Tmj surgical anatomy and approaches (nx power lite) /certified fixed orthodontic courses by Indian dental academy

Temporomandibular Joint
-Surgical Anatomy and
Approaches
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


TEMPOROMANDIBULAR JOINT
Unique features
•
•

Covered with fibrocartilage

•

•

Simultaneous movements

Presence of teeth

Bicondylar, ginglymoarthroidal, compound, complex,
secondary, synovial joint.


Evolution

Agnatha

Gnathostomes

Osteichthyes

Amphibians

Reptiles

Mammals

Mammals like reptiles

Prenatal development


Post natal development
Condyle


Mediolateral width
• 9.6mm at birth
• 12.4mm at deciduous point
• 15mm in permanent dentition



Anteroposterior
• Faster than mediolateral growth
• 6.5mm - from eruption to completion
of deciduous teeth.
• 7.3mm - adult size

Glenoid fossa


3 times more deeper in adult than infant.



Cartilage slowly replaced by fibrous tissue with age.

Articular eminence :


Rudimentary at birth



Growth increases after eruption of permanent incisors


Age changes in Mandible


ANATOMY &
BIOMECHANICS OF THE
TEMPOROMANDIBULAR
JOINT

TMJ

BONY COMPONENTS

SOFT-TISSUE
COMPONENTS
1. Articular disk
2. Joint capsule
3. Ligaments

1. Glenoid fossa
2. Condylar head
3. Articular eminence



MUSCLES
1.
Muscles of mastication
2.
Muscles attached to the joint
3.
Muscles of facial expression
4.
Muscles of the neck


BONY COMPONENTS


CONDYLAR HEAD


Oval – mediolaterally – ‘Rugby ball’



15-20 mm long (M-L); 8-10 mm wide (A-P); 8-120 mm thick



Medial pole > lateral pole



Posterior surface > anterior surface



Articulating surface – Fibrous tissue



140o with line connecting EAM on both sides



Axes – meet anterior to foramen magnum


ARTICULAR EMINENCE
•

Sigmoid shape, Anterior & posterior slopes

•

Saddle – shaped in coronal section – concave
mediolaterally – path of condyle

•

With disc, guides mandibular movement during
jaw opening

•

Has 3 layers
−

Fibrocartilagenous layer (gradually
diminishes with age but persists)

−

Undifferentiated connective tissue

−

Fibrous connective tissue

JOINT CAPSULE / CAPSULAR
LIGAMENT


Fibrous, non-elastic membrane
surrounding the TMJ

Functions:


Seals joint space



Provides passive stability



Active stability - proprioceptive
nerve-endings in capsule

Articular Disc


Attachments of articular disk –

1. Anteriorly – Joint capsule,
Lateral pterygoid muscle fibres –
‘Sphenomeniscus’ fibres
- stabilize disk during mastication &
deglutition
2. Posteriorly disc attached Retrodiscal tissue

Discal ligaments


Retrodiscal tissue


loose connective tissue



Between bilaminar
zone of disc



SRL – Meniscotemporal frenum



IRL – Meniscomandibular frenum



Rich blood supply &
nerve supply,
Compressible

SYNOVIAL MEMBRANE


Lines inner surface of capsule – villi



Functions:

1.

Medium for metabolic exchange to avascular articulating
surfaces

2.

Lubricant – minimizes friction




Lubrication by 2 mechanisms –

1.

BOUNDARY LUBRICATION
- primary mechanism
- moving joint
- synovial fluid forced from one area of cavity to
another

2.

WEEPING LUBRICATION:
- Compressed but not moving joint
- synovial fluid forced in & out of articular surfaces
by compression
- prolonged loading will exhaust fluid
- mechanism of www.indiandentalacademy.com
metabolic exchange

LIGAMENTS


Non-elastic collagenous structures - restricts and limits
movements a joint



Maintains – joint spaces, without causing tissue damage



True ligaments:
1. COLLATERAL / DISCAL LIGAMENTS
2. CAPSULAR LIGAMENT
3. TEMPOROMANDIBULAR / LATERAL LIGAMENT



Accessory ligaments:
1. SPHENOMANDIBULAR LIGAMENT
2. STYLOMANDIBULAR LIGAMENT

COLLATERAL / DISCAL
LIGAMENT
Functions:
1.

