{"paper_id":"f7a5499c-4539-4650-ab45-4b0d04cb8646","body_text":"Abstract\nObjective\nThe use of energy during minimally invasive surgery is associated with thermal damage that can affect the process of wound healing.\nMethods\nThis was a randomized clinical trial including 78 women who underwent total laparoscopic hysterectomy. Patients were randomized based on the device used for colpotomy, monopolar hook versus harmonic scalpel. The thickness of the cauterized margins in the cervicovaginal tissues of the hysterectomy specimens was measured by the pathologist.\nResults\nThe primary outcome was the amount of lateral thermal damage based on histologic assessment. Secondary endpoints included postoperative pain scores and postoperative complications. Baseline characteristics were comparable between the two groups. The amount of thermal injury in the monopolar group was significantly greater in only one region, the right lateral order of the cuff (3.85 ± 1.01 mm vs. 3.08 ± 0.95 mm (p = 0.001)). With regard to secondary outcome measures, there was no significant difference between the two groups.\nConclusion\nThe use of the harmonic device was associated with significantly less tissue damage during colpotomy in the right lateral cuff region. This is especially important in overweight and obese women in whom the distance between the cervix and the ureter is shorter.\nTrial Registration\nhttps://en.irct.ir/trial/33902?revision=61236. IRCT20180130038567N2.\nKeywords: Surgical diathermy, Thermal destruction, Colpotomy, Laparoscopy, Hysterectomy, Monopolar hook, Harmonic scalpel\nIntroduction\nLaparoscopic hysterectomy (LH) as a mode of minimally invasive surgery (MIS) is being used increasingly for benign and even malignant gynecologic conditions [1]. The many advantages, including better visualization, less intraoperative bleeding, reduced postoperative pain, and faster recovery compared to abdominal hysterectomy have rendered this method more popular among surgeons [1–3]. Total laparoscopic hysterectomy (TLH) is considered more challenging than vaginal-assisted laparoscopic hysterectomy or abdominal hysterectomy mainly due to the skill needed to perform the colpotomy and cuff closure laparoscopically, especially in overweight and obese women [4, 5]. The tissue surrounding the cervix is at risk for bleeding and ureteral injury owing to its proximity to the uterine artery branches and ureters, respectively [5, 6]. Moreover, there is an inverse relationship between the ureteral distance to the cervix and body mass index (BMI). In other words, the ureters are more prone to injury in obese women [7].\nThermal damage adversely affects the process of wound healing of the vaginal cuff and is considered a risk factor for infection, inflammation, and dehiscence [8, 9]. The mean thermal spread of a monopolar instrument with a power of sixty watts (W) activated for one second is 3.5 mm and may extend to over 20 mm in two seconds. The thermal spread for the ultrasonic scalpel, which disrupts hydrogen bonds via the transmission of high-frequency vibration, is only 1.3 mm [10, 11]. According to a systematic review, perioperative outcome is significantly improved when using ultrasonic-based energy compared to traditional energy devices [12]. Ultrasonic and bipolar instruments produce less visual disruption from smoke than monopolar [12, 13]. Carcinogenic compounds have been extracted from electrocautery smoke though it has not yet been directly linked to carcinogenesis in those exposed [14]. Monopolar hook and harmonic scalpel are both frequently used to perform the colpotomy during a TLH [5, 15, 16]. Given the lack of studies comparing monopolar hook and harmonic scalpel, especially regarding thermal damage of the vagina during the laparoscopic hysterectomy, we performed a randomized control trial (RCT) to further investigate potential differences. We hypothesized that the harmonic scalpel would result in less thermal tissue damage.