Surgical anatomy of the temporomandibular joint and surgical (nx power lite) /certified fixed orthodontic courses by Indian dental academy

SURGICAL ANATOMY AND
APPROACHES TO THE
TEMPOROMANDIBULAR JOINT

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


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INTRODUCTION OF THE TMJ
ARTICULATORY SYSTEM
TMJ CAPSULE
ARTICULAR DISK
LIGAMENTS
BLOOD AND NERVE SUPPLY
MUSCLES
MOVEMENTS OF THE TMJ
SURGICAL ANATOMY

INTRODUCTION
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The TMJ is also known as the craniomandibular
joint/articulation.


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The TMJ is a gingylmoarthrodial joint that is freely mobile with superior and
inferior joint cavities separated by the meniscus (articular disc).
It is considered as a complex joint because it involves two separate joints (rt.
& lt.) in which there is presence of intracapsular disc and both joints have to
function in coordination.


ARTICULATORY SYSTEM
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The articulatory system comprises of the following :
The TMJ
The masticatory and accessory muscles
The occlusion of the teeth.
The function is governed by sensory and motor branches of he
third division of the trigeminal nerve (mandibular) and a few
fibers of the facial nerve.
The occlusion of the teeth plays an imp. role in he function of
the TMJ. Normally, the greatest part of the force of mastication
is borne by the dentition of the jaws, but in case of occlusal
disharmony, a great deal of force can be shifted to the joint itself.


CRANIAL COMPONENT
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Mandibular ( glenoid fossa) :
It is an anterior articular area formed by the inferior aspect of
temporal squama. It’s surface is smooth, oval and deeply hollow
and the bone is very thin at the depth of the fossa. The fossa is
lined by dense avascular fibrocartilage.


CRANIAL COMPONENT
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Limits are :
Anteriorly – articular
eminence or tubercle
Posteriorly – post glenoid
tubercle
Medially – spine of he
sphenoid bone
Laterally – root of the
zygomatic process of
temporal bone
Superiorly – separated from
MCF by thin plate of bone at
apex

MANDIBULAR COMPONENT
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Mandibular condyle :
The articular part of the
mandible is an ovoid
condylar process (head)
with narrow mandibular
neck. It is broad laterally
and narrower medially.
The articular part of the
condyle is covered by
fibrocartilage.

MANDIBULAR COMPONENT
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Mediolateral dimension
varies bn. 13 – 25 mm.
Anteroposterior width varies
bn. 5.5 – 16 mm.
Majority of the human
condyles (58%) are slightly
convex superiorly.
25% of the condyles may be
flat superiorly.
12% are pointed or angular
in shape.
3% are bulbous or rounded
in shape.

TMJ CAPSULE
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TMJ capsule is a thin sleeve of
fibrous tissue investing the joint
completely, it defines the
anatomic and functional
boundaries of the TMJ.
It is a funnel shaped capsule,
which blends with the
periosteum of the mandibular
neck and it envelops the
articular disc.
On the temporal bone, the
articular capsule surrounds the
articular surfaces of the
eminence and fossa.

TMJ CAPSULE
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Attachments

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Anteriorly – ant. border of the
articular eminence.
Posteriorly – lip of
squamotympanic fissure and
ant. sf. of postglenoid pss.
Laterally – edge of the
eminence and glenoid fossa.
Medially – along the
sphenosquamosal suture.
Below – neck of the condyle
medially and laterally.

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TMJ CAPSULE
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Each part of the joint is surrounded by short capsular fibers
which stretch from the condyle to the disc, and from the disc to
the temporal bone forming two joint capsules.
Longer bands extending from the condyle to the temporal bone
may be regarded as reinforcing fibers.
Capsular fibers passing bn. the mandible and temporal bone are
present only on the lateral side.
The cavities are lined with synovial tissue with villi extending
from anterior and posterior part of the articular disk to the
attachments to the temporal bone and mandibular condyle.


ARTICULAR DISK
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The articular disk, an oval
plate of fibrous tissue shaped
like a tweaked cap,
completely divides the
articular space into two
compartments:
The inferior compartment –
condylodiscal complex
between the condyle and the
disc.
The superior compartment –
temporodiscal complex
between the disc and the
glenoid fossa.

