RAJIV GANDHI UNIVERSITY OF HEALTH SCIENCES,

BANGALORE, KARNATAKA

ANNEXURE-II

PROFORMA FOR REGISTRATION OF SUBJECT FOR DISSERTATION

1. / NAME OF THE CANDIDATE AND ADDRESS (IN BLOCK LETTERS) / DR. SAVITHA V.
POST-GRADUATE IN ANATOMY
DEPARTMENT OF ANATOMY
MYSORE MEDICAL COLLEGE
AND RESEARCH INSTITUTE,
MYSORE-570001
2. / NAME OF INSTITUTION / MYSORE MEDICAL COLLEGE
AND RESEARCH INSTITUTE,
MYSORE.
3. / COURSE OF STUDY AND SUBJECT / M.D. ANATOMY
4. / DATE OF ADMISSION TO THE COURSE / 31ST AUGUST 2013
5. / TITTLE OF THE TOPIC / “A MORPHOMETRIC STUDY OF ADULT THYROID AND CRICOID CARTILAGES IN TERTIARY CARE CENTRE, MYSORE.”

6. BRIEF RESUME OF THE INTENDED WORK

6.1 NEED FOR THE STUDY

The larynx is an air passage, a sphincter and an organ of phonation. It extends from the tongue to trachea. It is mobile on deglutition. Until puberty the male and female larynges are similar in size. After puberty, the male larynx enlarges considerably in comparison with that of the female, all cartilages increase in size, the Thyroid cartilage projects in the anterior midline of the neck and its sagittal diameter nearly doubles (1).

The larynx is the upper part of the respiratory tract. Its main function is to protect the lower respiratory tract so that foreign bodies do not enter the trachea. If a foreign body comes in contact with the mucosa of the larynx, it reflexly gives rise to violent coughing till the foreign body is expelled (2).

Another function of the larynx is the production of voice. Hence the name voice box. The anterior border of each thyroid lamina fuses with its partner at an angle of 900 in men and 1200 in women. The shallower angle in men is associated with laryngeal prominence, the greater length of the vocal cords and the resultant deeper pitch of voice (1, 2).

From embryologic, anatomic, physiologic and surgical standpoints, the larynx is one of the most complex organs of the human body (3).

The increasing application of sophisticated electro-physiological and radiological methods for the diagnosis and treatment of laryngeal disorders requires an extensive knowledge of the size and proportions of the human larynx and its cartilaginous components(3,4).

Recent interest in the condition of subglottic stenosis and post-intubational stenosis of the lower respiratory tract led to a search through the literature to ascertain the measurements of the various cartilages of the larynx (3, 4, 5).

Morphometric data of the larynx is useful in otorhinolaryngology during procedures like intubation, endoscopy, laryngeal micro-surgeries (6,7) and surgery of laryngeal framework (partial/total laryngectomy) (6,7,8,9).

Pure anthropometry of laryngeal framework has potential application to studies in laryngeal physiology, advanced methods of laryngeal imaging techniques and advanced surgical procedures of the larynx (8, 9).

The elaboration of new surgical concepts for the treatment of phonatory disorders has recently awakened new interest in larynx morphometry (9, 10).

They are critical to the accurate placement of needles and probes in laryngeal electro-myography, vocal cord injection and medialization procedures (10).

The most common form of committing suicide in our region is “hanging”. We can expect the fracture of the Thyroid cartilage both in hanging and strangulation. The detailed description of Thyroid cartilage morphology can be used in further research to determine the connection between the location of the Thyroid cartilage fracture in strangulation, the level of ossification and the force applied in strangulation (11).

6.2 REVIEW OF LITERATURE

1.  Monica Jain and Usha Uhall (2010) studied on “Morphometry of the Thyroid and Cricoid cartilages in adults on CT SCAN”. The material used was 60 living individuals (30 male, 30 female) with the age group varying between 20-50 years, who were undergoing CT scan in the radiology department for the reasons other than laryngeal pathology.

For the Thyroid cartilage measurements were taken at one level where both Thyroid laminae were clearly visible and joined to each other at an angle and the length of the lamina was maximum.

For the Cricoid cartilage measurements were taken at one level where a complete ring of cartilage was clearly visible.

Their observations were a) All parameters except angle were found to be more in males as compared to females. The difference was statistically significant for all parameters of Thyroid cartilage. Sex difference was also found to be statistically significant for transverse diameter, thickness of arch and lamina of the Cricoid cartilage. b) There were no significant difference in various parameters between right and left side.