\nMethods\nStudy Design and Patient Selection\nA parallel RCT was conducted at a university-based hospital between October 2018 and March 2019 with registration number IRCT20180130038567N2. The ethics committee of the Iran University of Medical Sciences and the IRCT INSTITUTE obtained ethical approval and IRCT code. Seventy-eight women between the ages of 18–60 years old who were undergoing TLH for benign gynecologic conditions were included in the study. Women with a history of cervical or vaginal malignancy, active vaginal infection during the prior thirty days, medical conditions that affect wound healing, long-term use of corticosteroids, and a history of pelvic irradiation were excluded from the study. For each patient, a questionnaire including medical history was completed. All patients were examined in the clinic and cervicovaginal swabs were collected to test for microorganisms including Gardnerella, Chlamydia, Gonorrhea, E-coli, Mycoplasma, and Trichomonas. After explaining the operation, written informed consent was obtained from every eligible subject. Patients who met the inclusion criteria were randomized to two groups based on the instrument used for colpotomy, either monopolar hook or harmonic scalpel.\nIntervention\nA single laparoscopic surgery team consisting of the two peers of minimally invasive surgery assistant, fellows, and an MIS attending surgeon under the direct supervision of the MIS ward director carried out a standardized method of TLH. The intraperitoneal pressure was maintained between 12 and 16 mmHg. The instruments utilized for each patient were similar including a 10 mm laparoscope with 0° lens and bipolar grasper with power at 40W used for coagulation of the round, utero-ovarian, or infundibulopelvic ligaments. After exploration of the ureters on both sides, the uterine vessels were tied with polyglactin 910 sutures (0 Vicryl; Ethicon, Johnson & Johnson, Somerville, NJ) and cut with laparoscopic scissors. For all subjects, the RUMI® II Koh-Efficient uterine manipulator (Cooper Surgical Inc., Trumbull, CT, USA) was used. Colpotomy was performed in a circumferential manner using either the monopolar hook with 40W pure cutting current or the harmonic shears starting from the anterior border of the cup and cutting in a clockwise manner (Harmonic ACE; Ethicon, Somerville, NJ) at the level 5 power setting. Both fellows were equally familiar with each instrument. Surgical smoke produced while applying energy for hemostasis or during colpotomy was suctioned using the assistant's laparoscopic suction/irrigation system. The uterus was removed vaginally in all cases. The vaginal cuff was closed in the same fashion for all patients. First, the cuff angles were secured using polyglactin 910 sutures (0 Vicryl; Ethicon, Johnson & Johnson, Somerville, NJ) and then the remainder of the cuff was sutured with 0 barbed suture (V-Loc; Ethicon, Johnson & Johnson, Somerville, NJ). In addition to TLH, all the patients underwent bilateral opportunistic salpingectomy. Several other procedures including lysis of adhesions, oophorectomy, ureterolysis, and resection of deep infiltrative endometriosis were also carried out as indicated. Four data points were collected intraoperatively: 1. duration of colpotomy from activation of the instrument to detachment of the uterus measured by chronometer by operating room staff; 2. the total operative time from skin incision until skin closure; 3. estimated blood loss; and 4. intraoperative complications.\nOnce the specimen was removed from the colpotomy site, the cervix was sutured at the 12 o’clock position as a conventional landmark and sent to the pathology department where the vaginal border surrounding the cervix was histologically evaluated to measure the extent of thermal damage. One single pathologist who was blind to group allocation assessed thermal damage. Three-millimeter sections were taken from the cervicovaginal tissue at four zones (at 3, 6, 9, 12 o’clock of the cervical circumference) and stained with hematoxylin–eosin (H&E). The zone of thermal damage characterized by altered staining in the fibromuscular tissue of the vagina was measured using a histologic ruler. Each measurement consisted of the thickness of the cauterized margin of vaginal tissue from the surface using light microscopy (Fig. 1).\nThe primary outcome was the amount of lateral thermal damage. The degree of leukocytosis as a marker of acute inflammation, postoperative pain scores based on the visual analog scale [VAS] scoring system, and postoperative complications were secondary endpoints. Twenty-four hours after the operation, patients were asked to provide a VAS score for pain in three specific sites (the shoulder region, abdominopelvic area including trocar entry sites, and vaginal area). These scores were documented by a nurse who was blind to the study. All patients were evaluated seven days and again six weeks postoperatively and all postoperative complications were reported.