Anatomical considerations

Abstract

Background: Minimally invasive approaches and surgical techniques are becoming increasingly applied to the treatments of various cervical spine disorders recently. Therefore, a thorough knowledge of the muscle and fascia layers as well as the important anatomical contents inside the neck would be crucial for cervical endoscopy surgeon to deter the occurrence of any unexpected complications. Methods: The reported definition of “safety zone” would be the sum-up value of the distances from the operator’s fingertip to the digestive tract on the contralateral side and to the carotid artery on the ipsilateral side. Also reducing the finger distance less than 5 mm from the ventral surface of vertebral body is crucial during percutaneous approach to the cervical spine. Results: At C3-C4, the safety zone was measured as 18.9 ± 6.6 mm. The superior thyroidal artery (STA) was located in the safety zone of C3-C4 in 86.7%. At C4-C5, the safety zone was measured as 23.5 ± 6.5 mm. The STA and the right lobe of the thyroid gland (TG) were located in the safety zone in 26.7% and 30%, respectively. At C5-C6, the safety zone was measured as 33.7 ± 6 mm. The TG was located in the safety zone of C5-C6 in 76.7%. At C6-C7, the safety zone was 29.2 ± 4.5 mm. The TG was located on the approach plane in 90%. In addition, the needle should be approached toward the center of the disc and reducing the finger distance (FD) less than 5 mm from the ventral surface of vertebral body is crucial to allow a low risk of pharyngoesophageal structure injury during percutaneous approach to the cervical spine. Conclusions: Although cervical spinal endoscopy has been numerously described as a safe procedure, an accurate and vigilant placement of the working channel of endoscope is the most important step while still serious complications may occur either during the needle insertion or during the procedure that can entail a fatal vascular, neurological, or visceral injury.