Temporomandibular joint (abbr. TMJ), Lat Temporomandibular joint (abbr. TMJ), Lat. – articulatio temporomandibularis Prof. Peter Stanko, MD, PhD Oral and Maxillofacial Surgeon Dpt. of Stomatology & Maxillofacial Surgery Comenius University, St Elisabeth Hospital

Questions to the examination 39. Functional anatomy of the temporomandibular joint 40. Topographic relations

TOPOGRAPHIC RELATIONS OF THE TEMPOROMANDIBULAR JOINT TMJ is located preauricularly in deep part of the regio parotideomasseterica at the cranial base.

TMJ is designed as composed joint = of two separate cavities (in one capsula articularis) ● the upper (superior) discotemporal cavity which is twice larger than ● the lower (inferior) discomandibular cavity.

CAVITIES of TMJ ● Upper discotemporal ● Lower discomandibular

FOSSA MANDIBULARIS (articular fovea) is bordered: -anteriorly by tuberculum articulare (eminentia) -cranially separated from fossa cranii media only by a thin bone plate. Cranial base may be translucent by light at this area (on a cadaver skull).

ARTICULAR DISC (Lat. ̶ discus articularis) ▪ Divides TMJ into two cavities ▪ Very thin centrally (above 1 mm, in elderly may be with perforations), on margins it is thicker (3-4 mm). ▪ Dorsally the disc continues into a vascular tissue, called retroarticular plastic Zenker´s pillow. Alternating filling and evacuation of the vessels compensates negative pressure and empty space by mouth opening.

CONDYLAR PROCESS of the mandible (Clin. – Processus articularis) SIZE + SHAPE: ► 15 – 20 mm long ► elipsoid convex.

CONDYLAR PROCESS of the mandible ► PROJECTION of the condylar process is one half on the bony and one half on the cartilaginous meatus acusticus externus ► AXES form an angle of 150˚ - 160˚. In elderly the condyls get flatter.

TMJ CAPSULE (Lat. – capsula articularis) PROPERTIES: -Better fixed laterally than anteroposteriorly -Stronger in posterior direction than anteriorly.

TMJ capsule - SUPPORT TMJ is supported by following LIGAMENTS: ▪ lig. laterale ▪ lig. mediale ▪ lig. stylomandibulare ▪ lig. pterygomandibulare (raphe pterygomandibulare) ▪ lig. sphenomandibulare (enters the medial ear to hammer/stapes and continues laterally from chorda tympani to the disc).

Meatus acusticus externus, ossicula auditus (malleus, incus, stapes), membrana tympani, tuba auditiva Eustachii

Cavum tympani (middle ear), apparatus statoacusticus (inner ear = labyrintus + cochlea)

FUNCTIONAL ANATOMY OF THE TEMPOROMANDIBULAR JOINT ► TMJ is a paired joint ► Harmonic bilateral function (under physiological conditions).

MOVEMENTS in TMJ Division of movements: A/ by principle B/ by function (direction).

A/ Movements in TMJ by PRINCIPLE Rotation /acting in the lower cavity/, the rotation axis passes middles of both condyles. 2. Translation /in the upper cavity/. Inclination of the translation plane is in average 33˚.

Rotation and translation ▪ The movements follow consecutively i.e. after the rotation (condyle is remaining in articular fovea) follows translation of the articular disc together with condyle moving forwards to the highest point of the tuberculum articulare. ▪ The weak anterior part of the capsule is coming under the pressure (this is palpable). ▪ The movements are always bilateral (can not be any separate movement in one joint only without moving the opposite joint).

X-RAY of TMJ = NORMAL mouth opening

B/ Movements in TMJ by FUNCTION (direction) 1. Elevation (adduction, closing of the mouth) 2. Depression (abduction, opening of the mouth) 3. Protraction (propulsion, movement of the mandible forward), it must be preceded by a mild mouth opening avoid overjet of the upper frontal teeth) 4. Retraction (retropulsion, , movement of the mandible backward) which has minimal extent (above 1 mm) 5., 6. Lateropulsions i. e. sinistropulsion (movement to the left) and dextropulsion (movement to the right).

See more in question No 55 MUSCLES of MASTICATION →