Normal radiological anatomy of thyroid cartilage in 600 Chinese individuals: implications for anterior cervical spine surgery

Lateral Deviation of the Hyoid Bone and Thyroid Cartilage Influences Prevertebral Soft-Tissue Swelling and Dysphagia After Anterior Cervical Diskectomy and Fusion

BACKGROUND AND OBJECTIVES

Prevertebral soft-tissue swelling (PSTS) after anterior cervical diskectomy and fusion (ACDF) is known to be influenced by several factors. We considered the effect of lateral deviation on the traction force and attempted to find a relationship with the PSTS. This study was designed to evaluate the preoperative lateral deviation of the hyoid bone and thyroid cartilage and its effect on PSTS, airway collapse, and clinical outcomes after ACDF.

METHODS

Preoperative lateral deviations of the hyoid bone and thyroid cartilage at the superior cornu and inferior cornu were measured. To assess the effect of lateral deviation, patients who underwent 1 or 2 level ACDF with the left-sided approach were divided into a deviation group (left-sided deviation >5 mm or >10 mm) and a nondeviation group (left-sided deviation <5 mm or <10 mm). Difference of preoperative and postoperative PSTS (dPSTS), airway collapse, dysphagia score, and Neck Disability Index were compared between the 2 groups.

RESULTS

Lateral deviation was measured in 290 patients, and 145 were enrolled to assess the effect of lateral deviation. Left-sided deviation was more common than right-sided deviation in all 3 structures (the hyoid bone, superior cornu, and inferior cornu of the thyroid cartilage). The deviation group demonstrated a significantly larger dPSTS at the C3 and C4 levels, more airway collapse at the C4 level, and a higher dysphagia score. There was no significant difference in the Neck Disability Index between the 2 groups. Lateral deviation significantly correlated with dPSTS (C3, C4, C5, and C6 levels) and airway collapse (C3 and C4 levels).

CONCLUSION

A left-sided deviation of more than 5 mm of the hyoid bone or thyroid cartilage discouraged the left-sided approach for ACDF because of the aggravation of dPSTS, airway collapse, and dysphagia postoperatively.

The Right Internal Jugular at the Cricoid Cartilage Level May Represent the Optimal Central Vein Puncture Site in Pediatric Patients

OBJECTIVE

Internal jugular vein puncture or cannulation is far more difficult in children compared with adults. Anthropometric measures of the internal jugular vein acquired by two-dimensional ultrasound are useful in the practice of puncture and catheterization. The aim of this study is to measure anthropometric parameters of bilateral internal jugular veins in children and to determine the best puncture site based on these parameters.

MATERIALS

A total of 107 pediatric patients undergoing elective operation were included. Ultrasound-visible evaluation of bilateral internal jugular veins was used to obtain the depth from skin, maximum antero-posterior diameter, and cross-sectional area at the levels of the superior border of thyroid cartilage and cricoid cartilage. Statistical analysis was performed using these anthropometric data and demographic variables of all studied pediatric patients, such as age, height, and weight.

RESULTS

A very weak correlation was noted between the depth, maximal antero-posterior diameter, and cross-sectional area of both internal jugular veins and the age, height, weight, and body surface index of all included children. All Pearson's R correlation coefficients were <0.45. The largest diameter and cross-sectional area were in the right internal jugular vein at the cricoid cartilage level (p < 0.01) followed by the left internal jugular vein at this level (p < 0.01). In addition, the internal jugular vein at the cricoid cartilage level was more superficial than that of the superior border of the thyroid cartilage (p < 0.01).

CONCLUSION

The right internal jugular vein at the cricoid cartilage level is the best site for puncture. The most appropriate alternative site is the left internal jugular vein on the same level. Better correlation was not observed between the anthropometric parameters of the internal jugular vein and children's biological characteristics. This finding should be confirmed in a larger-scale demographical study in the future.

Recommended Maximum Laryngeal Prominence Size in Adult Females: A Cross-Sectional Study Proposing a Laryngeal Prominence Size Standard for Chondrolaryngoplasty in Male-to-Female Transgender Individuals

BACKGROUND

Although the World Professional Association for Transgender Health has provided international, multidisciplinary, evidence-based standards of care for various aspects of transgender health care, there is a lack of evidence-based guidelines for facial feminization surgery, including chondro laryngoplasty. The aim of this study was to define the recommended maximum laryngeal prominence size in adult females to propose an evidence-based laryngeal prominence size standard for chondrolaryngoplasty in male-to-female transgender individuals.

METHODS

This cross-sectional study was conducted in a tertiary care hospital. The study sample consisted of cisgender patients aged 18 to 60 years old with no history of surgery or radiotherapy in the head and neck area who visited the Otolaryngology/Head and Neck Surgery outpatient clinic. Laryngeal prominence size data were collected using three-dimensional scanning of the head and neck area.

RESULTS

Seventy-nine participants, 43 males and 36 females, were included in data analysis. Laryngeal prominence size was larger in male participants (median, 0.16 mm; range, 0 to 9.40 mm) than in female participants (median, 0.00 mm; range, 0 to 1.24 mm) (p < 0.001). The proportion of participants with a laryngeal prominence size larger than 0 mm was greater in male participants (55.81 percent) than in female participants (22.22 percent) (p = 0.002).

CONCLUSIONS

To the authors' knowledge, this is the first study to assess laryngeal prominence size in the general population. Their results suggest that 2 mm would be the recommended maximum laryngeal prominence size in females. Therefore, a laryngeal prominence size standard of 2 mm could be considered for chondrolaryngoplasty in male-to-female transgender individuals.

The Presence of Thyroid Cartilage at the Surgical Level Reduces Early Dysphagia after Single-Level Anterior Cervical Surgery: A Retrospective Study

Background: Early dysphagia is a frequent complication of anterior cervical (AC) spine surgery. However, there are no reports that have discussed the correlation between early dysphagia and the positional relationship between thyroid cartilage and the surgical level.Methods: We retrospectively enrolled 82 patients in our hospital who underwent single-level AC discectomy performed by the same surgeon using the same internal fixation apparatus from 2015 to 2017. Swallowing difficulty was rated during the first five postoperative days using a 10-point scoring system. The positional relationship between the thyroid cartilage and the surgical level was defined as discectomy within the thyroid cartilage (IN group) or outside the thyroid cartilage (OUT group) using preoperative computed tomography (CT) images. The confounding factors such as gender, age, body mass index (BMI), hypertension, diabetes mellitus, drinking, smoking, operative level, operative time, and blood loss were analyzed by a binomial logistic regression.Results: The thyroid cartilage was most commonly located above the C5 level (65.1%). Early dysphagia developed in 47.6% of the patients during the first five postoperative days. The IN and OUT groups each contained 41 cases. The difference in the cumulative postoperative early dysphagia score between the IN and OUT groups was statistically significant (p < .05). The factors of gender, age, BMI, hypertension, diabetes mellitus, drinking, smoking, operative level, operative time, blood loss did not significantly influence the incidence of postoperative early dysphagia.Conclusions: We found that early dysphagia, which is a self-limiting complication, was correlated with surgery performed at levels outside the thyroid cartilage region. Preoperative review of the positional relationship between the thyroid cartilage and the surgical level can predict the incidence of postoperative transient dysphagia.