20/21: Rearfoot Varus/Valgus - Mahoney

Question 1

define rearfoot varus

Answer 1

• Inversion of rearfoot (calcaneus) relative to the ground when the STJ is in neutral

Question 2

what allows heel to reach vertical position in rearfoot varus?

Answer 2

Combination of tibial varum (normal is 0 to 7 degrees varus) and the available range of STJ pronation (calcaneal eversion) to allow the heel to reach a vertical position

Question 3

A positional abnormality which causes the calcaneus to be inverted to the ground when the subtalar joint (STJ) is in the neutral position

Answer 3

rearfoot varus

Question 4

how do you determine rearfoot varus?

Answer 4

• Determined by measuring tibial influence or tibial position

Question 5

pathological rearfoot varus

Answer 5

anything other than 0 degrees measured by tibial influence or tibial positon

Question 6

why is rearfoot varus a positional deformity and not structural?

Answer 6

Called positional because the type of RF varus is dependent upon the amount of soft tissue motion of the STJ in eversion to try and correct the deformity

Question 7

blount’s disease

Answer 7

premature closure proximal tibial epiphysis

- medial portion closest to knee closes, allowing continued lateral growth –> varus shape

Question 8

etiology of rearfoot varus

Answer 8

• tibial varum
• subtalar varum
• calcaneal varum

Question 9

etiology of tibial varum

Answer 9

• genu varum
• blount’s dz
• failure of tibia to straighten from the infantile position

Question 10

etiology of subtalar varum

Answer 10

• uneven epiphyseal growth
• wedge shaped talus
• retention of varus calcaneal torsion at birth

Question 11

etiology calcaneal varum

Answer 11

• improper development

- malaligned calcaneal fracture

Question 12

Rule of Compensation for RF Varus

Answer 12

• All RF varus deformities compensate by attempting to get the heel to vertical in Resting Calcaneal Stance Position (RCSP), but will NEVER exceed heel vertical
• foot seeks to get its medial aspect on the ground
• To calculate whether the rearfoot varus has compensated or corrected by reaching heel vertical in stance, subtract the amount of STJ eversion from the amount of tibial varum (STJ must be placed in neutral position while standing to calculate the amount of tibial varum)
• Although eversion of the STJ to get the heel to vertical is the most common compensation, occasionally you may find a patient who plantarflexes the 1st ray to get the medial side of the foot to the ground (much more common with forefoot varus)

Question 13

The amount of STJ eversion is _________ the amount of eversion you measure (with the patient NWB) from heel vertical after you bisect the lower leg and the heel

Answer 13

equal

Question 14

The amount of STJ eversion from neutral position is _____ of the total range of motion of the STJ

Answer 14

1/3

Question 15

calculate STJ neutral
10° of eversion of the STJ
26° of inversion of the STJ

Answer 15

STJ neutral equals 1/3 of the total range of motion from the maximally everted position

STJ neutral equals 2° of varus

In this case, you have 10° of eversion of the STJ from vertical, but 12° from STJ neutral position

You still will be able to evert the heel maximally in both cases to 10° past vertical

Question 16

RF varus = ________ – __________

Answer 16

RF varus = tibial stance position – amount of STJ eversion

Remember: to calculate tibial stance position, we must place the STJ in neutral position while standing

Question 17

The amount of tibial varum is greater than the amount of calcaneal eversion available through compensatory STJ pronation (in uncompensated RF varus, STJ eversion is 0°)

Answer 17

uncompensated RF varus

Heel functions in an inverted position

Question 18

Example

	- 10 degrees of tibial varum
	- 20 degrees STJ inversion
	- 0 degrees of STJ eversion

what type of varus?

Answer 18

uncompensated RF varus

As a result, the heel is at 10 degrees varus at relaxed calcaneal stance position (RCSP)

This is the maximally pronated position of this patient’s foot, even though it is varus

Question 19

s/s uncompensated rearfoot varus or partially compensated RF varus

Answer 19

LATERAL stress on foot and ankle, LATERAL ankle instability, may be compensation at knee, apropulsive gait due to lack of toe off

Question 20

The degree of tibial varum is greater than the calcaneal eversion available with STJ pronation

Heel is inverted relative to the ground, but not as inverted as the degree of tibial varum

Answer 20

partially compensated RF varus

Question 21

Example:

	- 10 degrees of tibial varum
	- 20 degrees of inversion of STJ
	- 5 degrees of eversion of STJ

what type of RF varus?

