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Harmonic Scalpel Compared to Conventional Hemostasis in Thyroid Surgery: A Meta-Analysis of Randomized Clinical Trials

Harmonic Scalpel Compared to Conventional Hemostasis in Thyroid Surgery: A Meta-Analysis of... Hindawi Publishing Corporation International Journal of Surgical Oncology Volume 2010, Article ID 396079, 8 pages doi:10.1155/2010/396079 Review Article Harmonic Scalpel Compared to Conventional Hemostasis in Thyroid Surgery: A Meta-Analysis of Randomized Clinical Trials Adrienne L. Melck and Sam M. Wiseman Department of Surgery, Saint Paul’s Hospital, University of British Columbia, C303-1081 Burrard Street, Vancouver, BC, Canada V6Z 1Y6 Correspondence should be addressed to Adrienne L. Melck, melckal@upmc.edu Received 23 August 2009; Revised 9 November 2009; Accepted 6 December 2009 Academic Editor: Perry Shen Copyright © 2010 A. L. Melck and S. M. Wiseman. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. The study’s aim was to determine whether conventional hemostasis (CH) or the Harmonic Scalpel (HS) results in shorter operative times for thyroidectomy and to evaluate the incidence of postoperative complications with each approach. Methods. A literature search was conducted from study inception to September 30, 2008. Included studies randomized thyroidectomy patients to either CH or HS and reported the incidence of postoperative transient recurrent laryngeal nerve dysfunction (RLND) and hypocalcemia. Results. Nine RCTs were included. Use of the HS reduced operative time by 23.1 minutes (95% CI = 13.8, 32.33). There was no difference in the incidence of transient RLND (RR = 1.25, 95% CI = .56, 2.76), but a lower rate of transient hypocalcemia with the use of the HS (RR = .69, 95% CI = .51, .92). Conclusions. The use of HS in thyroidectomy significantly reduces operative time and is associated with a reduction in postoperative hypocalcemia compared to CH. 1. Introduction tissue injury, a lack of neuromuscular stimulation, and the avoidance of electrical energy transmission either to There have been few developments in the technical aspects or through the patient [3]. Since the adoption of the of thyroid surgery since the surgical approach described by Harmonic Scalpel (HS) into modern surgical practice, its Kocher greater than a century ago [1]. Given the significant utility for a wide variety of operations has been well vascularity of the thyroid gland [2] and the relatively small documented. For example, a randomized prospective clinical operative field, meticulous hemostasis has and will always be trial demonstrated its ability to diminish blood loss as well as an important prerequisite for a successful outcome in thyroid operative time for laparoscopic Nissen fundoplication [4]. surgery. The mainstay for achieving hemostasis in thyroid Over the last decade, many reports have evaluated the surgery has been tying and/or clipping of blood vessels, utility of the HS for thyroid surgery and the majority of both effective but time-consuming techniques. In the current these studies have been carried out at European centers. The climate of healthcare constraints and long surgical waiting investigators have shown similar results regarding reduced lists, any methodology that can reduce operative times operative times with its utilization, but conflicting results while maintaining acceptable complication rates warrants regarding other postoperative outcomes such as transient investigation. postoperative hypocalcemia and recurrent laryngeal nerve The Harmonic Scalpel (Ethicon Endosurgery, Cincin- dysfunction (RLND). These complications are relatively nati, Ohio) was introduced into the surgeon’s armamentar- uncommon and the number of cases reported in individual ium almost two decades ago. Using mechanical vibrations studies is limited. Consolidating the data may allow for at 55.5 kHz, this device is able to cut and coagulate tissue elucidation of significant associations between HS utilization simultaneously. The proposed advantages of using this device and postoperative complications. To date, no meta-analysis over traditional electrocautery include less lateral thermal evaluating the utilization of HS in thyroid surgery has 2 International Journal of Surgical Oncology been reported. The purpose of this study was to determine not describe how postoperative hypocalcemia was defined. whether conventional hemostasis (CH) or the HS results in Although studies could report on a variety of secondary shorter operative times for thyroidectomy and to evaluate postoperative outcomes (e.g., amount and/or duration of the incidence of postoperative complications with each wound drainage, postoperative hematoma formation, pain, approach. analgesic requirements, time to hospital discharge, cost- effectiveness), they were excluded if they did not report these two specific outcomes. 2. Methods To be included, studies had to be prospective, ran- domized clinical trials and observational studies were not 2.1. Identification of Trials. We sought to identify prospec- included in the analysis. Clearly blinding is not feasible in tive, randomized clinical trials comparing HS to CH methods studies evaluating two different surgical techniques, though (i.e., ties, clips, and/or electrocautery) for thyroidectomy it was noted if assessors of the postoperative outcomes were utilizing a computerized literature search. We searched the blinded to the intervention. Cochrane Central Register of Controlled Trials, MEDLINE Regarding data collection and analysis, the two authors and EMBASE (January 1, 1995 to September 30, 2008), using (AM and SMW) independently assessed the titles and the following index terms: thyroidectomy, thyroid surgery, abstracts of studies retrieved from the literature search harmonic scalpel, harmonic shears, ultrasonic shears, ultra- and obtained full articles for all those that appeared to sonic scalpel, ultrasonic coagulator, ultrasonic dissector, satisfy inclusion criteria, ultimately including those that ultrasonic dissection, ultrasonically activated scalpel, ultra- met inclusion criteria after in depth review. The data sonic scissors, and coagulating shears. In addition, we from those studies were extracted independently by the reviewed the reference lists of retrieved articles, contacted authors, and any differences were resolved by discussion. experts in the field, and contacted the major manufacturer The following information was abstracted for each study: of the HS (Ethicon Endosurgery) to determine if they year of publication, language of publication, country of were funding or aware of any trials being conducted using origin, study design (including details on randomization, their product. We also searched the proceedings of major blinding, allocation concealment, intention-to-treat analysis, endocrine surgery conferences for any reported trials that and losses to follow-up), provision of industrial support for may not have been published. All studies were considered the study, reason for ineligibility