Postoperative Pain Evaluation After Robotic Transaxillary Thyroidectomy Versus Conventional Thyroidectomy: A Prospective Study

Abstract

Background:

Robot-assisted transaxillary thyroidectomy (RATT) is an emerging technique with excellent cosmetic results but is supposedly more invasive and painful than conventional thyroidectomy (CT). This prospective study compared pain after RATT and CT.

Methods:

Inclusion criteria were a nodule <5 cm and volume <30 mL. Patients received the same analgesia. Pain was evaluated by visual analog scale (VAS) in the recovery room (VASrr), on the first postoperative day at 8:00 a.m. (VAS 8 a.m.) and 8:00 p.m. (VAS 8 p.m.), at 8:00 a.m. on the second postoperative day (VAS 8*a.m.), and after 7 days (VAS 7). Operative time and complications were evaluated.

Results:

From May 2015 to September 2015, 124 patients (all women) underwent thyroidectomy: 62 underwent RATT and 62 underwent CT. Mean age was 39.7 ± 10.2 years in the RATT group and 41.4 ± 12.5 years in the CT group. Groups were comparable for thyroid volume and nodule diameter. Operative time was longer in the RATT group than in the CT group (119.4 ± 25.5 versus 70.3 ± 11.0 minutes). Complications were three transient hypocalcemia in RATT and four in the CT group. No definitive complications occurred. VASrr was lower in the RATT group (1.79 ± 2.06 versus 2.5 ± 1.18; P < .0001). There was no difference between groups for VAS 8 a.m., VAS 8 p.m., and VAS 8*a.m., but VAS 7 was higher in the RATT group (0.85 ± 1.77 versus 0.17 ± 0.52; P < .010).

Discussion:

RATT is as safe and effective as CT. Patients undergoing RATT, surprisingly, experienced less pain in the immediate postoperative period. However, the VAS 7 score was higher in the RATT group, probably because the intact neck is favorable in the early phase of recovery, but the large dissection takes longer for healing.

Introduction

Conventional open thyroidectomy (CT) is still considered the gold standard for the surgical treatment of thyroid diseases and is extremely safe when performed by expert surgeons. CT has a low level of pain and a short hospital stay; however, it results in a 5- to 6-cm scar in the neck that is usually barely visible but sometimes has a poor cosmetic outcome, especially when a hypertrophic scar develops.¹

Robot-assisted transaxillary thyroidectomy (RATT) was described in 2007 by Woong Youn Chung from South Korea. This technique combines the use of transaxillary access and the assistance of the da Vinci Si robot (Intuitive Surgical, Inc.). The robot increases operating capability and makes working in small spaces easier. The advantages are granted by magnified and enhanced three-dimensional vision, computer-controlled movement, and wrist-articulated instruments.²

RATT quickly gained a widespread consensus in Eastern countries, probably because poor wound healing is more frequent and an aversion for a neck scar is typical in Asian culture.³ Several current studies have demonstrated its feasibility, safety, and oncologic completeness, as well as excellent cosmetic result and patient satisfaction.^4–7 A few centers in Europe have started performing RATT, but until now, no large series have been available to rate the effect of RATT on the European population, which might be different because of higher body mass index (BMI) and larger mean thyroid volume.^8,9

The technique was introduced in 2011 at our institution, and from the beginning, optimal results were recorded, particularly in patient satisfaction and cosmetic outcome.¹⁰ Regarding both of these parameters, RATT has been demonstrated in our experience to be at the same level of minimally invasive video-assisted thyroidectomy (MIVAT), confirming that RATT may be an optimal therapeutic option for patients who are concerned about cosmetics but for whom MIVAT is not applicable or for those patients who totally refuse a scar in the neck.

Other aspects, such as postoperative pain, remain unclear. This feature cannot be considered unimportant because it deeply affects the surgical outcome, especially for RATT. RATT cannot be assumed to be a minimally invasive technique because large subcutaneous dissections are required to perform the access and prolonged flap retraction is necessary to maintain the operating space. Furthermore, the patient is positioned on the operating table with the neck and the arm hyperextended, and this position lasts for a longer time in RATT than in CT.

Our aim was to prospectively compare pain after RATT and CT.

Methods

Patients and study design

From May 2015 to September 2015, we enrolled in this prospective double-arm study 124 patients undergoing total thyroidectomy in the University Hospital of Pisa Endocrine Surgery Unit. All patients were preoperatively assessed with an ultrasound examination of the neck, thyroid hormones sampling, and fine-needle aspiration cytology. Criteria for inclusion in the study were (1) age between 18 and 65 years; (2) preoperative ultrasound-estimated thyroid volume of <30 mL; (3) size of the largest nodule <5 cm; and (4) American Society of Anesthesiologists Physical Status Classification score of 1 or 2.

