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A systematic approach to the recurrent laryngeal nerve dissection at the cricothyroid junction Butskiy, Oleksandr; Chang, Brent A; Luu, Kimberly; McKenzie, Robert M; Anderson, Donald W Sep 17, 2018

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ORIGINAL RESEARCH ARTICLE Open AccessA systematic approach to the recurrentlaryngeal nerve dissection at thecricothyroid junctionOleksandr Butskiy1,2* , Brent A. Chang1, Kimberly Luu1, Robert M. McKenzie1 and Donald W. Anderson1AbstractBackground: To describe and evaluate a four step systematic approach to dissecting the recurrent laryngeal nerve(RLN) starting at the cricothyroid junction during thyroid surgery (subsequently referred to as the retrograde medialapproach).Methods: All thyroidectomies completed by the senior author between August 2014 and January 2016 wereretrospectively reviewed. Patients were excluded if concurrent lateral or central neck dissection was performed. Afollow up period of 1 year was included.Results: Surgical photographs and illustrations demonstrate the four steps in the retrograde medial approach todissection of the RLN in thyroid surgery.Three hundred forty-two consecutive thyroid surgeries were performed in 17 months, including 213 hemithyroidectomies,91 total thyroidectomies, and 38 completion thyroidectomies. The rate of temporary and permanent hypocalcemiawas 13% (95% confidence interval [CI]: 8–20%) and 3% (95% CI: 1–8%) respectively. The rate of temporary andpermanent vocal cord palsy was 9% (95% CI: 6–12%) and 0.3% (95%CI: 0.01–2%) respectively. The median surgicaltimes for hemithyroidectomy, total thyroidectomy, and completion thyroidectomy were 39 min (Interquartile range[IQR]: 33–47 min), 48 min (IQR: 40–60 min), and 40 min (IQR: 35–51 min) respectively. 1% of cases required conversionto an alternative surgical approach.Conclusion: In a tertiary endocrine head and neck practice, the routine use of the retrograde medial approach to RLNdissection is safe and results in a short operative time, and a low conversion rate to other RLN dissection approaches.Keywords: Surgical technique, Thyroidectomy, Recurrent laryngeal nerve, Retrograde dissection, Surgical anatomyBackgroundThyroid surgeries are the most frequent operations per-formed by head and neck surgeons in the United States[1]. 2015 American Thyroid Association Guidelines rec-ommend “Visual identification of the recurrent laryngeal[RLN] during dissection in all cases” on moderate-qualityevidence [2]. Three approaches to RLN identification havebeen described: lateral approach, inferior approach, andthe superior approach [3].The lateral approach is routinely used by most sur-geons for uncomplicated thyroid surgery and wasadvocated since the time of Theodor Kocher (Fig. 1) [4].In this approach the thyroid lobe is retracted medially,middle thyroid vein is divided, and the RLN is identifiedat the mid-polar level.For revision cases and for goiter surgery, the inferiorapproach is often used. In this approach the RLN isfound in the soft areolar tissue in the tracheoesophagealgroove proximal to the inferior thyroid artery crossingpoint. One advantage of this technique is that the RLNis found proximally prior to extra-laryngeal branchingand away from thyroid bed scarring that might havebeen caused by prior surgery [3].The superior Superior approach is the least used ap-proach. In this approach, the RLN is identified as it en-ters under the inferior constrictor muscle proximal to* Correspondence: butskiy.alex@gmail.com1Division of Otolaryngology – Head & Neck Surgery, University of BritishColumbia, Vancouver, BC, Canada2Gordon & Leslie Diamond Health Care Centre, 4th. Fl. 4299B-2775 LaurelStreet, Vancouver, BC V5Z 1M9, Canada© The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link tothe Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Butskiy et al. Journal of Otolaryngology - Head and Neck Surgery  (2018) 47:57 https://doi.org/10.1186/s40463-018-0306-7the cricothyroid junction [3]. This approach is advanta-geous as the RLN position relative to the cricothyroidjunction is consistent regardless of thyroid pathologyand congenital variations [5–8].The surgical technique for the superior approach hasnot been described in sufficient detail and its outcomeshave not been documented well in literature. Only threestudies report on the routine use of the superior approach:one study used a single sentence to describe the surgicaltechnique [9], and the authors of the other two studiesfollowed a technique that appears to be a modification ofthe lateral approach [6, 10]. In this technique the thyroidis retracted medially, and the RLN is found by searchingbetween Zukerkandl’s tubercle and the cricopharyngeusmuscle [6]. Thus, the RLN is not found right at the crico-thyroid junction. While a method of identifying the RLNat the cricothyroid junction is likely known to experiencedthyroid surgeons, this method has not been described indetail nor evaluated previously in literature.The main objective of this study was to describe a fourstep standardized surgical technique to identifying theRLN at the cricothyroid junction (subsequently referredto as the retrograde medial approach). The primary out-come of interest was the rate of surgical complications(temporary and permanent hypocalcemia and vocal cordpalsy). The secondary outcomes were surgical time andconversion rate to other techniques.MethodsThe University of British Columbia (UBC) Research Eth-ics Board granted approval (H15–01667) for the study.STROBE Statement for cohort studies was followed inreporting the study [11]. Study was designed as a retro-spective review of a cohort of consecutive thyroidectomypatients. All eligible patients were referred to a tertiaryhead and neck surgical practice affiliated with the Uni-versity of British Columbia (UBC) for consideration of athyroidectomy.All thyroidectomies were performed at teaching hospi-tals where residents assumed increasing responsibility tocomplete the procedure as their experience developed.The operations were performed between August 2014and January 2016.ParticipantsAll patients who underwent a hemi-, total, or comple-tion thyroidectomy between August 2014 and January2016 were selected. To obtain an estimate of the surgicaltime attributed solely to thyroid dissection, patients wereexcluded if concurrent lateral or central neck dissectionwas performed. Pre-operatively all patient underwentvisual examination of the larynx, but PTH, Calcium andVitamin D levels were not routinely measured.Post-operative careAfter hemithyroidectomy, all patients were observed for4 hours and were discharged home barring complica-tions. Completion thyroidectomy and total thyroidec-tomy patients were admitted overnight and their ionizedcalcium level was checked in the morning. Patients weredischarged if the ionized calcium level was aboveFig. 1 Illustration to Theodor Kocher’s 1895 surgical textbook demonstrating the dissection in the tracheo-esophageal groove after the thyroid isswept medially [4]Butskiy et al. Journal of Otolaryngology - Head and Neck Surgery  (2018) 47:57 Page 2 of 91.00 mmol/L. Routine calcium/vitamin D supplementa-tion and surgical drains were not used.Follow-upPost-operative follow-up consisted of an office visit2 weeks after the operation or earlier on patient request.Post-operative larynx visualization was performed only ifpatients described voice or swallowing abnormalities onspecific questioning. If any abnormality was detected onthe first post-operative visit, such as hypocalcemia orvocal cord palsy, the patients were followed monthly forup to a year or until the abnormality resolved.Data collection, variables and data sourcesFour co-investigators (OB, BAC, RMM, and KL) col-lected data retrospectively from August 2016 to May2017. Patient demographic and surgical indications datawas obtained from clinic notes. Procedures performed,surgical times, and admission duration data were ob-tained from hospital records. Surgical time was definedas the time from first incision to wound closure comple-tion as documented by the nursing staff.Operative dicta-tions were used to establish if conversion to analternative RLN dissection technique occurred. Patho-logical diagnoses and thyroid weights were determinedreviewing the final pathology reports.Data on the following complications were