if the study was ultimately relevant irrespective of publication status or the language of excluded, number of patients enrolled in each study arm, publication. indication for thyroidectomy, type of thyroidectomy car- ried out (e.g., partial versus total versus subtotal), details 2.2. Study Eligibility. We restricted our study to adults older regarding type of HS and CH utilized (ties versus clips than 18 years of age. Only studies comparing traditional open versus electrocautery), mean operative time for total and thyroidectomy utilizing CH techniques to thyroidectomy subtotal thyroidectomies in each group, number of cases using the HS were considered. Any studies evaluating video- of transient and permanent postoperative hypocalcemia assisted or endoscopic thyroidectomy were excluded. Studies (either symptomatic or biochemical), number of cases of postoperative transient or permanent RLND, and number of where additional procedures were carried out at the time of thyroidectomy (e.g., lateral neck lymph node dissection) cases of postoperative hematoma formation. Study validity is were also excluded, unless these additional procedures presented qualitatively though no formal validity score was assigned. were accounted for by subtracting the time for the added procedurefromthe overalloperative time.Thyroid surgery for either benign or malignant histology was included. The principal outcome evaluated was the mean operative 2.3. Statistical Analysis. For the primary outcome, the meta- time, measured in minutes, for total or subtotal thyroidec- analysis evaluated the weighted mean difference in operative tomies carried out utilizing the two surgical techniques. times between thyroidectomy groups (HS versus CH) and Although studies could include a combination of total and the standard deviation of the difference from individual stud- subtotal thyroidectomies and thyroid lobectomies, they were ies using the METAN command in STATA 9.2 (StataCorp, excluded if they did not report a mean operative time College Station, Texas). In one study, the data regarding specifically for the total and subtotal thyroidectomies. The operative times was not reported as a mean with standard secondary outcomes we evaluated were the incidence of deviation, but after correspondence with the authors, the transient postoperative RLND and hypocalcemia. Transient data was provided in such a format as to allow inclusion RLND was not well defined in most studies. One study in the analysis [11]. In 2 cases, attempts to contact the defined RLND as transient if vocal cord function recovered authors were unsuccessful and thus these papers could not within twelve months of the operation [5]. Some studies be included in the analysis, though they had otherwise met did not provide an explanation for how transient RLND inclusion criteria [14, 15]. Significant heterogeneity across was diagnosed [6–8]. In the majority of the papers, post- studies was noted; thus a pooled estimate of the difference in operative laryngoscopy was performed on every patient to operative time was generated using a random effects model assess vocal cord function [5, 9–13]. Transient postoperative [16]. A sensitivity analysis excluding the two studies that hypocalcemia was defined either by biochemical parame- disclosed financial support from the HS manufacturers was ters or by clinical symptoms or both. Some studies did also carried out. International Journal of Surgical Oncology 3 34 potentially relevant studies screened for retrieval 15 retrieved for more 19 excluded detailed evaluation 1evaluated 18 retrospective 6 excluded 9 included additional or non- procedures randomized 3 duplicate reports on same patient cohort 3 relevant data not provided Figure 1: Flow diagram showing the number of studies initially identified and the reasons for study exclusion. For the secondary outcomes of postoperative RLND and overall number of cases of this was small and this was not hypocalcemia, results are presented as risk ratios (RRs). a statistically significant finding (see Figure 4). Two studies The fixed effects model was utilized to obtain the summary reported no cases of transient RLND [10. 12] and were estimates of the logRR from the group of studies. We did excluded from this analysis. The χ test for heterogeneity was not proceed to a random effects model once the fixed not significant (P-value = .51); thus we did not proceed to a effects analysis did not reveal any significant heterogeneity random effects analysis. (Q statistic). The pooled estimate and 95% confidence interval of the Publication bias was assessed with Begg’s and Egger tests relative risk of postoperative transient hypocalcemia from a and Begg’s funnel plot [17, 18]. A P-value of <.05 was fixed effects model was 0.69 (P = .01; 95% CI = 0.51, 0.92). considered statistically significant. Thus, there was a statistically significant reduced risk of transient postoperative hypocalcemia with the use of HS (see Figure 5). The χ test for heterogeneity was not significant 3. Results (P-value = .53); so a random effects analysis was not carried out. Thirty-four studies that potentially met inclusion criteria A sensitivity analysis excluding studies with industry were identified from the literature search. After abstract supportrevealedanevengreater reductioninoperative time screening, 19 were excluded for variety of reasons. Of the with use of the HS (25 minutes; 95% CI = 16.3, 33.62). 15 that were reviewed in depth, 6 were excluded, leaving Interestingly, there were a total of 3 cases of postoperative 9 studies that were incorporated into the meta-analysis. hematoma in the CH group and 1 in the HS group Figure 1 depicts a flow diagram of the study selection process (Table 1) suggesting a trend toward a lower incidence of this and Table 1 summarizes the characteristics of the studies serious postoperative complication with the HS. However, included in the meta-analysis. There were no incidents of the overall numbers are too small to draw any meaningful author disagreement in either the study selection or data conclusions. extraction phase The quality of the studies was assessed based on the Regarding the primary outcome of mean operative time, following criteria: appropriateness of randomization, alloca- the pooled estimate of the weighted mean difference (WMD) tion concealment, blinding of patients, blinding of outcome in operative time obtained from a random effects model was assessors, utilization of intention-to-treat analysis, and a 23.1 minutes (95% CI = 13.8, 32.33). This was statistically 2 description of any patients that were lost to follow-up. In significant, with a P-value of <.001 (Figure 2). The χ test most cases, these parameters were not specified and thus the for heterogeneity was significant with a P-value of <.001. methodological quality of the included studies could only be Tests for publication bias were not statistically significant deemed as fair. These results are presented in Table 2. (P = .97). See Figure 3 for Begg’s funnel plot. Regarding secondary