Exclusion criteria were (1) local invasion of adjacent organs (e.g., trachea, esophagus, recurrent laryngeal nerve, and larynx); (2) presence of cervical lymph nodes suspicious for metastatic involvement; (3) absence of euthyroidism; (4) intrathoracic goiter, previous neck operation, or neck irradiation; or (5) chronic use of analgesic drugs for chronic diseases.

Patients were grouped according to whether they underwent RATT (group robotic thyroidectomy [RT]) or CT (group CT), with 62 in each group. A surgeon expert in both procedures explained to each patient considered for the study the details of RATT and CT. Each patient was free to choose the procedure to undergo according to personal preference. All patients provided an informed consent for this study. All procedures were performed by the same surgeon (G.M.) to avoid any possible bias due to different surgical skills.

In all cases, general anesthesia was induced with propofol (1–3 mg/kg) and a neuromuscular blocking agent (rocuronium, 0.3 mg/kg) to facilitate orotracheal intubation. Total intravenous anesthesia was performed in all patients with propofol (5–6 mg/kg/hour) and remifentanil (0.25–0.35 μg/kg/minute) and with fraction of inspired oxygen of 0.5. All patients received intraoperative intravenous paracetamol (1 g), ketorolac (30 mg), and morphine (0.1 mg/kg) plus ondansetron (4 mg) and dexamethasone (8 mg) to prevent postoperative nausea and vomiting. On emergence from anesthesia, the pain protocol used (if required) in the recovery room was as follows: patients with a pain score of 5 or more on the 11-point (0–10) verbal pain scale rating received morphine (1–3 mg). As postoperative analgesia, all patients received ketorolac (30 mg every 8 hours) and, as rescue dose, paracetamol (1 g maximum every 6 hours).

Study primary endpoint was to compare the postoperative pain between the two procedures. Postoperative pain was determined in both groups using the visual analog scale (VAS), an 11-point scale from 0 to 10, where 0 represents absence of pain and 10 represents the worst pain imaginable by the patient. Postoperative pain was assessed in the recovery room (VASrr), then on the first postoperative day at 8 a.m. and 8 p.m. (VAS 8 a.m. and VAS 8 p.m.), on postoperative day 2 at 8 a.m. (VAS 8*a.m.), and finally, 7 days after surgery (VAS 7).

Secondary endpoints were operative time and hospital length stay as variables to assess the whole outcome of the two procedures. Data were collected on age, sex, BMI, thyroid volume, nodule diameter (in case of multiple nodules, the largest and/or the suspicious one was considered), operative time from oral intubation to extubation, final histology report, and hospital postoperative length of stay.

Complications were also assessed, but due to the limited number of the patients and the small incidence of complications in thyroid surgery, no statistical comparison was possible. Endoscopic laryngoscopy was performed in all patients immediately before and 3 months after thyroidectomy to assess vocal cord motility. Recurrent laryngeal nerve injury was considered permanent if persistent 6 months after surgery. Serum calcium levels were sampled to determine hypoparathyroidism on first and second day after surgery, 5 days after surgery, and once weekly for 1 month.

The Shapiro–Wilk test was performed to verify normality of the distributions. The Mann–Whitney test was used to compare the variables of the two groups. Post hoc power analysis was performed to estimate the sample size, and the 1-β values of the significant variables were >0.8, ensuring a low risk of type II error and an appropriate sample size. Statistical analysis was performed using the IBM SPSS 17.0.1 software (IBM Corp.).

Surgical techniques

CT was performed with the patient supine, with neck hyperextension, through a central transverse 5- to 6-cm incision that placed two fingers above the sternal notch. Hemostasis was achieved by means of standard ligatures, ultrasonic dissector, and titanium clips. One drain was placed at the end of the procedure.

Robot-assisted transaxillary thyroidectomy

The da Vinci Si system was used in all procedures. The patient was placed supine with one arm extended over the shoulder, and the neck was slightly hyperextended. A 5- to 7-cm skin incision was placed along the posterior border of the pectoralis major muscle. After the working space was created, Chung's retractor was used to maintain the operative space. Only three robotic arms were used in all operations. During the docking of the robot, the dual-channel endoscope was positioned on the central robotic arm; the harmonic curved shears were positioned on the upper side arm in the corner of the wound, and the Maryland dissector (Intuitive Surgical) was positioned on the lower side arm in the opposite corner.