\nSample Size and Randomization\nThermal damage of 1 mm was considered clinically significant consistent with similar in vitro and in vivo studies [15, 16]. Using a t test with a two-sided alpha of 0.05 and considering a standard deviation of 1.5 with 80% power and effect size of 1 mm, a sample size of thirty-five (NNT) was confirmed. Given a presumed loss to follow-up around 15%, we decided to enroll 40 patients in each group. A simple randomization method was used. On the day of surgery and before induction of general anesthesia, each patient was randomly assigned to the monopolar group or the harmonic group using sequentially numbered pockets by a study investigator who was not involved in the surgery. Patients and the pathologist were blind to the allocation sequence. The surgeons were aware of the colpotomy device only on the day of surgery. Eighty-two eligible patients were assessed and included in this trial. One patient refused to undergo TLH. Of the remaining, three patients were also excluded due to midline scars and a history of severe adhesions. Therefore, a total of seventy-eight patients were randomized and included in the final analysis with thirty-nine in the monopolar group and thirty-nine in the harmonic group (Fig. 2). Patient characteristics, including age, body mass index, and parity, were similar between both groups (Table 1).\nTable 1.\n| Parameter | Monopolar group (N = 39) | Harmonic group (N = 39) | P value |\n|---|---|---|---|\n| Age a | 39.92 ± 10.62 b | 38.50 ± 11.96 | 0.578 |\n| BMI c | 27.46 ± 5.71 | 28.26 ± 5.54 | 0.532 |\n| Parity | 1.92 ± 0.295 | 2.00 ± 0.381 | 0.874 |\n| Number of vaginal delivery | 1.44 ± 0.289 | 1.58 ± 0.238 | 0.771 |\n| Virgin (%) | 9 (23%) | 14 (36%) | 0.504 |\n| Menopause (%) | 6 (15.4%) | 7 (17.9%) | 0.801 |\n| History of Cesarean Section | 14 (35.9%) | 18 (46.1%) | 0.409 |\n| History of medical diseases d | 10 (25.6%) | 7 (18%) | 0.372 |\n| Indications for surgery | 0.487 | ||\n| Trans-sexual | 12 (30.7%) | 15 (38.4%) | |\n| Endometrial pathology | 10 (25.6%) | 6 (15.4%) | |\n| Endometriosis | 5 (12.8%) | 9 (23.1%) | |\n| Adnexal mass | 5 (12.8%) | 2 (5.1%) | |\n| Leiomyoma | 4 (10.2%) | 2 (5.1%) | |\n| Adenomyosis | 3 (7.7%) | 5 (12.8%) | |\n| Uterine size; Long axise Short axise | 85.65 ± 17.29 | 86.56 ± 17.11 | 0.565 |\n| 49.13 ± 13.73 | 47.14 ± 12.68 | 0.846 | |\n| Uterus weight | 142.45 ± 63.29 | 144.29 ± 105.36 | 0.934 |\n| Cervical diameter | 2.71 ± 0.55 | 2.66 ± 0.67 | 0.805 |\n| Hematocrit (%) | 37.68 ± 3.66 | 38.31 ± 4.04 | 0.469 |\n| White blood cells f | 6938 ± 309 | 7080 ± 262 | 0.727 |\nayears\nbMean ± SD\ncKg/m2\ndIncluded hypothyroidism, diabetes mellitus, hypertension, coronary artery diseases\nemm\nfNumber of cells\nStatistical Analysis\nDescriptive analyses were presented as mean ± SD for continuous, frequency, and percentage for categorical variables. The normal distribution of data was assessed using the Kolmogorov–Smirnov test. Categorical variables were compared by using the chi-square test or Fisher’s exact test. Continuous variables were compared using the independent t test. The linear regression was applied to predict the effect of dependent variables, right lateral border, and independent variables which were significant in the independent t-test (P < 0.05), including surgery duration, Colpotomy mode, and Colpotomy duration. The statistical analyses were used using SPSS-20 software (SPSS Inc., Chicago, IL). The level of significance of statistical tests was 0.05.\nResults\nOverall, 82 patients were assessed for eligibility and were included in this trial. One patient refused to undergo a laparoscopic hysterectomy. Of the remaining, two patients in the monopolar group and one patient in the harmonic group were excluded after randomization because the TLH converted to abdominal hysterectomy due to severe adhesions in two patients and ureteral injury in one patient. Therefore, a total of 78 patients, 39 in the monopolar group and 39 in the harmonic group, were included in the final analysis (Fig. 2). Patient characteristics including age, body mass index (BMI), and parity were similar between groups (Table 1).