TEMPOROMANDIBULAR JOINT

DR.MEHUL JANIRESIDENT-I(M.D.S)DEPARTMENT OF

ORAL & MAXILLOFACIAL SURGERY

EMBRYOLOGY OF THE TMJ:-

TMJ develops relatively late compared with the large joints of the extremities.

STAGES OF DEVELOPMENT:-

Seventh prenatal week:-

Meckel’s cartilage gives scaffolding for mandibular development.

Provides temporary articulation between mandible and base of the skull.

Articular disk is the first component of joint to become recognizable at this stage.

There is no proper joint capsule and mandibular condyle.

Only mesenchymal condensation is seen.

At this stage lateral pterygoid muscle inserts not on the mandible but on the posterior end of Meckel’s

cartilage.

The future condyle is still only condensation of the mesenchyme.

Twelth prenatal week:-

The condylar growth cartilage makes it’s first appearance and condyle

becomes to develop a hemispherical articular surface.

Thirteenth prenatal week:-Condyle and articular disk moves up in contact with

temporal bone.

Joint cavities start developing.

Inferior cavity appears first.

Twenty second prenatal week:-

Appearance of gasserian fissure(opening between the squamous and tympanic part of the temporal bone through which Meckel’s Cartilage passes into the middle ear in the fetus)and it becomes a squamo tympanic & petrotympanic

fissure.After birth it becomes narrow.

Joint cavities are now lined with synovial tissue.

Meckel’s cartilage degenerates.

Twenty-sixth prenatal week:-

All the components of the TMJ present except for the articular eminence.

Gasserian fissure transformed into sphenomandibular ligament.

Thirty-first week:-

Gasserian fissure closes.

Meckel’s cartilage becomes ant.ligament of malleus.

Thirty-sixth week:-

Ossification of bone of this region.

Attachments of ligaments.

ANATOMY

• It is the most complex joint in the body & is the area where mandible articulates with the cranium.

• It provides hinge movement in one plan around the transverse axis & there for can be considered a GINGLYMOID JOINT.

• At the same time it also provides for gliding movement which classifies it as an ARTHRODIAL JOINT .

• Thus the TMJ has been considered a GINGLYMOARTHRODIAL JOINT.

Mandibular fossa

• TMJ is formed by the 1.MANDIBULAR CONDYLE2.ARTICULAR DISC3. MANDIBULAR FOSSA.• TMJ is classified as a compound joint.• As a compound joint requires at least three bones

the articular disc serves as a nonossified bone and function as a 3rd bone.

Mandibular fossa

MANDIBULAR CONDYLE

• Condyle is the portion of the mandible that articulates with the cranium.

• From the anterior view it has a two poles. 1.medial

2.lateral.• Medial pole is more prominent then

lateral. Total mediolateral length of the condyle is 15 to 20 mm. & the anteroposterior width is 8 to 10mm.

15-20mm.

Lateral medial

• The actual articulating surface of condyle extends anteriorly & posteriorly to the most superior aspect of the condyle.

• The posterior articulating surface is greater than anterior.

• The articulating surface of the condyle is quite convex anteroposteriorly and only slightly convex mediolaterally. ANTERIOR POSTERIOR

MANDIBULAR FOSSA• Condyle articulates at the base of the

cranium with the squamous portion of the temporal bone.

• This concave portion is known as mandibular fossa/articular fossa/glenoid fossa.

• Posterior to mandibular fossa is the squamotympanic fissure which extends mediolaterally.

• As the fissure extends medially it divides into the petrosquamous fissure anteriorly & petrotympanic fissure posteriorly.

• Immediately anterior to fossa is the convex prominence called the articular eminence.

• The steepness of this surface dictates the pathway of the condyle when mandible is positioned anteriorly.

• The posterior roof of the fossa is quite thin, indicating that this area of the temporal bone is not designed to sustain heavy forces.

• where the articular eminence is consist of thick,dense bone & more likely to tolerate such forces.

