Establishing surface projection of Temporo- Mandibular Joint using tragus of ear as landmark

Abstract

Introduction: The temporo-mandibular joint (TMJ) is a synovial joint between the articular fossa of the temporal bone and the mandibular condyle. It is condylar variety of joint. The most important functions of the TMJ are mastication and speech and are of great interest to anatomists, dentists, orthodontists and oro-maxillo-facial surgeons. The study was conducted with objective to establish the surface projection of Temporo-mandibular joint (TMJ) using tragus of ear as land mark.
 Materials and methods: Twenty five cadavers dissected in pre auricular area on both right and left side were studied. Out of 25 cadavers, 18 were male and seven were females. The temporo-mandibular joints were exposed on both sides, keeping the tragus of the ear intact. Altogether fifty temporo-mandibular joints were studied. On living persons, condylar head of TMJ were palpated while the subjects were carrying out side to side movement of lower jaw. The distance between the summit of the tragus and the marking on condylar head was measured with the help of divider and scale.
 Result: The mean distance in millimeter (mm) from midpoint of condylar head to the summit of tragus in all living subjects and cadavers (n=150) was 12.5 ± 3.5 mm and the mean length of distal phalanx of fore finger in all living subjects and cadavers (n=150) was 22 ± 4 mm.
 Conclusion: The mandibular condyle can be palpated at 12.5 ± 3.5 mm distance from summit of tragus of ear (i.e. Half-length of distal phalanx of fore finger which is 22 ± 4 mm) just below the inferior border of zygomatic arch.

Use of “Bicondylar” as a Descriptive Term for the Temporomandibular Joint: A Scoping Review

“…Two calibrated researchers conducted the search and each article were analyzed according to specific categories: authors, year of publication, country of origin, language and the Regarding the use of the term "bicondylar", it was determined that 50 % of the articles referred to this term but did not explain it (category I); 25 % cited this term to refer to the location in the left and right mandibular condyles (category II); and 25 % the articles use the term and explain it according to the morphology of the articular surfaces (category III). In category II, the articles used phrases such as "The right and left TMJ form a bicondylar articulation" (Baral et al, 2020) or "It is considered a bicondylar joint, since it works simultaneously at both ends of the mandible" (Veras et al, 2021). In category III, the articles used phrases such as "(TMJ is) bicondylar (…) since the condyle of the mandible faces the condyle of the temporal bone" (Contreras et al, 2017); "(TMJ) is a large bicondylar joint consisting of the osseous components which are the glenoid fossa and the mandibular condyle" (Al-Bahrani, 2017) and "the TMJ between the articular fossa of temporal bone above and the mandibular condyle is bicondylar variety of synovial joint" (Nripendra et al, 2017).…”

“…Regarding the way TMJ is described, while 13 articles (54.17 %) considered (explicitly or implicitly) that TMJ is a single joint between a single bone (the jaw) and two bones of the cranium (i), 11 articles (45.83 %) consider that TMJ are actually two different TMJs that work at the same time (ii). While in category (i), the articles referred to the TMJ as a single joint complex, in category (ii), the articles used phrases such as "the TMJs form a bilateral functional joint" (Contreras et al, 2017); "there are two TMJs connected to the same bone (the mandible)" (Pai et al, 2019), "Seventeenth patients (34 TMJs)" (Al-Bahrani et al, 2017), "a bicondylar articulation (…) formed by the right and left TMJ" (Subawari et al, 2020;Baral et al, 2020) or "the left TMJ" (Nripendra et al, 2017;Lemos et al, 2018).…”

“…The temporomandibular joint (TMJ) is the joint between the mandibular condyles with the mandibular fossa and the articular tubercle of the temporal bone (Duman et al, 2020). TMJ is a ginglymoarthrodial joint formed by the glenoid fossa of the temporal bone and the mandibular condyle; it is a composite anatomical joint that allows both hinge motion (inferior joint between the articular disc and condyle) and gliding motion (superior joint between articular disc and temporal bone) (Moore et al, 2014;Baral et al, 2020). Pai et al (2019) describe the TMJ as a compound joint made up of two different TMJs connected to the same bone (the mandible), carry out both different functions but always influencing one another.…”