We retrospectively reviewed medical records of 701 consecutive patients who underwent surgery for treatment of PTC between March 2006 and December 2007 in the Department of Surgery, Yonsei University College of Medicine, by one experienced surgeon (KHN). Preoperative diagnoses of thyroid nodules were made by ultrasonographic-guided fine needle aspiration biopsy and neck computed tomography.

In October 2006, we began routine use of HS in thyroid surgery. Thus, of the 701 patients treated, 200 had conventional total thyroidectomy (CT group; from March to September 2006), and 501 had TT by use of HS (HS group; from October 2006 to December 2007).

We excluded patients who underwent less than TT, completion thyroidectomy, lateral neck node dissection, endoscopic thyroidectomy, or robotic-assisted endoscopic thyroidectomy.

In all, a total of 212 PTC patients were selected who met the following four inclusion criteria:

1) The TT was performed in our hospital.

2) ¹³¹I ablation was performed after surgery without a preliminary diagnostic ¹³¹I whole body scan.

3) Serum Tg levels in the absence of serum anti-Tg antibodies (TgAb) were determined at the time of ¹³¹I ablation when serum TSH should be above 30 mU/L, minimal criteria for optimal ablation based on American Thyroid Association (ATA) guidelines [15]. Thyroiditis patients with positive levels of TgAb were excluded from the study due to possible false reduction in measured serum Tg levels.

4) Patients had no preoperative or postoperative distant metastases.

According to ATA guidelines [15], TT is recommended in the following circumstances: 1) primary thyroid cancer >1 cm; 2) presence of contralateral thyroid nodules or regional or distant metastases; 3) history of radiation therapy to the head and neck; 4) patient has a first-degree relative with differentiated thyroid cancer; 5) age >45 years; 6) presence of extracapsular invasion or multifocality.

Of the 212 patients with PTC enrolled in this study, 104 were in the HS group and 108 in the CT group. All had prophylactic ipsilateral central compartment node dissection (CCND). In order to reduce interoperator confounding factors, all operations were performed by the same principal surgeon. The study was approved by the hospital's Institutional Review Board.

After surgery, all patients began treatment with a TSH-suppressing dose of LT4 (2 µg/kg). In the present study, radioactive iodine (RI) was given therapeutically without a diagnostic ¹³¹I whole-body scan in order to avoid a "stunning effect" (i.e., decreased uptake by a thyroid remnant of ¹³¹I after diagnostic administration of ¹³¹I) [16]. RI was administered 6 to 8 weeks after surgery when each patient was in hypothyroidism after LT4 had been withdrawn for 4 weeks. After 2 weeks on a low-iodine diet, all patients were treated with 30 mCi of RI. Patients received written instructions and were assisted by a dietician. The ¹³¹I whole body scan was done on the second day after RI treatment.

Stimulated serum Tg, serum TgAb, and serum TSH were measured at ablation. Serum TSH was measured by chemiluminescence immunoassay (Centaur; Bayer Health Care, Mannheim, Germany). Serum Tg was measured by immunoradiometric assay (Dynotest TgS, Brahms, Berlin, Germany), and, similarly, for TgAbs (Anti-Tgn RIA, Brahms). The Tg assay had a sensitivity of 0.2 ng/mL. TgAb status was considered negative when readings were <20 IU/mL.

TT is defined as total bilateral extracapsular thyroidectomy. Each patient was placed in a supine position and the neck was extended while the patient was under general anesthesia. A 5 to 6 cm transverse collar skin incision was made two fingerbreadths above the sternal notch, and the lower layer of the platysma was exposed under direct vision. Subplatysmal flap dissection was performed for achievement of adequate working space from the sternal notch to the hyoid bone level superiorly and both medial sides of the anterior border of the sternocleidomastoid muscle laterally. The midline of the strap muscle was divided vertically, and the thyroid gland was exposed. In patients assigned to the HS group, only Harmonic ACE Curved Shears (23-mm long; Johnson & Johnson Medical, Cincinnati, OH, USA) were used for vascular control of the thyroid gland. The named vessels of the superior, middle, and inferior thyroidal arteries and veins were controlled by using a low power level (70 µm vibration). Other small vessels and surrounding soft tissues were controlled by using a higher power level (100 µm vibration) for easy cutting. For patients in the conventional TT group, electrocautery was used for control of the small vessels of the gland and conventional hand-tied ligation was used for the named vessels and some arterial branches. The upper pole of the gland was divided carefully in order to avoid injury to the superior laryngeal nerves. The greatest attention was paid to identification of all of the superior and inferior parathyroid glands and to their preservation with the intact vascular pedicle. Parathyroid autotransplantation was performed as needed. Careful dissection was performed for identification of the inferior thyroid artery and the RLN in the usual anatomic relationship. The whole cervical course of the RLN was traced and the gland was then dissected from the trachea. When CCND (the prelaryngeal, pretracheal, and paratracheal area of the tumor side) was performed, while monitoring the RLN track, soft tissue and lymph nodes were removed within an area limited cranially by the hyoid bone and superior thyroid vessels, caudally by the thyro-thymic ligament area, and laterally by the medial border of the carotid artery. In the HS group, special care was taken to avoid damage to the RLN in the tracheoesophageal groove due to the collateral energy of the HS. A Jackson-Pratt closed suction drain (100 mL, 3.2 mm in diameter; Barovac Sewoon Medical, Seoul, Korea) was placed through a separate skin incision in all patients. This drain was removed when drainage decreased to less than 20 mL/day. Wounds were closed with absorbable suture material using a continuous subcutis suture method.

Based on clinical and pathologic records, a retrospective analysis was performed on numerous variables in both patient groups. These included demographic and pathological findings, operating time (from skin incision to closure), intraoperative bleeding, total amount of drainage, length of hospital stay, incidence of perioperative complications (hematoma, RLN palsy, hypoparathyroidism, seroma, other injuries), and measurement of stimulated serum Tg, serum TgAb, and serum TSH at the time of ¹³¹I ablation.

Laryngoscopy was performed preoperatively for evaluation of vocal cord mobility in all patients. Gauze pieces were weighed before and after use for estimation of the amount of intraoperative bleeding (1 g, 1 mL of blood). Postoperative calcium, phosphorus, and parathyroid hormone (PTH) levels were monitored in all patients. Hypocalcemia was defined as a serum calcium level <8.0 mg/dL, even in a single measurement. Hypocalcemic patients received supplementation therapy with oral calcium and vitamin D (calcitriol), even if asymptomatic. Supplementation therapy was gradually tapered on the basis of serum calcium and PTH measurements in the outpatient clinic. We defined transient hypocalcemia and RLN palsy based on recovery from symptoms and normalization of laboratory data within 6 months.

All data were expressed as mean ± standard deviation, proportions, or absolute numbers. We used SPSS ver. 13.0 (SPSS Inc., Chicago, IL, USA) for statistical analysis. Statistical differences between the two groups were assessed by the Student's t-test or the Mann-Whitney test for continuous variables, depending on distribution. Interarm comparisons of categorical variables were performed using the chi-square test. P < 0.05 was accepted as a significant difference.