TMJ Kinematics Review Flashcards
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
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
TMJ Structure
Mandibular Fossa and Articular Eminence
-
Articular Eminence
- forms Anterior border of mandibular fossa and serves as point of functional contact for TMJ
TMJ Structure
Styloid Process
Attachments for muscles of tongue and pharynx and stylohyoid lig
TMJ Structure
Mastoid Process
Facial Nerve (CN VII) exits skull @ stylomastoid foramen
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
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
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
TMJ Structure
Articular Disc and Superior Head of Lateral Pterygoid
Lateral pterygoid attaches DIRECTLY to Biconcave articular disc ANTERIORLY
*see pics
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
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
Articular Disc
Capsular Attachements
- Attached to medial and lateral aspects of capsule
- Sup/Inf anterior caps ligs
- Sup/Inf posterior caps ligs
Articular Disc
Attached MORE FIRMLY to ______
Head of mandible
- Med/Lat bands→ aka medial and lateral collateral ligs
Articular Disc
ANT. margin attached to _______
Superior head of lateral pterygoid muscle
Articular Disc
Attachments allow for easy _________
Easy ANT. translation of disc
Limited POST glide
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!!!
-
Clinical implications:
TMJ Structure
Capsule
- LOOSE Inferiorly
- STRONG Laterally
-
Highly innervated
-
Clinical Imps:
- Capsulitis
-
Clinical Imps:
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
- *SUP head attached to ANT margin of disc
- Innervated by mandibular branch of Trigeminal N.
-
Clinical Implication: Trigeminal Neuralgia (Tic douloureux)
- pain triggered by chewing
-
Clinical Implication: Trigeminal Neuralgia (Tic douloureux)
- 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
-
Clinical Implication?
- Position: tongue up, teeth slightly apart, lips together
- Say “EMMA” and bring lips together
TMJ Kinematics:
Opening→ Mandibular DEPRESSION
AROM
40-55mm; normally symmetrical
TMJ Kinematics:
Opening→ Mandibular DEPRESSION
Produced by:
Digastrics
Lateral pterygoid
Gravity
TMJ Kinematics:
Opening→ Mandibular DEPRESSION
2 components
-
Anterior Rotation of condyle UNDER disc (and/or post rotation of disc relative to condyle
- occurs in LOWER compartment
- accts for 11-25mm of opening
- in MOST→ this occurs FIRST, typ overlaps THEN FOLLOWED BY:
-
Translation of disc/condyle complex
- occurs in UPPER compartment
- disc is firmly against head due to lig tension from rotation
- disc/condyle glides ANT and INF along articular eminence of temporal bone
- accts for remainder of opening
- retrodiscal pad limits excess forward motion of disc during translation
TMJ Kinematics:
Opening→ Mandibular DEPRESSION
Abnormal Trajectories
*it is normal to be “abnormal”
- Deviation
- Deflection
- does NOT return to middle
TMJ Kinematics:
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
- FIRST
- 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
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
Lateral Deviation
ROM?
10-15mm each side
TMJ
Lateral Deviation
controlled by:
- Controlled by:
- contralateral medial and lateral pterygoids
- ipsilateral temporalis (post fibers)
- ipsilateral lateral pterygoid
- ipsilateral masseter
TMJ
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!
-
Greatest on side where mandible moves UP
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
