8: Midtarsal Joint - Frush Flashcards
chopart’s joint is composed of …
talonavicular joint and calcaneocuboid joint
what ligaments are associated with midtarsal joint?
- bifurcate ligament
- short plantar ligament
- long plantar ligament
- plantar calcaneonavicular ligament
longitudinal axis of midtarsal joint
15 degrees from transverse and 9 from sagittal plane
what is the primary plane of motion in longitudinal midtarsal joint?
frontal plane - inversion and eversion
oblique axis of the midtarsal joint
52 from transverse and 57 from sagittal plane
primary motion oblique midtarsal joint
plantarflexion with adduction (PAD)
dosiflexion with abduction (DAB)
allows foot to adapt to subtalar joint variations
longitudinal axis
forefoot can ______ on everted rearfoot
invert
evert of inverted rearfoot
allows foot to remain plantargrade
“secondary ankle joint”
oblique axis can compensate for lack of ankle dorsiflexion
what does STJ pronation do to the midtarsal joint?
- 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
what is the stable position of the MTJ?
pronated position of MTJ
supinated is unstable position
what happens to the calcaneocuboid jt with a pronated MTJ?
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
how do you manually lock the MTJ?
- place STJ in neutral while nonweightbearing
- push up on 4th and 5th met heads (from plantar side)
OKC oblique angle, longitudinal angle
OA - pronated ( EDL and peroneus tertius contacted) (dorsiflexion and abduction)
LA: supinated (Anterior tib m. contracted - inversion)
STJ in OKC
pronating to allow shock absorption
midstance CKC oblique and longitudinal angle
OA: pronated (dorsiflexed and abducted)
LA: pronated (begins to evert in reaction to STJ supination, helps to lock MTJ into lever)
STJ in midstance CKC
supinating in preparation for propulsion
CKC propulsion - oblique angle, longitudinal angle
OA: supinated (windlass mechanism aids, contraction intrinsics aids)
LA: pronated (locking still present at cc joint)
STJ CKC propulsion
supinated
windlass effect
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
STJ supination cuases _______- in MTJ ROM
decrease
pronation causes an increase
MTJ position is controlled by GRF during stance phase of gait and by ___________ during other phases
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)
how do you measure forefoot to rearfoot relationship?
- 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
compensation for forefoot varus deformity
- 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
compensation for forefoot valgus
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