Restricts movement of disc
away from condyle

2.

Hinge movement between
condyle & disc

3.

Disc moves passively with
condyle

TEMPOROMANDIBULAR /
LATERAL LIGAMENT


FUNCTIONAL LIGAMENT



Fan-shaped reinforcement of
lateral wall of capsule



2 parts

1.

Outer oblique – outer surface of
condylar neck
resists excessive dropping of
condyle
limits extent of mouth opening




Horizontal part –
lateral pole of condyle & lateral margin of disk
•
•
•

limits posterior movement of condyle & disc
protects RDT from trauma
protects lateral pterygoid from over lengthening or
extension

Functions:

Prevents lateral (same side) & medial (contralateral) dislocation


Accessory Ligaments


Sphenomandibular L
igament – no role
• Remnants of Meckel’ s cartilage
• Important landmark during surgery



Stylomandibular L
igament – limits excessive
protrusive movements



Retinacular ligament


MUSCLES INVOLVED
IN JAW-MOVEMENTS


Classification:
1.

Jaw-closing group –
1. Temporalis
2. Masseter
3. Medial pterygoid

2.

Jaw-opening group –
1. Lateral Pterygoid
2. Suprahyoid muscles
3. Infrahyoid muscles



TEMPORALIS



Three parts
• Anterior part – almost vertical –
elevation
• Middle part – oblique – elevate
& retrude
• Posterior portion – almost
horizontal - retrusion & joint
loading shared with pterygo
massetric sling




MASSETER
• Origin
 superficial –
• Ant 2/3rd of zygomatic
arch
 Middle layer• ant 2/3rd of deep surface
and post 1/3rd of lower
border of Z arch
 Deep layer• Deep surface of Z arch
• Insertion
 Angle of mandible and ramus
 Lower part of lat surface of
ramus
 Middle & deep fibers – middle
and upper part of ramus


MEDIAL PTERYGOID:
OriginSuferficial – tuberosity of maxilla and
adjoining bone
deep – medial surface of lat pterygoid
plate
Insertion
roughened medial surface of angle of
mandible
Functions
Elevation
 Protrusion
 Unilateral – Mediotrusive
 With masseter – muscular sling to
support angle of mandible




LATERAL PTERYGOID:



Origin• Upper head- Crest of greater wing
of sphenoid.
• Lower head- lat surface of lateral
pterygoid plate.



Insertion• Pterygoid fovea
• Ant margin of articular disc &
capsule


SUPRAHYOID MUSCLES:
Digastrics
Mylohyoid
 Stylohyoid

FUNCTIONS
Jaw opening & swallowing
 Pull mandible downward & hyoid
backward

BIOMECHANICS OF
TMJ


At Rest


Occlusion - physiological rest position



Tonus of elevators – maintain constant contact



Intra articular pressure


1. INFERIOR JOINT CAVITY




Tightly bound – discal ligaments
Condyle + disc
Rotational / Hinge

2. SUPERIOR JOINT CAVITY


Disc not tightly attached to fossa



Translatory / sliding movements


Jaw Movements


TMJ Relations
Superficial relations


Skin, superficial fascia and branches of the facial
nerve



Auriculo-temporal nerve



Superficial temporal artery



Glenoid lobe of the parotid gland

Superior relations


Temporal lobe of brain



Tympanic cavity



Chorda tympani and anterior ligament to malleus

Inferior relations


Parotid gland



Lower head of the lateral pterygoid.



Venous channels.



Branches from the pterygoid venous plexus

Anterior relations


The lateral pterygoid.



The masseteric and deep
temporal nerves


Posterior relations


Auriculo-temporal nerve



Superficial temporal artery.