\nRegarding lateral thermal damage, the amount of thermal injury to the right lateral border of the cervix was significantly different between the two groups, 3.85 ± 1.01 mm for the monopolar group versus 3.08 ± 0.95 mm for the harmonic group (p = 0.001). Mean lateral thermal damage to the anterior, posterior, and left lateral borders was clinically milder in the ultrasonic blade group, but it was not statistically significant between the two groups (p > 0.05) (Table 2). The time needed for the colpotomy was significantly shorter in the monopolar group compared to the harmonic group, 8.47 ± 1.54 min versus 9.97 ± 2.07 min, respectively (p = 0.001), but total operative times were not significantly different between the groups. The degree of leukocytosis between the groups six hours after surgery was comparable (p > 0.05). VAS scores for both vaginal and shoulder pain after twenty-four hours did not show a significant difference between the two groups (p > 0.05).\nTable 2.\n| Parameter | Monopolar group | Harmonic group | P valuea | Cohen’s d effect size | 95% Confidence interval of the difference lower upper | |\n|---|---|---|---|---|---|---|\n| Thermal damage b Anterior border | 3.26 ± 1.07 c | 3.23 ± 1.28 | 0.924 | 0.0001 | − 0.508 | 0.509 |\n| Posterior border | 3.49 ± 1.47 | 3.15 ± 1.01 | 0.247 | 0.018 | − 0.235 | 0.902 |\n| Right lateral border | 3.85 ± 1.01 | 3.08 ± 0.95 | 0.001 | 0.135 | 0.325 | 1.214 |\n| Left lateral border | 3.33 ± 1.08 | 2.92 ± 0.81 | 0.062 | 0.045 | − 0.21 | 0.841 |\naUsing Student’s t test\nbmm\ncMean ± SD\nWith regard to other surgical endpoints including blood loss, hematocrit level change, and transfusion rate, no significant difference was found between the groups (Table 3). As for postoperative complications, three patients in the monopolar arm and one in the harmonic arm had complaints of trivial bleeding, which were all managed expectantly (p > 0.05). Four patients in the monopolar group and three patients in the harmonic group developed a fever within the first postoperative week. All were treated effectively using broad-spectrum antibiotics. One patient in each group developed cuff cellulitis (p > 0.05). There was no dehiscence as the late complication of TLH among our patients.\nTable 3.\n| Parameter | Monopolar group | Harmonic group | P value |\n|---|---|---|---|\n| Vaginal paina (VAS score) | 1.67 ± 0.19 b | 1.62 ± 0.17 | 0.839 |\n| Shoulder paina (VAS score) | 2.13 ± 1.19 | 2.05 ± 1.11 | 0.267 |\n| Operative blood lossc | 63.81 ± 27.53 | 36.71 ± 26.04 | 0.477 |\n| Hematocrit change (%) | 2.66 ± 0.40 | 2.88 ± 0.34 | 0.67 |\n| Secondary Leukocytosisd | 9697 ± 2276 | 7650 ± 406 | 0.381 |\n| Surgery duratione | 132.95 ± 41.7 | 119.00 ± 36.64 | 0.118 |\n| Colpotomy duratione | 8.47 ± 1.54 | 9.97 ± 2.07 | 0.001 |\n| Transfusion (%) | 0 | 2 (5) | 0.494 |\n| Fever (%) | 4 (10) | 3 (8) | 0.489 |\n| Cuff bleeding (%) | 3 (7.7) | 1 (2.5) | 0.305 |\n| Cuff cellulitis (%) | 1 (2.5) | 1 (2.5) | 0.986 |\naPain after 24 h based on visual analogue scale\nbMean ± SD\ncml\ndThe increase in white blood cell count 6 h after surgery\nemin\nThe confounding variables (surgery duration, Colpotomy mode, Colpotomy duration) were controlled using the linear regression analysis, which revealed Colpotomy mode had a significant effect on the right lateral border (B = − 0.618, p < 0.05). So, on average, the monopolar group reported a right lateral border score that is 0.618 points higher than the harmonic group (Table 4).\nTable 4.\n| Unstandardized coefficients | Standardized coefficients | T-score | P value | 95.0% Confidence interval for B | |||\n|---|---|---|---|---|---|---|---|\n| B | Std. Error | Beta | Lower bound | Upper bound | |||\n| Colpotomy mode | − .618 | .257 | − .295 | − 2.405 | .019 | − 1.130 | − .106 |\n| Colpotomy duration | − .045 | .065 | − .083 | − .689 | .493 | − .173 | .084 |\n| Surgery duration | .005 | .003 | .163 | 1.420 | .160 | − .002 | .011 |\nDependent variable: right lateral border\nDiscussion\nThis study was designed to compare thermal complications of the two devices commonly used for colpotomy at the time of TLH. We had expected to see less thermal spread in the harmonic group. However, although the amount of thermal injury in the four zones of the cervical section was greater in the monopolar group, this difference was statistically significant only on the right lateral zone or 9 o’clock position. This is mainly because many factors affect the amount of energy transferred to tissue using either the electrosurgical or harmonic device including the current intensity, blade characteristics, tissue tension, type of the tissue and its pathology, surgical technique, and device activation time [17, 18]. Generally speaking, laparoscopic surgery is associated with less inflammatory response as it causes less tissue damage [19]. Also, one popular device used for laparoscopic hysterectomy is the Harmonic scalpel which produces tissue