25 - Inverted Forefoot Deformities Flashcards
Types of inverted forefoot deformities
- Forefoot Varus (bony varus)
- Forefoot Supinatus (soft tissue varus)
- Metatarsus Primus Elevatus
- Plantarflexed Cuboid
- Plantarflexed 5th Metatarsal
Forefoot varus
- OSSEOUS abnormality
- Inverted position of plantar surface of all metatarsals (forefoot) relative to the plantar surface of the calcaneus (rearfoot) at the level of the STJ…
- With the STJ neutral and the MTJ locked (fully pronated) – 1st metatarsal is higher than the 5th
- If all the metatarsals are inverted on the same plane, you cannot plantarflex the 1st metatarsal during examination
Etiology of forefoot varus
- Inadequate valgus torsion of the head and neck of the talus (?)
- Normal fetal position of talar head and neck is varus rotation to the transverse plane.
- During normal development, there is a valgus rotation to the talar head and neck which creates a valgus curvature to the lesser tarsus.
- If this fails to occur, there is an inverted position of the forefoot to the rearfoot (i.e., the forefoot is not perpendicular to the bisection of the heel).
STUDY - Anatomical origin of forefoot varus malalignment
- Using cadaveric specimens “…there was no association between forefoot alignment and talar torsion (twist in talar head and neck).”
The most common cause of a FF varus is: o Metatarsus primus elevatus o Plantarflexed cuboid o Lack of valgus rotation of the talar head o Plantarflexed 5th metatarsal o Plantarflexed 1st metatarsal
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Types of forefoot varus
- Uncompensated forefoot varus
- Partially compensated forefoot varus
- Compensated forefoot varus
Rule for compensation of forefoot varus
- The heel will evert past vertical the same number of degrees as the FF varus deformity to get the medial aspect of the forefoot on the ground
- This is different than rearfoot varus, where the compensation will get the heel to vertical but no further
Uncompensated forefoot varus
- Exists when there is no calcaneal eversion beyond the vertical available
- However, most people have adequate ROM available at the MTJ (midtarsal joint – calcaneocuboid/talonavicular) or within the 1st ray’s ROM to allow forefoot to purchase ground
- If a forefoot varus is compensated by plantarflexing the first metatarsal, when seen in non-weightbearing neutral position, metatarsals 2 through 5 will be in varus with the 1st metatarsal flexibly plantarflexed (can dorsiflex 1st metatarsal to the level of the 2nd metatarsal)
- The heel remains at vertical in RCSP (the STJ does not have to evert past vertical because the 1st metatarsal compensates by plantarflexing)
- Unlike osseous forefoot varus where all the metatarsals are in varus, a 1st metatarsal that compensates to get the forefoot to the ground will form a forefoot deformity known as a flexible plantarflexed 1st ray with varus 2 through 5
Example of forefoot and rearfoot varus
Biomechanical exam
o 4 degrees of FF varus (rigid)
o 20 degrees of STJ inversion
o 4 degrees of STJ eversion
o 8 degrees of tibial varum (***RF varus compensates before any FF deformity!!!!)
o As a result, the resting calcaneal stance position is 4 degrees inverted
o This is the maximally pronated position, and the FF varus is uncompensated
Solution
o The rearfoot varus must compensate before the forefoot varus
o 8° tibial varum - 4° eversion of STJ = 4° RF varus
o To compensate for 4° of FFV, need to evert heel 4° past vertical
o No more eversion of STJ is available
Pathology of uncompensated forefoot varus in the skin
Callus sub 4th & 5th metatarsal heads and hallux, corn dorsum 2nd toe
This is caused by a LOT of stress being placed on the lateral side of the foot
Pathology of uncompensated forefoot varus in the muscle and fascia
Equinus, functional
Ankle sprains, peritoneal tendonitis can also occur
Pathology of uncompensated forefoot varus in the bones (osseous)
Don’t need to memorize the entire list
o Retrocalcaneal exostosis (because heel is in varus and lateral posterior aspect of heel will rub on shoes) o Heel spur syndrome o Sinus tarsi syndrome o Ankle valgus (attempt to compensate) o Genu valgum (attempt to compensate) o Tailor’s bunion o Hammertoe - 2nd
