Thursday, February 26, 2015
TMJ Anatomy
The temporomandibular joint (TMJ) or jaw joint is a bi-arthroidal hinge joint that allows the complex movements necessary for eating, swallowing, talking and yawning. Dysfunction of the TMJ can cause severe pain and lifestyle limitation. Temporomandibular disorders are common and sufferers will often seek physiotherapeutic advice and treatment. Good knowledge of the anatomy of the TMJ and related structures is essential to correct diagnosis and appropriate treatment.
Joint
Capsule - The capsule is a fibrous membrane that surrounds the joint and attaches to the articular eminence, the articular disc and the neck of the mandibular condyle.
Articular disc - The articular disc is a fibrous extension of the capsule that runs between the two articular surfaces of the temporomandibular joint. The disc articulates with the mandibular fossa of the temporal bone above and the condyle of the mandible below. The disc divides the joint into two sections, each with its own synovial membrane. The disc is also attached to the condyle medially and laterally by the collateral ligaments. The anterior disc attaches to the joint capsule and the superior head of the lateral pterygoid. The posterior portion attaches to the mandibular fossa and is referred to as the retrodiscal tissue.
Retrodiscal tissue - Unlike the disc itself, the retrodiscal tissue is vascular and highly innervated. As a result, the retrodiscal tissue is often a major contributor to the pain of Temporomandibular Disorder (TMD), particularly when there is inflammation or compression within the joint
Ligaments
The ligaments give passive stability to the TMJ.
The temporomandibular ligament is the thickened lateral portion of the capsule, and it has two parts, an outer oblique portion and an inner horizontal portion.
The stylomandibular ligament runs from the styloid process to the angle of the mandible. The sphenomandibular ligament runs from the spine of the sphenoid bone to the lingula of mandible.
The oto-mandibular ligaments are the discomalleolar ligament (DML), which arises from the malleus (one of the ossicles of the middle ear) and runs to the medial retrodiscal tissue of the TMJ, and the anterior malleolar ligament (AML), which arises from the malleus and connects with the lingula of the mandible via the sphenomandibular ligament. The oto-mandibular ligaments may be implicated in tinnitus associated with TMD. A positive correlation has been found between tinnitus and ipsilateral TMJ disorder. It has been proposed that a TMJ disorder may stretch the DML and AML, thereby affecting middle ear structure equilibrium. “It thus seems that otic symptoms (tinnitus, otalgia (ear pain), dizziness and hypoacusis) corresponding to altered ossicular spatial relationships (such as conductive middle ear pathologies) can also be produced from masticatory system pathologies.”
Muscles and Jaw Movement
The jaw can move forward and back, side to side and can open and close. Each of these movements are performed by a number of muscles working together to perform the movement while controlling the position of the condyle within the mandibular fossa. Chewing and talking require a combination of jaw movements in a number of directions.
- Opening – inferior head of lateral pterygoid, anterior digastric, mylohyoid. Opening is also controlled by eccentric contraction of the closing muscles against gravity. Opening is a complex movement consisting of an early rotary component in the first 2-3cms of movement with a forward glide towards the end of range. The articular disc moves forward with the condyle as it glides forward, effectively extending the superior articular surface of the mandibular fossa.
- Closing – masseter, anterior and middle temporalis, medial pterygoid, superior head lateral pterygoid.
- Protrusion – bilateral contraction of the lateral pterygoid.
- Retrusion – middle and posterior temporalis, possibly helped by deep posterior portion of masseter
- Laterotrusion (side to side) – ipsilateral middle and posterior temporalis, contralateral inferior head lateral pterygoid.
 |  |  |
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment