Correlation of Neck Dimensions of Airway Evaluation

Correlation of Thyromental Distance And Mandibular Triangle Perpendicular Length With Incisor Vallecular Distance In Adult Pre-Surgical Patients: An Observational Study

The goal of this observational study is to evaluate thyromental distance (TMD) and mandibular triangle perpendicular length (MTPL); to know which correlates better with the incisor vallecula distance (IVD). Based on the direction and strength of the correlation measure, a multiple regression equation can then be created to first predict the IVD with external linear measure, and second, based on IVD length prediction, the appropriate laryngoscope blade size can be ascertained.

Study Overview

• Status: Recruiting
• Conditions: Laryngoscopy; Airway Assessment

Detailed Description

Preoperative evaluation of the upper airway is vital to the success, safety, and quality of airway access. The evaluation primarily aims to anticipate the course of direct laryngoscopy and intubation (DLI) of the trachea. While assessment of mouth opening, neck extension, and dentition forms the preliminary step of knowing whether DLI is feasible; there are certain other parameters whose evaluation facilitates understanding as to how the actual DLI will turn out. Among the secondary parameters, the linear thyromental distance (TMD) is an important measure that determines how the direct laryngoscopy aspect of conducting DLI will go - in terms of ease-of-laryngoscopy to gain the desired visual access to the view to the vocal cords. The ease of laryngoscopy involves as to how the laryngoscope blade would be able to displace tongue to one side, create forward space enhancement, and reach the vallecula at the base of the tongue; before lifting the epiglottis to view the cords. Though in use for over 4 decades, the TMD suffers from weakness, including, low sensitivity and specificity, not relating to the actual and direct teeth vallecular distance, and getting confounded by neck dimensions (thickness, length), state of dentition, and the tongue size.

The present study is built on the premise that it's the mandibular space to which the tongue is displaced at the time of DLI, the bony mandibular space is more exclusive of the confounders, and that the teeth (lower incisors) vallecular distance represent the actual distance that needs to be predicted.

The present study aims to evaluate TMD and mandibular triangle perpendicular length (MTPL); to know which correlates better with the incisor vallecula distance (IVD). Based on the direction and strength of the correlation measure, a multiple regression equation can then be created to first predict the IVD with external linear measure, and second, based on IVD length prediction, the appropriate laryngoscope blade size can be ascertained.

• Study Type: Observational
• Enrollment (Estimated): 240

Contacts and Locations

• Study Contact: Name: Amitabh Dutta, MD; Phone Number: 00919810848064; Email: duttaamitabh@yahoo.co.in

Study Locations

• India
  • National Capital Territory of Delhi
    • New Delhi, National Capital Territory of Delhi, India, 110060
      • Recruiting
      • Sir Ganga Ram Hospital
      • Contact: Amitabh Dutta, MBBS, MD, PGDHR; Phone Number: 9810848064; Email: duttaamitabh@yahoo.co.in

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: N/A

• Sampling Method: Probability Sample

Study Population

Patients undergoing elective surgery under general anaesthesia

Description

Inclusion Criteria:

1. Age 18-65 years
2. Males and females
3. ASA (American Society of Anaesthesiologists) physical status I and II
4. Patients scheduled for elective surgery with controlled ventilation through orotracheal tube conduit

Exclusion Criteria:

1. Smokers (those who have smoked ≥100 cigarettes in their lifetime), chewing tobacco dependence or substance abuse
2. Submucous fibrosis: progressive fibrosis of the submucosal tissue leading to rigidity, relative trismus, and progressive decrease of mouth opening
3. Anticipated difficult airway
4. Patients requiring intubation with MacIntosh blade #4 or #5

5. Dental issues:

   • missing tooth (upper/lower incisors, upper/lower premolar)
   • crowded dentition: - irregular, misaligned, or overlapping teeth within a relatively small oral cavity

   • presence of artificial teeth and/or dental implants

     • Mandible/mandibular structure related issues:

   • Retrognathia: - posterior displacement of the mandible relative to the maxilla or cranial base
   • Prognathia: - anterior displacement of the mandible relative to the maxilla or cranial base
6. Emergency Surgery
7. Those requiring urgent rapid-sequence intubation due to the presence of a full-stomach status secondary to gastro-esophageal reflux disease, diaphragmatic hernia, among others.
8. Refusal to informed consent

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Correlation of thyromental distance (TMD) and mandibular triangle perpendicular length (MTPL) with incisor vallecular distance (IVD)	In all patients thyromental distance (TMD) and mandibular triangle perpendicular length (MTPL) will be measured. TMD will be measured as a straight line distance between the bony mentum (tip of the chin) and the superior thyroid notch (upper border of the thyroid cartilage). MTPL will be measured as the perpendicular of the mandibular triangle formed by joining the mental protuberence and point at angle of mandible on either side. During direct larygngosocpoy when the tip of the laryngoscope blade lies on the vallecula, the distance between the laryngoscope blade tip and the point of laryngoscope blade flange overlying the lower incisors will be measured. A correlation between TMD and MTPL with IVD if any will be established.	From entry into preoperative area (0 minutes) to time patient is shifted to operating room ( 10-minutes)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Correlation of incisor vallecular distance (IVD), mandibular triangle perpendicular length (MTPL), and thyromental distance (TMD) with Macintosh blade (MCB) size#3 length	Macintosh blade size # 3 length will be determined by measuring the linear distance between the tip of the blade and the point where the concave surface of the blade flange joins the heel of the the laryngoscope blade. A correlation between IVD, MTPL, and TMD with Macintosh blade size # 3 length if any will be established	From induction of anaesthesia (0 minutes) to insertion of endotracheal tube ( 10-minutes)
Cormack and Lehane score	The grade view to the glottic-opening upon direct laryngoscopy will be done using the 4-point Cormack-Lehane grading system (grade 1: entire glottic opening is seen; grade 2: anterior larynx not visualised, only posterior laryngeal aperture is seen; grade 3: only tip of epiglottis is seen; grade 4: neither glottis or epiglottis is visible, only soft palate is seen)	From induction of anaesthesia (0 minutes) to insertion of endotracheal tube ( 10-minutes)

Collaborators and Investigators

• Sponsor: Sir Ganga Ram Hospital
• Investigators: Principal Investigator: Amitabh Dutta, MD, Sir Ganga Ram Hospital, New Delhi-110060, India; Principal Investigator: Paridhi Saboo, MBBS, Sir Ganga Ram Hospital, New Delhi-110060, India; Study Director: Nitin Sethi, DNB, Sir Ganga Ram Hospital, New Delhi-110060, India

Study record dates

Study Major Dates

• Study Start (Actual): June 25, 2026
• Primary Completion (Estimated): July 1, 2027
• Study Completion (Estimated): August 1, 2027

Study Registration Dates

• First Submitted: June 19, 2026
• First Submitted That Met QC Criteria: June 19, 2026
• First Posted (Actual): June 25, 2026

Study Record Updates

• Last Update Posted (Actual): June 30, 2026
• Last Update Submitted That Met QC Criteria: June 25, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Laryngoscope; Thyromental distance; Mandibular triangle perpendicular; incisor vallecula distance
• Other Study ID Numbers: EC/06/26/2981

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No