A new protecting method for the inferior parathyroid gland in situ: the meticulous thyrothymic ligament dissection technique

Objective To explore the anatomical features and the dissection technique of thyrothymic ligament (TTL) , and to explore the clinical significance of protecting the inferior parathyroid gland (IPTG) with this structure. Methods Patients who received the initial thyroid surgery in the Department of Thyroid Surgery of the First Affiliated Hospital with Nanjing Medical University from May. 2017 to Dec. 2017 were prospectively analyzed. We dissected TTL, identified and located the IPTG, described the structural features of TTL, and investigated the position relationship of TTL and IPTG to evaluate the possibility and value of protecting IPTG in situ. Results About 121 patients underwent the dissection, totally 194 sides dissected that included 96 left sides and 98 right sides. TTL was found in 143 sides (73.7%) , 78 left sides (81.3%) and 65 right sides (66.3%) . Nearly 70.6% IPTG can be proactively identify and located by the TTL during the operation. TTL was a kind of adipose connective tissue that was wide at the bottom and narrow at the top, accompanying with the inferior thyroid vein, from the thymus to the thyroid. 76.2% TTL were attached to the lower pole and the lower 1/3 dorsal of thyroid, containing fat and vessels. 33.5% IPTGs were located in the area surrounding around the ends of the TTL. 25.3% IPTGs were located in the TTL. 4.6% IPTGs were located in the thymus and 7.2% IPTGs surrounding around the TTL. The incidence rate of post-operation hypoparathyroidism was 14.9%. Conclusions TTL commonly exists and has significant relationship with IPTG. TTL connects thymus and IPTG, which would be considered a complex (thymus-thyrothymic ligament-IPTG complex, TLIC) . The meticulous TTL dissection technique will help proactively identify, locate and protect IPTG during operation, and reduce the incidence rate of post-operation hypoparathyroidism. Key words: Parathyroid gland; Thyrothymic ligament; Hypoparathyroidism; Thymus-thyrothymic ligament-IPTG complex