First Ray Flashcards
the biomechanical definition of the 1st ray includes
1st MT
1st cuneiform
articularions btwn the navicular-cuneiform joint
MT-cuneiform joint
surgical definition of the 1st ray does not include what
the cuneiform
the axes for the navicular-cuneiform joint and the MT-cuneiform joint are
equal
motion in one joint does not occur w/o motion in the other - therefore they are treated as one unit
very little motion occurs at what joint (navicular cuneiform or MT-cuneiform)
MT-cuneiform
what type of joint is the 1st ray
uniaxial
triplanar
the 1st ray axis is in what direction
axis passes anterior, lateral and plantar to posterior, medial and dorsal
does the 1st ray provide for pronation and supination
NO
axis is directed opposite to those joints that provide pronation and supination
1st ray axis is deviated — from sagittal and frontal planes allowing for — amounts of inversion w/ dorsiflexion and eversion w/ plantarflexion
45
equal
1st ray is deviated — from the transverse plane allowing for what
9
adduction with inversion/ dorsiflexion and slight abduction w/ eversion/plantarflexion
1st ray axis is independent of the
lesser ray axes
neutral position of the 1st ray axis is at
the centre of its ROM (evaluated in the sagittal plane)
how do you calculate the neutral position of the 1st ray
subtract the amount of dorsiflexion MINUS amount of plantarflexion DIVIDE by 2
how do you measure the 1st ray ROM
compare excursion of 1st ray dorsally and plantarly relative to plane of 2nd through 4th MT heads w/ subtalar neutral position and the midtarsal joint maximally pronated
remember: equal amounts of inversion and eversion are also occuring
total range of motion of 1st ray should be
1cm with 1/2 cm in direction of dorsiflexion and 1/2 cm in the direction of plantarflexion
minimum ROM of 1st ray
for gait is not known
***first ray function is very dependent upon
position of other joints, particularly the subtalar joint:
PL function is dependent upon normal subtalar joint function
1st ray function is dependent upon normal PL function
PL applies a — and — force to the 1st ray
plantarflexion
abduction
in OKC the PL — the 1st ray and the ankle joint — the subtalar joint
plantarflexes
pronates
*in CKC PL applies a — moment to the 1st ray but a — moment at the subtalar joint
plantarflexion
supination
in CKC the 1st ray cannot plantarflex through the floor, instead the proximal aspect of the 1st ray is
raised
as the medial column is elevated, the talus is
dorsiflexed
a component of CKC subtalar joint supination and ankle joint pronation
PL may initiate — during the gait cycle, and stabilizes the 1st ray against the ground
resupination
peroneus longus passes — and — to the cuboid
lateral
inferior
PL passes — and — to its insertion at the base of the 1st MT and medial cuneiform
suepriorly
medially
orientation of PL allows it to apply a — and –pull to its insertion
plantar
lateral
the plantar pull allows the PL to — the 1st ray or — dorsiflexion of the 1st ray
plantarflex
resist
PL exerts a — force that stabilizes the 1st ray on the navicular
posterior
PL exerts a — force that stabilizes the 1st ray to the 2nd ray
lateral
subtalar joint pronation results in
medial column drops planatary
reduced plantarflexion moment of the PL on the 1st ray
more pronation of subtalar joint results in
less efficient at resisting dorsiflexory ground reactive forces
unstable 1st ray
if the subtalar joint pronates enough to drop the medial column below the level of the cuboid, what happens to the PL
the PL as it passes around the cuboid will not be dorsal to its insertion
will then pass dorsal lateral to planar medial
may apply a dorsiflexory force on the 1st ray
what happens to PL when the subtalar joint is pronated
PL can’t provide plantarflexory moment on 1st ray
1st ray is hypermobile
what is the biomechanics definition of hypermobility
a part that is moving when it should be stable
NOT increase ROM
when does 1st ray hypermobility occur
when the subtalar joint is excessively pronated, the PL loses its pull allowing the 1st ray to dorsiflex when it should be stable against the ground
Kirby refers to 1st ray hypermobility as
lack of adequte 1st ray stiffness
hyermobility of 1st ray decreases the amount of
1st metatarsophalangeal joint dorsiflexion available
hypermobile 1st ray can lead to
1st MTPJ subluxation
hallux limitus/rigidus
hallux valgus
the width of the foot, particularly the forefoot, may have an effect on PL function by
increasing the length of the lever arm
makes the plantarflexion moment more effeicient
in order to have normal 1st ray function, the 1st MT head must be able to drop (plantarflex) below what
the plane of the MT heads 2-4
if the 1st ray can’t plantar below the plane of MT heads 2-4 it can cause
hallux limitus
in order for the 1st ray plantarflexion to occur during gait
The subtalar joint needs to be supinated
The heel needs to lift
The sesamoids must function properly
The second metatarsal should be longer than the first
the calcaneus is represented by the calcaneal inclination angle, forms the
posterior aspect of the medial arch