ARTICULAR DICS

• It is composed of dense fibrous connective tissue & most part devoid of any blood vessels or nerve fibers.

• The extreme periphery of the disc is slightly innervated.• In saggital plane it can be divided in to 3

regions according to the thickness. Anterior

Intermediate(thinnest) Posterior.(thickest)

• In normal joint the articular surface of the condyle is located on the intermediate zone bordered by thicker anterior & posterior region.

• The disc is thicker medially.• Shape of the disc is determined by

the morphology of the condyle & mandibular fossa.

• Disc is flexible & can adapt to the functional demand of the articular surface.

• Disc maintains its morphology unless destructive forces or structural changes occur in the joint.

• If they occur, the morphology of the disc can be irreversibly altered, producing biomechanical changes during function.

• Posteriorly it is attached to the RETRODISCAL TISSUE.

• Which is bordered superiorly by the superior retrodiscal lamina which contains elastic fibers.

• This superior retrodiscal lamina is attached to the articular disc posteriorly to the tympanic plate.

• At the lower border there is inferior retrodiscal lamina which contains collagenous fibers.

• The remaining body of the retrodiscal tissue is attached posteriorly to a large venous plexus which fills with blood as the condyle moves forward.

• The retrodiscal tissue attaches to the posterior edge of the articular disc and fills the space between the disc and the posterior wall of the capsule. This is the bilaminar zone.

• Anteriorly the disc is attached to the capsular ligament which surrounds most of the joint.

• Superior attachment is to the articular margin of the temporal bone & inferior attachment is to the anterior articular margin of the mandibular condyle.

• Between the attachment of the capsular ligament the disc is attached to the superior lateral pterygoid muscle.

• Disc is attached to the capsular ligament medially & laterally.

• This attachment divide the joint in to two cavities.

superior cavity/upper compartmentinferior cavity/lower compartment

• Superior cavity is bounded superiorly by articular surface of mandibular fossa & inferiorly by the superior surface of articular disc.

• Inferior cavity is bounded superiorly by inferior surface of articular disc & inferiorly by the articular surface of condyle.

• Specialized endothelial cells that form the synovial lining surround the internal surface of both cavities.

• The synovial fringe are located at the anterior border of the retrodiscal tissue and produce the synovial fluid which fills both the joint cavities. so this joint is also known as SYNOVIAL JOINT.

1.2ml.

0.9ml.

• Synovial fluid act as medium for providing metabolic reqiurements & also act as lubricant.

• Synovial fluid lubricates the articular surface by two mechanisms.1.BOUNDARY LUBRICATION:-

it is occur when joint moves & the synovial fluid is forced from one area of the cavity into another.it prevents friction in moving joint.2.WEEPING LUBRICATION:-

it refers to the ability of the articular surface to absorb a small amount of synovial fluid.

the forces between the articular surface drives the small amount of synovial fluid in & out of the tissue by which metabolic exchanges takes place.

weeping lubrication helps eliminate friction in the compressed joint.

THE ARTICULAR DISC IS NOT A MENISCUS:-•

•A meniscus is a crescent shaped sheet of fibrocartilage,one of which forms a marginal attachment at the articular capsule and other extends in to the joint cavity as a free edge.

•The structure does not divide the joint cavity into separate compartments , nor does it restrict or confine the synovial fluid.

•It facilitates movement of the bony parts but does not act as a true articular surface. •A meniscus is a passive structure that facilitates joint function through synovial fluid action.

•Its surface are not capsule enclosed and , as such, are not true articular facets.

•A removal of a meniscus does not seriously alter the functional behavior of the joint.

•Such meniscus is seen in simpler joints such as knee joint.

NERVE SUPPLY OF TMJ

•Most innervation is provided by auriculotemporal nerve.•As it leaves mandibular nerve behind the joint & ascends lateally and superiorly to wrap around the posterior region of the joint.•Deep temporal and masseteric nerves provides additional innervation.