outcomes, the pooled estimate and 95% confidence interval of the relative risk of postoperative 4. Discussion transient RLND from a fixed effects model was 1.25 (P = .59; 95% CI = 0.56, 2.76). Thus, there is a trend toward an Utilization of the HS for total and subtotal thyroidec- increased risk of transient RLND with the use of HS, but the tomy significantly reduced operative time compared to CH 4 International Journal of Surgical Oncology Mean OR Author Year Country Industry CH # Time (min) for Transient Permanent Transient Permanent Postoperative funding techniques patients TT/ST (SD) RLND RLND hypocalcemia hypocalcemia hematoma Electrocautery CH = 24 CH = 168.8 (4.8) CH =1CH =0CH =7CH =1CH = 0 Hallgrimsson [11] 2008 Sweden No ligatures clips HS = 27 HS = 134.7 (5.6) HS =4HS =0HS =5HS =0HS = 0 Electrocautery CH = 100 CH = 75.2 (23.5) CH =1CH =0CH = 29 CH =0CH = 1 Lombardi [5] 2008 Italy No ligatures HS = 100 HS = 53.1 (20.7) HS =2HS =0HS = 28 HS =0HS = 1 Electrocautery CH = 54 CH = 105 (16) CH =5CH =1CH =7CH =1CH = 0 Yildirim [13] 2008 Turkey No ligatures HS = 50 HS = 77.9 (12.5) HS =1HS =0HS =6HS =1HS = 0 Electrocautery CH = 40 CH = 57.8 (12) CH =0CH =0CH =5CH =0CH = 0 Kilic [6] 2007 Turkey No ligatures HS = 40 HS = 47.1 (8.2) HS =1HS =0HS =2HS =0HS = 0 Electrocautery CH = 50 CH = 46.7 (10.8) CH =0CH =0CH = 16 CH =0CH = 0 Miccoli [12] 2006 Italy Yes ligatures HS = 50 HS = 40 (6.8) HS =0HS =0HS =5HS =0HS = 0 Electrocautery CH = 60 CH = 96 (17) CH =2CH =0CH =6CH =0CH = 0 Frazzetta [8] 2005 Italy No ligatures HS = 60 HS = 56 (18) HS =1HS =0HS =4HS =0HS = 0 Electrocautery CH = 12 CH = 136 (37) CH =0CH=0CH=9CH=0CH = 0 Cordon [9] 2005 Mexico Yes ligatures clips HS =7HS = 104 (29) HS =1HS =0HS =3HS =0HS = 0 CH = 57 CH = 101 (16) CH =1CH =0CH =6CH =0CH = 2 Ortega [7] 2004 Spain No Ligatures HS = 57 HS = 86 (20) HS =2HS =0HS =5HS =0HS = 0 Electrocautery CH = 17 CH = 96.5 (28.9) CH =0CH =0CH =4CH =0CH = 0 Defechereux [10] 2003 Belgium No Ligatures clips HS=17 HS = 70.7 (18.3) HS=0HS=0HS=1HS=0HS=0 CH = 414 CH = 10 CH =1CH = 89 CH =2CH = 3 TOTAL HS = 408 HS = 12 HS =0HS = 59 HS =1HS = 1 CH: conventional hemostasis; OR: operative; HS: harmonic scalpel; TT: total thyroidectomy; ST: subtotal thyroidectomy; SD: standard deviation; RLND: recurrent laryngeal nerve dysfunction. International Journal of Surgical Oncology 5 Conventional Harmonic hemostasis scalpel WMD (95% CI) Weight (%) Hallgrimsson 34.1 (31.25,36.95) 12.5 Lombardi 22.1 (15.96,28.24) 12 Yildirim 27.1 (21.60,32.60) 12.2 Kilic 10.7 (6.20,15.20) 12.3 Miccoli 6.7 (3.16,10.24) 12.5 Frazzetta 40 (33.74,46.26) 12 Cordon 32 (2.00,62.00) 5.4 Ortega 1 15 (8.35,21.65) 1.9 Defechereux 25.8 (9.54,42.06) 9.1 Overall (95% CI) 23.07 (13.8,32.33) −62 0 23.1 62 WMD (mins) Figure 2: Forest plot depicting individual and pooled weighted mean difference (WMD) in operative times with 95% confidence intervals. Table 2: Study validity. Author Randomization Concealed Patients Outcome assessors Intention- to-treat Patients LTFU? Done Adequate allocation blinded blinded Analysis Hallgrimsson Yes UC UC UC UC Yes UC Lombardi Yes UC UC Yes UC UC UC Yildirim Yes UC UC UC UC UC UC Kilic Yes UC UC UC UC UC UC Miccoli Yes UC UC Yes UC UC UC Frazzetta Yes UC UC UC UC UC UC Cordon Yes Yes UC UC Yes UC UC Ortega Yes UC UC UC UC UC UC Defechereux Yes Yes UC UC UC UC UC UC: unclear; LTFU: loss to follow-up. 60 there was also no statistically significant difference in the risk of transient postoperative RLND between the two groups (pooled RR = 1.25, P-value = .59). We conclude that not only is HS utilization for total thyroidectomy significantly faster than the conventional approach, with acceptable 20 postoperative complication rates, but also it may even protect against the development of transient postoperative hypocalcemia. All of the studies uniformly report decreased operating time with the use of an HS. This is not a surprising observa- −20 tion, given that the same outcome has been reported repeat- 0 5 10 15 edly foravarietyofothersurgicalprocedures[19–21]. With Standard error of WMD the exception of a single Mexican study, all of the reports were from European centers. There is no reason to believe that the Figure 3: Begg’s funnel plot with pseudo 95% confidence limits. patients requiring thyroid surgery are any different in Europe than in North America and thus we believe that our results are generalizable to other patient populations. From the techniques by greater than 23 minutes (P-value <.001). literature search, two reports from U.S. centers evaluating HS Furthermore, there was a 31% decreased risk of transient use for thyroidectomy were identified but excluded because postoperative hypocalcemia with HS utilization compared of their retrospective study design. Both of these studies also to CH techniques (pooled RR = 0.69, P-value = .01) and found the HS to be safe and time-saving [22, 23]. 6 International Journal of Surgical Oncology Conventional Harmonic hemostasis scalpel RR (95% CI) Weight (%) Hallgrimsson 3.56 (0.43,29.66) 10 Lombardi 2 (0.18,21.71) 9.5 Kilic 3 (0.13,71.51) 4.7 Frazzetta 0.5 (0.05,5.37) 18.9 Cordon 4.88 (0.22,105.76) 3.6 Ortega 2 (0.19,21.44) 9.5 Yildirim 0.23 (0.03,1.92) 43.8 Overall (95% CI) 1.25 (0.56,2.76) −1 1 1.25 10 RR Figure 4: Forest plot depicting individual and pooled risk ratios (RRs) with 95% confidence intervals (CIs) for transient postoperative recurrent laryngeal nerve dysfunction. Harmonic Conventional scalpel hemostasis RR (95% CI) Weight (%) Hallgrimsson 0.63 (0.23,1.74) 8.5 Lombardi 0.97 (0.62,1.50) 33.4 Kilic 0.4 (0.08,1.94) 5.8 Frazzetta 0.67 (0.20,2.24) 6.9 Cordon 0.57 (0.23,1.43) 7.6 Ortega 0.83 (0.27,2.58) 6.9 Yildirim 0.93 (0.33,2.57) 7.8 Miccoli 0.31 (0.12,0.79) 18.4 Defechereux 0.25 (0.03,2.01) 4.6 Overall (95% CI) 0.69 (0.51,0.92) −1 −69 1 10 RR Figure 5: Forest plot depicting individual and pooled risk ratios (RRs) with 95% confidence intervals (CIs) for transient postoperative hypocalcemia. All studies reported an increased risk of postopera- directly or indirectly, with either mechanical forces or tive hypocalcemia with conventional hemostasis techniques, electrical currents. Thus, this finding of reduced transient though only one report had a large enough cohort for the postoperative hypocalcemia with HS utilization does seem association to be statistically significant [12]. Though the biologically plausible and highlights an important rationale mechanism is not fully understood, transient hypocalcemia for conducting the meta-analysis. When an outcome is observed after total thyroidectomy is believed to be related relatively uncommon, individual studies may all trend to traumatization of the parathyroid glands, which are toward that same outcome though none may have the anatomically intimately related to the thyroid gland and power to support statistical significance, but calculating share its blood supply. We speculate that use of the HS a pooled estimate may allow for the determination of a may facilitate dissection of the parathyroid glands in a statistically significant