the 1st ray is represented by the 1st MT declination angle, forms the
anterior aspect of the medial arch
the medial arch is partly maintained by
plantar fascia
plantar fascia is described as a
truss
what is a truss
a 3 sided structure w/ 2 compression sides (the calcaneus and the 1st ray) and 1 tension side (the plantar fascia)
as the subtalar joint pronates, the arch of the foot is
lowered and lengthened
increased length of the foot during subtalar joint pronation increases tension on the —
plantar fascia
as the subtalar joint supinates what happens to the arch
arch comes up
tension on plantar fascia is reduced
what is the spanish windlass
incorporates the truss w/ a lever arm
the lever arm of the spanish windlass is the
hallux
The hallux can dorsiflex much easier when the subtalar joint is supinated and tension on the plantar fascia is reduced
If the foot is pronated, tension is increased on the plantar fascia, and hallux dorsiflexion range of motion will be reduced
1st MTPJ function is dependent on
proper function of 1st ray
anatomy of 1st MTPJ
comprised of:
articular surfaces of the head of the 1st MT
base of proximal phalanx of hte hallux
medial and lateral sesamoids
what type of joint is the 1st MTPJ
biaxial
at the “transverse axis” of the 1st MTPJ motion occurs purely in what plane
sagittal plane
at the “vertical axis” of the 1st MTPJ motion occurs purely in what plane
transverse plane
what motion is available at the 1st MTPJ
dorsiflexion/plantarflexion
abduction/adduction
1st MTPJ ROM primarily in
sagittal plane motion
what degree of dorsiflexion of the 1st MTPJ is normal
65 °
the 1st 20-30° dorsiflexion on the 1st MTPJ is a result of what motion
pure rolling motion (ginglymus-type joint)
remaining 35° or greater dorsiflexion of 1st MTPJ occurs as a result of
1st ray plantarflexion allowing the base of the proximal phalanx to slide up and over the 1st MT head
what allows for sliding motion of the 1st MTPJ
The instantaneous axis of rotation moves more superiorly and posteriorly within the metatarsal head
With plantarflexion of the first ray, the 1st metatarsal head also glides posteriorly on the sesamoids
during gait, the hallux is in a — position
fixed
The rest of the body must then pass over the hallux
Movement of the proximal segment of the joint allows for the motion
the Spanish windlass effect of the 1st MTPJ during gait lifts
the heel instead of the hallux
the spanish windlass effect of the 1st MTPJ during gait is normal if
the subtalar joint is supinating as the heel is listed
foot will be allowed to move over the hallux
the spanish windlass effect of the 1st MTPJ during gait is abnormal if
the heel is lifting, but the subtalar joint is pronating, tension on the plantar fascia will prevent proper dorsiflexion of the hallux
at push-off before the digits leave the floor the tibia is — degrees anterior to vertical
45°
at push-off before the digits leave the floor the ankle joint is plantarflexed — degrees
20°
what is the minimum amount of 1st MTPJ dorsiflexion required for normal gait
65 °
5th ray
5th MT
independent axis of motion
what type of joint is the 5th ray
uniaxial
triplanar
what motion does the 5th ray provide
pronation
supination
how is the 5th ray axis oriented
posterior, lateral, plantar to anterior, medial dorsal
5th ray axis is located:
- from transverse plane
- from the sagittal plane
- from frontal plane
20°
35°
70°
how do you measure 5th ray
measured relative to the plane of MT heads 2-4
5th ray axis is deviated greatest from
frontal plane, but motion that is measured is sagittal plane motion
where is the neutral position of the 5th ray
at its centre of ROM
NOTE
the function of the 5th ray during locomotion is not understood
rays 2 and 3 include
the MT and the corresponding cuneiform
ray 4 includes
MT 4
ray 2-4 provide purely — plane motion
sagittal
during stance phase in a normal foot, rays 2-4 should be
maximally dorsiflexed
some plantarflexion motion is required during propulsion to allow for dorsiflexion of the associated MTPs
lesser MTPJ have similar motion to
1st MTPJ except less ROM is required for normal gait (b/c they leave the ground earlier than the 1st)
lesser MTPJ joints have vertical and horizontal axes providing — and — plane motion
transverse
sagittal
(bi-axial)
the deep transverse ligament of the lesser MTPJ may function similarly to
the sesamoids by allowing the MT heads to glide posteriorly as the lesser ray plantarflex
motion at the interphalangeal joint occurs about — axes located in the phalax shaft just proximal to the joint
transverse
the axis of the digits is horizontal and provides — plane motion
sagittal
the motion of the digits that occur is in the direction of
plantarflexion
no dorsiflexion beyond fully extended
minimal motion of the digits is required during gait bc the digits should be
fully extended during the propulsive phase
— plays an important role in assisting the FDL and FDB in stabilizing the digits
intrinsic musculature
Consider the wing and sling mechanisms
Consider the role of plantar and dorsal interossei
Consider the powerful dorsifexory force provided by the long extensors
