[Role of preoperative ultrasound-guided inferior parathyroid gland localization and new classification to assist intraoperative search and protection of parathyroid glands].

Objective: To investigate the role and significance of ultrasound-guided inferior parathyroid gland (IPTG) localization in searching and protecting parathyroid glands before thyroid surgery. Methods: A randomized controlled trial study was conducted. A total of 306 patients (433 cases of lateral parathyroidectomy) who underwent primary thyroidectomy and central lymph node dissection in Beijing Tongren Hosipital from March to October 2021 were enrolled. In order to locate IPTG more quickly and effectively, new IPTG classification and the definition of quadrant position were carried out. The patients were divided into the study group (n=228) and the control group (n=205). The study group underwent ultrasound-guided IPTG examination before operation and measured the distance between the IPTG and the lower pole of the thyroid and the midline of the trachea. During the operation, the IPTG was found and protected depending on the localization. The control group did not use any auxiliary preoperative positioning method. The distribution ratio of IPTG and the coincidence rate between intraoperative validation and ultrasound localization were calculated. Results: There were 306 patients enrolled in the final analysis (95 males and 211 females), with a median age of 41 years old (18-70). Type Ⅱ and Ⅲ IPTG accounted for 77.2% (176/228) of the total cases. The total coincidence rate ranged from 72.8% to 79.4% in different IPTG groups. Type Ⅲ and quadrant 2 IPTG had the highest coincidence rate [92.4% (73/79) and 92.9% (79/85), respectively]. The study group had better in situ retention rate [82.0% (187/228) vs 73.2% (150/205), χ2=4.896, P=0.027] and less implantation rate [8.8% (20/228) vs 16.1% (33/205), χ2=5.393, P=0.020] than those of the control group. The in situ retention rate were better in type Ⅲ IPTG group, compared with those of the control group [94.9% (74/78) vs 77.4% (48/62), χ2=7.898, P=0.005]. There was no permanent hypoparathyroidism in two groups and the temporary hypoparathyroidism rate was 32.0% (24/75) and 34.6% (18/52), respectively (χ2=0.095, P=0.758). Conclusion: Ultrasound-guided IPTG localization examination has important implications for searching and protecting IPTG during operation, which can significantly increase in situ retention rate of IPTG and decrease the implantation rate.