Parotid gland



Styloid process

Medial relations


squamo-tympanic fissure, chorda tympani nerve



spine of the sphenoid, sphenomandibular ligament.



middle meningeal artery, carotid sheath.



auriculo-temporal nerve, mandibular nerve.



middle, inner ear, auditor tube.

Distances of important structures medial to TMJ.
Structures
from
zygomatic
arch

Mean
mediolateral

Mean
anteroposte
rior

Middle
meningeal
artery

31mm

2.4mm

Carotid artery

37mm

-6.5mm

Internal
jugular
vein

38.3mm

-8.7mm

Mandibular
nerve (from
GF)

18.7mm

9.2mm

Nojan et al [OOO 1999; 88: 674-8].

IMPORTANT STRUCTURES
Auriculotemporal nerve


Runs from deep to superficial
layers as it reaches
preauricular region.



Inevitable damage –
preauricular approach.

Superficial temporal artery


Deep to parotid.



Posterior to neck of condyle
and crosses zygomatic process



Runs in superficial fascia

Maxillary artery


Beneath – condylar neck.



Immediate posteromedial relation.



Subperiosteal guard.



Endangered in condylotomy and
resection of bony ankylosis.


Facial nerve


Mandibular and cervical branch


Approaches



Many approaches have been proposed.
Can be grouped as follows
•
•
•
•
•
•
•
•

Pre-auricular
Endaural
Post auricular
Submandibular
Intra-oral
Closed condylotomy
Rhytidectomy incision
Horizontal incision along the lower border of the malar
arch
• Through soft tissue lacerations or scars.



Ideal approach characteristics.
• Be based on sound anatomical principles. Have clear
anatomical landmarks.
• Be designed to give protection to both the facial and the
auriculo-temporal nerves, and to the external auditory
canal.
• Provide a relatively bloodless field.
• Provide excellent visibility of the lesional site without flap
tension.
• Be rapidly and confidently executed.
• Be uncomplicated in its repair.
• Give a good cosmetic result with minimal functional
sequelae.

Pre-auricular


Started by Risdon in 1934


•Popularized by Blair (1936) –
inverted L shape.
•Dingman used Blairs
modification - obtuse angulated
vertical incision.
Vertical component –
anterior to tragus.
Superior leg – obliquely
anterior to pinna.



1979 extensive study by Alkayat and Bramley – the first
modified preauricular incision


Indications


When maximum exposure is required.



When lateral and anterior exposure is desired.

Advantage:


There is minimal bleeding and less sensory loss.
• Spares the main branches of vessels and nerves.



Fascial planes are easily identified.



There is excellent visibility.



The potential complications of muscle herniation and
fibrosis are avoided.
• The muscle is never exposed.


Disadvantages:
 Scarring present.
 Threat of damage to facial nerve
branches.
 Sensory loss over post-auricular skin.
 Frey syndrome.
 Damage to superficial temporal artery.


Endaural approach







Introduced by Shanbaugh – middle ear surgeries.
Lemperts – use for TMJ.
Different from Dingman that it involved external auditory
meatus to a greater depth.
Davidson modification – superior preauricular component.


Surgical approach
I-part



•

Anterior endaural incision in superior meatal
wall (depth-bony cartilagenous junction).

•

Then outward incision for 3-5mm at conchal
cartilage.
II-part



•

Extends from superior extent endaural incision
directly upwards to a point about halfway
between meatus and upper edge of the auricle.
III-part



•

Continuous superiorly in the inter
cartilagenous cleft and becomes the facial

Indications:


When lateral and posterior exposure is required.



To avoid scarring.

Advantages:


Excellent lateral and posterior exposure.



Scar exposure is less.

Disadvantage:


Limited anterior visibility.



Demands greater skills.



Tragal cartilage degeneration.


Post-auricular approach


Introduced by Bockenheimer (1920)



Modified by Axhausen.