association. It is difficult to draw plane farther away from the parathyroid gland capsule, any conclusions regarding permanent hypoparathyroidism thus reducing the chance of damaging their blood supply, and HS utilization. Permanent hypoparathyroidism is a rare International Journal of Surgical Oncology 7 complication of thyroidectomy, and there were only three majority of thyroidectomies in the study reporting the fastest reported cases of this among the nine studies, two of which mean operative time excluded patients with Graves’ disease occurred in the CH group and one in the HS group (Table 1). or extensive goiters [12]. The complication of RLND after thyroidectomy is also One must consider whether or not benign versus an extremely uncommon occurrence. Included studies had malignant thyroid pathology affected our results. All of the conflicting results in terms of the risks of RLND with HS studies incorporated in the meta-analysis excluded patients utilization compared to CH, and all reported either very requiring either a central or lateral compartment lymph node few or no cases of this complication. In the current meta- dissection; thus this could not have played a role in operative analysis, there were only twenty-two incidents of transient time or incidence of postoperative hypocalcemia. Of the 9 RLND out of 822 total thyroidectomies (.03%) or 1,644 studies, 4 excluded malignant disease (7, 10, 11, 13), 3 had nerves at risk (.01%). Given that HS has been shown no significant difference in the proportion of malignant cases to cause less collateral thermal injury than conventional between the HS and CH groups (5, 6, 9), 1 only included low- electrocautery, we would expect to see less RLND in the HS risk T1N0M0 papillary thyroid cancers (12), and 1 did not group. Unfortunately, the numbers in this analysis are too clearly outline the pathologies. Given this, we do not feel that small to generate any meaningful conclusions. Only one case thyroid pathology is confounding our results for the primary of permanent RLND occurred in a patient who underwent or secondary outcomes. the CH technique. The time cutoff to differentiate between Another consideration when interpreting the results of transient and permanent RLND was not well defined in the current meta-analysis is that surgeons who conduct these the studies, but most investigators did use postoperative trials may have significantly more experience with the HS laryngoscopy in all patients to document vocal cord paralysis. than the average thyroid surgeon, and the timesaving effect Regarding the internal validity of included studies, one of the HS might be exaggerated compared to what a less- must accept that for studies evaluating surgical techniques, familiar surgeon would experience when first adopting its use blinding of the surgeon is not possible. However, patients into their practice. can be blinded to the procedure they have undergone Future prospective, randomized trials of larger patient to minimize reporting bias when evaluating postoperative cohorts with more detailed and uniform definitions of outcomes such as symptomatic hypocalcemia or pain. Fur- postoperative complications, randomization procedures, thermore, those individuals evaluating outcomes (operative intention-to-treat analyses, and blinding of outcome asses- time, RLND, hypocalcemia) can also be blinded to the sors are needed to draw more meaningful conclusions with intervention to reduce observation bias, and this was only regard to the influence of HS utilization on complications explicitly carried out in a single study [9]. Ideally, authors after total or subtotal thyroidectomy. In addition, cost- should also give a detailed description of their randomization effectiveness analyses to determine whether the costs saved procedures, allocation concealment, and use of intention- from the reduced time spent in the operating theater to-treat analysis, which was not consistently reported in the outweigh the added cost of the HS scalpel would also be studies included in this meta-analysis. To assure internal important. Several of the studies did report reduced overall validity, future randomized studies evaluating this question cost associated with the HS [7, 8, 10] while another reported should include details addressing these issues. The quality of no difference in overall costs when comparing the two a meta-analysis is only as good as the reports from which techniques [5]. Other benefits seen with HS demonstrated in it is derived, and so our study is inherently limited by the these studies included less operative bleeding [6, 8–12], fewer methodological limitations of the included reports. cases of postoperative hematoma formation [7], fewer ties No tests of publication bias were statistically significant. used [6, 8, 9, 13], less drain utilization [13], less postoperative Begg’s funnel plot for the pooled estimate of the WMD in pain or analgesic requirements [10, 12], and smaller incisions operative time did exhibit some asymmetry, but this was not [6]. The impact of a recently introduced, smaller handheld statistically significant. The asymmetry was likely a result HS on thyroid surgery outcomes also warrants further study. of between-study heterogeneity (tau-squared = 175.88). Reports of the use of another vessel sealing technology, the When between-study heterogeneity is large and when the Ligasure (Covidien, Boulder, Colorado), for thyroid surgery number of included studies is small, none of these tests have emerged in the recent literature, and comparisons to detect publication bias work well. Though all studies between this device and the HS would also be of interest. found that thyroidectomy was faster with the HS, they were From the current study, we are able to definitively conclude quite heterogeneous in terms of the baseline length of time that not only does the use of the HS significantly decrease required to carry out a conventional thyroidectomy (range operative time compared to CH techniques with ties, clips, from 46.7 to 168.8 minutes). This observed difference in and/or electrocautery but it is also safer in terms of reducing time required to carry out the same operation is quite the incidence of transient postoperative hypocalcemia. striking. The heterogeneity may have been due to the size of the gland that was being resected, which was not clearly defined in all studies. In addition, all of the thyoidectomies Acknowledgments in the Hallgrimsson study, which reported the longest mean operative time for conventional thyroidectomy, were carried The authors would like to thank Dr. Andrea Petrucci and Mr. out for Graves’ thyrotoxicosis, wherein the vascularization Antonio Canino for their help with translation of the French of the thyroid gland can be very extensive. In contrast, the and Italian articles. In addition, they would like to thank 8 International Journal of Surgical Oncology Dr. Rob van Dam and Ms. Christie Jeon of the Harvard [15] P. E. Voutilainen and C. H. 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Harmonic Scalpel Compared to Conventional Hemostasis in Thyroid Surgery: A Meta-Analysis of Randomized Clinical Trials

