no study has compared the barbed suture to intracorporeal and extracorporeal suturing techniques in relation to knot strength and cuff closure spread ability as well as suturing time.
Therefore, the aim of this study was to compare different types of suture materials and knotting techniques using Vicryl 2/0 (intracorporeal knotting), Vicryl 2/0 (extracorporeal knotting), and V-Loc 180 3/0 in cuff closures using an ex-vivo model and to examine whether the extracorporeal knotting technique had comparable benefits in reducing operating times and tension resistance.

Study design
We conducted a randomized study at the University Hospital Basel from the 1 st November 2021 to 30th April 2022.The required sample size was estimated using a pragmatic approximation.Eighteen participants were randomized in block randomizations of three.All participants performed interrupted intracorporeal, extracorporeal, and continuous barbed suturing for VCC using each technique according to their randomization.For the primary endpoint, the time required to complete a task was recorded during each participant's performance.Following the task, the secondary endpoints (i) precision, (ii) knot strength, (iii) cuff closure spread ability, and (iv) number of mistakes made were measured.Before and after completing the tasks, participants were given questionnaires.
The first asked about their background and the second about their experience while completing the exercises (Fig. 1).All methods were carried out in accordance with the CONSORT statement guidelines.

Study population
In total, 18 experts were successfully recruited with a dropout rate of zero, and 54 measurements were obtained.Qualifying as an expert required one to be a surgeon with more than five years of operative experience and more than thirty laparoscopic interventions per year.Study participants were recruited from one tertiary and three secondary hospitals.All participants gave their written, informed consent to participate in the study.The anonymization of personal data was guaranteed.

Instrument set-up
All exercises were carried out on a box trainer.An endoscopy tower was equipped with a 24-inch monitor and a 300 W Xenon light source (Karl Storz SE & Co., Tuttlingen, Germany) and a Storz Hopkins II, 10 mm, 0° telescope with a Xenon Nova 300 light source and an Image 1 H3-Z Full HD camera (Karl Storz SE & Co., Tuttlingen, Germany) was used.Two access points equivalent to the lateral ancillary trocar entry points were used for the instruments.Two needle holders (Geyl Medical 801.023), laparoscopic scissors, and a closed jaw type knot pusher (Karl Storz 26596 D closed jaw end) were used.

Exercises
The colpotomy model was made of mesh-augmented silicone with a similar shape and size as a real colpotomy and was set up on the posterior wall of the box trainer.A brief instructional video showed the three different suturing techniques.After a short individual warm-up (20 min maximum) the experts began the different suturing techniques according to their randomization, completing one run per suture type for three runs in total.Vaginal cuff closure with barbed continuous suturing Suture C was a continuous, unidirectional barbed suture made with V-Loc™ (180 Absorbable Wound Closure Device; Covidien, Mansfield, MA, USA).This suture was made unidirectional.Thus, after the first stitch, the thread was pulled through the loop.After 5 more stitches from right to left, the thread was cut at the end of the colpotomy without extra anchoring stitches (Video 3).

Questionnaires
Participants answered questionnaires before and after the exercises.The questionnaire given before the exercises concerned general participant characteristics including sex, age, whether and how often they played video games, what types of sports and instruments they played, and their background regarding surgical and technical skills.
After completing the exercises, participants answered a questionnaire regarding how they felt, both mentally and physically, about their experience with the different suturing techniques.

Statistical analyses
Descriptive statistics are presented as counts and frequencies for categorical data.For metric variables, means with standard deviations, medians, and interquartile ranges were used.Linear mixed-effects models were used to predict spreading capacity with technique and run as predictor variables.Results are presented as mean differences.For total run time and changes in knot strength, the variables were log transformed, and the results presented as geometric mean ratios.A p-value < 0.05 was considered significant.The statistical software R (version 4.1.3)was used for the analyses.

Ethical approval and consent to participate
All study activities were conducted in accordance with Institutional Review Board (IRB) guidelines for exempt studies.All methods were carried out in accordance with relevant guidelines and regulations.A formal IRB certification of exemption (Req-2021-01075) was provided by the ethics committee of Northwest and Central Switzerland (EKNZ) on the 21st of September 2021.The EKNZ can confirm that the research project (Req-2021-01075) fulfilled the general ethical and scientific standards for research with human subjects.All participants gave their written informed consent to participate in this study.The anonymization of personal data was guaranteed.

