Morphometric measurements of the cartilaginous larynx: An anatomic correlate of laryngeal surgery

A Morphometric Study of the Pars Plana of the Ciliary Body in Human Cadaver Eyes

This study aimed to determine the pars plana length in postmortem human eyes using advanced morphometric techniques and correlate demographics to ocular metrics such as age, sex, ethnicity, and axial length. Between February and July 2005, we conducted a cross-sectional observational study on 46 human cadaver eyes deemed unsuitable for transplant by the SBO Eye Bank. The morphometric analysis was performed on projected images using a surgical microscope and a video-microscopy system with a 20.5:1 correction factor. The pars plana length was measured three times per quadrant, with the final value being the mean of these measurements. Of the 46 eyes collected, 9 were unsuitable for the study due to technical constraints in conducting intraocular measurements. Overall, the average axial length was 25.20 mm. The average pars plana length was 3.8 mm in all quadrants, with no measurements below 2.8 mm or above 4.9 mm. There were no statistically significant variations across quadrants or with age, sex, axial length, or laterality. Accurately defining the pars plana dimensions is crucial for safely accessing the posterior segment of the eye and minimizing complications during intraocular procedures, such as intravitreal injections and vitreoretinal surgeries.

Gender-Affirming Facial Surgery: Lower Third of the Face

This article is intended to give the reader an overview of facial gender-affirming procedures applicable to the lower face and neck. A review of facial analysis in the context of masculine versus feminine facial features and the contributions of both soft tissue and bone to this anatomy is provided. The use of systematic facial evaluation and patient-driven concerns as a guide for presurgical planning is reviewed. Detailed descriptions of the unique surgical interventions to feminize the soft tissues and the skeletal framework of the lower face and neck are provided.

Laryngeal Framework Surgical Anatomy: A Radiological Study

PURPOSE

Awareness of variations in laryngeal anatomy among different age and gender groups is crucial during laryngeal framework surgery. The aim of this study is to demonstrate the relationship between gender and laryngeal radiologic morphometrics among different age groups and the applicability of important anatomical landmarks of laryngeal surgery.

METHODS

Laryngeal images of 180 adult patients older than 18 years of age were obtained by computed tomography and assessed. A total of 11 measurements of important laryngeal landmarks were taken from the patients' computed tomography images. Results were subgrouped according to gender and age, and these groups were compared for each measurement.

RESULTS

The majority of laryngeal measurements obtained in the study were higher in males than females, with the exception of the interlaminar angle. The mean interlaminar angle value was 88.27°± 14.99 for males and 103.04°± 14.81 for females (P <0.005). The distance from the anterior commissure to the inferior border of the thyroid cartilage was 10.46 ± 2.5 mm for males and 7.72 ± 1.9 mm for females. The anterior commissure locates slightly higher than the midpoint of the distance from the thyroid notch to the thyroid inferior border. The shortest distance between the muscular process of the arytenoid cartilage and the thyroid cartilage was found to be 9.60 ± 3.47 mm for males and 7.72 ± 2.33 mm for females (P <0.001).

CONCLUSION

Observation of obvious diversities in the size and distance of the important laryngeal structures between the gender groups is an important factor to be considered for successful laryngeal framework surgery. Also, using the midpoint of the thyroid cartilage as a landmark for anterior commissure is a practical method during surgery, especially for thyroplasty.

Chondrolaryngoplasty

Chondrolaryngoplasty is a surgical procedure that reduces the prominence of the thyroid notch. Although frequently performed on transgender (man to woman) women, anyone wishing to reduce the prominence of their thyroid notch for aesthetic purposes may consider undergoing a chondrolaryngoplasty. Direct visualization of the vocal cords with flexible laryngoscopy and intraoperative needle localization of the anterior commissure directs the extent of resection, helps increase safety, and avoids devastating postoperative voice complications. This procedure can be safely performed in combination with other facial feminization surgeries.

Post-pubertal developmental trajectories of laryngeal shape and size in humans

Laryngeal morphotypes have been hypothesized related to both phonation and to laryngeal pathologies. Morphotypes have not been validated or demonstrated quantitatively and sources of shape and size variation are incompletely understood but are critical for the explanation of behavioral changes (e.g., changes of physical properties of a voice) and for therapeutic approaches to the larynx. This is the first study to take this crucial step and results are likely to have implications for surgeons and speech language pathologists. A stratified human sample was interrogated for phenotypic variation of the vocal organ. First, computed tomography image stacks were used to generate three-dimensional reconstructions of the thyroid cartilage. Then cartilage shapes were quantified using multivariate statistical analysis of high dimensional shape data from margins and surfaces of the thyroid cartilage. The effects of sex, age, body mass index (BMI) and body height on size and shape differences were analyzed. We found that sex, age, BMI and the age-sex interaction showed significant effects on the mixed sex sample. Among males, only age showed a strong effect. The thyroid cartilage increased in overall size, and the angulation between left and right lamina decreased in older males. Age, BMI and the age-height interaction were statistically significant factors within females. The angulation between left and right lamina increased in older females and was smaller in females with greater BMI. A cluster analysis confirmed the strong age effect on larynx shape in males and a complex interaction between the age, BMI and height variables in the female sample. The investigation demonstrated that age and BMI, two risk factors in a range of clinical conditions, are associated with shape and size variation of the human larynx. The effects influence shape differently in female and male larynges. The male-female shape dichotomy is partly size-dependent but predominantly size-independent.