Pathology of uncompensated forefoot varus in the gait
o Apropulsive
o Pronated throughout
Pathology of uncompensated forefoot varus in the foot type
Stable cavus
There will be LATERAL ankle strain in this case
NEED TO KNOW THIS - TEST QUESTION
Partially compensated forefoot varus
- The amount of STJ eversion is less than the amount of FF varus, but enough to position the heel in eversion in RCSP, but less than the amount of FF varus
- Many feet will also compensate by plantarflexing the 1st metatarsal (metatarsals 2 through 5 are in varus and the 1st metatarsal is flexibly plantarflexed) - some “youngin’s” will do this - stated this many times, so probably need to know***
Example of partially compensated forefoot varus
Biomechanical exam
o 4 degrees of FF varus (rigid)
o 15 degrees of STJ inversion
o 4 degrees of STJ eversion
o 3 degrees of tibial varum
o As a result, the resting calcaneal stance position is 1 degree everted
o This is the maximally pronated position which is less than the 4 degrees of FF varus so the FF varus is only partially compensated
Solution
o Correct rearfoot deformity first
o 3° RF varus - 4° eversion of STJ = 0° of heel (heel vertical) with 1° of eversion left over
o Need 4° of eversion past heel vertical to compensate, but only have 1° available
o Therefore, RCSP is 1° valgus
Pathology of partially compensated forefoot varus in the skin
o Callus sub ball of foot and hallux
o IPK sub 1st met head
Pathology of partially compensated forefoot varus in the muscle or fascia
o Posterior tibial strain
o Anterior tibial strain
o Extensor substitution
Pathology of partially compensated forefoot varus in the bones (osseous)
o Genu valgum
o Tailor’s bunion
Pathology of partially compensated forefoot varus in the gait
o Apropulsive and pronated throughout
Pathology of partially compensated forefoot varus in the foot type
Stable mild cavus
KNOW THIS - still will have lateral ankle strain
Compensated forefoot varus
- When the degree of calcaneal eversion is equal to the amount of FF varus, the FF varus is considered to be fully compensated.
Example of compensated forefoot varus
Biomechanical exam
o 4 degrees of FF varus (rigid)
o 15 degrees of STJ inversion
o 6 degrees of STJ eversion
o 2 degrees of tibial varum
o As a result, the resting calcaneal stance position is 4 degrees everted
o This is the maximally pronated position, so the 4 degrees of FF varus is totally compensated
Solution
o Correct RF varus first
o 2° tibial varum - 6° of eversion of STJ = 0° of heel with 4° of eversion left over
o Need 4° of eversion past heel vertical to compensate for 4° of FFV, so RCSP is 4° of valgus
Pathology of compensated forefoot varus seen in the skin
MEDIAL strain on the foot and ankle
o Medial calcaneal callus
o Callus sub 2nd & 3rd metaheads
o Corn on 2nd, 4th, & 5th toes
Pathology of compensated forefoot varus seen in the muscle and fascia
MEDIAL strain
o Plantar fasciitis and posterior tibial strain
Pathology of compensated forefoot varus seen in the bones (osseous)
o Heel spur
o Sinus tarsi syndrome
o Cuboid syndrome
o Bunion
Pathology of compensated forefoot varus seen in the gait
PRONATION o Progression normal o Calcaneus everted o Collapse of arch at forefoot loading o Late midstance pronation
Pathology of compensated forefoot varus - foot type
Hypermobile flatfoot
NEED TO KNOW
- A patient exhibits the following: Tibial stance of 3° varus, STJ eversion of 6°, FF varus of 2°. This is an example of: o Partially compensated FF varus o Compensated FF varus o Uncompensated FF varus o A foot with an RCSP of 2° valgus o A foot with an RCSP of 3° valgus
Answer: 2, 4
It doesn’t need to go to 3 degrees
Forefoot supinatus
- Soft tissue or positional abnormality
- Inverted position of the forefoot relative to the rearfoot at the level of the STJ
- However, unlike osseous FF varus which is rigid, an off weight-bearing plantarflexion force on the 1st metatarsal will result in a complete or partial reduction of the FF varus.