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Copyright © 2010 Adrienne L. Melck and Sam M. Wiseman. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Hindawi Publishing Corporation International Journal of Surgical Oncology Volume 2010, Article ID 396079, 8 pages doi:10.1155/2010/396079 Review Article Harmonic Scalpel Compared to Conventional Hemostasis in Thyroid Surgery: A Meta-Analysis of Randomized Clinical Trials Adrienne L. Melck and Sam M. Wiseman Department of Surgery, Saint Paul’s Hospital, University of British Columbia, C303-1081 Burrard Street, Vancouver, BC, Canada V6Z 1Y6 Correspondence should be addressed to Adrienne L. Melck, melckal@upmc.edu Received 23 August 2009; Revised 9 November 2009; Accepted 6 December 2009 Academic Editor: Perry Shen Copyright © 2010 A. L. Melck and S. M. Wiseman. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. The study’s aim was to determine whether conventional hemostasis (CH) or the Harmonic Scalpel (HS) results in shorter operative times for thyroidectomy and to evaluate the incidence of postoperative complications with each approach. Methods. A literature search was conducted from study inception to September 30, 2008. Included studies randomized thyroidectomy patients to either CH or HS and reported the incidence of postoperative transient recurrent laryngeal nerve dysfunction (RLND) and hypocalcemia. Results. Nine RCTs were included. Use of the HS reduced operative time by 23.1 minutes (95% CI = 13.8, 32.33). There was no difference in the incidence of transient RLND (RR = 1.25, 95% CI = .56, 2.76), but a lower rate of transient hypocalcemia with the use of the HS (RR = .69, 95% CI = .51, .92). Conclusions. The use of HS in thyroidectomy significantly reduces operative time and is associated with a reduction in postoperative hypocalcemia compared to CH. 1. Introduction tissue injury, a lack of neuromuscular stimulation, and the avoidance of electrical energy transmission either to There have been few developments in the technical aspects or through the patient [3]. Since the adoption of the of thyroid surgery since the surgical approach described by Harmonic Scalpel (HS) into modern surgical practice, its Kocher greater than a century ago [1]. Given the significant utility for a wide variety of operations has been well vascularity of the thyroid gland [2] and the relatively small documented. For example, a randomized prospective clinical operative field, meticulous hemostasis has and will always be trial demonstrated its ability to diminish blood loss as well as an important prerequisite for a successful outcome in thyroid operative time for laparoscopic Nissen fundoplication [4]. surgery. The mainstay for achieving hemostasis in thyroid Over the last decade, many reports have evaluated the surgery has been tying and/or clipping of blood vessels, utility of the HS for thyroid surgery and the majority of both effective but time-consuming techniques. In the current these studies have been carried out at European centers. The climate of healthcare constraints and long surgical waiting investigators have shown similar results regarding reduced lists, any methodology that can reduce operative times operative times with its utilization, but conflicting results while maintaining acceptable complication rates warrants regarding other postoperative outcomes such as transient investigation. postoperative hypocalcemia and recurrent laryngeal nerve The Harmonic Scalpel (Ethicon Endosurgery, Cincin- dysfunction (RLND). These complications are relatively nati, Ohio) was introduced into the surgeon’s armamentar- uncommon and the number of cases reported in individual ium almost two decades ago. Using mechanical vibrations studies is limited. Consolidating the data may allow for at 55.5 kHz, this device is able to cut and coagulate tissue elucidation of significant associations between HS utilization simultaneously. The proposed advantages of using this device and postoperative complications. To date, no meta-analysis over traditional electrocautery include less lateral thermal evaluating the utilization of HS in thyroid surgery has 2 International Journal of Surgical Oncology been reported. The purpose of this study was to determine not describe how postoperative hypocalcemia was defined. whether conventional hemostasis (CH) or the HS results in Although studies could report on a variety of secondary shorter operative times for thyroidectomy and to evaluate postoperative outcomes (e.g., amount and/or duration of the incidence of postoperative complications with each wound drainage, postoperative hematoma formation, pain, approach. analgesic requirements, time to hospital discharge, cost- effectiveness), they were excluded if they did not report these two specific outcomes. 2. Methods To be included, studies had to be prospective, ran- domized clinical trials and observational studies were not 2.1. Identification of Trials. We sought to identify prospec- included in the analysis. Clearly blinding is not feasible in tive, randomized clinical trials comparing HS to CH methods studies evaluating two different surgical techniques, though (i.e., ties, clips, and/or electrocautery) for thyroidectomy it was noted if assessors of the postoperative outcomes were utilizing a computerized literature search. We searched the blinded to the intervention. Cochrane Central Register of Controlled Trials, MEDLINE Regarding data collection and analysis, the two authors and EMBASE (January 1, 1995 to September 30, 2008), using (AM and SMW) independently assessed the titles and the following index terms: thyroidectomy, thyroid surgery, abstracts of studies retrieved from the literature search harmonic scalpel, harmonic shears, ultrasonic shears, ultra- and obtained full articles for all those that appeared to sonic scalpel, ultrasonic coagulator, ultrasonic dissector, satisfy inclusion criteria, ultimately including those that ultrasonic dissection, ultrasonically activated scalpel, ultra- met inclusion criteria after in depth review. The data sonic scissors, and coagulating shears. In addition, we from those studies were extracted independently by the reviewed the reference lists of retrieved articles, contacted authors, and any differences were resolved by discussion. experts in the field, and contacted the major manufacturer The following information was abstracted for each study: of the HS (Ethicon Endosurgery) to determine if they year of publication, language of publication, country of were funding or aware of any trials being conducted using origin, study design (including details on randomization, their product. We also searched the proceedings of major blinding, allocation concealment, intention-to-treat analysis, endocrine surgery conferences for any reported trials that and losses to follow-up), provision of industrial support for may not have been published. All studies were considered the study, reason for