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Kinesiology and Biomechanics > TMJ Mechanics > Flashcards

TMJ Mechanics Flashcards

1
Q

how many joints are there in the TMJ articulation

A

4
-disc makes additional 2 joints. the disc is concave inferiorly and convex superiorly, making for 2 different joint arthrokinematics within the TMJ joint itself

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2
Q

each TMJ consists of..

A
  • mandibular condyle
  • articular eminence of temporal bone
  • articular disc
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3
Q

types of joints of TMJ

A
  1. hinge joint
    - -mandbibular condyle and inferior surface of disc
  2. plane/gliding joint
    - -articular eminence and superior surface of disk
    - TMJ is a synovial joint but without hyaline cartilage, rather, fibrocartilage is present
    - -leads to improved healing properties b/c vascularized
    - lots of wear+tear in joint, hyaline cartilage would disappear too quick
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4
Q

retrodiscal bilaminar tissue

A

-attaches disc posteriorly to surface. viscoelastic properties that prevent the disc from being pulled forward by the lat. pterygoid, the stretch pulls the disc back into place

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5
Q

3 regions of disc

A

anterior, middle, posterior

  • anterior and posterior are both thick regions with high vascularity
  • middle region is thin with low vascularity
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6
Q

joint arthrology: mandible

A
  • body and rami, angle=intersection of the two

- mandibular condyles

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7
Q

mandibular condyles

A
  • medial protrusion 15-20mm from rami
  • palpate lateral pole ant. to ext. auditory meatus
  • unable to palpate medial pole
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8
Q

joint arthrology: coronoid process

A
  • ant to mandibular condyle
  • closed mouth=present under zygomatic arch
  • palpable with mouth open
  • temporalis muscle attachment
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9
Q

joint arthrology: temporalis bone

A
  • condyle at glenoid fossa
  • -thin, translucent: not a lot of stress on bone
  • articular eminence: where articular occus with condule. greatest fibrocartilage, densest bone. compression forces occur
  • -trabecular bone
  • -primary articular surface
  • -convex on convex
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10
Q

joint arthrology: articular eminence and condyle

A
  • dense, avascular collagenous tissue covering with some cartilage cells=fibrocartilage
  • most found at articular eminence and anterosuperior condyle
  • -evidence for compression
  • deep fibers aligned perpendicular
  • superficial fibers aligned parallel
  • fibro vs hyaline cartilage repair process?
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11
Q

articular disc

A
  • biconcave
  • is TMJ congruent?-yes (matching up.fitting together
  • -convex condyle on concave inferior disc, concave superior disc on convex articular eminence
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12
Q

articular disc attachments

A
  • firm attachment with medial and lateral poles of condyle
  • not firmly attached to capsule medial and lateral
  • -allows for free rotation (disc allowed to freely rotate with condyle)
  • anteriorly attached to joint capsule and lateral pterygoid muscle
  • -restricts posterior translation
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13
Q

-articular disc attachments

A
  • posteriorly attached to the bilaminar retrodiskal pad
  • complex structure
  • allows for anterior disk translation with mouth opening and repositioning of disk with mouth closed
  • neither lamina (superior and inferior) under tension with TM joint at rest
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14
Q

articular disk morphology

A
  • thickness varies between 2 mm anteriorly to 3 mm posteriorly to 1 mm in the middle
  • -variation aids in congruency
  • anterior and posterior portions are vascular and neural
  • middle portion avascular and aneural
  • -force accepting portion of disk avascular and aneural
  • -middle portion subtly shifts anterior and posterior when the tmj is at rest to repair
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15
Q

articular disc function

A
  • 3 functions
    1. provides increased congruence of joint surfaces (biconcave)
    2. shape allows for greater flexibility of disc to conform to bony surfaces with rotation and translation arthrokinematics
    3. thick/thin/thick arrangement provides a self-centering mechanism for disc on condyle
  • increase pressure=disc rotation so thinnest portion is btwn articulating surfaces
  • decreased pressure=joint disarticulation=rotation of a disc to a wider portion (may be ant. or post.)
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16
Q

muscular control of the TM joint

A
  • ant. and post. digastrics
  • medial and lateral pterygoids
  • temporalis
  • masseter
17
Q

mandibular elevation/mouth closure

A
  • temporalis: fan shaped with extensive attachments inserting at coronoid process for elevation
  • masseter: quadrilateral shaped mm
  • superior portion of lateral pterygoid
  • -rotates disc anteriorly on condyle with mouth closing (holds it steady as jaw comes back. maintaining ant. position
18
Q

mandibular depression/mouth opening

A
  • lower portion of lateral pterygoid=depression
  • digastrics: primary mandibular depression
  • accounts for 40-55 mm normal opening
  • concentric contraction of both digastrics may cause choking
  • usually ant. is a concentric contraction, isometric contraction post
19
Q

mandibular osteokinematics: protrusion

A

-bilateral masseter, medial pterygoids and lateral pterygoids

20
Q

retrusion

A

-bilateral posterior fibers of temporalis and assist by anterior portion of digastrics