extractedfrom hospital and clinic records: temporary and perman-ent hypocalcemia and vocal cord palsy, hematoma, ser-oma, wound infection, and subcutaneous emphysema.Superior laryngeal neve palsy was not looked for duringthe follow up visit unless deemed necessary. Temporaryhypocalcemia was defined as any hypocalcemia requiringcalcium or vitamin D supplementation within 6 monthsof surgery. Permanent hypocalcemia was defined as anyhypocalcemia requiring supplementation for greater than6 months after surgery. Temporary vocal cord palsy wasdefined as the loss of true vocal cord adduction lastingless than 6 months of surgery, after which the palsy wasdeemed permanent. Hematoma was defined as anybleeding requiring reoperation or drain placement. Inaddition, the provincial health care database wasscreened for post-operative complications related hos-pital visits that might not have been captured in cliniccharts. Patients with missing data were included in thestudy.Surgical techniqueSkin incision, elevation of subplatysmal flaps, separationof strap muscles, and release of the sternothyroid mus-cles to expose the thyroid gland were performed in theusual manner. Unless invaded by the tumor, sternothyr-oid muscles were not cut. All vessel ligation was per-formed with Adson insulated bipolar forceps (KirwanSurgical Products, Marshfield, MA) without routine useof suture ties or surgical clips. RLN monitor was notused. The next four steps are critical to the describedtechnique.1. Isolation and division of the isthmus:The thyroid isthmus is isolated and divided over thetrachea using bipolar cautery.2. Subtotal division of Berry’s suspensory ligamentsand exposure of the cricothyroid region (Fig. 2):The divided edge of the isthmus is grasped with Babcockclamps and retracted laterally (Fig. 2a). Inferior to the firsttracheal ring, Berry’s suspensory ligaments are divided toseparate the thyroid away from the trachea (Fig. 2b).Retraction of the trachea toward the contralateral sidea b cFig. 2 Subtotal division of Berry’s suspensory ligaments and exposure of the cricothyroid region. a Schematic demonstrating anatomy andinstrument orientation; b Subtotal division of Berry’s ligaments; c Placing Berry’s ligament remnant on the stretch with avascular space openButskiy et al. Journal of Otolaryngology - Head and Neck Surgery  (2018) 47:57 Page 3 of 9facilitates performance of this step. Care is taken to dissectdirectly on the trachea, as the RLN will be protected by alayer of fascia and ligamentous tissue. Lateral to the firsttracheal ring the full thickness of Berry’s suspensory liga-ment is left intact (Fig. 2c).The avascular space between the superior pole and thecricothyroid muscle is developed avoiding damage to thesuperior laryngeal nerve and the cricothyroid muscle(Fig. 2c). Differential traction between the superior poleand the trachea (demonstrated by the Langenbeck re-tractors in Fig. 2a & c) is critical for exposure and identi-fication of the anatomical structures. Bowstring tensionpromotes isolation and identification of the Berry’s liga-ment remnant. Subsequent to injury-free identificationof the cricothyroid muscle, care is then taken to exposethe inferior border of the cricopharyngeus muscle, a crit-ical landmark for RLN identification (Fig. 2c).3. Identification and dissection of the recurrentlaryngeal nerve (Fig. 3):At this point, the remnant of the Berry’s ligamenttethers the thyroid to the superior portion of the firsttracheal ring and protects the RLN from the stretch ofthe retractors (Fig. 3a). Deep to the remnant are theRLN and the inferior thyroid artery terminal branches.The RLN runs in a plane posterior to Berry’s ligamentsand then turns medially to enter the larynx at the super-ior aspect of the ligamentous tissue, forming an anatom-ical ‘genu’ [8]. Careful dissection through the superiorportion of this ligamentous tissue using a fine mosquitoforceps and bipolar cautery allows identification of theRLN insertion under the inferior constrictor (Fig. 2b).Inferior border of the cricopharyngeus muscle is visual-ized at all times and serves as a landmark for the depthat which the RLN is found. Dissection is facilitated byjudicious and