HILTON’S LAW

• States that nerves which supply a joint also innervate the muscle that move it.

BLOOD SUPPLY OF TMJ• Anteriorly by middle meningeal

artery.• Posteriorly by superficial

temporal artery.• Inferiorly internal maxillary

artery.• Deep auricular ,anterior

tympanic,ascending pharyngeal arteries are other blood supply.

• condyle receives its vascular supply through marrow space by the way of inferior alveolar artery and some major feeder vessels.

• Venous drainage is via superficial temporal,maxillae & pterygoid plexus of veins.

LYMPHATIC DRAINAGE:-

• Lateral surface:preauricular,parotid nodes• Posterior & medial surface: submandibular

nodes• Anterior surface: parotid nodes

LIGAMENTS

• 3 functional ligaments support the tmj:-1. The collateral(discal)ligament

2. The capsular ligament3. The temporomandibular ligament.

• 2 accessory ligaments:-1. The sphenomandibular ligament2. The stylomandibular ligament.

COLLATERAL LIGAMENTS• It attach the medial & lateral borders of the

articular disc to the poles of the condyle.• Medial discal ligament attaches the medial

edge of the disc to the medial pole of condyle.• Lateral discal ligament attaches the lateral edge

of the disc to the lateral pole of condyle.• Discal ligament are responsible for dividing the

joint mediolaterally into superior & inferior joint cavities.

• This ligament do not stretch.• They functiion to restrict movement of disc

away from the condyle.• It allows the disc to move with condyle as it

glides anterio-posteriorly.• Thus discal ligaments are responsible for the

hinging movements which occurs between the articular disc.

CAPSULAR LIGAMENT• It encompass and surround the entire

TMJ.• Fibers of the capsular ligaments are

attached superiorly to the temporal bone along with the border of the articular surface of mandibular fossa & articular eminence.

• Inferiorly it attach to the neck of the condyle.

• It act to resist any medial, lateral & inferior forces that tend to separate or dislocate the articular surface.

• A significant function is to encompass the joint & thus retaining the synovial fluid.

• It provides the proprioceptive feedback regarding the position & movement of the joint.

TEMPOROMANDIBULAR LIGAMENT• It composed of outer oblique portion(oop) and

inner horizontal portion(ihp).• Oop extends from the outer surface of the articular

eminence & posteroinferior surface of zygomatic process to the outer surface of the condylar neck.

• Ihp extends from outer surface of the articular eminence and zygomatic process posteriorly & horizontally to the lateral pole of the condyle & the posterior part of the articular disc.

• Oop resists excessive dropping of the condyle,therefore limiting the extent of mouth opening.

• During initial stage condyle can rotate around a fixed point untill the oop of ligament becomes tight.

• When it is taut,condyle can not rotate further,if mouth were open wide condyle will move forward and downward across the articular eminance.

• Inner horizontal portion of ligament limits posterior movement of the condyle & disc.

• Therefore tm ligament protects the retrodiscal tissue from trauma created by the posterior displacement of condyle.

• The effectiveness of this ligament is demonstrated during cases of extreme trauma to the mandible.

• In such cases the neck of the condyle will fracture before the retrodiscal tissues are severed or before the condyle enters the middle cranial fossa.

Sphenomandibular & stylomandibular ligament

• Sphenomandibular ligament arise from the spine of sphenoid bone & extends downwards & to lingula.

• Stylomandibular ligament arises from the styloid process & extends downwards &forward to the angle & posterior border of the ramus .

• It become taut when mandible is protruded.

• It is most relaxed when mandible is open.

MUSCLES OF MASTICATION

• Four pair of muscles makes up a group called MUSCLES OF MASTICATION.

1. Masseter2. Temporalis3. Medial pterygoid4. Lateral pterygoid• Digastric muscle is not a masticatory

muscle but has a important role in mandibular function.

MASSETER• Shape:-rectangular • Origin & insertion:-from zygomatic arch

& extends downwards to lateral surface of the lower border of the ramus of mandible.