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.

A Dissectional Study of the Level of Anterior Commissure of the Larynx

PURPOSE

Precise knowledge of the level of the vocal fold as projected on the external thyroid cartilage is of critical importance for the performance of many surgical approaches. This study aims to identify the level of the anterior commissure, as well as the lengths of the vocal muscle and arytenoid cartilage in Turkish population.

MATERIALS AND METHOD

Specimens were collected after autopsy from the Council of Forensic Medicine. One hundred human larynges (52 men, 48 women; age range: 25-80 years) were dissected under a stereomicroscope. Projection of the vocal fold was analyzed in relation to the superior thyroid (A) and the inferior border of the thyroid cartilage (B). Then, the larynx was dissected parallel to the level of the vocal fold to measure the length of the vocal muscle (C) and the length of the interarytenoid space (D).

RESULTS

The mean value of the "a" was 9.15 ± 1.99 mm in male and 9.38 ± 3.43 mm in female. Mean value of the "b" was 10.54 ± 1.73 mm and 8.88 ± 1.81 mm in male and female, respectively. The mean value of the parameter corresponding the length of vocal muscle which was "c" was found 15.00 ± 3.18 mm in male and 12.88 ± 4.12 mm in female. The mean value of the interarytenoid space "d" was 8.31 ± 1.76 mm in male and 8.13 ± 1.90 mm in female. Comparing between genders, no statistical differences were observed in parameters of a, c, d, a + b, a + b/2 (P > .05). However, the difference with female and male for the parameters of b and c + d was statistically significant (P < .05).

CONCLUSION

Our results indicate that the anterior commissure projects slightly above the midline height for male and at the level to slightly below in female subjects in Turkish population.

Comparative Anatomy of Pig Arytenoid Cartilage and Human Arytenoid Cartilage

OBJECTIVE

This study aims to investigate the feasibility of pig arytenoid cartilage as an animal model for simulating arytenoidectomy under microlaryngoscope by comparing the similarities and differences between pig arytenoid cartilage and human arytenoid cartilage.

STUDY DESIGN

This is a methodological study on the excised pig arytenoid cartilage and human arytenoid cartilage.

METHODS

Five excised human adult cadaver larynges and five adult excised porcine larynges were dissected and all the soft tissue and mucous membrane attached to the arytenoid and cricoarytenoid joint were removed. The anatomical structure and morphology of the arytenoid cartilage were observed and measured with a vernier caliper. Measurements included cricoarytenoid articular facet major and minor diameter, cricoarytenoid articular facet center distance, cricoarytenoid facet major and minor diameter, length of vocal process and muscular process, and distance between tip of vocal process, muscular process, and junction/apex of arytenoid cartilage. Data were then compared across these major anatomic markers using student t test.

RESULTS

The gross anatomy of the pig arytenoid cartilage was similar to the human. However, the size of the pig larynx arytenoid cartilage was obviously larger in total, and there was statistical significance for almost all measurements (P < 0.05), except the mean value of cricoarytenoid articular facet center distance, the cricoarytenoid facet minor diameter, and the length of vocal process of pig and human, without statistically significant difference (P > 0.05). Moreover, the biggest differences between the pig arytenoid cartilage and the human arytenoid cartilage were that the pig arytenoid cartilage apex had the angle winding structure toward the back, and that the posterior part of the bilateral arytenoid cartilages was partially connected. Whereas after the angle winding was removed from the junction, pig arytenoid cartilage and human arytenoid cartilage were shaped both like a triangular pyramid.

CONCLUSION

The data of this metric comparative study indicate that pig arytenoid, after resecting the angle winding structure and incising the interarytenoid cartilage, is similar to the human's. Therefore, pig larynx is an appropriate experimental model for endoscopic arytenoidectomy. In addition, regarding the pig laryngeal angle winding structure, we still require further basic and clinical research to clarify its physiological function and significance.

Novel Anatomic Characteristics of the Laryngeal Framework

Objective

The thyroid cartilage (TC) in men has a more prominent thyroid notch and a narrower interlaminae angle (ILA) as compared with women. Anatomy textbooks classically stipulate that the ILA is 90° in men and 120° in women. Our observation, based on thyroid chondroplasty operations, of a much narrower angle led to the current investigation.