ARTICULAR DISK
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The disk is biconcave in the sagittal section.
The superior surface is concavoconvex to
match the anatomy of the glenoid fossa and the
inferior surface is concave to fit over the
condylar head.
Histologically the disk is a meshwork of firmly
woven avascular fibrous connective tissue.


ARTICULAR DISK
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The disc is a complex
structure.
It has three different zones
(Rees 1954) posterior band,
intermediate band and
anterior band.
The disk blends medially and
laterally with the capsule,
which is attached to the
medial and lateral poles of
the condyle.

ARTICULAR DISK
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The meniscus projects
anteriorly to form a footshaped process the pes
meniscus. This pss. is attached
superiorly to the articular
eminence and superior belly
of the lat. pterygoid muscle.
Inferiorly the pes meniscus is
attached to the articular
margin of the condyle.


ARTICULAR DISK
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The posterior meniscus
attachment is the bilaminar
zone, composed if two strata
of fibres separated by a
central zone composed of
loose areolar connective
tissue.
The meniscus is highly
vascular in this region and is
called the genu vasculosa.
( sensory branches of the
auriculotemporal n.)


ARTICULAR DISK
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The posterior meniscus
attaches via the superior
stratum (elastic fibers) to
the tympanic plate of the
temporal bone.
The inferior stratum
(inelastic collagen)
attaches to the neck of
the condyle.


SYNOVIAL MEMBRANE
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The inside of the TMJ capsule and the nonarticulating surfaces
of the disk ligaments are lined with synovial membrane.

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It has been estimated that the volume of synovial fluid in the
superior joint compartment is 1.2ml and in the posterior
compartment is 0.9ml.

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The synovial fluid contains a glycoprotein known as lubricin,
which serves to lubricate and minimize friction between articular
surfaces of the joint.

TEMPOROMANDIBULAR LIGAMENT

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TMJ capsule is reinforced by
this main stabilizing ligament.
It extends downward and
backward from the lat. aspect of
the articular eminence to the
external and posterior aspect of
the condylar neck.
This ligament functions like a
pendulum, which allows
translation but resists abnormal
lateral condyle displacement.


SPHENOMANDIBULAR LIGAMENT
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It is a flat, thin band
descending from the spine of
the sphenoid and widening to
reach the lingula of the
mandibular foramen.
It is imp. landmark during
surgery as the maxillary artery
and the auriculotemporal n.
lies between it and the
mandibule.


STYLOMANDIBULAR LIGAMENT
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The stylomandibular
ligament, a specialized band
of deep cervical fascia
stretches from the apex and
adjacent anterior aspect of
the styloid process to the
mandible’s angle and
posterior border.


BLOOD SUPPLY
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The lateral aspect is supplied by superficial temporal artery.
Rich vascular supply to the deep and posterior aspect of the
retrodiscal capsular part by deep auricular, posterior auricular
and the masseteric artery.
Vascular supply to the lateral pterygoid muscle also supplies the
head of the condyle by penetration of numerous nutrient
foramina vessels.
The venous pattern is more diffuse forming a plentiful plexus all
around the capsule.


NERVE SUPPLY
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The mandibular nerve innervates the TMJ.
Three branches from this nerve send terminals to the joint
capsule:
Largest – Auriculotemporal n. – posterior, medial and lateral
parts of the joint.
Massseteric nerve.
Branch from the posterior deep temporal nerve supplies the
anterior parts of the joint.


MUSCLES OF MASTICATION
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MASSETER : Two heads
The superficial head originates
on the anterior zygomatic arch,
runs downward and backward
and inserts on the angle and the
ramus.
The deep head originates from
the posterior part of the zygoma,
runs vertically downwards and
inserts on the ramus and the
coronoid process.

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TEMPORALIS :
Originates from – the lower
temporal line, the temporal fossa,
temporal fascia.
Fibers converge into a tendinous
band which then divides into 2
parts.
Superficial group of fibers inserts
on the superolateral sf. of the
coronoid pss.
Deeper larger fibers form a band
along the inner coronoid pss.
extending inferiorly to the ant.
border of the ramus.

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MEDIAL PTERYGOID :
Superficial head from
tuberosity and adjoining
bone.
Deep head from medial sf.
of lat. Pterygoid plate and
palatine bone.
Fibers run posteroinferiorly
inserting on the medial
surface of the ramus and the
angle.