• Heads:-2 heads.1:superficial portion in which fibers

running downwards & backwards.2.deep portion in which fibers

running in predominantly vertical direction.

Action:-elevation of mandible & bring the teeth in contact.

•Superficial portion may also aid in protruding the mandible.

•When the mandible is protruded & biting force is applied the deep portion stabilize the condyle against the articular eminence.

TEMPORALIS•Shape:-large-fan shape•Origin & insertion:-from the temporal fossa & lateral surface of the skull,fibers come together as they extend downward to form a tendon that inserts on the coronoid process & anterior border of the ascending ramus.•Can be divided into 3 portion.

1. Anterior portion consists of fibers directed almost vertically.

2. Middle portion contains fibers that run obliquely.

3. Posterior portion consists of fibers that are aligned almost horizontally.

Action:-elevation of mandible & bring the teeth in contact.•When anterior portion is contract the mandible is raised vertically.•When middle portion is contract it will elevate & retrude the mandible.•When posterior portion is contract it will elevate the mandible & slight retrusion takes place.

MEDIAL PTERYGOID• Shape:-rectangular• Origin & insertion:-from the pterygoid

fossa on the medial surface of lateral pterygoid plate & extends downward –backward-outward to insert on the medial surface of the mandible angle.

• Along with the masseter it forms a muscular sling that supports the mandible at the angle.

• Action:- elevation of mandible & bring the teeth in contact & also active in protrusion of mandible.

• Unilateral contraction will bring a mediotrusive movement of the mandible.

LATERAL PTERYGOID• 2 portions:-1.inferior lateral pterygoid2.Superior lateral pterygoid.

INFERIOR LATERAL PTERYGOID :-• Origin & insertion:from the lateral surface of

the lateral pterygoid plate & extends upward-backward-outward to insert on the neck of the condyle.

• When rt.& lt. Muscle contract simultaneously,condyle are pulled down the articular eminence & mandible is protruded.

• Unilateral contraction creates the mediotrusive movement of the condyle & lateral movement of the mandible.

• When function with mandibular depressors,the mandible is lowered & the condyle glide forward & downward on the articular eminence.

SUPERIOR LATERAL PTERYGOID :• Origin & insertion:from the infratemporal

surface of the greater wing of sphenoid bone,extending almost horizontal-backward-outward to insert on the articular capsule,disc & the neck of the condyle.

• Majority 60%to70% fibers insert on the neck of the condyle .

• Only 30%to40% fibers attach to the disc.• Active only in conjuction with elevator

muscles.• Especially active during the power stroke &

teeth are held together.

•The pull of the lateral pterygoid on the disc & condyle is in a medial direction.•80% of the fibers are slow muscle fibers,so these muscles are relatively resistant to fatigue.

DIGASTRIC MUSCLE• It is divided in 2 portion.

POSTERIOR BELLY :Origin & insertion:from the mastoid

notch,extends forward -inward-downward to intermediate tendon attached to the hyoid bone.ANTERIOR BELLY :

Origin & insertion:from the digastric fossa on the mandible,extends downward-backward to intermediate tendon attached to the hyoid bone.

•When rt.& lt. Muscle contract & the supra hyoid & infra hyoid muscles fix the hyoid bone,the mandible is depressed & pulled backward & teeth are brought out of the contact.•When the mandible is stabilized,the digastric muscle with suprahyoid & infrahyoid muscles elevates the hyoid bone which is necessary for swallowing.

RELATIONS OF TMJ• Lateral – Skin and fasciae, parotid gland,

temporal branch of the facial nerve.

• Medial – Tympanic plate, spine of sphenoid, sphenomandibular ligament, auriculotemporal & chorda tympani nerves & middle meningeal artery.

• Anteriorly – Lateral pterygoid, masseteric nerve & vessels.

• Posteriorly – Parotid gland,Superficial temporal vessels & auriculotemporal nerve.

