The results of complications are listed in Table 3. None of the cases required conversion to open surgery. One patient treated by each surgeon experienced transient hoarseness (total: 2.0%; A: 1/56 cases, 1.8%; B: 1/45 patients, 2.2%). Transient hypoparathyroidism (serum level of parathyroid hormone<12 pg/mL) was observed in 8 of the 101 patients (7.9%), including 4 of 56 cases (7.1%) treated by surgeon A and 4 of 45 patients (8.9%) treated by surgeon B. There were 5 patients (5.0%) who needed parathyroid autograft, including 1 of 56 cases (1.8%) in surgeon A and 4 of 45 patients (8.9%) in surgeon B. The rate of postoperative skin ecchymosis was 3%, and included 2 of the 56 cases (3.6%) treated by surgeon A and 1 of the 45 patients (2.2%) treated by surgeon B. Postoperative subcutaneous fluid was observed in 2 patients (2.0%) treated by surgeon A. No patients experienced recurrent laryngeal injury, permanent hypoparathyroidism, facial numbness/paresis, maxillofacial/wound infection, or other serious complications (eg, tracheal injury, esophagus injury, teeth injury, fever, bleeding). There were no patients requiring reoperation or readmission after the operation.
According to some previously published articles on transoral vestibular endoscopic thyroid surgery,8,9,11,12 ETOVA is associated with good safety and feasibility, despite some challenges, and allows the complete avoidance of visible cutaneous scars.8,11 However, the oral-vestibular approach is limited with respect to the ability to create an artificial workspace. Furthermore, the operating and observation ports are very close together, thus causing increased interference and operating difficulties. Therefore, the learning curve and steps associated with ETOVA are distinct from those of other thyroidectomy approaches.
The learning curves vary for different endoscopic thyroidectomy procedures. For areola approach, Cao et al13 reported that the primary stage comprised 25 cases, whereas Liu et al14 reported that at least 60 cases were required to achieve a shorter operative time and low complication rate. In our opinion, different institutes and surgical teams may experience different learning curves even for the same procedure. In the present study, the 56 and 45 patients treated by surgeons A and B, respectively, were divided according to stage. From the learning curve determined in our study (Fig. 7), both surgeons reached advanced levels of procedural skills, proficiency, and stability after 19 or 20 cases. ETOVA was initially reported by surgeons with sufficient endoscopic thyroidectomy experience2,15 and a detailed understanding of the anatomy of the neck. Accordingly, no significant differences between stages were observed in terms of the intraoperative blood loss and postoperative hospital stay duration. During the primary stage, both surgeons gained a perceptual awareness of the procedural steps while refining their skills, leading to significant reductions in operation times and a steady state after a small number of cases (~20). In addition, the rate of drainage tube reservation decreased greatly during the advanced stage.
We have identified several challenges that should be noted. (1) The separation of the mucous membrane in oral vestibule and loose tissue in the neck represented a critical difficulty. Accordingly, sufficient cases are needed to ensure that the surgeon’s manipulation and workspace-building skills improve. We recommend that a training surgeon initially imitate and practice under the watchful guidance and feedback of a supervisor. (2) Insertion of the trocars around the mandibular chin also represented a considerable difficulty and required an appropriate understanding of the operating steps. (3) The subcutaneous dissection area during this procedure was reduced in comparison with that of the areola or breast approach. However, operative bleeding and injury were minimized with increased experience, and drainage tubes were rarely needed during the advanced stage. (4) A training surgeon should initially adapt to the change in endoscopic view and overcome the challenging operating restrictions. As these restrictions are onerous, we recommend that trainees have surgical experience with endoscopy. (5) As the operating and endoscopy ports are located in close proximity, the endoscope holder should cooperate expertly with the surgeon by adjusting the position and angle of the endoscope to maintain a good video image and prevent fogging. (6) During the primary stage of training, this technique should only be used to target benign thyroid disease or malignant tumors <3 cm in size. With increased experience and the evolution of surgical skills (eg, other learning curves),16,17 the indications for ETOVA can be expanded to include PMTC, total thyroidectomy, and central lymph node dissection. In this study, we found that ETOVA provided a better endoscopic view and approach for the steps of central lymph node dissection.
In this study, we observed a low rate of complications. Transient hoarseness and recurrent laryngeal nerve injury occurred at respective rates of 2.0% and 0%, which were similar to those reported for conventional open surgery.18,19 The transient and permanent hypoparathyroidism rates of 7.9% and 0%, respectively, were also comparable with those of open thyroidectomy20,21 (0% to 11% and 0% to 5.7%, respectively). The skin ecchymosis (n=3) and subcutaneous fluid (n=2) accumulation occurred in the primary stage, but none of these cases occurred in the advanced stage. The reason was that inexperience skill mainly attributed to excessive damage during workspace building. In our opinion, most complications can be controlled and prevented as experience accumulates (especially in the advanced stage). However, transient hoarseness and transient hypoparathyroidism still occurred in the primary and advanced stages. Both of these complications are the most common problems in thyroid surgery. It was worth mentioning that no other serious complications occurred. Furthermore, in comparison with the oral cavity approach, ETOVA allowed us to more easily treat or compress incisions to avoid bleeding and wound infection. Therefore, we consider ETOVA to be safe and effective.
We note that this study of the learning curves of 2 surgeons had some limitations. First, the patients enrolled in our study were almost exclusively female (92.1%), young (mean age: 28.7±9.1 y), and nonoverweight (body mass index, 20.8±1.9 kg/m2). Therefore, future studies should include larger, more diverse patient populations (eg, male, overweight/obese, and/or older patients). Second, more surgeons (especially those with little endoscopic experience) and a larger number of cases are needed to further assess the learning curve. Third, beyond the operation time, additional parameters should be evaluated to more accurately assess a surgeon’s proficiency. Finally, a randomized and prospective study should be conducted to assess the effects of a standardized training program on the learning curves of training surgeons.
On the basis of our results, a training surgeon with sufficient endoscopic surgical experience could be expected to achieve proficiency with ETOVA and a stable state after a learning curve of ∼20 cases. We further note that for selected patients, the postoperative outcomes and complication rates were comparable with those reported for the conventional open approach. Finally, more research is needed to determine the accurate assessment criteria for the learning curve and to establish a standardized training program.
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Keywords:Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.
endoscopic thyroidectomy; oral-vestibular approach; learning curve; endoscopic surgery