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LATERAL PTRYGOID :
Upper head arises from the
infratemporal sf. and crest of
of the greater wing of the
sphenoid.
Lower head arises from lat.
Pterygoid plate.
Fibers run posterolaterally
and converge to insert onto:
Pterygoid fovea
Ant. margin of the articular
disc and capsule of the TMJ.

ACCESSORY MUSCLES - SUPRAHYOID
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DIGASTRIC :
The ant. belly originates near
the mandibular symphysis.
The post. belly originates on
the mastoid notch.
The ant. belly runs downwards
and backward and post. belly
forwards to meet the
intermediate tendon.
This tendon is held by a
fibrous pulley attached to the
hyoid bone

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GENIOHYOID : Originates from
the genial tubercle and runs
backward to insert into anterior
surfacef of body of the hyoid.
MYLOHYOID : Originates from
the mylohyoid line.
Fibers run medially and slightly
downwards. Post. Fibers insert into
body of hyoid. Middle & ant. fibers
insert into the median raphe that
unites the rt. & lt. muscles.


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STYLOHYOID : Originates from the post. surface of the styloid process.

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The tendon divides into two slips that pass on either sides of the digastric
tendon to insert into the hyoid bone.


ACCESSORY MUSCLES - INFRAHYOID
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STERNOTHYROID : Originates on the manubrium of the sternum and
inserts at the thyroid cartilage.
THYROHYOID :Originates on the thyroid cartilage and inserts on the hyoid
bone.


ACCESSORY MUSCLES - INFRAHYOID
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OMOHYOID :Originates on the superior part of the scapula
and inserts at the lateral border of the hyoid bone.
STERNOHYOID : Originates on the manubrium of the
sternum and inserts on the body of the hyoid bone.


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Motions of the TMJ are manifold. It is a ginglimus, diarthrodial
type of joint, as it is capable of rotating around more than one axis
and is capable of hinge/rotatory movement and also capable of
gliding/translatory movement.

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A hinge type of movement takes place in the lower compartment
between inferior aspect of the stationary disc and the moving
condyle.

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Gliding type of movement takes place in the upper compartment
between the superior surface of the disc, which moves with the
condyle ,and the stationary mandibular fossa and eminence.

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The mandible can be depressed, elevated, protruded or retruded.

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Lateral excursions can also be carried out.

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There is a variation of normal patterns of motion in different
individuals, which are caused by many factors, including the
following:
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Condyle head size, shape and inclinaiton.

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Glenoid fossa depth and angulation.

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Articular eminence height and degree of inclination.

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Length and laxity of ligaments comprising the joint capsule.

MOVEMENTS
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Degenerative joint disease state resulting either from local
causes or systemic causes.
Strength, length, position and tonicity of muscles of
mastication and the suprahyoid musculature.
Neuromuscular control of the muscles.


MOVEMENTS (CLOSURE)
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It is accomplished by the
simultaneous contraction
of the masseter, medial
pterygoid and temporalis
muscle of both the sides.


MOVEMENTS (DEPRESSION)
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Digastric muscle contraction
depresses the body of the
mandible.
This action is assisted by the
suprahyoid, sternohyoid, and
geniohyoid muscles.
The lateral pterygoid is the
trigger and contracts to pull
the condylar head downward
and forward on the articular
eminence.

MOVEMENTS (PROTRUSION)
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Protrusive movement is
brought about by equal
and simultaneous
contracture of the lateral
and medial pterygoid
muscles.

MOVEMENTS (RETRUSION)
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Retrusion is brought
about by the posterior
fibres of the temporalis
muscle, assisted by the
masseter, digastric and
geniohyoid muscles.

MOVEMENTS (RIGHT & LEFT LATERAL)


FACIAL NERVE
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The main trunk of the facial nerve exits from the skull at the
stylomastoid foramen.
Approximately 1.3 cm of the nerve is visible before it divides
into temporofacial and cervicofacial branches.


