TMJ Kinematics Review Flashcards by Josh Sewekow

Cranial Nerves Mnemonics

Oh Oh Oh To Touch And Feel Virgin Girls Vaginas And Hymens

Some Say Marry Money But My Brother Says Big Boobs Matter More

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What is wrong with saying “I have TMJ”

EVERYONE has TMJ bc its a joint→ actually TWO of them

We refer to it as TMD or TemporMandibular Disorder/Dysfunction

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TMJ Structure

Mandibular Fossa and Articular Eminence

Articular Eminence
- forms Anterior border of mandibular fossa and serves as point of functional contact for TMJ

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TMJ Structure

Styloid Process

Attachments for muscles of tongue and pharynx and stylohyoid lig

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TMJ Structure

Mastoid Process

Facial Nerve (CN VII) exits skull @ stylomastoid foramen

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TMJ Structure

External Auditory Meatus→ Middle ear→ Inner ear

*Clinical Relevance?

TMJ dysf→ ear sx’s (due to direct pressure on ear, OR referral)
- ear ache/pain
- tinnitus
- hypobaroacusis→ water in ear feeling

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TMJ Structure

Mandible

U-shaped body
angle
vertically oriented rami→ ea. w/ condylar processes (head of mandible) and coronoid processes→ for attachment of temporalis tendon
- Ant and Sup surface of head form articular surface for articulation w/ disc/articular eminence of temporal bone
- Head narrows inferiorly (forming “neck”) for attachment of lateral pterygoid muscle

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2 TMJs→ “Compound” joint

BOTH move simultaneously w/ any mandibular mvmt
- swallowing, vocalizing, chewing
Articular surfs covered w/ fibrocartilage
- protects from damage when sliding/translating

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TMJ Structure

Articular Disc and Superior Head of Lateral Pterygoid

Lateral pterygoid attaches DIRECTLY to Biconcave articular disc ANTERIORLY

*see pics

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Articular Disc

General Overview

Biconcave→ divides joint into upper/lower compartments
- UPPER→ SUP surf of disc + articular eminence
- LOWER→ INF surf of disc + condylar head

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Biconcave articular disc divides TMJ joint into UPPER/LOWER compartments

explain…

UPPER→ SUP surf of disc + articular eminence
LOWER→ INF surf of disc + condylar head

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Articular Disc

Capsular Attachements

Attached to medial and lateral aspects of capsule
Sup/Inf anterior caps ligs
Sup/Inf posterior caps ligs

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Articular Disc

Attached MORE FIRMLY to ______

Head of mandible

Med/Lat bands→ aka medial and lateral collateral ligs

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Articular Disc

ANT. margin attached to _______

Superior head of lateral pterygoid muscle

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Articular Disc

Attachments allow for easy _________

Easy ANT. translation of disc

Limited POST glide

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Bilaminar retrodiscal pad is essential what?

A posterior continuation of the disc

Bilaminar Retrodiscal Pad

*post continuation of disc

Sup fibroelastic layer attach disc TO post aspect of mandibular fossa (temporal bone)
Inf INelastic layer attach disc TO condyle of mandible
Fuses w/ post aspect of TMJ capsule
Highly vascularized and innervated**
- Clinical implications:
  - Retrodiscitis→ assoc’d w/ TMD
  - if overstretched→ can contribute to disc instability or derangements
    - sublux or disloc’s
    - Remember the hat will fall forward!!!

TMJ Structure

Capsule

LOOSE Inferiorly
STRONG Laterally
Highly innervated
- Clinical Imps:
  - Capsulitis

TMJ Structure

Ligaments

Temporomandibular

Temporomandibular
- Strong “suspensory” lig
- Checks→ downward, post, lateral motion of mandible

TMJ Structure

Ligaments

Stylomandibular and Sphenomandibular

Stylomandibular and Sphenomandibular
- MINOR roles in stability
- MAY help check protrusion of mandible

TMJ Structure

Ligaments

Oto-ligaments

*think connect malleaus of middle ear TO TMJ

Malleomandibular
Disco-mallear
Clinical Implication
- Connect inner ear→ mandible = ear sx’s

TMJ Structure

Innervation

Trigeminal Nerve (CN V)

Trigeminal Nerve
- Trigeminal-cervical complex
- Clinical Implications?
  - TMJ probs cause pain in upper CS OR CS refers to TMJ
  - Direct neural relationship***

TMJ

Muscles of Mastication

Everything***

ALL have somewhat oblique orientations relative to axis of TMJ
- Masseter
- Temporalis
  - ANT Vertical fibers→ mandibular elevation
  - INF Horizontal fibers→ ipsilateral lateral deviation
- Med pterygoid
- Lat pterygoid
  - *SUP head attached to ANT margin of disc
    - contracts ecc. during closing
Innervated by mandibular branch of Trigeminal N.
- Clinical Implication: Trigeminal Neuralgia (Tic douloureux)
  - pain triggered by chewing
With chewing, only mandible moves
- bc CS mm’s prevent head from moving→ act as stabilizers

