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Flashcards in Midtarsal Joint Deck (34)
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1
Q

What does the midtarsal joint consist of?

A

calcaneocuboid joint + talonavicular joint

2
Q

what is midtarsal joint aka?

A

Chopart’s joint

3
Q

the midtarsal joint has a longitudinal axis and an oblique axis. what is the longitudinal axis?

A

(runs proximal, plantar and lateral to distal, dorsal and medial)
-is 15 degrees from transverse plane and 9 degrees from sagittal plane

4
Q

what is the primary motion about the longitudinal axis of MTJ?

A

frontal plane motion (inversion/eversion)

5
Q

describe the oblique axis of the MTJ.

A

(runs proximal, plantar and lateral to distal, dorsal and medial)
-is 52 degrees from transverse plane and 57 degrees from sagittal plane

6
Q

what is the primary motion about the oblique axis of MTJ.

A

There is equal motions about the transverse plane (abduction/adduction) and sagittal plane (dorsiflexion/plantarflexion)
*PADs/DABs

7
Q

what does the longitudinal axis of MTJ allow the foot to do?

A

allows foot to adapt to subtalar joint variations and allows foot to remain plantargrade
Ex. forefoot can:
-invert on everted rearfoot
-evert on inverted rearfoot

8
Q

what is the purpose of the oblique axis of the MTJ?

A

“secondary ankle joint”- oblique axis can compensate for lack of ankle dorsiflexion

9
Q

in which position is the “unlocked” MTJ?

A

STJ pronation

10
Q

what happens in STJ pronation?

A

MTJ axes become more parallel –> unlocks MTJ –> allows foot to become mobile adaptor

11
Q

what happens in STJ supination?

A

MTJ axes cross –> locks MTJ –> foot becomes rigid lever and decreases ROM

12
Q

in which position is the “locked” MTJ and rigid lever?

A

STJ supination

13
Q

in which position are the MTJ axes crossed? paralle?

A

STJ pronation = MTJ axes parallel

STJ supination = MTJ axes crossed

14
Q

which position of STJ is more stable?

A

STJ supination (axes crossed = rigid lever)

15
Q

which position of MTJ is more stable?

A

MTJ pronation

as STJ supinates- which is more stable, MTJ pronates

16
Q

which position of MTJ is unstable?

A

MTJ supination

17
Q

what happens to calcaneocuboid joint when MTJ pronates?

A

calcaneocuboid joint dorsiflexes (cuboid rotates up into dorsolateral overhang on the calcaneus)
*ligaments also tighten, preventing excessive motion

18
Q

what happens to bones and ligaments when MTJ supinates?

A

ligaments will also tighten

bones, however, are not tightly packed (osseous locking not present)

19
Q

how do you “lock” MTJ?

A

place STJ in neutral. then push up on 4th and 5th metatarsal heads to simulate WB.

20
Q

what happens during contact period of gait? (in regards to OA, LA, STJ)?

A

OA- pronated (EDL and peroneus tertius activated –> allows dorsiflexion and abduction)
LA- supinated (anterior tibialis muscle contracted –> inversion)
STJ pronated to allow for shock absorption

21
Q

what hapens during midstance?

A

STJ- supinated to prepare for propulsion
LA- pronated to help lock the MTJ to become a rigid lever
OA- pronated (dorsiflexed and abducted)

22
Q

what happens during propulsion?

A

STJ is supinated
LA- pronated (locking still present at CC joint)
OA- supinated (windlass mechanism- big toe dorsiflexes and pulls on plantar fascia to help contract intrinsic muscles and the arch height increases)

23
Q

MTJ ROM is controlled by what?

A

passively control by the position of STJ
STJ supination - causes decrease in MTJ ROM - “locked axes”
STJ pronation- causes increase in MTJ ROM

24
Q

MTJ position is controlled by what?

A

GRF during stance phase of gait and by surrounding muscles during other phases

25
Q

which muscle inverts the longitudinal axis?

A

tibialis anterior

26
Q

which muscles pronate the oblique axis?

A

peroneus tertius
extensor digitorum longus
*also helps to shift weight from lateral to medial

27
Q

which muscles help to decelerate the foot at heel strike to prevent foot slap?

A

anterior tibial
peroneus tertius
EDL

28
Q

how do you measure forefoot to rearfoot relationship?

A
  1. place patient in prone position
  2. place patient in STJ neutral
  3. lock MTJ
  4. look straight down and elavuate if plantar heel is parallel with met head
29
Q

what is the ideal compensation for a forefoot varus?

A

calcaneus ideally everts to same degree of forefoot varus

30
Q

what happens in uncompensated forefoot varus?

A

forefoot varus > calcaneal eversion available

*bc calcaneus is unable to evert pass netural

31
Q

what happens in partially compensated forefoot varus?

A

forefoot varus > calcaneal eversion available

  • calcaneus is able to evert pass neutral but not to same degree of FF varus
  • additional compensation gained thru oblique axis of MTJ and 1st ray
32
Q

what happens in compensated forefoot varus?

A

forefoot varus >= calcaneal eversion

33
Q

how do you compensate for a forefoot valgus?

A

LASOS

  1. LA supination
  2. subtalar supination
  3. OA supination
  4. further subtalar supination
34
Q

what is a flexible deformity?

A

if only LA compensation

-heel remains vertical but foot is unstable in midstance due to midfoot supination