FACIAL NERVE
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In the classis article by Al-Kayat and Bramley the distance from
the lowest point of the external bony auditory canal to the
bifurcation was found to be 1.5 cm to 2.8 cm (mean 2.3 cm)
Distance from the post-glenoid tubercle to the bifurcation was
2.4 to 3.5 cm (mean 3.0 cm)
The distance from the most anterior concavity of the bony
external auditory canal to the most posterior significant temporal
branch of the facial nerve was 0.8 to 3.5 cm (mean 2.0 cm)


FACIAL NERVE
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Knowledge of the distances and the range of the facial nerve
branches from fixed bony landmarks within the surgical field
alerts the surgeon to the areas of highest risk.
During surgery by incising the superficial layer of the temporalis
fascia and the periosteum over the arch inside the 8 mm
boundary, damage to the branches of the upper trunk can be
prevented.


FACIAL NERVE
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The temporal branch of the facial nerve emerges from the
parotid gland and crosses the zygoma under the temporoparietal
fascia to innervate the frontalis, the corrugator, the procerus and
occasionally a portion of he orbicularis oculi muscle.
Post surgical palsy manifests as an inability to raise the eyebrow
or wrinkle the forehead and ptosis of the brow.
Damage to the zygomatic branch results in temporary or
permanent paresis to the orbicularis oculi. (may require
temporary patching of the eye to prevent corneal dessication)


AURICULOTEMPORAL NERVE
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The auriculotemporal nerve
supplies sensation to parts of the
auricle, the external auditory
meatus, the tympanic membrane,
and skin in the temporal area.
It courses form the medial side of
the posterior neck of the condyle
and turns superiorly, running over
the zygomatic root of the temporal
bone.
Just anterior to the auricle, the
nerve divides into its terminal
branches in the skin of the
temporal area.


AURICULOTEMPORAL NERVE
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Damage to this nerve can be prevented during surgery by
incising and dissecting in close apposition to the cartilaginous
portion of the external auditory meatus.
The nerve runs somewhat anteriorly as it courses from lateral to
medial.
Temporal extension of the skin incision should be located
posteriorly so that the main distribution of the nerve is dissected
and retracted forward with the flap.


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The superficial temporal artery one of the terminal branches of
the ECA, begins behind the mandibular condylar neck deep to
the parotid gland as it emerges from behind the parotid gland.
It crosses over the posterior root of the zygomatic process of the
temporal bone and enters the temporal region of the scalp.


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The transverse facial artery arises form the base of the superficial
temporal artery and runs almost transversely across the face,
lying upon the outer surface of the masseter muscle about 1.5 cm
below the zygomatic arch but above the parotid duct.


LAYERS OF THE TEMPOROPARIETAL
REGION
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The temporoparietal fascia is the most superficial layer beneath
the subcutaneous fat.

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This fascia is the lateral extension of the galea and is continuous
with the superficial musculoaponeurotic layer (SMAS).

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The blood vessels of the scalp run along its superficial aspect
closely related to the subcutaneous fat.

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The motor nerves run on the deep surface of the
temporoparietal fascia.

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The temporalis fascia is the fascia of the temporalis muscle.

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This fascia arises from the superior temporal line and fuses with
the pericranium.

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Inferiorly at the level of the superior orbital rim, the temporalis
fascia splits into the superficial layer attaching to the lateral
border and the deep layer attaching to the medial border of the
zygomatic arch.

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A small quantity of fat is found in between these two layers and
it is sometimes referred to as the superficial temporal fat pad.

REFERENCES
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GRAY’S ANATOMY – 38 TH EDITIION
COLOR ATLAS OF TMJ SURGERY – PETER D. QUINN
FONSECA ORAL AND MAXILLOFACIAL SURGERY
VOL. 4 – BAYS and QUINN
THE TMJ AND RELATED OROFACIAL DISORDERS –
BUSH and DOLWICK
SURGICAL APPROACHES TO THE FACIAL SKELETON
– EDWARD ELLIS
THE ANATOMICAL BASIS OF DENTISTRY – LEIBGOTT
SURGERY OF THE TMJ. SURGICAL ANATOMY AND
SURGICAL INCISIONS – KREUTZIGER (ORAL
SURGERY. 58; 637-646, 1984)
CLINICALLY ORIENTED ANATOMY – KEITH L.
MOORE

POSTERIOR FIBER DRAWS
MANDIBLE BACKWARDS


ELEVATION OF MANDIBLE


The combinded efforts of the Digastrics and Lateral
Pterygoids provide for natural jaw opening.


Medial and lateral pterygoid act together to
protrude the mandible


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Surgical anatomy of the temporomandibular joint and surgical (nx power lite) /certified fixed orthodontic courses by Indian dental academy

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