21
Q

-lateral deviation

A
  • contralateral medial and ipsilateral lateral pterygoids
  • ex: R LD by R lat pterygoid and L med pterygoid
  • temporalis deviates to ipsilateral side
22
Q

force couple during deviation

A
  • temporalis and lateral pterygoid work together to rotate
  • mandible slides contralateral and rotates ipsilateral to direction of deviation
  • fibers of lateral pterygoid and temporalis are on opposite side of mandible, pull in opposite but parallel directions. make the ipsilateral side rotate
23
Q

TM joint arthrokinematics: mouth opening

A
  • initial anterior roll of condyle followed by anterior and inferior translation of disc and condyle nearing full opening
  • instantaneous center of rotation shifts anterior during opening
  • 40-55 mm normal mouth opening
  • -condyle rotates 11-25 mm anteriorly
  • -disk and condyle translates remainder
24
Q

abnormal muscle mechanics

A
  • muscle adaptively tightened, limits antagonist direction

- muscle organically weak, limits agonist direction

25
Q

joint is a compression or tension loaded structure

A

-tension loaded, compression only in pathology

26
Q

TM joint arthrokinematics: mouth closing

A
  • reverse of opening
  • initial posterior and superior translation of disc and condyle followed by posterior roll of condyle on the disc
  • instantaneous center of rotation shifts posterior during closing
  • C shaped curve if dysfunction/derangement, deviate towards tight side
27
Q

TMJ arthrokinematics: protrusion/retrusion

A
  • bilateral condyle translation anterior and inferior or posterior and superior respectively along articular eminence (likely just post. if retrusion from neutral position)
  • protrusion: 6-9mm
  • retrusion: 3 mm
  • ant inf for protrusion, from the protruded position will have post and sup, but from neutral will most likely just be posterior
28
Q

TMJ arthrokinematics: mandibular lateral deviation

A

Ex left

  • left condylar and disk spin about a vertical axis combined with right condylar anterior translation or gliding
  • lateral deviation= 8mm
29
Q

dentition

A
  • intimate involvement of teeth in the function of the TMJ
  • 1.5-5 mm freeway space b/w upper and lower teeth=resting position of mandible
  • -space btwn upper and lower central incisors
  • -firm approximation=occlusal position (bruxism. bad position)
  • resting position allows for decreased intra-articular pressure, decreased stress on articular structures allowing tissue rest and repair
  • resting position allows for healing of disc
30
Q

pathomechanics

A
  • insult secondary to direct trauma such as MVA, fall, fight
  • poor posture or oral habits (bruxism-grinding/clenching)
  • reciprocal click (intracapsular dysfunction, joint out of place)
  • locking
  • osteoarthritis
31
Q

reciprocal click

A

=anteromedial displacement of the disk-anterior part is most problematic

  • noted on opening and a second click upon closing
  • condyle 1st in contact with retrodiskal tissue
  • click noted with disk contact upon opening
  • upon closing, late clikc as condyle leaves the anteromedially displaced disk
  • late vs early click?
  • -late=further displaced disc, worse condition
  • -early=less pathology, less anteromedially displaced
32
Q

locking

A
  • only roll occurs, with not anterior or posterior translation of condule
  • anteriorly displaced disk acts as a buttress (prevents further motion)
  • inability to close vs decreased ability to open
33
Q

closed lock

A
  • cannot open fully
  • disc is sig anteromedial to condyle disallowing anterior and inf glide
  • cannot open fully secondary to mechanical buttress
34
Q

open lock

A
  • cannot close
  • disk is post to condyle disallowing post and sup glide
  • cannot close fully secondary to mechanical buttress
35
Q

osteoarthritis

A
  • due to increased and/or altered compressive and shear loading of TMJ surfaces
  • most often unilateral
  • loss of posterior teeth may lead to OA due to simple occlusion of remaining teeth creates impact b/w TMJ surfacess
  • teeth extracted, limites force per unit area. erosion of bone where teeth removed b/c wolffs law

Kinesiology and Biomechanics (6 decks)

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