Anatomy of head and neck

TemporoMandibular Joint (TMJ)

 

 

Temporomandibular Joint (TMJ)

 

1)Overview and Topographic Anatomy

GENERAL INFORMATION

The temporomandibular joint (TMJ) is the articulation between the squamous portion of the temporal bone and the condyle of the mandible

Structural Components

The TMJ comprises 2 types of synovial joints—hinge and slidingand consists of the

following:

Squamous portion of the temporal bone

Articular disc (contained within the TMJ)

Condyle of the mandible

Ligaments (serve as boundaries)

TMJ Dysfunction

Affects approximately 25% of the population and may be severe in a small subgroup

Causes include arthritis, trauma, infection, bruxism, and disc displacement

More common in females

 

Temporomandibular Joint

 

 

 

2)Anatomy :

 

Temporomandibular Joint

Temporomandibular Joint

Temporomandibular Joint Temporomandibular Joint

3)Arterial Supply :

 

Temporomandibular Joint

Temporomandibular Joint

Temporomandibular Joint

Temporomandibular Joint

4)Venous Supply :

  Temporomandibular Joint 11

5)Nerve Supply :

Temporomandibular Joint Temporomandibular Joint

 

6)Clinical Corelate :

OPENING THE MANDIBLE

Opening the mandible involves a complex series of movements Initial movement is rotational, which occurs in the lower TMJ compartment:

Lateral pterygoid (inferior head) initiates the opening of the jaw (the superior head of

the lateral pterygoid is described as being active during elevation of the mandible in a

“power stroke”)

As the mandible is depressed, the medial and collateral ligaments tightly attach the condyle to the articular disc, thereby allowing only for rotational movement

Once the TMJ becomes taut, no further rotation of the condyle can occur

Normally, rotational movement continues until the upper and the lower teeth are about 20 mm away from each other For additional movement of the mandible, translational movement must occur:

A translational movement occurs in the upper TMJ compartment and provides for

most of the mandible’s ability to open

In this movement, the articular disc and the condyle complex slide inferiorly on the articular eminences, allowing for maximum depression of the mandible.

 

Temporomandibular Joint  

 

MANDIBULAR DISLOCATION

 Mandibular dislocation (or subluxation of the TMJ) occurs when the condyle moves anterior to the articular eminence

With dislocation, the mouth appears “wide open”

Because the condyle is displaced anterior to the articular eminence, a depression can be palpated posterior to the condyle Spontaneous dislocations can occur from a variety of actions ranging from an extended dental treatment to a simple yawn Because the mandible is dislocated, the patient has a great deal of difficulty verbalizing his or her predicament

Relocation involves repositioning the condyle posterior to the articular eminence

Temporomandibular Joint  

 

 

ARTHRITIS AND ANKYLOSIS

 

ARTHRITIS

Arthritis is the most common cause of pathologic changes in the TMJ When rheumatoid arthritis occurs, usually both TMJs are affected, and other joints tend to be affected before the TMJ Radiologic images in the initial disease stages show decreased joint space without osseous changes Radiologic images in the late disease stages show decreased joint space with osseous changes, possibly including ankylosis In osteoarthritis, causes include normal wear, trauma, and bruxism, and clinical manifestations may range from mild to severe

 

ANKYLOSIS

Ankylosis is an obliteration of the TMJ space with abnormal osseous morphologic

features, which often occurs as a result of trauma or infection

Classified as either true (intracapsular) or false ankylosis (extracapsular condition usually

associated with an abnormally large coronoid process or zygomatic arch)

Treatment varies in accordance with the cause but may include a prosthetic replacement

or condylectomy

 

Temporomandibular Joint