They have compared the dimensions with autopsy measurements of other studies and concluded that, all CT measurements were lower than the autopsy measurements (8).

2.  H E Eckel et al (1994) studied “The internal diameter of the Cricoid and the angle of the laminas of the Thyroid cartilage in larynges of German origin. The material used was, larynges of 53 postmortem cases (28 male and 25 female) with the age group varying between 25-88 years (mean age 59 years) were removed during routine autopsy done within 12-48 hours following death. Immediately morphometric measurements were taken with a pair of compasses and a caliper rule. The observations were a) The external angle of the Thyroid cartilage varied between 58.80 -100.40 for males, 79.20 -109.30 for females. b) The average antero-posterior diameter of Cricoid cartilage was greater than the average transverse diameter of the Cricoid cartilage (9).

3.  Tanja Kovac et al (2009) studied “Morphometric characteristics of Thyroid cartilage in people of Eastern Croatia”. The research was carried out on 68 samples of adult Thyroid cartilages (39 male, 29 female). The average age for male sample was 62; whereas for female sample was 70 years. Dissection was done to isolate Thyroid cartilage samples which were fixed in 10% formalin during 48 hours. The measurements were taken directly on the preparations using a digital caliper with the precision of 0.03mm. Thyroid angle was determined with an optical goniometer with the precision of 0.080.Conclusion of the study was, comparison of dimensions obtained on samples of both the sexes showed that the presence of sexual dimorphism. There was statistically significant difference in all measured values except in the distance between the tips of the superior horns. All measured values were greater in men than in women except for the thyroid angle (11).

4.  Mohini Joshi et al (2011) conducted study on “Morphometric study of Cricoid cartilages in western India”. The sample used was 50 laryngeal specimens (age range was between 59- 78 years) dissected from cadavers. Various measurements were taken from Cricoid cartilage with vernier caliper. The study concluded that the mean antero-posterior diameter of the Cricoid cartilage was greater than the average transverse diameter (3).

5.  Jose Raindrop S Embate et al (2003) studied on “Anatomic measurements of the laryngeal framework in Filipino adult cadavers.” The material used was 20 human larynges (15 male and 15 female) harvested from cadavers. The age was ranging between 36 to 65 years for males and 37 to 56 years for females. They have concluded that a) Most of the laryngeal framework measurements (except thyroid angle) were more in males compared to females.

b) Considerable gender and race related difference in many of the geometric measurements of the laryngeal framework were observed in the study (10).

6.  Ajmani M L et al (1980) studied on “A metrical study of laryngeal cartilages and their ossification”. The study was carried out on laryngeal cartilages of 150 postmortem/dissection specimens of adult age group ranging between 16 to 55 years in both the sexes. The age, sex and height were noted. Various measurements of the laryngeal cartilages were taken from the inner surface. They have concluded that a) all measurements were more marked in male than female except thyroid angle and length of the superior horn. b) There was no correlation with the total body height.c) The presence of cuneiform cartilage, cartilage-triticea and corniculate cartilage was not constant. They were seen more commonly in females than males (12).

7.  Ajmani M L (1990) studied on “A metrical study of the laryngeal skeleton in adult Nigerians”. The study was done on 40 laryngeal specimens ( 28 male, 12 female) age was ranging between 17 to 50 years dissected from embalmed human cadavers available in department of Anatomy. The various measurements were taken using thread, a vernier caliper and goniometer. They have concluded that a) The thyroid angle in the female larynx was significantly more than that in the male. b) The transverse diameter of the Cricoid cartilage was more than the antero-posterior diameter in both the sexes (5).

8.  G Pereira Jotz et al (1999-2000) studied on “The asymmetry of the Cricoid cartilage and the external angle of the thyroid cartilage, a sex related study” to determine the degree of asymmetry in relation to age and sex. The study was conducted on specimens of larynges from 100 cadavers (50 male, 50 female). The age was ranging between 40-98 years with an average of 58.68years. Thyroid angle was measured using goniometer. The transverse and antero-posterior diameter of the Cricoid-cartilage including mucous membrane were measured with the aid of a digital pachymeter, measurements were taken on the horizontal plane, at the caudal limit of the Cricoid cartilage. They have concluded that a) There was no relation between the angle of Thyroid cartilage and the measurement of the Cricoid cartilage. b) In males they have observed that only 50% of the sample showed antero-posterior diameter more than those of the transverse diameter. In females 70% of the specimens showed transverse diameter more than the antero-posterior diameter (7).