Participant characteristics
In total, 18 experts were included with 66.6% (12/18) being male and 33.3% (6/18) female.The mean age was 40 years.Six experts were trained gynecologists, 11 were trained surgeons, and one expert had completed training in both specialties.On average, the experts were trained in laparoscopic procedures for 10.2 years (range: 5-20) years and performed 83 (30-250) laparoscopies annually (Table 1).

Time
The barbed suture (suture C) led to significantly faster times with a mean of 7.55 min compared to the intracorporeal suture (suture A; mean = 15.46 min; p < 0.001) and extracorporeal knotting (suture B; mean = 17.23 min; p < 0.001).Furthermore, there was a significant difference between the interrupted A and B sutures (p = 0.04).Sutures A and B were consistently slower compared to suture C independent of the first, second, or third run, and the median time for the extracorporeal knot suture varied widely between the experts.However, the experts sutured significantly faster in the third run compared to the first and second run (run 1/2 p = 0.899, run 1/3 p = 0.048, and run 2/3 p = 0.036) (Tables 2 and 3; Fig. 2).

Stitch precision
The cumulatively added distance of stitch imprecision for each suture technique was 8.91 mm for suture A, 10.33 mm for suture B, and 7.06 mm for suture C. Concerning the added distance deviation, there was no significant difference between the sutures themselves (A/B p = 0.811, A/C p = 0.12 and B/C p = 0.132) or between the individual runs (p > 0.05).

Tension resistance
The colpotomy cuff without traction had a mean baseline looseness between the figure-eight knots of sutures A and B, which was significantly more than in suture C (A/C p = 0.002, B/C p = 0.003).There was no significant difference between sutures A and B (p = 0.832 www.nature.com/scientificreports/

Knot strength
The knot strength of the first knot in suture C compared to A and B under a 5 N pull was significantly stronger (A/C p = 0.003, B/C p < 0.001), while B knot strength was significantly stronger than A (A/B p = 0.034).Under 10 N and 15 N conditions, the same results, with C being significantly stronger, was observed (A/C p < 0.001, B/C p < 0.001).The knot strength of the second knot showed that suture C was significantly stronger than A under 5, 10 and 15 N (p = 0.017, p = 0.018, and p = 0.003, respectively).Suture C was also significantly stronger than suture B under 15 N (p = 0.03).The knot strength of the third knot showed a significant difference between C and B under 10 and 15 N (p = 0.045, p = 0.006), and a significant difference between C and A under 5 N (p = 0.026).
The p-values of the other comparisons were not significant.

Mistakes
In total, there were two errors, and both were statistically insignificant (p = 0.71).

Questionnaire results
General demographic parameters such as gender, age and leisure activities (gaming, instruments, or ball sports) did not have significant effects on the simulation outcomes (p > 0.05).In addition, the medical specialty (gynecology versus surgery) did not demonstrate a significant impact on tension resistance or time (p = 0.413 and p = 0.298, respectively).However, experts that were already habituated to the V-Loc™ suture were significantly faster than those not as experienced with the suture material (p = 0.003).A positive, significant association www.nature.com/scientificreports/ between precision and a faster suture time was observed (p = 0.004).Experts who are performing more laparoscopic surgeries per year were significantly faster in completing the tasks (p = 0.007).Importantly, the surgeon's years of experience did not correlate with suturing time (p = 0.293) (Table 4).