- Prior to the plantarflexion force, all the metatarsals are on the same inverted plane (unlike a forefoot that has metatarsals 2 through 5 on the same inverted plane with a flexibly plantarflexed 1st metatarsal)
- With forefoot supinatus, all the metatarsals are in varus and when you push down on the 1st metatarsal, it plantarflexes
NOTES…
- Forefoot supinatus is in the SOFT TISSUE - it is NOT in the bone
- It develops AFTER the forefoot varus corrects itself
- In a forefoot varus that we have discussed previously, all the metatarsals are in the same plane and if you try to push down the 1st metatarsal, it will NOT move
- In this deformity, you will be able to push the 1st metatarsal down either a little or a lot
Example of forefoot supinatus
Biomechanical exam o 4 degrees of FF varus (rigid) o 15 degrees STJ inversion o 6 degrees STJ eversion o 0 degrees of tibial varum o 6 degrees of eversion in RCSP o As a result, there is 2 degrees of excessive compensatory STJ pronation o This 2 degrees is considered an abnormal amount of pronation
Solution
o Correct RFV first
o Next, correct for FFV
o Since, the heel everts past 3°, it keeps moving until it reaches the end range of STJ eversion which is a RCSP of 6°
o This is 2° more than is needed to correct the FFV of 4°
Notes on the biomechanical exam of our example of forefoot supinatus
o In our example, the calcaneus everts an extra 2°…
o But the metatarsals cannot evert with the heel another 2° because the 1st metatarsal has struck the ground, and so…
o The forefoot inverts an additional 2° around the midtarsal joint (MTJ) as the heel everts to 6° which over time causes a FF varus of 6°.
o The forefoot is inverted relative to the everted position of the heel
Another way to describe the example of forefoot supinatus
o The rearfoot overcompensates for a FF varus deformity, but only when the FF varus deformity is greater than 3° (the so-called “tipping point”)-in other words, will not develop a forefoot supinatus if the forefoot varus is 3° or less
o This results in a soft tissue or positional varus position of the forefoot relative to the rearfoot which becomes stiff over time.
Solution to our example of forefoot supinatus
o True FF varus always includes an osseous component, and possibly a soft tissue (supinatus) component
o To detect if a soft tissue component is present, press down on the 1st metatarsal head-if it moves, you have some component of soft tissue forefoot varus
o Very difficult to separate the osseous from the soft tissue component (don’t bother), so we are just including both when we measure the amount of forefoot varus
o Essentially, we are claiming that it is all osseous because over time the soft tissue will also stiffen and adapt to the positional change
Overview of types of forefoot varus
- Forefoot varus can be from osseous or soft tissue
deformity (or both) - Soft tissue factors contributing to forefoot varus
is known as supinatus - Osseous factors can manifest as pathology in
digits 1-5 or just 2-5 with a flexible plantarflexed
first ray
Select all the correct answers pertaining to FF supinatus
o It is an osseous deformity similar to FF varus
o It contributes to the total amount of FF varus
o It usually forms when the rearfoot overcompensates for an osseous FF varus
o It is not necessary to consider when posting the forefoot of an orthosis
Answer: 2, 3, 4
Metatarsus primus elevatus
- Structural (osseous abnormality)
- More dorsiflexion than plantarflexion of the 1st ray when measured with the STJ in neutral position.
- Acquired: Soft tissue (ruptured PL tendon) or osseous (dislocation) abnormality
- Congenital
Pathology of metatarsus primus elevatus
- Total range of motion may be normal (10 mm), but dorsiflexion > plantarflexion of 1st ray
- Prominent dorsal aspect 1st metatarsal head
- Usually have associated hallux limitus
- 1st metatarsal head has trouble purchasing ground during midstance and propulsion.
Plantarflexed cuboid
CUBOID IS INVERTED
- 4th and 5th metatarsals are plantarflexed more than the other metatarsals (relationship of 4 & 5 with the cuboid is normal).
- Cuboid is actually inverted on the calcaneus (which brings the 4th and 5th metatarsals closer to the ground), resulting in an inverted forefoot.
Plantarflexed 5th metatarsal
- Very rare deformity
- The plantarflexed position of the 5th results in an inverted position of the forefoot.
Pediatric forefoot varus
- We have learned that is natural for a child to be born with FF varus which is then corrected by valgus torque of the head and neck of the talus
- It usually takes up to 6 years for the forefoot varus deformity to correct itself and get the forefoot on the ground or parallel to the plantar surface of the heel
Orthotic for pediatric forefoot varus
- If we make an orthotic on a child under the age of 6 who still has FF varus, we cannot cast them in the standard neutral position
- If we do, we will make permanent the remaining amount of FF varus because we have prevented the medial forefoot from reaching the ground
- So, after placing the foot in STJ neutral and locking the MTJ, we plantarflex the 1st metatarsal to the level of the 5th metatarsal to bring the forefoot to the ground and prevent a permanent FF varus from developing
Called rectus position casting
o Raises the arch, but still everts the forefoot
o Tells the talus that it still has time to derotate and get the foot to the ground
FOCUS
- What foot type each is seen in each pathology
- Know which pathologies lead to medial or lateral ankle pathology