Study Design

Cohort imaging study.

Setting

Tertiary academic referral center.

Subjects and Methods

Computed tomography angiography neck images of adult patients were studied. The ILA was measured on 2 axial planes: at the level of the vocal processes (and the upper portion of thyroarytenoid muscles) and 5 mm superior and parallel to the former. The anterior projection of the TC and the vertical dimensions of the midline cricothyroid membrane (CTM) were also measured.

Results

A total of 126 patients were included in the study. The average ILAs were 63.5°±20.6° and 93.3°±16.6° for men and women, respectively ( P < 10−14), and were significantly narrower at the upper level in comparison with the vocal process level ( P < 10−7 for men, P = .004 for women). The anterior projection of the TC in men was more prominent as compared with women ( P = .0003) and significantly correlated with the ILA ( P = .0159). The length of the midline CTM was 11.1±2.3 mm in men and 10.3±1.7 mm in women ( P = .0355).

Conclusions

The ILA is narrower than that reported in the classic anatomy textbooks. In male patients, the upper part of the TC becomes narrower and projects anteriorly like a “jug’s spout.” The mean vertical dimension of the midline CTM was 10 to 11 mm.

Development and Validation of a High-Fidelity Porcine Laryngeal Surgical Simulator

Objective

Design and validate a laryngeal surgical simulator to teach phonomicrosurgical techniques.

Study Design

Device development and prospective validation.

Setting

Tertiary medical center.

Subjects and Methods

A novel laryngeal fixation device and custom laryngoscope were produced for use with ex vivo porcine larynx specimens. Vocal fold lesions such as nodules and keratotic lesions were simulated with silicone injections and epithelial markings. A prospective validation using postsimulation surveys, global rating scales, and procedure-specific checklists was performed with a group of 15 medical students, otolaryngology residents, fellows, and attending laryngologists. Three procedures were performed: vocal fold augmentation, excision of a simulated vocal fold nodule, and excision of a simulated vocal fold keratosis.

Results

Participants overwhelmingly agreed that the simulator provided a realistic dissection experience that taught skills that would transfer to real operating scenarios. Expert performance was statistically superior to novice performance for excision of simulated vocal fold nodules and keratotic lesions, while no difference was observed for injection laryngoplasty.

Conclusion

The ability to learn and rehearse surgical procedures in a safe environment is invaluable, particularly for delicate and highly technical phonomicrosurgical operations. We have developed a high-fidelity laryngeal surgical simulator complete with pathological lesions such as nodules and keratoses to teach these procedures. A prospective study demonstrated validity of our global rating scale and checklist assessments for vocal fold nodule and keratosis excision procedures, allowing them to be confidently incorporated into phonomicrosurgical training programs for surgeons of all levels of expertise.

Superior thyroid cornu anatomical variation causing globus pharyngeous and Dysphagia

Objective. Rare case presentation of thyroid cartilage variation causing globus sensation and dysphagia. Method. Case report and review of the literature concerning thyroid cartilage variant of clinical significance. Results. Middle-aged male patient presented with globus sensation and painful swallow without previous injury of the larynx. Clinical examination and diagnostic procedures revealed a rare anatomic aberrance of the thyroid cartilage. Surgical treatment was declined by the patient who accepted a yearly followup. Conclusion. Morphometric studies do not report the dislocation of the superior thyroid cornu, and very few cases have been described either of which were attributed to trauma or to unknown cause. The present case is to be added to the very few cases of superior thyroid cornu dislocation of unknown aetiology. Clinicians should be aware of this rare variation using CT neck as the imaging study of choice. Direct endoscopy rules out any synchronous disease or malignancies.

Influence of gender and injection site on vocal fold augmentation

OBJECTIVE: To determine the influence of gender and injection site on the amount of injectate needed to medialize an immobile vocal fold, and to describe the distribution patterns of the injected bolus.

STUDY DESIGN: Surgical intervention in human cadaveric larynges in experimental setting.

SUBJECTS AND METHODS: Cadaveric larynges were injected with calcium hydroxylapatite into the lateral or medial aspect of the vocal fold. High-resolution CT scans were obtained before and after injection.

RESULTS: Males required 50% to 60% more material than females ( P = 0.03). For both genders, lateral injections required more than medial injections ( P < 0.001). Laterally injected boluses tended to distribute toward the cricothyroid space, with frank extrusions more common in females.

CONCLUSION: The amount of injectate required to medialize male and female vocal folds is significantly different. The smaller size of the female larynx likely accounts for a higher incidence of extrusion through the cricothyroid space. These gender differences should be taken into consideration when performing injection laryngoplasty.