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Biomechanics > 8: Midtarsal Joint - Frush > Flashcards

8: Midtarsal Joint - Frush Flashcards

1
Q

chopart’s joint is composed of …

A

talonavicular joint and calcaneocuboid joint

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2
Q

what ligaments are associated with midtarsal joint?

A
  • bifurcate ligament
  • short plantar ligament
  • long plantar ligament
  • plantar calcaneonavicular ligament
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3
Q

longitudinal axis of midtarsal joint

A

15 degrees from transverse and 9 from sagittal plane

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4
Q

what is the primary plane of motion in longitudinal midtarsal joint?

A

frontal plane - inversion and eversion

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5
Q

oblique axis of the midtarsal joint

A

52 from transverse and 57 from sagittal plane

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6
Q

primary motion oblique midtarsal joint

A

plantarflexion with adduction (PAD)

dosiflexion with abduction (DAB)

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7
Q

allows foot to adapt to subtalar joint variations

A

longitudinal axis

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8
Q

forefoot can ______ on everted rearfoot

A

invert

evert of inverted rearfoot

allows foot to remain plantargrade

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9
Q

“secondary ankle joint”

A

oblique axis can compensate for lack of ankle dorsiflexion

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10
Q

what does STJ pronation do to the midtarsal joint?

A
  • midtarsal joint axes becomes more parallel - “unlocks” MTJ
  • allows foot to become mobile adaptor

A supinated STJ will cause MTJ axes cross - locks midtarsal joint allow foot to become rigid level

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11
Q

what is the stable position of the MTJ?

A

pronated position of MTJ

supinated is unstable position

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12
Q

what happens to the calcaneocuboid jt with a pronated MTJ?

A

dorsiflexes

  • cuboid rotates up into dorsolateral overhang on calcaneus
  • ligaments tighten, preventing excessive motion
  • ligaments will also tighten in supinated MTJ, osseous locking will not be present
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13
Q

how do you manually lock the MTJ?

A
  • place STJ in neutral while nonweightbearing

- push up on 4th and 5th met heads (from plantar side)

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14
Q

OKC oblique angle, longitudinal angle

A

OA - pronated ( EDL and peroneus tertius contacted) (dorsiflexion and abduction)

LA: supinated (Anterior tib m. contracted - inversion)

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15
Q

STJ in OKC

A

pronating to allow shock absorption

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16
Q

midstance CKC oblique and longitudinal angle

A

OA: pronated (dorsiflexed and abducted)
LA: pronated (begins to evert in reaction to STJ supination, helps to lock MTJ into lever)

17
Q

STJ in midstance CKC

A

supinating in preparation for propulsion

18
Q

CKC propulsion - oblique angle, longitudinal angle

A

OA: supinated (windlass mechanism aids, contraction intrinsics aids)

LA: pronated (locking still present at cc joint)

19
Q

STJ CKC propulsion

A

supinated

20
Q

windlass effect

A

as heel lifts during gait, toes passively dorsiflex

  • met heads are pulley mechanism
  • plantar fascia tightens aiding in arch rise, heel rise and compression of bones
21
Q

STJ supination cuases _______- in MTJ ROM

A

decrease

pronation causes an increase

22
Q

MTJ position is controlled by GRF during stance phase of gait and by ___________ during other phases

A

surrounding muscles

  • anterior tibial m. inverts the longitudinal axis
  • peroneus tertius and EDL pronate the oblique axis (also shift weight from lateral to medial)
  • both help decelarte foot at heel strike to prevent slap)
23
Q

how do you measure forefoot to rearfoot relationship?

A
  • prone pt
  • STJ neutral
  • lock midtarsal jt by pushing up on 4th and 5th met head
  • look straight down and evaluate if plantar heel is parallel with met head
24
Q

compensation for forefoot varus deformity

A
  • calcaneus ideally everts to same degree of forefoot varus
  • uncompensated: forefoot varus greater than calc eversion available
  • partial comp: calc can compensate with eversion but not to same degrees as forefoot varus. additional comp gained through oblique axis MTJ and 1st ray
  • compensated: forefoot varus equal or less than calcaneal eversion available
25
Q

compensation for forefoot valgus

A

LASOS

  • longitudinal axis supination
  • subtalar supination
  • oblique axis supination
  • further subtalar supination

flexible = only longitudinal axis comp, heel remais vertical but foot unstable in midstance due to midfoot supination

rigid= if STJ or OA comp needed, heel will be inverted

Biomechanics (15 decks)

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