effects by converting electrical energy into vibrations at more than 20,000 cycles per second which is above the audible range. It has got approval of the US food and drug administration (FDA) for sealing vessels up to 5 mm in diameter [20]. In a study carried out by Manoj et al. comparing harmonic scalpel with conventional electrocautery for dissection and hemostasis during laparoscopic cholecystectomy, harmonic instrument offered effortless dissection with good hemostasis [21]. But failing to reliably seal larger than 5 mm vessels, like the infundibulopelvic and uterine pedicles, is the main disadvantage of the harmonic device which makes surgeons use bipolar energy for safety issues [22–24]. This is why we used bipolar energy for coagulation of the main vascular pedicles in both groups. Therefore, changes with regard to serum inflammatory markers could also have resulted from the use of this energy source. However, according to our findings, the degree of leukocytosis was comparable in both groups. Toz et al. studied the inflammatory response in patients who underwent laparoscopic hysterectomy and bilateral salpingo-oophorectomy for benign gynecologic pathology using four different energy instruments, ligasure, and monopolar cautery in one group and harmonic plus conventional bipolar cautery in another group. According to their results, more inflammatory changes in serum markers were seen in the first group but none of these were of significant clinical importance [25]. Therefore, our main concern was to measure the thermal effect and charring of the tissue in the cervical tissue which can directly affect adjacent organs. Most of the studies found in this line are in vitro studies. Hefermehl et al. studied the influence of the time, power setting, and Maryland forceps as a heat sink in the thermal spread in a study using bovine muscle fascia and found that increase in either time or power significantly increases thermal damage. When the harmonic power setting was increased from level 1 (30 W) to level 5 (90 W), thermal spread increased from 1.1 mm to 1.8 mm. The thermal spread reached nearly 3 mm when the device was activated for about four seconds [11]. The only similar in vivo study is by Choi et al., in which the Harmonic hook blade and monopolar devices utilized for colpotomy were compared in terms of lateral thermal damage and surgical smoke. Although lateral thermal injury in the Choi et al. study was significantly higher for the monopolar group than the ultrasound group (1.5 mm versus 0.95 mm), due to the fact that this difference was only 0.5 mm, the authors did not regard it as clinically significant [26]. However, it should be mentioned that they measured thermal spread at only one undefined location on the cervix, which is in contrast to our study where four critical sites were evaluated to better delineate areas at greater risk of thermal damage. All these four sites are of paramount importance due to their proximity to critical organs; the bladder in the anterior, the rectum in the posterior, and the ureters at the lateral locations. In a study by Hurd et al. determining the location of ureters in relation to the cervix by computed tomography, the ureter was within 5 mm of the cervical margin in 12% of women studied [7]. This finding further adds to the importance of the thermal injury to the lateral margins of the cervix. In another radiological study by Gemer et al., the right ureter was significantly closer to the cervix than the left [27]. Therefore, it is crucial to be more cautious when working near the cervix's lateral margins, especially during laparoscopic hysterectomy and when energy is applied during colpotomy. Our measures were about three times higher than that of Choi et al. study [26]. Also, the difference in thermal damage between the two devices was only significant for the right lateral border where the right ureter is highly at risk. We can justify these results in these ways: Firstly, the patient population between the two studies varied, with ours having a lower mean age and a lower rate of vaginal delivery, two factors leading to thicker vaginal tissue [28]. Secondly, more patients in our study were overweight with BMI > 25 (Table 1). In overweight patients, the hyper vascularity and distance between the right and left lateral trocars is increased and surgical ergonomics may be compromised [29]. This may explain the increased activation time and force applied on tissue, resulting in a greater thermal spread in