Indications:
 When lateral and posterior exposure is required.
 Normal scar formation in the patient's history.
 Healthy ear apparatus and absence of aural
sepsis.
 Normal width of the external auditory canal.
 Absence of infection or inflammation of the
joint structures.
 General health of the patient does not restrict
length of operating period.


Advantages:
 Excellent accessibility especially
posterior and lateral.
 Reduction in facial nerve damage.
 No excessive bleeding.
Disadvantages:
 Limited anterior accessibility.
 Perforation of cartilaginous external
auditory meatus.
 External auditory canal
stenosis.
 Infections.


Risdon’s approach (Submandibular)


Incision about finger breadth
below angle of mandible
parallel to lower border.



Lies between cervical
branches of facial nerve,
lower boundary of bony
EAM at least 3cm inferior.

Indications


Usually for subcondylar procedure



Severe bony ankylosis



Direct condylar fracture fixation



Costochondral grafting

Advantages:


Less chances of facial nerve damage

Disadvantages:


Inadequate accessibility



Increased reflection and traction of tissue



Temporary parasthesia may be present


Retromandibular approach


Developed by E.C. Hinds and W.J. Girotin (1967)


Indications
 For condylar neck fractures
 Condylotomy
 Vertical ramus osteotomies
Advantages:
 Less chances of damage to facial nerve
Disadvantages:
 Reduced accessibility
 Parasthesia of facial nerve
 Damage to retromandibular vessels

Rhitidectomy approach


A variant of retromandibular approach.


Indications


Esthetic is a concerned and extensive exposure
is required.

Advantages


Less conspicuous facial carve



Good exposure

Disadvantage


Added time required

Bicoronal flap


Incision following hair line about
4cm behind it.



Depth – till subgleal loose tissue



Inferior extent – continue as
preauricular



Blunt dissection to reflect the flap till
2cm above the infraorbital rim and
superior temporal line.



Pericranium is incised about 3-4cm
superior to orbital rim,



Incision of Alkayat and Bramley
continued

Indication
 Bilateral exposure
 Extensive exposure required
Advantages
 Good exposure
 Easy to get the facial phase
 Reduced risk of damage to facial nerve branches
 Hidden scar
Disadvantages
 Bleeding in initial phase
 Extensive dissection required
 Not esthetic in completely bald patients

Intra-oral approach


Vertical incision in the retromolar region along the ascending
ramus.



Expose the entire medial surface of the ramus protecting the
lingual nerve and inferior dental bundle with a retractor.



The condylar notch is visualize.



Elevation of temporal attachment might be necessary.



Winstanely’s used a long, vertical incision from the tip of the
coronoid process to the depth of the buccal sulcus.



Sear….. advocates lateral and medial exposure for
condylectomy.

Indications
 Oblique subcondylar osteotomy
 Open condylotomy (asymmetry)
Advantages
 No risk to facial and auricular temporal nerves
 No scar
Disadvantages
 Limited accessibility
 Risk of damage to lingual nerve, Inferior
alveolar bundle and maxillary artery.


Arthroscopic approach




Arthroscopy of human TMJ
was first described Ohnishi
(1975).
3 primary approaches
•
•
•



Lateral posterior (most safe)
Lateral anterior
Endaural

Landmarks
• Condyle, zygomatic arch,
superficial temporal artery
and posterior aspect of
mandible.




2 points are marked on tragocanthal line
• 10mm and 15mm anterior to tragus



18 or 19 gauge needle is passed in the upper joint cavity from point A
through posterior approach inclining 30° anterior and superior
direction.



For the inferior joint cavity needle and cannula are passed at the same
point and directed inferiorly and posteriorly at 45° rather than
anteroinferiorly


Indications
 Joint arthritis
 For diagnostic purpose
 Hyperextensibility
Advantages
 Closed procedure
 No scar
Disadvantages
 Risk of damage to the encountering structures
 Massive bleeding
 AV fistula formation
 Intracranial entry


Conclusion


References


Thank you…

Tmj surgical anatomy and approaches (nx power lite) /certified fixed orthodontic courses by Indian dental academy

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