Ultrasound studies on the shift of cervical tissues in different head and neck positions--impact on transoral endoscopic, minimally invasive and conventional thyroid surgery.

During the development of a transoral endoscopic, minimally invasive approach for thyroidectomy, the question arose as to how the distances of the submandibular gland (SG)-hyoid bone (HB)-thyroid gland (TG) change in differing head positions and how the TG itself changes shape. In a prospective, two-armed ultrasound study we studied 20 healthy volunteers each, all with no history of neck surgery or thyroid disease. Distances were measured in normal, reclined and "reclined with open mouth" positions. We found no remarkable differences and the distances were comparable with conventional open or minimally invasive thyroidectomy approaches. The TG lengthened significantly during reclination. This may result in a difficult preparation in the region of the suspensory ligament and may therefore increase the rate of postoperative vocal cord palsy caused by stretching of the recurrent laryngeal nerve. A supine flat position may minimize the risk of this postoperative complication of thyroidectomy.