Rearfoot deformity Flashcards
Rearfoot deformity
position of the rearfoot (calcaneus) relative to the floor when the subtalar joint is in neutral position
NCSP
Rearfoot deformity or NCSP formula
Subtalar joint neutral position +Tibial influence
STJNP
The FRONTAL PLANE relationship of the leg bisection to the calcaneal bisection while the subtalar joint is neutral position
STJNP Is affected by
The shape of the calcaneus
The shape of the talus
The orientation of the STJ itself
(in reality because the way we measure STJNP , the shape/orientation of the ankle joint also affects the measurements )
Tibial influence
The Frontal plane relationship of the tibia to the ground while the STJ is in neutral position
The pt should be standing in what position while measuring TI?
NCSP
Tibial influence affected by
Frontal plane deformities proximal to the STJ
- Tibial varum/valgum
- Genu Varum/Valgum
- and anything that will effect the frontal plane
Rearfoot deformity formula
NCSP=STJNP+TI
Rearfoot varus
The rearfoot (calcaneous) is inverted with respect to the ground when standing in neutral calcaneal stance position
Rearfoot varus is composed of
-STJ varus
AND/OR
-varus TI
STJ varus may be caused by
- calcaneal varus
- Talar varus
- Varus orientation of the joint
- inverted tibial plafond ( not a true STJ varus but will appear as an inverted calcaneal bisection)
calcaneal varus is due to
Lack of normal ontogeny
medial hypoplasia of the calcaneus or assymetric growth meaning medial and lateral are not growing at the same rate
Talar varus is due to
medial hypoplasia of talus
Varus TI may be a result of
- tibial varum
- Genu varum
Tibial Varum
- bowing of the lower 1/3 of the leg (inadequate ontogenous change )
- pathiphysiological bowing (rickets, etc)
- hypoplasia of medial tibial epiphysis
compensation
The way body responds to a deformity or abnormal function
How many forms of compensation?
- compensated
- partially compensated
- uncompensated
- overcompensated
compensated
GRF are equal across the STJ axis, plantar aspect of the heel and plantar aspect of the foot
Partially compensated
- at end ROM , a fully compensted position is unable to reached
- GRF are unable to equialized
uncompensated
No motion has occurred to provide compensation
Overcompensated
Motion has occurred beyond what was required for full compensation
compensation is represented by
RCSP
What is RCSP?
RCSP represents STJ position as a result of compensation for deformities in all 3 planes
Frontal plane deformities examples
Valgus/Varus
Sagittal plane deformities
equinus
Transverse plane deformities examples
abducted/adducted
What are the possible motions for MTJ
- maximally pronated
- supinated
- maximally supinated
what is the compensation for rearfoot varus
STJ pronation will occur until GRF are equal across the STJ /plantar aspect of the heel/plantar aspect of the foot
(look at the notes for clarification)
what does isolated rear foot varus mean?
it means the only deformity present is rear foot varus
compensation of rearfoot varus in an isolated rearfoot varus?
pronation at STJ occurs until the calcaneal bisection is perpendicular to the ground or until the end of ROM , whichever comes first
maximally pronated stance position can be determined
using TI and STJ eversion
STJ ROM is measured using
leg bisection
Maximally pronated stance position formula
maximally pronates stance position = TI-STJ eversion
In a fully compensated rearfoot varus defromity RCSP is
0
RCSP represent
rearfoot deformity
and also
compensation at the STJ
STJNP
eversion + inevrsion/3- eversion
NCSP
STJNP+TI
when the RCSP is 0
Fully compensated rearfoot varus
Rearfoot valgus
The rearfoot (calcaneus ) is everted with respect to the ground when standing in NCSP
Rearfoot valgus is composed of
-STJ valgus
and/or
-Valgus tibial influence
STJ valgus is rare or common
RARE
Valgus TI
Genu valgum
Tibial valgum
where will GRF be in RF valgus?
GRF will be on the medial side of the foot , medial to the MTJ and STJ axis providing an external supinatory moment
How far would the LMJA compensate
LMJA would be able to supinate 4-6º ( end of ROM) to compensate
if the rearfoot valgus deformity is more than 4-6º
The STJ may aslo supinate
if the LMJA is supinating for compensation, the forefoot
is unstable
Any deformity that puts the STJ in an everted position of greater than 5º will force the STJ
to go to the end of range of pronation
The more everted the calcaneal bisection to the ground,
the more inverted the forefoot to the rearfoot