9.  Mohini M Joshi et al (2007-2009) studied on “Morphological study of adult human larynx in a western Indian population” The sample consisted of 50 laryngeal specimens from adult cadavers (47 male, 3 female). The age was ranging between 59 to 78 years; average age was being 67.5 years. Larynx was separated from the level of hyoid bone to 3rd tracheal ring. The dissection was performed using standard dissecting instruments under magnification with the help of hand lens and dissecting microscope. The various measurements of larynx with the help of digital vernier caliper were taken. The observations were a) The laryngeal framework was asymmetric to some extent in all larynges b) By comparing the observations of this study with other populations revealed that the absolute values differ in different populations which could be due to differences in body built and racial differences (6).

10.  Monica Jain and Usha Dhall (2008) have conducted a study on “Morphometry of the Thyroid and Cricoid cartilages in adults”. The sample used was larynges obtained from 40 adult cadavers (20 male, 20 female) varying in age from 20- 40 years, on whom medico legal postmortem had been performed. Height of the individuals was noted from records. Measurements were taken on each larynx with the help of vernier caliper and goniometer. The cartilages were weighed on a single pan electronic balance. They have compared the measurements between both the sexes and concluded that a) All the measurements of Thyroid and Cricoid cartilages were more in male than in female except for the angle and the length of the left inferior cornu which were more in female. b) Thyroid breadth decreases from cranial to caudal side in both the sexes and is maximum at the level of superior tubercle. This obliquity appears to be more in females as compared to male. c) Bilateral asymmetry in the size of thyroid lamina and cornu was seen in majority of specimens and in 25% of cases the thyroid prominence was not in the median plane. d) The length of thyroid lamina, transverse diameter and height of arch of Cricoid cartilage showed a significant correlation with the height of an individual (4).

6.3 OBJECTIVES OF THE STUDY

Morphometric data of the larynx may be very useful in Otorhinolaryngology laryngeal microsurgery and evaluation of results of diagnostic techniques. Hence the present study is undertaken.

1.  To measure the various morphometric measurements of the Thyroid and Cricoid cartilages in an adult human larynx.

2.  To observe for

a)  Any variations in the measurements of the Thyroid and Cricoid cartilages with reference to gender.

b)  Any variations in the measurements of Thyroid and Cricoid cartilages between Living (CT measurements) and cadaver (measurements taken after dissection).

3.  To compare the data obtained with other studies.

7. MATERIALS AND METHODS

7.1 Source of data

(a) The data for the present study will be collected from the department of Radiology, K.R Hospital, attached to MMC and RI, Mysore. The 44 (22 Male, 22 Female) CT scans done for the cases attending Radiology Department which are referred from other departments will be taken for the study. The study will be done for the period of 18 months by collecting CT scans.

(b) The 44 (22 Male, 22 Female) postmortem larynx specimens will be collected from the department of Forensic medicine, MMC and RI, Mysore.

Inclusion criteria

1. CT scans of both the sexes will be collected.

2. CT scans of adult age group (18 to 70 years) will be collected.

3. Post-mortem larynx specimens of both the sexes will be collected.

4. Post-mortem larynx specimens of adult age group (18 to 70 years) will be collected.

Exclusion criteria

·  CT scans of below 18 years and above 70 years age group will be excluded.

·  CT scans with history of any previous laryngeal surgery will be excluded.

·  Postmortem larynx specimens of hanging, strangulation, lacerated wound over the neck will be excluded.

·  Postmortem larynx specimens of below 18 years and above 70 years age group will be excluded.

·  Postmortem larynx specimens with history of any previous laryngeal surgery will be excluded.

7.2 Method of collection of data (including sampling procedure if any)

a) The details of the case such as age, sex, inpatient/outpatient number and indications for CT scan will be collected. Morphometric measurements of Thyroid and Cricoid cartilages will be taken from CT. Collection of the data by CT scans will be done by ambidirectional method (both retrospective and prospective methods).

b) A written consent will be taken from the relatives of the subject. Soon after postmortem, larynx specimens will be collected prospectively and fixed in 10% formalin solution. After fixation careful dissection will be done to isolate thyroid and Cricoid cartilages by removing muscles, ligaments, small cartilages (aretynoid, epiglottis). Measurements will be taken with the help of vernier caliper and goniometer.