ineligibility if the study was ultimately relevant irrespective of publication status or the language of excluded, number of patients enrolled in each study arm, publication. indication for thyroidectomy, type of thyroidectomy car- ried out (e.g., partial versus total versus subtotal), details 2.2. Study Eligibility. We restricted our study to adults older regarding type of HS and CH utilized (ties versus clips than 18 years of age. Only studies comparing traditional open versus electrocautery), mean operative time for total and thyroidectomy utilizing CH techniques to thyroidectomy subtotal thyroidectomies in each group, number of cases using the HS were considered. Any studies evaluating video- of transient and permanent postoperative hypocalcemia assisted or endoscopic thyroidectomy were excluded. Studies (either symptomatic or biochemical), number of cases of postoperative transient or permanent RLND, and number of where additional procedures were carried out at the time of thyroidectomy (e.g., lateral neck lymph node dissection) cases of postoperative hematoma formation. Study validity is were also excluded, unless these additional procedures presented qualitatively though no formal validity score was assigned. were accounted for by subtracting the time for the added procedurefromthe overalloperative time.Thyroid surgery for either benign or malignant histology was included. The principal outcome evaluated was the mean operative 2.3. Statistical Analysis. For the primary outcome, the meta- time, measured in minutes, for total or subtotal thyroidec- analysis evaluated the weighted mean difference in operative tomies carried out utilizing the two surgical techniques. times between thyroidectomy groups (HS versus CH) and Although studies could include a combination of total and the standard deviation of the difference from individual stud- subtotal thyroidectomies and thyroid lobectomies, they were ies using the METAN command in STATA 9.2 (StataCorp, excluded if they did not report a mean operative time College Station, Texas). In one study, the data regarding specifically for the total and subtotal thyroidectomies. The operative times was not reported as a mean with standard secondary outcomes we evaluated were the incidence of deviation, but after correspondence with the authors, the transient postoperative RLND and hypocalcemia. Transient data was provided in such a format as to allow inclusion RLND was not well defined in most studies. One study in the analysis [11]. In 2 cases, attempts to contact the defined RLND as transient if vocal cord function recovered authors were unsuccessful and thus these papers could not within twelve months of the operation [5]. Some studies be included in the analysis, though they had otherwise met did not provide an explanation for how transient RLND inclusion criteria [14, 15]. Significant heterogeneity across was diagnosed [6–8]. In the majority of the papers, post- studies was noted; thus a pooled estimate of the difference in operative laryngoscopy was performed on every patient to operative time was generated using a random effects model assess vocal cord function [5, 9–13]. Transient postoperative [16]. A sensitivity analysis excluding the two studies that hypocalcemia was defined either by biochemical parame- disclosed financial support from the HS manufacturers was ters or by clinical symptoms or both. Some studies did also carried out. International Journal of Surgical Oncology 3 34 potentially relevant studies screened for retrieval 15 retrieved for more 19 excluded detailed evaluation 1evaluated 18 retrospective 6 excluded 9 included additional or non- procedures randomized 3 duplicate reports on same patient cohort 3 relevant data not provided Figure 1: Flow diagram showing the number of studies initially identified and the reasons for study exclusion. For the secondary outcomes of postoperative RLND and overall number of cases of this was small and this was not hypocalcemia, results are presented as risk ratios (RRs). a statistically significant finding (see Figure 4). Two studies The fixed effects model was utilized to obtain the summary reported no cases of transient RLND [10. 12] and were estimates of the logRR from the group of studies. We did excluded from this analysis. The χ test for heterogeneity was not proceed to a random effects model once the fixed not significant (P-value = .51); thus we did not proceed to a effects analysis did not reveal any significant heterogeneity random effects analysis. (Q statistic). The pooled estimate and 95% confidence interval of the Publication bias was assessed with Begg’s and Egger tests relative risk of postoperative transient hypocalcemia from a and Begg’s funnel plot [17, 18]. A P-value of <.05 was fixed effects model was 0.69 (P = .01; 95% CI = 0.51, 0.92). considered statistically significant. Thus, there was a statistically significant reduced risk of transient postoperative hypocalcemia with the use of HS (see Figure 5). The χ test for heterogeneity was not significant 3. Results (P-value = .53); so a random effects analysis was not carried out. Thirty-four studies that potentially met inclusion criteria A sensitivity analysis excluding studies with industry were identified from the literature search. After abstract supportrevealedanevengreater reductioninoperative time screening, 19 were excluded for variety of reasons. Of the with use of the HS (25 minutes; 95% CI = 16.3, 33.62). 15 that were reviewed in depth, 6 were excluded, leaving Interestingly, there were a total of 3 cases of postoperative 9 studies that were incorporated into the meta-analysis. hematoma in the CH group and 1 in the HS group Figure 1 depicts a flow diagram of the study selection process (Table 1) suggesting a trend toward a lower incidence of this and Table 1 summarizes the characteristics of the studies serious postoperative complication with the HS. However, included in the meta-analysis. There were no incidents of the overall numbers are too small to draw any meaningful author disagreement in either the study selection or data conclusions. extraction phase The quality of the studies was assessed based on the Regarding the primary outcome of mean operative time, following criteria: appropriateness of randomization, alloca- the pooled estimate of the weighted mean difference (WMD) tion concealment, blinding of patients, blinding of outcome in operative time obtained from a random effects model was assessors, utilization of intention-to-treat analysis, and a 23.1 minutes (95% CI = 13.8, 32.33). This was statistically 2 description of any patients that were lost to follow-up. In significant, with a P-value of <.001 (Figure 2). The χ test most cases, these parameters were not specified and thus the for heterogeneity was significant with a P-value of <.001. methodological quality of the included studies could only be Tests for publication bias were not statistically significant deemed as fair. These results are presented in Table 2. (P = .97). See Figure 3 for Begg’s funnel plot. Regarding