25: Inverted Forefoot Deformities - Mahoney

Question 1

name 5 inverted forefoot deformities

Answer 1

forefoot varus
forefoot supinatus
metatarsus primus elevatus
plantrflexed cuboid
plantarflexed 5th metatarsal

Question 2

define osseous forefoot varus

Answer 2

• 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)
• If all the metatarsals are inverted on the same plane, you cannot plantarflex the 1st metatarsal during examination

Question 3

1st met higher than the 5th

Answer 3

forefoot varus

Question 4

etiology of forefoot varus

Answer 4

• 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 (ie, the forefoot is not perpendicular to the bisection of the heel).

Question 5

most common cause of FF varus

Answer 5

lack of valgus rotation of the talar head

Question 6

rule of compensation for FF varus

Answer 6

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

Question 7

Exists when there is no calcaneal eversion beyond the vertical available

Answer 7

uncompensated forefoot varus

However, most people will have adequate r.o.m. available at the MTJ or within the 1st ray’s r.o.m. to allow the forefoot to purchase the ground

Question 8

RCSP rearfoot varus
RCSP forefoot varus

what does a compensated heel look like?

Answer 8

vertical heel

heel everted

Question 9

If a forefoot varus is compensated by plantarflexing the first metatarsal, when seen in non-weightbearing neutral position …

Answer 9

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)

Question 10

all the metatarsals are in

varus =

Answer 10

osseous forefoot

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

Question 11

what is the RCSP?

4 degrees of FF varus (rigid)
20 degrees of STJ inversion
4 degrees of STJ eversion
8 degrees of tibial varum

Answer 11

4 degrees inverted

• RF varus compensates before FF deformity
• this is the maximally pronated position and the FF varus is uncompensated

8° tibial varum - 4° eversion of STJ = 4° RF varus
To compensate for 4° of FFV, need to evert heel 4° past vertical
No more eversion of STJ is available

Question 12

what pathologies associated with uncompensated forefoot varus?

Answer 12

• cavus foot type ***
• lateral foot strain ***
• callus sub 4th and 5h met heads and hallux
• corn dorsum 2nd toe
• functional equinus

Question 13

describe partially compensated forefoot varus

Answer 13

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)

Question 14

RCSP = ?

4 degrees of FF varus (rigid)
15 degrees of STJ inversion
4 degrees of STJ eversion
3 degrees of tibial varum

Answer 14

resting calcaneal stance position is 1 degree everted

This is the maximally pronated position which is less than the 4 degrees of FF varus so the FF varus is only partially compensated

Correct rearfoot deformity first
3° RF varus - 4° eversion of STJ = 0° of heel (heel vertical) with 1° of eversion left over
Need 4° of eversion past heel vertical to compensate, but only have 1° available
Therefore, RCSP is 1° valgus

Question 15

foot type partially compensated FF varus

Answer 15

stable mild cavus

Question 16

RCSP = ? compensation = ?
4 degrees of FF varus (rigid)
15 degrees of STJ inversion
6 degrees of STJ eversion
2 degrees of tibial varum

Answer 16

resting calcaneal stance position is 4 degrees everted

This is the maximally pronated position, so the 4 degrees of FF varus is totally compensated

Correct RF varus first
2° tibial varum - 6° of eversion of STJ = 0° of heel with 4° of eversion left over
Need 4° of eversion past heel vertical to compensate for 4° of FFV, so RCSP is 4° of valgus

Question 17

pathology compensated forefoot varus

Answer 17

hypermobile flat foot, medial strain

Question 18

A patient exhibits the following:Tibial stance of 3° varus, STJ eversion of 6°FF varus of 2°. This is an example of:

Answer 18

• compensated FF varus

- foot with a RCSP of 2 valgus

Question 19

• Inverted position of the forefoot relative to the rearfoot at the level of the STJ
• 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

Answer 19

forefoot supinatus
- soft tissue or positional abnormality

(unlike a forefoot that has metatarsals 2 through 5 on the same inverted plane with a flexibly plantarflexed 1st metatarsal)

Question 20

With forefoot supinatus, all the metatarsals
are in varus and when you push down on the 1st
metatarsal, it …

Answer 20

plantarflexes

Question 21

4 degrees of FF varus (rigid)
15 degrees STJ inversion
6 degrees STJ eversion
0 degrees of tibial varum
6 degrees of eversion in RCSP

Answer 21

2 degrees of excessive compensatory STJ pronation
- this is an abnormal amount of pronation

Correct RFV first
Next, correct for FFV
Since, the heel everts past 3°, it keeps moving until it reaches the end range of STJ eversion which is a RCSP of 6°
This is 2° more than is needed to correct the FFV of 4°

Question 22

you can not develop forefoot supinatus unless …

Answer 22

your forefoot varus is greater than 3 degrees

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

This results in a soft tissue or positional varus position of the forefoot relative to the rearfoot which becomes stiff over time = forefoot supinatus

Question 23

True FF varus always includes an osseous component, and possibly a soft tissue (supinatus) component
To detect if a soft tissue component is present …

Answer 23

press down on the 1st metatarsal head-if it moves, you have some component of soft tissue forefoot varus

Question 24

Select all the correct answers pertaining to FF supinatus
A It is an osseous deformity similar to FF varus
B It contributes to the total amount of FF varus
C It usually forms when the rearfoot overcompensates for an osseous FF varus
DIt is not necessary to consider when posting the forefoot of an orthosis

Answer 24

B, C, D

Question 25

what is metatarsus primus elevatus?

Answer 25

More dorsiflexion than plantarflexion of the 1st ray when measured with the STJ in neutral position

structural/osseous deformity

Total range of motion may be normal (10 mm), but dorsiflexion > plantarflexion of
1st ray

Question 26

what is plantarflexed cuboid?

Answer 26

Cuboid is actually inverted on the calcaneus (which brings the 4th and 5th metatarsals closer to the ground), resulting in an inverted forefoot

4th and 5th metatarsals are plantarflexed more than the other metatarsals (relationship of 4 & 5 with the cuboid is normal).

Question 27

The plantarflexed position of the 5th results in an inverted position of the forefoot

Answer 27

plantarflexed 5th metatarsal

Question 28

it is natural for a kid to have flat feet until about …

Answer 28

6 years old

• 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

Question 29

If we make an orthotic on a child under the age of 6 who still has FF varus, we …

Answer 29

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

Question 30

recuts position casting

Answer 30

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