our study, particularly on the right side. In addition, the surgeons in our study were in training and likely less experienced, which could also explain the longer colpotomy duration (9.97 ± 2.07 min for the harmonic group and 8.47 ± 1.54 min for the monopolar group in our study compared to 7.2 ± 2.8 min for the harmonic group and 4.1 ± 1.2 min for the monopolar group in Choi et al.). Regardless, both studies found that colpotomy took longer with the harmonic device compared to the monopolar device, meeting statistical significance (p < 0.001) [26]. While this difference did not reflect a change in the thermal spread measured in our study, efficiency in the operating room is important to decrease the times patients are under anesthesia and operating room costs.\nThe difficulty of the colpotomy was a category captured by Choi et al., who found that colpotomy with the Harmonic hook blade was rated as easier to perform than with the monopolar device despite the longer colpotomy time. While we did not rate the difficulty in our study, our surgeons subjectively found the Harmonic shears handpiece bulky and more difficult to handle during the colpotomy since the jaws would not rotate when closed, while the monopolar device could be grasped like a pen making it easier to handle. We believe that the higher BMI of our patients had also influenced the handling of the instruments. Additionally, previous laparoscopic and open pelvic surgery, obliterated posterior cul-de-sac, and post-menopausal atrophic changes also influence the colpotomy timings. The smoke produced by monopolar devices can make colpotomy more difficult by obscuring the view and requiring breaks in surgery to wait for the operation field to be cleared [14]. However, since our assistant surgeon suctioned the surgical smoke during colpotomy, we were able to maintain an adequate view even with the monopolar device. In addition, peritoneal irritation and phrenic nerve stimulation resulting from gas retention in the peritoneal cavity have been suggested as causes of postoperative shoulder pain following laparoscopic surgeries [30, 31]. Our postoperative VAS scores for shoulder pain after twenty-four hours were not significantly different between the groups. This finding could be because surgical smoke was evacuated from the abdominal cavity both throughout the operation and at the end of the surgery in reverse Trendelenburg position.\nPostoperative complications related to vaginal cuff, including bleeding and vaginal cuff dehiscence, could result from vaginal tissue damage and necrosis following the use of thermal energy at the time of colpotomy. Beran et al. looked at vaginal cuff perfusion in twenty patients undergoing LH where two sources of energy (ultrasonic and monopolar) and two suture types (barbed and non-barbed) used for cuff closure were compared. Following intravenous injection of indocyanine green (ICG), laser angiography of the cuff prior to and after suturing showed fluorescence to a similar degree of perfusion with no recorded complications [32]. Another study assessed the thermal damage caused in the vagina in swine models that underwent laparoscopic hysterectomy. According to this study, all energy types resulted in lateral thermal damage with the least from the harmonic device and the most from bipolar cautery [15]. In our study, although the overall rate of vaginal complications (including bleeding cuff cellulitis was comparable between the two groups (Table 3), it was twice in the monopolar group (four versus two cases) suggesting that the use of monopolar energy could have had an effect on these complications. The major strength of this study is that patients were randomized with comparable baseline characteristics and blinding to treatment allocation minimizing selection bias. The same surgical team performed all of the surgeries which limits intervention bias. In addition, the pathologist was blind to the groups and examined multiple samples of the cervicovaginal tissue to delineate the effects of thermal damage better.\nThis study had also some limitations. First, our pathologist evaluated thermal damage by measuring the cauterized zones in samples stained by H&E. There are specific dyes available for collagen staining, like picrosirius red dye, which can show degraded collagen fibers more precisely with the help of electron microscopes [33]. Furthermore, the thermal spread on the specimen is a proxy for the thermal spread on the vaginal cuff. There are other highly accurate ways of evaluating thermal spread using infrared cameras and temperature probes, but this was not financially feasible for our study [34, 35].