TMJ Rest Position

SOME mm activity req’d to keep mouth closed w/ body upright
Neg. Air Pressure @ point of contact b/w tongue and hard palate reduces mm forces needed to support jaw
- Clinical Implication?
  - Clenching mm’s dont need to work as hard
Position: tongue up, teeth slightly apart, lips together
- Say “EMMA” and bring lips together

TMJ Kinematics: ## Footnote **Opening→ Mandibular DEPRESSION** **AROM**

40-55mm; normally symmetrical

TMJ Kinematics: ## Footnote **Opening→ Mandibular DEPRESSION** **Produced by:**

Digastrics Lateral pterygoid Gravity

TMJ Kinematics: ## Footnote **Opening→ Mandibular DEPRESSION** **2 components**

1. **Anterior Rotation** of condyle UNDER disc (and/or post rotation of disc relative to condyle 1. occurs in **LOWER compartment** 2. accts for 11-25mm of opening 3. in MOST→ this occurs FIRST, typ overlaps **THEN FOLLOWED BY:** 2. **Translation** of disc/condyle complex 1. occurs in **UPPER compartment** 2. disc is firmly against head due to lig tension from rotation 3. disc/condyle **glides ANT and INF** along articular eminence of temporal bone 4. accts for remainder of opening 5. retrodiscal pad **limits excess forward motion of disc during translation**

TMJ Kinematics: ## Footnote **Opening→ Mandibular DEPRESSION** **Abnormal Trajectories** **\*it is normal to be “abnormal”**

* Deviation * Deflection * does NOT return to middle

TMJ Kinematics: ## Footnote **Closing→ Mandibular ELEVATION** **Produced by:**

* Temporalis * Masseter * Medial pterygoid

TMJ Kinematics: **Closing→ Mandibular ELEVATION** Everything else

* **Reverse kinematics of OPENING** * FIRST * **post/sup _Translation_ of disc/condyle in UPPER COMPARTMENT followed by:** * SECOND * **post _Rotation_ of condyle underneath disc in LOWER COMPARTMENT** * Elastic fibers in the SUP lamina of bilaminar retrodiscal pad help **return the disc to its POST pos after opening** * SUP Head of **Lat Pterygoid is ACTIVE (eccentrically)** during closing to _control posterior movement of disc_

TMJ **Protrusion**

* Controlled by **bilateral action of Lateral Pterygoids, medial pterygoids, masseters** * **Forward movement→ Ant/Inf translation** of disc/condyle in **upper compartment of joint** * **“freeway space” req'd**

TMJ ## Footnote **Retrusion**

* **Opposite of protrusion** * **Checked by:** * ligamentous tension and space occupying function of bilaminar retrodiscal pad * **Min. mm activity required to retrude** * temporalis contributes

TMJ ## Footnote **Lateral Deviation** **ROM?**

10-15mm each side

TMJ ## Footnote **Lateral Deviation** **controlled by:**

* Controlled by: * **contralateral medial and lateral pterygoids** * **ipsilateral temporalis (post fibers)** * **ipsilateral lateral pterygoid** * **ipsilateral masseter**

TMJ ## Footnote **Lateral Deviation** **further elaborate on movement…**

* **Contralateral pterygoids** * produce ANT/INF/MED translation of **contralateral condyle** * **Ipsilateral temporalis (post fibers) and ipsilateral lateral pterygoid** * _Force Couple_ (2 mms acting on joint in opp. directions) acting on the **ipsilateral condyle** causing it to spin while the **contralateral condyle translates ANT**

Frontal Plane tilting of mandible

* allows for chewing of bolus * **implications for JRFs?** * **Greatest on side where mandible moves UP** * **ex. if you chewing food on right side, the LEFT SIDE will have greatest JRFs!**

Mastication

* **Chewing stroke:** elliptical loop of **mandibular depression→ lateral dev→ elevation** to help crush/grind food * Automatic and complex interplay of mms of mastication, tongue, suprahyoids, buccinator, and CS mm's * **working side→ chewing food** * **balancing side→ exp's large _compressive forces:_** * mm activity * lateral tilt of mandible * bolus on chew side→ narrows joint space on **balancing side (non-chew side)**

TMJ **Relationship w/ Head/Neck Posture**

* **FHP→** stretches ANT tissues including **suprahyoids,** tending to create a **retrusive force** * **Chronic retrusion→** irritates retrodiscal pad→ inflammation→ pain