careful control of the inferior thyroid ar-tery terminal branches to avoid bleeding that can makeRLN visualization difficult. We use bipolar cautery tocontrol the terminal branches, with tips cooled with awet gauze between applications. As the remnant of theBerry’s ligament is transected, the retraction is reducedto avoid stretch injury to the RLN. Once the RLNbranches are identified, they are traced inferiorly by div-iding the remainder of the Berry’s suspensory ligamentand releasing the RLN from the thyroid gland. The max-imum extent of RLN dissection is 1 to 2 cm (Fig. 3c).4. Capsular dissection with preservation of parathyroidtissue and ligation of superior pole vessels (Fig. 4):The thyroid gland is then swept medially, deliveredthrough the wound, and retracted in an anterosuperiordirection (Fig 4a). With the RLN in direct view, a capsulardissection is undertaken from inferior to superior direc-tion. Elevation of the gland assists in exposure and isola-tion of the blood vessels feeding the parathyroid glands,helping their preservation under direct visualization(Fig. 4a).The thyroid lobe remains pedicled on the superiorpole vessels (Fig. 4b). Gentle retraction of the lobe infer-iorly allows for their ligation and division, releasing thethyroid from the wound (Fig. 4c). Hemostasis is achievedand multi-layered closure is performed in the usualfashion.ResultsThree hundred sixty-seven operations were eligible forinclusion. Twenty-five operations were excluded as ei-ther a central or a lateral neck dissection was performedconcurrently. Out of 342 surgeries included in the ana-lysis, 213 (62%) were hemi-, 91 (27%) were total, and 38a b cFig. 3 Identification and dissection of the recurrent laryngeal nerve (RLN). a RLN path deep to the Berry’s ligament remnant; b Berry’s ligamentremnant dissected to reveal the RLN and the terminal branch of the inferior thyroid artery (nerve is placed on retraction to demonstrate anatomyto the photographer); c Thyroid fascia divided. Superior Laryngeal Nerve (SLN)Butskiy et al. Journal of Otolaryngology - Head and Neck Surgery  (2018) 47:57 Page 4 of 9(11%) were completion thyroidectomies. The mean ageof the patients was 50 years (range: 13–89 years), and84% of patients were female.The most common indications for a total thyroidec-tomy were papillary thyroid carcinoma (40%) and thyro-megaly (27%) (Table 1). The most common indicationsfor a hemithyroidectomy were nodules of intermediatesuspicion for malignancy (54%) and thyromegaly (38%)(Table 1).The final pathology results showed a variety of benignand malignant conditions (Table 2). The median surgicaltimes for a total, hemi-, and completion thyroidectomywere 48 min (Interquartile range [IQR]: 40–60 min),39 min (IQR: 33–47 min) and 40 min (IQR: 35–51 min)respectively (Table 3).Complications experienced by the patients are summa-rized in Table 4. Out of 129 patients who underwenttotal or completion thyroidectomy, 17 (13%; 95% confi-dence interval [CI]: 8–20%) experienced transient and 4(3%; 95% CI:1–8%) experienced permanent hypocalce-mia. Out of 342 patients, 30 (9%; 95% CI: 6–12%) expe-rienced temporary (i.e. 7% of nerves at risk), and 1experienced permanent vocal cord palsy (0.3%; 95%CI:0.01–2%). There were no instances of bilateral vocalcord palsy. It was unclear what caused the majority oftemporary vocal cord palsies. In a minority of cases ofa b cFig. 4 Capsular dissection with preservation of parathyroid tissue and ligation of superior pole vessels. a Identification of parathyroid glands whilekeeping the recurrent laryngeal nerve (RLN) under direct view; b Isolation and ligation of superior pole vessels; c Surgical bed after resectionTable 1 Indications for surgeryTotal thyroidectomyn = 91Hemi-thyroidectomyn = 213Completion thyroidectomyn = 38Totaln = 342Nodules requiring diagnosisIntermediate suspicion for malignancy – 114 (54%) 2 (5%) 116 (34%)High suspicion for malignancy 15 (16%) 2 (1%) 1 (3%) 18 (5%)ThyromegalyObstructive/Symptomatic 20 (22%) 73 (34%) 6 (16%) 99 (29%)Substernal goiter 5 (5%) 8 (4%) – 14 (4%)MalignancyPapillary carcinoma 36 (40%) 2 (1%) 17 (45%) 55 (16%)Follicular carcinoma – – 8 (21%) 8 (2%)Poorly differentiated carcinoma – – 1 (3%) 1 (0.3%)Lymphoma – – 1 (3%) 1 (0.3%)Endocrinological diseasesGraves’ disease 13 (14%) 1 (0.5%) 1 (3%) 15 (4%)Hashimoto thyroiditis 1 (1%) 2 (1%) – 3 (1%)OtherSymptomatic cyst – 9 (4%) – 9 (3%)PET incidentaloma 1 (1%) 2 (1%) – 3 (1%)Butskiy et al. Journal of Otolaryngology - Head and Neck Surgery  (2018) 47:57 Page 5 of 9temporary vocal cord palsy, the dictating surgeon com-mented on the difficulty due to inflammation and bleed-ing. In the single instance of permanent vocal cordparalysis, a RLN nerve branch was cut.In 3 patients (1%) a conversion to an alternativemethod of RLN dissection was needed, this was due todifficulty in controlling bleeding (2 cases) and densescarring superior to Berry’s ligament (1 case).DiscussionIn this study we introduce a systematic approach to dis-secting the RLN at the cricothyroid junction, referred tohere as the retrograde medial approach. The outcomes ofthis approach were investigated through a retrospectivereview of a single surgeon’s cohort of patients. The ratesof transient and permanent vocal cord palsy were 9% (95%CI: 6–12%) and 0.3% (95%CI: 0.01–2%) respectively, whilethe rates of transient and permanent hypocalcemia were13% (95% CI: 8–20%) and 3% (95% CI: 1–8%) respectively.The retrograde medial approach appears to be fast, with amedian surgical time of 41 min.Three previous studies have described using the super-ior approach to finding the RLN. While the authors of onestudy do not describe the specific technique [9], the au-thors of the other two studies followed the technique firstdescribed by Shindo et al [6, 10]. This technique involvesreleasing the superior pole, finding and releasing the tu-bercle of Zuckerkandl, retracting the gland medially, andthen searching for the RLN as it courses towards thecricothyroid junction. Shindo et al. acknowledged the vari-ability in the angle that the RLN takes as it approaches thecricothyroid junction and classified it into four categories.The authors also acknowledged that their technique is dif-ficult in cases of nonrecurrent RLN, presence of large tu-bercle of Zuckerkandl, and extrathyroidal extension ofcancer along the distal RLN segment.Table 2 Pathological diagnosesTotal thyroidectomy(n = 91)Hemi-thyroidectomy(n = 213)Completion thyroidectomy(n = 38)Total(n = 342)MalignanciesPapillary 50 (54%) 22 (10%) 12 (32%) 84 (25%)Follicular 1 (1%) 11 (5%) 2 (5%) 14 (4%)Poorly differentiated 1 (1%) 1 (0.5%) – 2 (1%)B-Cell lymphoma – 1 (0.5%) – 1 (0.3%)Renal cell carcinoma 1 (1%) – – 1 (0.3%)GoitersMultinodular goiter 16 (18%) 73 (34%) 9 (24%) 98 (29%)Diffuse goiter 1 (1%) 5 (2%) 1 (3%) 7 (2%)Endocrine diseasesGraves’ disease 8 (9%) 1 (0.5%) – 9 (3%)Hashimoto’s thyroiditis 7 (8%) 10 (5%) 1 (3%) 18 (5%)Other benign pathologyFollicular adenoma 4 (4%) 65 (31%) 1 (3%) 70 (20%)Thyroid cyst – 5 (2%) – 5 (2%)Not otherwise specified 2 (2%) 19 (9%) 12 (32%) 33 (10%)Table 3 Surgical timesTotal thyroidectomyMedian (IQR)Hemi-thyroidectomyMedian (IQR)Completion thyroidectomyMedian (IQR)TotalMedian (IQR)All indications 48 min (40–60 min) 39 min (33–47 min) 40 min (25–93 min) 41 min (35–51 min)Nodules requiring diagnosis 42 min (39–50 min) 38 min (32–44 min) 29 min (27–56 min) 39 min (32–45 min)ThyromegalyObstructive/Symptomatic 57 min (47–66 min) 41 min (35–50 min) 41 min (33–54 min) 44 min (37–53 min)Substernal goiter 84 min (50–98 min) 60 min (52–65 min) 93 min 64 min (51–81 min)Malignancy 47 min (40–53 min) 51 min (45–55 min) 39 min (36–46 min) 43 min (38–51 min)Graves’ disease 55 min (43–63 min) 60 min 67 min 56 min (43–65 min)Abbreviations: IQR interquartile range, min minutesButskiy et al. Journal of Otolaryngology - Head and Neck Surgery  (2018) 47:57 Page 6 of 9In the presented retrograde medial approach, theRLN nerve is found early prior to the release of thesuperior pole and exploration of the thyroid’s lateralside. Given that the RLN is found superior to theBerry’s ligament, the variability in the angle that RLNtakes in its approach has no impact on the dissection.Furthermore, the retrograde medial approach is pref-erential in cases with nonrecurrent RLN, large Zuck-erkandl’s tubercle, and in the majority of cases withextrathyroidal extension of