Discussion
The hypothesis that interrupted sutures with extracorporeal knots perform as well as intracorporeal interrupted and continuous barbed sutures for VCCs could not be verified.However, we found that the continuous barbed colpotomy closure technique performed significantly better in terms of time and cuff resistance to tension than interrupted sutures.Concerning the primary endpoint, the use of the continuous barbed suture resulted in significantly faster closures of the colpotomy cuff.The barbed, continuous suture does not require knots, which likely accounted for the difference in suturing time, yet represents a major technical challenge for many surgeons 21 .In line with our findings, previous research has shown that the use of continuous barbed sutures, compared to interrupted stitches, results in shortened operative time during laparoscopic hysterectomies 10,16,22 .Moreover, it has been demonstrated that the barbed knotless suture is quick and easy to learn, and expert surgeons as well as trainees can perform faster wound closures with this type of thread compared to interrupted sutures 23 , which can lead to saving time in the OR and reducing costs 10,16,22 .
Our data also demonstrated that with each run the experts were faster in finishing their sutures-independent of the suturing technique-with run number three being the overall fastest for all experts.This was also reflected in the questionnaire results where the number of laparoscopic surgeries performed per surgeon was significantly more important in regard to faster suturing times than the overall surgical experience in years.
We found a significantly higher ability to withstand tension for the continuous suture technique compared to the interrupted closure one, independent of intra or extracorporeal knotting.In this instance, the increased tension resistance of the continuous suture technique could potentially translate to a reduced incidence of VCD.VCD is the most severe complication following a hysterectomy and can lead to evisceration.Thus, patients, in most cases, need to be admitted to the hospital for further treatment [5][6][7] .Therefore, cuff dehiscence is an issue of major concern for gynecologists and different methods of cuff closure have been proposed for improved outcomes.However, to accurately predict the effect of the three different suturing techniques on the incidence of VCD, a prospective randomized trial in vivo needs to be performed.The literature suggests that interrupted and continuous (barbed or braided) suturing techniques have similar outcomes concerning VCD, irrespective of thread material 16,24,25 .Concerning the thread material, studies have shown that continuous cuff closures had a comparable risk of VCD regardless of the thread material (barbed versus braided/monofilament) 25,26 .Some risk factors associated with VCD are known to be patient-specific such as coitus, cuff infection or hematoma, or chronic coughing in the postoperative period 27,28 and could not be objectively accounted for in this study.Apart from these parameters, tissue injury related to surgical thermal devices are regarded as other potential causes for VCD.Amongst these devices, it has been shown that ultrasonic dissection causes the least tissue damage, whereas monopolar and bipolar energy may cause deeper tissue necrosis 29 .Table 4. Correlations between the parameters from the questionnaire and the outcomes of run time, stitch precision, and tension resistance.a The p-values were calculated using Kruskal-Wallis test or Spearman correlation as appropriate.A p-value < 0.05 was considered significant.The principal limitation of our study was the ex-vivo setting.In comparison, in-vivo tissue is fragile and can bleed, depending on where it is stitched or held by the needle holder, which can influence operation time and the visibility of puncture sites.Furthermore, the colpotomy surrounding ex-vivo tissue is stable and clean without confounding factors such as bleeding, bowel movements, or camera problems.However, all participants in this study had the same conditions, and no confounders influenced the results.Another limitation concerns the comparison between interrupted and continuous suture techniques, which was difficult due to differences in material and physical suture mechanisms; although, the material used in our study is considered to be standard.In addition, in our ex vivo setting, we were not able to measure the risk of the rare but serious complication of bowel obstruction 30,31 and other long-term outcomes such as vaginal pain and dyspareunia following the use of barbed sutures for VCC 32 .
One strength of our study was the inclusion of 18 experts, which provided an extensive data set of measurements and reduced the selection bias that can occur in trials where only a few surgeons perform operations.Moreover, we were able to compare three different suturing techniques due to the ex-vivo setting.Finally, we were able to measure knot strength and cuff closure spread ability, which would not be possible in a patient setting.

Conclusions
The results of our study suggest that the barbed suture is a time-saving technique with increased tension resistance for VCC.However, prospective randomized controlled studies in the OR are needed to validate these findings and standardize laparoscopic cuff closures.

Figure 1 .
Figure 1.Flow diagram of the study design.

Figure 2 .
Figure 2. A comparison of the three different suturing techniques for (A) time, (B) tension resistance, and (C) precision according to the geometric mean ratio.
Vaginal cuff closure with intracorporeal interrupted suturing Suture A was a closure technique using three interrupted figure-eight sutures and intracorporeal knotting with a polyfilament thread (Vicryl, polyglactin 910, Johnson & Johnson).These three sutures were performed with a surgeon's knot, which translated to securing the knot with three loops (Video 1).

Table 1 .
General expert characteristics and questionnaire results.n, number.

Table 2 .
Comparison of different suturing techniques by time, knot strength, tension resistance, precision, and mistakes.a The p-values were calculated using a mixed-effects model.A p-value < 0.05 was considered significant.

Table 3 .
Overall descriptive statistics of the measured parameters time, stitch precision, and tension resistance (0 and 10 Newton) for all three laparoscopic knot techniques for every run.a SD, standard deviation.b IQR, interquartile range.