\nSecond, in addition to leukocytosis, we could have measured other inflammation markers, which could suggest the degree of tissue necrosis, like C-reactive protein or interleukin-6 [35]. Third, the colpotomy time does not account for actual device activation time within in, so it is impossible to determine if the activation time was different between the two groups and if that could be responsible for our findings. Limited sample size could be another limitation since with more patients more robust results smaller effect size could have been achieved i.e., less than 1 mm. In our view, however, the smaller difference in thermal damage did not provide any clinical significance in the other three cervical margins. In similar studies, where two energy sources or two manipulators were compared regarding resultant thermal damage being made in tissues, the extent of the thermal injury was too small to signify any clinical relevance [8, 16, 26].\nConclusion\nThe work showed that harmonic scalpel was associated with significantly less tissue damage. This is especially important at the right lateral part of the colpotomy, where the right ureter is even more in danger of thermal damage when compared to the monopolar hook. This suggests that an ultrasonic scalpel can be used with fewer concerns regarding excessive thermal damage. This is especially important in overweight and obese women since the distance between the cervix and the ureters is shorter and the vessels are more prominent in this group of patients. Based on this finding, one may recommend using a harmonic scalpel instead of a monopolar device, especially in obese patients and by less experienced surgeons. However, using energy sources in OBGYN surgeries is highly individualized and subject to availability, expertise with specific sources, and patient factors. Thermal damage may change pathological reporting, a concern in oncological surgeries.\nAcknowledgements\nWe are grateful to the personnel of the Endometriosis Research Center for helping us with the collection and documentation of data. We also thank the staff of the operating room of the Rasoul-e-Akram Hospital for their cooperation in performing this project. We also appreciate the help of Catherine Breed, employed by Becton Dickinson, in helping to condense the manuscript. No compensation was provided to those acknowledged.\nFunding\nThis study has been financially supported by the Iran University of Medical Sciences, which was not involved with study design, data collection, analysis, interpretation of data, writing of the report, and/or decision to submit the article for publication.\nData Availability\nData will be available by request.\nDeclarations\nConflict of interest\nThe authors have no conflicts of interest to declare that are relevant to the content of this article.\nEthical Approval\nThe ethics committee of the Iran University of Medical Sciences and the IRCT INSTITUTE obtained ethical approval and IRCT code.\nInformed Consent\nWritten and informed consent obtained from the participants.\nFootnotes\nMansoureh Gorginzadeh is a Gynecologist, Obstetrician, Laparoscopic Surgeon; Abolfazl Mehdizadehkashi is a Professor, Gynecologist, Obstetrician, Laparoscopic Surgeon; Shahla Chaichian is Professor, Gynecologist, Obstetrician, Laparoscopic Surgeon; Kobra Tahermanesh is a Associated professor, Gynecologist, Obstetrician, Laparoscopic Surgeon; Samaneh Rokhgireh is a Assistant professor, Gynecologist, Obstetrician, Laparoscopic Surgeon; Pegah Babaheidarian is a Associate Professor, Pathologist; Elaheh Afshari is Gynecologist, Obstetrician, Laparoscopic Surgeon; Banafsheh Nikfar is a Ph.D. Student; Atena Asiaii is a Gynecologist, Obstetrician, Laparoscopic Surgeon; Farr Nezhat is a Professor, Gynecologic Oncologists, Laparoscopic Surgeon\nPublisher's Note\nSpringer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.\nReferences\n- 1.Nieboer TE, Hendriks JC, Bongers MY, Vierhout ME, Kluivers KB. 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Acta Cirurgica Brasileira. 2017;32:576–86. [DOI] [PubMed] [Google Scholar]\nAssociated Data\nThis section collects any data citations, data availability statements, or supplementary materials included in this article.\nData Availability Statement\nData will be available by request.","source_license":"public-domain-us","license_restricted":false}