The first step was the section of the upper pedicle; then, the thyroid lobe was retracted medially. The surgeon started the identification of the recurrent laryngeal nerve, dissecting the tracheoesophageal groove with the harmonic shears by cutting or, alternatively, with the Maryland dissector bluntly. The parathyroid glands were identified and prepared. Once the critical structures were identified, the thyroid lobe was dissected with the harmonic scalpel, and the specimen was removed. The contralateral lobectomy started with the complete mobilization of the isthmus and the separation of the lobe from the strap muscles. The upper pedicle was exposed, and the lobe was dragged downward laterally and then cut and sealed with harmonic shears. After the lower pole was completely mobilized, the recurrent laryngeal nerve was identified, the parathyroid glands were identified and preserved, and the lobe was removed. A drain was left in the operative space, and the skin was closed with subcuticular running suture.

Results

All of the 124 recruited patients were women. The two groups were well matched for age, thyroid volume, nodule diameter, and BMI (Table 1). The mean age was 39.7 ± 10.2 years in group RT and 41.4 ± 12.5 years in group CT (P = .294). Mean patient BMI was 20.9 ± 2.21 kg/m² in group RT and 22.1 ± 2.75 kg/m² in group CT (P = .059). Mean preoperative estimated thyroid volume was 18.3 ± 4.75 mL in group RT and 17 ± 5.03 mL in group CT (P = .296). Mean nodule diameter was 21.6 ± 12.1 mm in group RT and 23.9 ± 9.4 mm in group CT (P = .125).

Table 1.

Preoperative Features and Results After Transaxillary Robotic Thyroidectomy Versus Conventional Thyroidectomy

	Group RT	Group CT	P
Age, years	39.7 ± 10.2	41.4 ± 12.5	.294
Thyroid volume, mL	18.3 ± 4.75	17 ± 5.03	.296
Nodule diameter, mm	21.6 ± 12.1	23.9 ± 9.4	.125
Body mass index, kg/m²	20.9 ± 2.21	22.1 ± 2.75	.059
Preoperative diagnosis
Multinodular goiter	21	24
Microfollicular nodule	29	27
PTC	12	11
Operative time, minutes	119.4 ± 25.5	70.3 ± 11	<.001
Complications
Hypocalcemia	3	4
RLN palsy	0	0
Postoperative bleeding	1	0
Hospital length of stay, days	3.9 ± 2.15	2.8 ± 1.13	.0128

Continuous data are shown as mean ± standard deviation, and categoric data as numbers of patients.

RT, robotic thyroidectomy; CT, conventional thyroidectomy; PTC, papillary thyroid carcinoma; RLN, recurrent laryngeal nerve.

The preoperative diagnosis was 21 multinodular goiters, 29 microfollicular nodules, and 12 papillary carcinomas in group RT, and 24 multinodular goiters, 27 microfollicular nodules, and 11 papillary carcinomas in group CT. The final histology report confirmed malignant diseases in the 23 patients of the two groups. In group RT, 2 of 24 patients with multinodular goiter as the preoperative diagnosis presented microfoci of papillary carcinoma (0.4 and 0.7 mm), and 15 of 29 patients with a microfollicular nodule as preoperative diagnosis were confirmed to have papillary carcinoma at the definitive pathologist's report. In group CT, no patients with a preoperative diagnosis of multinodular goiter presented malignancy, and 10 of 27 patients with microfollicular nodule as the preoperative diagnosis were confirmed to have papillary carcinoma at the definitive pathologist's report.

Mean operative time was 119.4 ± 25.5 minutes in group RT and 70.3 ± 11.0 minutes in group CT (P < .001). No conversions to open cervicotomy were recorded in group RT. No permanent complications were observed. Transient hypocalcemia occurred in 3 patients in group RT and in 4 patients in group CT. One patient presented a minimal hematoma at the level of the tunnel, which was treated conservatively with observation and antibiotics. The patient was discharged on postoperative day 3. Mean hospital length of stay was 3.9 ± 2.15 days in group RT and 2.8 ± 1.13 days in group CT (P = .0128).

The mean VASrr was 1.79 ± 2.07 in group RT and 2.5 ± 1.18 in group CT (P < .0001). The mean VAS 8 a.m. was 2.11 ± 2.02 in group RT and 1.65 ± 1.06 in group CT (P = .504). The mean VAS 8 p.m. was 1.37 ± 1.94 in group RT and 0.61 ± 0.73 in group CT (P = .076). The mean VAS 8*a.m. was 0.87 ± 1.7 in group RT and 0.3 ± 0.53 in group CT (P = .473). The mean VAS 7 was 0.86 ± 1.77 in group RT and 0.18 ± 0.53 in group CT (P < .01; Table 2).

Table 2.

Pain Evaluation After Conventional Thyroidectomy and Robotic Thyroidectomy

	Group RT	Group CT	P
VASrr	1.79 ± 2.07	2.5 ± 1.18	<.0001
VAS 8 a.m.	2.11 ± 2.02	1.65 ± 1.06	.504
VAS 8 p.m.	1.37 ± 1.94	0.61 ± 0.73	.076
VAS 8^*a.m.	0.87 ± 1.7	0.3 ± 0.53	.473
VAS 7	0.86 ± 1.77	0.18 ± 0.53	<.01

Mean ± standard deviation.

RT, robotic thyroidectomy; CT, conventional thyroidectomy; VAS, visual analog scale; rr, recovery room; 8^*a.m., second postoperative day.

Discussion

In the field of thyroid surgery, a group of Korean surgeons developed the RATT in the last decade, with the major purpose to increase the cosmetic outcome, which plays an important role because most of the patients undergoing thyroid surgery are women.² The RATT procedure shifts the surgical scar from the well-exposed anterior neck region to the hidden axillary region, with an excellent cosmetic outcome and better patient satisfaction.^4,6,10 Several studies have demonstrated the optimal results of this technique in Asian patients, reporting good safety, cosmetic outcome, and oncologic radicality.^4–6

Recent studies comparing RATT with CT⁷ have also confirmed good results for RATT in terms of postoperative pain, which is considered to have a major effect on patient wellness. In fact, high or prolonged pain is not only a major reason for worsening the postoperative psychological patient's experience but it might be also the most frequent cause of prolonged hospital stay that may lead to an increase of sanitary costs.¹¹ In addition, untreated acute pain is a significant predictor of chronic pain and disability, itself a major societal burden.¹² Effective pain management is a mark of a civilized society, and some have argued that it should be considered a basic human right.¹³ Finally, patients often worry preoperatively about the amount of pain they will experience after surgery, and they may refuse the proposal of a surgical treatment that causes major pain. Hence, further studies are required to investigate the outcomes of RATT in a European population, which may differ substantially from an Asiatic population, as it was done with a North American population in other publications.¹⁴

The results of this study show that immediately after surgery, patients in group RT experienced less pain than patients in group CT. Possible reasons are attributable to the different site of the incision, because the skin of the neck presents more pain receptors than the skin of the axilla, and the different mobility of the incision site. The patient can keep easily the shoulder fixed in an antalgic position, but keeping the neck in a fixed position is more difficult. Plus, the neck during RATT is only slightly hyperextended, whereas the neck hyperextension in CT is commonly thought to represent an important source of pain.¹⁵

The pain experienced between the two groups during the remaining hospitalization period was not statistically different. However, a difference between the two groups was observed a week after surgery, with patients in group CT referring less pain than those in group RT. We believe this is explained by the more extended dissection in RATT that takes longer to heal completely. Another potential explanation is that after a week, patients return almost completely to active life, moving the arm and, subsequently, the skin of the axilla with more energy than the skin of the neck. A potential drawback of this result is that RATT could have a slower recovery after surgery, prolonging patient's inactivity and increasing social costs. However, both techniques showed low scores of postoperative pain in the entire period, suggesting that even if there was some statistically relevant difference between the two procedures in postoperative pain, these differences were not clinically relevant.

An unexpected finding was that the extended dissection required in RATT to create the access did not play a significant role in determining postoperative pain. This aspect may be connected with the surgical concept that if the dissection is performed respecting the surgical plane of the major pectoralis fascia, where few pain receptors are located, the pain produced is low, even if the dissection is more extended.

In the present series, there were no differences in complications, but a statistical comparison was not possible because of the small number of patients enrolled. RATT probably balances with the three-dimensional enhanced endoscopic view and with the steadiness of robotic arms, the narrower the operating field. The absence of permanent complications was similar to those reported in several other reports, which have showed a similar complication rate in both techniques, proving that RATT can be considered a safe procedure.^4,16

When analyzing the duration of the procedures, we found that RATT is significantly longer than CT. In addition, hospital stay was longer for group RT patients. Both aspects represent important disadvantages in terms of indirect costs. Although a cost analysis was not one of the aims of this study, several studies have demonstrated that RATT produces a significant increase of costs, raising many objections concerning the correct allocation of resources.^17,18

In conclusion, RATT is not disadvantaged from an increase of immediate postoperative pain, as the large dissection required may suggest, but seems to be characterized by a greater persistence of pain, which may result in a longer convalescence.

Footnotes

Disclosure Statement

No competing financial interests exist.

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