secondary outcomes, the pooled estimate and 95% confidence interval of the relative risk of postoperative 4. Discussion transient RLND from a fixed effects model was 1.25 (P = .59; 95% CI = 0.56, 2.76). Thus, there is a trend toward an Utilization of the HS for total and subtotal thyroidec- increased risk of transient RLND with the use of HS, but the tomy significantly reduced operative time compared to CH 4 International Journal of Surgical Oncology Mean OR Author Year Country Industry CH # Time (min) for Transient Permanent Transient Permanent Postoperative funding techniques patients TT/ST (SD) RLND RLND hypocalcemia hypocalcemia hematoma Electrocautery CH = 24 CH = 168.8 (4.8) CH =1CH =0CH =7CH =1CH = 0 Hallgrimsson [11] 2008 Sweden No ligatures clips HS = 27 HS = 134.7 (5.6) HS =4HS =0HS =5HS =0HS = 0 Electrocautery CH = 100 CH = 75.2 (23.5) CH =1CH =0CH = 29 CH =0CH = 1 Lombardi [5] 2008 Italy No ligatures HS = 100 HS = 53.1 (20.7) HS =2HS =0HS = 28 HS =0HS = 1 Electrocautery CH = 54 CH = 105 (16) CH =5CH =1CH =7CH =1CH = 0 Yildirim [13] 2008 Turkey No ligatures HS = 50 HS = 77.9 (12.5) HS =1HS =0HS =6HS =1HS = 0 Electrocautery CH = 40 CH = 57.8 (12) CH =0CH =0CH =5CH =0CH = 0 Kilic [6] 2007 Turkey No ligatures HS = 40 HS = 47.1 (8.2) HS =1HS =0HS =2HS =0HS = 0 Electrocautery CH = 50 CH = 46.7 (10.8) CH =0CH =0CH = 16 CH =0CH = 0 Miccoli [12] 2006 Italy Yes ligatures HS = 50 HS = 40 (6.8) HS =0HS =0HS =5HS =0HS = 0 Electrocautery CH = 60 CH = 96 (17) CH =2CH =0CH =6CH =0CH = 0 Frazzetta [8] 2005 Italy No ligatures HS = 60 HS = 56 (18) HS =1HS =0HS =4HS =0HS = 0 Electrocautery CH = 12 CH = 136 (37) CH =0CH=0CH=9CH=0CH = 0 Cordon [9] 2005 Mexico Yes ligatures clips HS =7HS = 104 (29) HS =1HS =0HS =3HS =0HS = 0 CH = 57 CH = 101 (16) CH =1CH =0CH =6CH =0CH = 2 Ortega [7] 2004 Spain No Ligatures HS = 57 HS = 86 (20) HS =2HS =0HS =5HS =0HS = 0 Electrocautery CH = 17 CH = 96.5 (28.9) CH =0CH =0CH =4CH =0CH = 0 Defechereux [10] 2003 Belgium No Ligatures clips HS=17 HS = 70.7 (18.3) HS=0HS=0HS=1HS=0HS=0 CH = 414 CH = 10 CH =1CH = 89 CH =2CH = 3 TOTAL HS = 408 HS = 12 HS =0HS = 59 HS =1HS = 1 CH: conventional hemostasis; OR: operative; HS: harmonic scalpel; TT: total thyroidectomy; ST: subtotal thyroidectomy; SD: standard deviation; RLND: recurrent laryngeal nerve dysfunction. International Journal of Surgical Oncology 5 Conventional Harmonic hemostasis scalpel WMD (95% CI) Weight (%) Hallgrimsson 34.1 (31.25,36.95) 12.5 Lombardi 22.1 (15.96,28.24) 12 Yildirim 27.1 (21.60,32.60) 12.2 Kilic 10.7 (6.20,15.20) 12.3 Miccoli 6.7 (3.16,10.24) 12.5 Frazzetta 40 (33.74,46.26) 12 Cordon 32 (2.00,62.00) 5.4 Ortega 1 15 (8.35,21.65) 1.9 Defechereux 25.8 (9.54,42.06) 9.1 Overall (95% CI) 23.07 (13.8,32.33) −62 0 23.1 62 WMD (mins) Figure 2: Forest plot depicting individual and pooled weighted mean difference (WMD) in operative times with 95% confidence intervals. Table 2: Study validity. Author Randomization Concealed Patients Outcome assessors Intention- to-treat Patients LTFU? Done Adequate allocation blinded blinded Analysis Hallgrimsson Yes UC UC UC UC Yes UC Lombardi Yes UC UC Yes UC UC UC Yildirim Yes UC UC UC UC UC UC Kilic Yes UC UC UC UC UC UC Miccoli Yes UC UC Yes UC UC UC Frazzetta Yes UC UC UC UC UC UC Cordon Yes Yes UC UC Yes UC UC Ortega Yes UC UC UC UC UC UC Defechereux Yes Yes UC UC UC UC UC UC: unclear; LTFU: loss to follow-up. 60 there was also no statistically significant difference in the risk of transient postoperative RLND between the two groups (pooled RR = 1.25, P-value = .59). We conclude that not only is HS utilization for total thyroidectomy significantly faster than the conventional approach, with acceptable 20 postoperative complication rates, but also it may even protect against the development of transient postoperative hypocalcemia. All of the studies uniformly report decreased operating time with the use of an HS. This is not a surprising observa- −20 tion, given that the same outcome has been reported repeat- 0 5 10 15 edly foravarietyofothersurgicalprocedures[19–21]. With Standard error of WMD the exception of a single Mexican study, all of the reports were from European centers. There is no reason to believe that the Figure 3: Begg’s funnel plot with pseudo 95% confidence limits. patients requiring thyroid surgery are any different in Europe than in North America and thus we believe that our results are generalizable to other patient populations. From the techniques by greater than 23 minutes (P-value <.001). literature search, two reports from U.S. centers evaluating HS Furthermore, there was a 31% decreased risk of transient use for thyroidectomy were identified but excluded because postoperative hypocalcemia with HS utilization compared of their retrospective study design. Both of these studies also to CH techniques (pooled RR = 0.69, P-value = .01) and found the HS to be safe and time-saving [22, 23]. 6 International Journal of Surgical Oncology Conventional Harmonic hemostasis scalpel RR (95% CI) Weight (%) Hallgrimsson 3.56 (0.43,29.66) 10 Lombardi 2 (0.18,21.71) 9.5 Kilic 3 (0.13,71.51) 4.7 Frazzetta 0.5 (0.05,5.37) 18.9 Cordon 4.88 (0.22,105.76) 3.6 Ortega 2 (0.19,21.44) 9.5 Yildirim 0.23 (0.03,1.92) 43.8 Overall (95% CI) 1.25 (0.56,2.76) −1 1 1.25 10 RR Figure 4: Forest plot depicting individual and pooled risk ratios (RRs) with 95% confidence intervals (CIs) for transient postoperative recurrent laryngeal nerve dysfunction. Harmonic Conventional scalpel hemostasis RR (95% CI) Weight (%) Hallgrimsson 0.63 (0.23,1.74) 8.5 Lombardi 0.97 (0.62,1.50) 33.4 Kilic 0.4 (0.08,1.94) 5.8 Frazzetta 0.67 (0.20,2.24) 6.9 Cordon 0.57 (0.23,1.43) 7.6 Ortega 0.83 (0.27,2.58) 6.9 Yildirim 0.93 (0.33,2.57) 7.8 Miccoli 0.31 (0.12,0.79) 18.4 Defechereux 0.25 (0.03,2.01) 4.6 Overall (95% CI) 0.69 (0.51,0.92) −1 −69 1 10 RR Figure 5: Forest plot depicting individual and pooled risk ratios (RRs) with 95% confidence intervals (CIs) for transient postoperative hypocalcemia. All studies reported an increased risk of postopera- directly or indirectly, with either mechanical forces or tive hypocalcemia with conventional hemostasis techniques, electrical currents. Thus, this finding of reduced transient though only one report had a large enough cohort for the postoperative hypocalcemia with HS utilization does seem association to be statistically significant [12]. Though the biologically plausible and highlights an important rationale mechanism is not fully understood, transient hypocalcemia for conducting the meta-analysis. When an outcome is observed after total thyroidectomy is believed to be related relatively uncommon, individual studies may all trend to traumatization of the parathyroid glands, which are toward that same outcome though none may have the anatomically intimately related to the thyroid gland and power to support statistical significance, but calculating share its blood supply. We speculate that use of the HS a pooled estimate may allow for the determination of a may facilitate dissection of the parathyroid glands in a statistically significant