cancer along the distalRLN segment (with exception of cricothyroid junctioninvolvement). We find the retrograde medial approachespecially useful in cases of large goiters. Finally, anadditional advantage of the retrograde medial ap-proach is that no thyroid tissues is left unresected atthe cricothyroid junction.Some surgical situations make the use of retrogrademedial approach difficult. The method relies on split-ting the thyroid isthmus and identifying the inferiorborder of the cricopharyngeal muscle. If a surgeon isunable to complete these steps, either due to fear oftumor spillage with the isthmus division or extensivescarring, bleeding, or presence of tumor at the crico-pharyngeus muscle or the cricothyroid junction, it isadvisable that the lateral or inferior approach to thethyroidectomy is used.With the use of the retrograde medial approach, therates of permanent vocal cord palsy and hypocalcemiaare similar to the rates reported with other superiorapproaches to finding the RLN; however, the rates oftemporary vocal cord palsy and hypocalcemia appearhigher. With regard to the permanent complications, ina study of 181 patients, Sykes et al. reported permanentvocal cord palsy and hypocalcemia rates of 0.4% and2.2% respectively [10]. In a study of 67 patients, Veysel-ler et al. reported the corresponding rates to be 0 [9].With regard to the transient complications, Sykes et al.reported a 2.2% rate of temporary vocal cord palsy [10];whereas Veyseller et al. reported temporary vocal cordpalsy and hypocalcemia rates of 0% and 8.3% respect-ively [9].There are a number of possible reasons to why therates of temporary complications were higher in thepresented study than in the studies discussed above.First, given different sizes and compositions of popula-tions studied, the difference could be secondary tosampling variability. Second, the difference might bedue to different definitions of temporary complica-tions. Specifically, compared to the mentioned studieswe used a more liberal definition of hypocalcemia – re-quirement for calcium or vitamin D supplementationregardless of the reason. Finally, the technique de-scribed in this paper could be the reason for highertemporary complication rates. For example, the exclu-sive use of bipolar cautery could be responsible fortransient RLN and parathyroid gland heat damage.Some surgeons might also suggest that traction at theBerry’s ligament transferred to the RLN might be re-sponsible for higher transient vocal cord palsy rate.However, there is no tension on the nerve until thesuspensory ligament is divided. Recognizing this is apoint of importance and teaching. After division of thesuspensory ligament the nerve is dissected out fromtop to bottom while on the slack at the fixation pointat entrance to larynx.Comparing the outcomes of the retrograde medialtechnique to the outcomes of the two other approaches(lateral and inferior) is difficult given that one approachis rarely used exclusively. Perhaps the best estimate ofthyroidectomy complication rates comes from nationalstudies. For example, the 2008 study of ScandinavianQuality Register for Thyroid and Parathyroid SurgeryTable 4 Course in hospital and complicationsTotal thyroidectomyn = 91Hemi–thyroidectomyn = 213Completion thyroidectomyn = 38Totaln = 342Nights in hospital – median (Range) 1 (0–30) 0 (0–3) 1 (1–7) 1 (0 – 30)Conversion to alternative approach – n (%) 2 (2%) – 1 (3%) 3 (1%)Complications – n (%)Transient hypocalcemia 16 (18%) – 1 (3%) 17 (5%)Permanent hypocalcemia 1 (1%) – 2 (5%) 3 (1%)Temporary vocal cord paresis/Paralysis 13 (14%) 14 (7%) 3 (8%) 30 (9%)Permanent vocal cord paresis/Paralysis 1 (1%) – – 1 (0.3%)Hematoma 1 (1%) 4 (2%) 1 (3%) 6 (2%)Seroma – 1 (0.5%) –Wound infection 5 (6%) 3 (1%) 1 (2.6%) 9 (3%)Subcutaneous emphysema 1 (1%) 2 (1%) – 3 (1%)Butskiy et al. Journal of Otolaryngology - Head and Neck Surgery  (2018) 47:57 Page 7 of 9reported complication rates based on 3660 thyroidecto-mies [12]. In this report, the authors presented data onhypocalcemia defined identically to our study – the useof supplemental calcium and/or vitamin D at the firstpost-operative visit and 6 months after surgery. Usingthis definition, the