• Superiorly – Middle cranial fossa &

middle meningeal vessels.

• Inferiorly – Maxillary artery and vein.

APPLIED ASPECTS• The main trunk of the facial

nerve exits from the skull at stylomastoid foramen.

• The tympanomastoid suture is the reliable anatomical landmark because the main trunk lies 6-8mm. Inferoanteriar to the tympanomastoid suture.

• Appro.1.3cm.of facial nerve is visible untill it divide.

• Al Kayat & bramley (1979), have observed that the distance from the lowest point of the external auditory canal to bifurcation was 1.5-2.8cm.

• They also observed that distance from the post glenoid tubercal to the bifurcatiion was 2.4-3.5cm.

• The most variable measurement was the point at which the upper trunk crosses the zygomatic arch.it ranged from 8-35mm. Anterior to the most anterior portion of the bony external auditory canal.

• By incising the superficial layer of the temporalis fascia & the periosteum over the arch ,inside the 8mm.boundary surgeons can prevent damage to the branches of the upper trunk.

• Post surgical palsy manifests as an inability to raise the eyebrows & ptosis of the brow.

• The mean transverse distance from the zygomatic arch to the middle meningeal artery was 31 mm (range, 21 mm to 43 mm).

• The anterior-posterior distance from the height of the glenoid fossa to the middle meningeal artery was ranged from 2 mm to 8 mm.

• The transverse distance from the carotid artery to the zygomatic arch was a mean of 37.5 mm (29 mm to 48 mm).

• The mean distance from the internal jugular vein to the zygomatic arch was 38.3 mm (31 mm to 49 mm).

• The transverse distance from the trigeminal nerve to the arch was a mean distance of 35 mm (24 mm to 46 mm). The mean anterior-posterior distance was 9.2 mm (1 mm to 25 mm).

• The mean medial to lateral width of the glenoid fossa was 18.7 mm (16 mm to 23 mm).

• TMJ is anatomically similar to the sternoclevicular joint.• Auriculotemporal nerve can damage while doing the

surgery on the TMJ region for ankylosis results in auriculotemporal nerve syndrome which is also know as frey’s syndrome.

TMJ SURGERY APPROACHES:• Preauricular incision (Dingman’s)• Modified preauricular incisions

(Thoma’s,Blair’s,Al-Kayat & Bramley’s,Popowich & Crane’s)

• Endaural incision(Lamport’s)• Retroauricular incision• Coronal incision• Submandibular incision(Risdon’s)• Postramal incision(Hind’s)

BIBLIOGRAPHY

• FONSECA TRAUMA-I• JEFFRY P.OKESON• GREY’S ANATOMY• B.D.CHAURASIA VOL-HEAD & NECK

THANK YOU

Diseases of TMJ1)DEFORMATION OF ARTICULAR SURFACES:- It is cartilaginous &/ or osseous changes in temporal or condylar

joint surfaces through adaptation to functional loading of the joint surfaces.

•Painless,no limitation of active movements. •Occasionally causes clicking of low intensity with no deviation of the mandible.

2)OSTEOARTHROSIS:- Primary or secondary noninflammatory, degenerative cond.of

joint with structural changes in joint surfaces. •Painless,occasionally active movements limited. •Crepitus of varying intensity.

• 3)OSTEOARTHRITIS:- Inflammatory degenerative changes in cartilaginous & ossseous joint surfaces. •Pain & crepitus •Limitation of active movements.4)BONY ANKYLOSIS:- Growing together of bone at the joint surfaces with extreme restriction of mandibular movements. •Exteme restriction in movement •No pain •In spite of bony fusion,unilateral ankylosis permits mouth opening of upto 11mm. 5) PERFORATION OF BILAMINAR ZONE: Interrupted continuity of bilaminar zone Usually asymptomatic but severe pain in capsulitis & synovitis.