association. It is difficult to draw plane farther away from the parathyroid gland capsule, any conclusions regarding permanent hypoparathyroidism thus reducing the chance of damaging their blood supply, and HS utilization. Permanent hypoparathyroidism is a rare International Journal of Surgical Oncology 7 complication of thyroidectomy, and there were only three majority of thyroidectomies in the study reporting the fastest reported cases of this among the nine studies, two of which mean operative time excluded patients with Graves’ disease occurred in the CH group and one in the HS group (Table 1). or extensive goiters [12]. The complication of RLND after thyroidectomy is also One must consider whether or not benign versus an extremely uncommon occurrence. Included studies had malignant thyroid pathology affected our results. All of the conflicting results in terms of the risks of RLND with HS studies incorporated in the meta-analysis excluded patients utilization compared to CH, and all reported either very requiring either a central or lateral compartment lymph node few or no cases of this complication. In the current meta- dissection; thus this could not have played a role in operative analysis, there were only twenty-two incidents of transient time or incidence of postoperative hypocalcemia. Of the 9 RLND out of 822 total thyroidectomies (.03%) or 1,644 studies, 4 excluded malignant disease (7, 10, 11, 13), 3 had nerves at risk (.01%). Given that HS has been shown no significant difference in the proportion of malignant cases to cause less collateral thermal injury than conventional between the HS and CH groups (5, 6, 9), 1 only included low- electrocautery, we would expect to see less RLND in the HS risk T1N0M0 papillary thyroid cancers (12), and 1 did not group. Unfortunately, the numbers in this analysis are too clearly outline the pathologies. Given this, we do not feel that small to generate any meaningful conclusions. Only one case thyroid pathology is confounding our results for the primary of permanent RLND occurred in a patient who underwent or secondary outcomes. the CH technique. The time cutoff to differentiate between Another consideration when interpreting the results of transient and permanent RLND was not well defined in the current meta-analysis is that surgeons who conduct these the studies, but most investigators did use postoperative trials may have significantly more experience with the HS laryngoscopy in all patients to document vocal cord paralysis. than the average thyroid surgeon, and the timesaving effect Regarding the internal validity of included studies, one of the HS might be exaggerated compared to what a less- must accept that for studies evaluating surgical techniques, familiar surgeon would experience when first adopting its use blinding of the surgeon is not possible. However, patients into their practice. can be blinded to the procedure they have undergone Future prospective, randomized trials of larger patient to minimize reporting bias when evaluating postoperative cohorts with more detailed and uniform definitions of outcomes such as symptomatic hypocalcemia or pain. Fur- postoperative complications, randomization procedures, thermore, those individuals evaluating outcomes (operative intention-to-treat analyses, and blinding of outcome asses- time, RLND, hypocalcemia) can also be blinded to the sors are needed to draw more meaningful conclusions with intervention to reduce observation bias, and this was only regard to the influence of HS utilization on complications explicitly carried out in a single study [9]. Ideally, authors after total or subtotal thyroidectomy. In addition, cost- should also give a detailed description of their randomization effectiveness analyses to determine whether the costs saved procedures, allocation concealment, and use of intention- from the reduced time spent in the operating theater to-treat analysis, which was not consistently reported in the outweigh the added cost of the HS scalpel would also be studies included in this meta-analysis. To assure internal important. Several of the studies did report reduced overall validity, future randomized studies evaluating this question cost associated with the HS [7, 8, 10] while another reported should include details addressing these issues. The quality of no difference in overall costs when comparing the two a meta-analysis is only as good as the reports from which techniques [5]. Other benefits seen with HS demonstrated in it is derived, and so our study is inherently limited by the these studies included less operative bleeding [6, 8–12], fewer methodological limitations of the included reports. cases of postoperative hematoma formation [7], fewer ties No tests of publication bias were statistically significant. used [6, 8, 9, 13], less drain utilization [13], less postoperative Begg’s funnel plot for the pooled estimate of the WMD in pain or analgesic requirements [10, 12], and smaller incisions operative time did exhibit some asymmetry, but this was not [6]. The impact of a recently introduced, smaller handheld statistically significant. The asymmetry was likely a result HS on thyroid surgery outcomes also warrants further study. of between-study heterogeneity (tau-squared = 175.88). Reports of the use of another vessel sealing technology, the When between-study heterogeneity is large and when the Ligasure (Covidien, Boulder, Colorado), for thyroid surgery number of included studies is small, none of these tests have emerged in the recent literature, and comparisons to detect publication bias work well. Though all studies between this device and the HS would also be of interest. found that thyroidectomy was faster with the HS, they were From the current study, we are able to definitively conclude quite heterogeneous in terms of the baseline length of time that not only does the use of the HS significantly decrease required to carry out a conventional thyroidectomy (range operative time compared to CH techniques with ties, clips, from 46.7 to 168.8 minutes). This observed difference in and/or electrocautery but it is also safer in terms of reducing time required to carry out the same operation is quite the incidence of transient postoperative hypocalcemia. striking. The heterogeneity may have been due to the size of the gland that was being resected, which was not clearly defined in all studies. In addition, all of the thyoidectomies Acknowledgments in the Hallgrimsson study, which reported the longest mean operative time for conventional thyroidectomy, were carried The authors would like to thank Dr. Andrea Petrucci and Mr. out for Graves’ thyrotoxicosis, wherein the vascularization Antonio Canino for their help with translation of the French of the thyroid gland can be very extensive. In contrast, the and Italian articles. In addition, they would like to thank 8 International Journal of Surgical Oncology Dr. Rob van Dam and Ms. Christie Jeon of the Harvard [15] P. E. Voutilainen and C. H. 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