rates of transient and permanenthypocalcemia in the Scandinavian study (17% and 6% re-spectively) appear similar to our study (13% and 3% re-spectively). With regard to vocal cord palsy, the authorsof the Scandinavian study report temporary palsy rateslower than in our study (3.9% versus 9% respectively),but the permanent palsy rates appear similar to ourstudy (0.9% versus 1% respectively).With regard to surgical time, the authors of the studiesdescribed above do not report on the surgical speed.The speed of the described technique appears similar tothe techniques described in recent meta-analyses and re-views of ultrasonic and electrothermal devices in thyroidsurgery [13, 14]. For example, the authors of a recentmeta-analysis concluded that a total thyroidectomy isperformed faster with the use of Harmonic Focus® (Ethi-con Inc., Cincinnati OH) than with the use of clips andties [13]. The pooled average time for a total thyroidec-tomy using the Harmonic Focus® was 66 min and theaverage time for the conventional technique was 95 min[13]. In comparison, the average time for a total thyroid-ectomy in our series was 48 min.Short operative time with the retrograde medial ap-proach is possibly due to early RLN identification in aconsistent location. The remaining dissection can thenproceed quickly without concern of RLN injury. This isin contrast to the lateral approach in which completeRLN dissection is one of the last operating steps. We ac-knowledge that aside from the RLN dissection techniquethere might be other reasons for shorter operative time.These include the use of bipolar cautery in place of clipsand ties and the surgical experience of the author.The presented study has strengths. First, the describedapproach, while likely known to experienced thyroid sur-geons, has not been previously reported in surgical lit-erature. Second, while the presented technique is notmeant to be prescriptive, prior to this study there hasbeen no attempt to standardize identification of RLN atthe cricothyroid junction. Finally, this study reports onthe largest cohort of patients in literature for whom thesuperior approach to identifying RLN was used.This series has limitations. First, a retrospective reviewmight have resulted in missing data for complications. .Second, the study represents a single surgeon’s experi-ence, possibly limiting the generalizability of the find-ings. Finally, our study excluded patients requiringlateral and central neck dissection; therefore, further in-vestigation is required to determine the utility of theretrograde medial approach in such cases.ConclusionA retrograde medial approach to identifying the RLN atthe cricothyroid junction is described. This technique isuseful in dissecting large goiters and when lateral RLNidentification is difficult. In a tertiary endocrine headand neck practice, the routine use of the retrogrademedial approach is safe and results in short operativetime and a low conversion rate to other RLN dissectionapproaches.AcknowledgmentWe would like to thank Mr. Callum Faris for encouragement to publish theretograde medial approach and his assistance with study design.Availability of data and materialsThe datasets used and/or analysed during the current study are availablefrom the corresponding author on reasonable request.Authors’ contributionsAll authors contributed to study design. All authors with exception of DWAparticipated in data collection. OB analyzed the data and prepared themanuscript. All other authors edited the manuscript for publication. Allauthors read and approved the final manuscript.Ethics approval and consent to participateInstitutional ethics approval was granted for the project (H15-01667).Consent for publicationNot applicableCompeting interestsThe authors declare that they have no competing interests.Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims inpublished maps and institutional affiliations.Received: 14 April 2018 Accepted: 3 September 2018References1. Bhattacharyya N. The increasing workload in head and neck surgery: anepidemiologic analysis. Laryngoscope. 2011;121(1):111–5. https://doi.org/10.1002/lary.21193.2. 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