6)DISK DEFORMATION:- Reversible or irreversible as a sign of progressive or

regressive adaptation on the disk. •No clinical symptoms. •Occasionally clicking sound detected.7)DISK PERFORATION:- Interruption of continuity of articular disk. •With progressive adaptation,no clinical

symptoms. •With regressive adaptation symptoms such as

crepitus,clicking & pain manifested.

8)DISK HYPERMOBILITY:- Initial stage of ant.disk displacement relative to condyle with repositioning during mouth opening.It begins in medial or lateral part of joint. •Clicking sound during excursive movement

9)PARTIAL DISK DISPLACEMENT WITH REPOSITION:- It is relative to condyle with repositioning during mouth opening. Displacement of disk in medial or lateral part. •Clicking sound during excursive & incursive movements.

10)POSTERIOR DISK DISPLACEMENT:- Partial or total displacement of articular disk posteriorly at habitual occlusion & maximal jaw opening. •Jaw closure difficult in terminal phase. •Occasionally pain during return movement

11)DISK DISPLACEMENT DURING ECCENTRIC MANDIBULAR MOVEMENT:- Occupies physiological position in habitual occlusion but is displaced distally during mandibular movement & loses it’s functional contact with joint surfaces. •Terminal clicking during excursive movement.

12)STATIC JOINT COMPRESSION:- Sup,postsuperior,or posterior displacement of condyle due to corresponding static occlusal vector without constriction of joint capsule. •Usually asymptomatic or presents with mild pain.

13)FUNCTIONAL CAPSULE HYPOMOBILITY:- Sup,postsuperior,or posterior displacement of condyle with constriction of joint capsule. •Usually asymptomatic or presents with mild pain.

14)FIBROUS ANKYLOSIS:- Limited mandibular movement because of a generalized usually trauma induced retraction of joint capsule by binding of joint surfaces by connective tissue. •Restriction of all mandibular movement. •In unilateral condition marked deviation to affected side •Usually pain not a symptom.

15)SCLEROSING OF LATERAL LIGAMENT:- Hardening of the lateral capsular ligament following trauma or functional overloading.In rare cases medial ligament may also be affected. •Click during excursive md.movement.

16)CAPSULITIS WITH SPECIFIC LOADING VECTOR(LOCALIZED CAPSULITIS):- Localized changes that is inflammation in joint capsule or bilaminar zone. •Continuous or intermittent pain in joint region, radiating in different directions.

17)ACUTE CAPSULITIS(CAPSULITIS WITH UNSPECIFIED LOADING VECTOR):- Generalized painful inflammation of capsule caused by dysfunction or trauma. •Localized pain at rest. •Increased pain with active movements. •Usually extreme limitation of movement. •When unilateral md.deviates to affected side.

18)INSERTION TENOPATHY OF THE STYLOMANDIBULAR LIGAMENT (ERNEST SYNDROME):- Painful inflammatory irritation of stylomandibular ligament. •Pain at angle of jaw,also occasionally in the joint, ear,&/or radiating to the temporal region. •Hypersensitivity of molars as a reffered pain.

19)CAPSULE HYPERMOBILITY:- Increased mobility of joint due to lax ligaments &surrounding structures resulting from dysfunctionalor genetic influences. •No pain. •Sometimes above average length of excursive movements.

20)CONDYLAR LUXATION:- Sliding of disk condyle complex in front of the articular eminence without possibility of self repositioning. •Locked jaw after further opening. •Occasional muscle and or joint pain.

21)CONDYLAR HYPERMOBILITY:- Sliding of disk condyle complex in front of the articular eminence with possibility of self repositioning. •Springing of the condyle over zenith of the articular eminence when jaw is opened farther than usual. •Distinct click can occur at terminal jaw opening.

22)SYNOVITIS:-

Inflammation of synovial membrane with increased production of synovial fluid with acute capsulitis. •Localized pain at rest •Increased pain with active movements, especially during jaw closure. •Limitation of movements •When unilateral mandible deviates to affected side •Swelling in joint region