Answer 21

partially compensated RF varus

As a result, the heel is at 5 degrees varus at relaxed calcaneal stance position

This is the maximally pronated position of this patient’s foot, even though it is in varus

Question 22

The degree of tibial varum is equal to the amount of STJ pronation available

Heel assumes a vertical position relative to the ground

Answer 22

compensated RF varus

Question 23

normal tibial stance

normal total range of STJ

Answer 23

Normal tibial stance is 0 to 7° of varus
Normal total range of the STJ is 30°, of which 1/3 of the motion is eversion or 10°

Therefore, most people will have enough eversion to get to heel vertical (even with a maximum of 7° of tibial varum, you will usually have 10° of STJ eversion)

Question 24

10° tibial varum
20° STJ inversion
13° STJ eversion

what is RCSP?

Answer 24

The RCSP is 0°, even though there is still 3° of eversion still available

Question 25

what does a compensated RF varus do to gait?

Answer 25

Least abnormal of the RF varus deformities, but can lead to forefoot hypermobility secondary to delayed resupination in gait

To keep the forefoot in total contact with the ground, the STJ needs to pronate up to the time of heel lift (38% of stance phase)

However, need to start resupination at about 25% of stance phase of gait

pronated foot type because delays supination

Question 26

root theory

Answer 26

When you make an orthosis for someone with a rearfoot varus, post the rearfoot the same number of degrees as the deformity to prevent any compensatory change

Question 27

define rearfoot valgus

Answer 27

A STRUCTURAL abnormality which causes the calcaneus to be everted to the ground when the subtalar joint (STJ) is in the neutral position.

if you ever did see this deformity (theoretical) there would be no compensation – no soft tissue motion of the STJ to correct the deformity by inverting the heel towards vertical

Question 28

If you measure valgus, and not varus, for the tibial position, …

Answer 28

you have probably measured incorrectly
Normal tibial position is 0° to 7° varus

Can be due to traumatic injury or congenital deformity

Question 29

the heel cannot go past ____ degrees of eversion

Answer 29

13 - due to normal foot anatomy (navicular strikes the ground and prevents any further heel motion)

Whenever the heel is able to evert past 3°, it may evert its complete amount of STJ eversion or until approximately 13° of eversion, whichever comes first

Question 30

calculate RCSP

STJ neutral of 3° valgus and STJ eversion of 15°

STJ neutral of 5° valgus and STJ eversion of 7 °

STJ neutral of 5° of valgus and STJ eversion of 15°

Answer 30

RCSP of 3° everted

RCSP of 5° everted to 7° everted

RCSP of 5° everted to 13° everted

Question 31

casting in a “pronated position”

Answer 31

When you make an orthosis for someone with rearfoot valgus (e.g., STJ arthritis with STJ fixed in a valgus position), the neutral position will be in valgus, so the orthosis must have a rearfoot post in valgus

Patient could not tolerate a heel in vertical on the orthosis

Question 32

A patient has a STJ neutral position of 7° valgus. The amount of STJ eversion is 10°. The RCSP is:

Answer 32

7-10 valgus

Question 33

WB or NWB to determine rearfoot varus/valgus

Answer 33

Rearfoot varus and valgus are deformities which can only be determined with the patient in weightbearing

Forefoot varus and valgus are deformities which can only be determined with the patient in NWB

Question 34

When there is a combination of RF and FF deformities ….

Answer 34

rearfoot deformity will compensate before the forefoot deformity

Question 35

what should the heel of orthotic for rearfoot varus look like?

Answer 35

make the orthosis so that the heel is vertical to the ground because it is the position of most comfort

assuming that the only foot, ankle, or leg deformity is a fully compensated RF varus

If you have an uncompensated or compensated RF varus (which are rare), post (or tilt) the heel the same number of degrees as the RF varus. Do same thing for valgus.