20/21: Rearfoot Varus/Valgus - Mahoney Flashcards Preview

Surg+BioMech [all exams] > 20/21: Rearfoot Varus/Valgus - Mahoney > Flashcards

Flashcards in 20/21: Rearfoot Varus/Valgus - Mahoney Deck (35)
Loading flashcards...
1
Q

define rearfoot varus

A
  • Inversion of rearfoot (calcaneus) relative to the ground when the STJ is in neutral
2
Q

what allows heel to reach vertical position in rearfoot varus?

A

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

3
Q

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

A

rearfoot varus

4
Q

how do you determine rearfoot varus?

A
  • Determined by measuring tibial influence or tibial position
5
Q

pathological rearfoot varus

A

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

6
Q

why is rearfoot varus a positional deformity and not structural?

A

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

7
Q

blount’s disease

A

premature closure proximal tibial epiphysis

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

8
Q

etiology of rearfoot varus

A
  • tibial varum
  • subtalar varum
  • calcaneal varum
9
Q

etiology of tibial varum

A
  • genu varum
  • blount’s dz
  • failure of tibia to straighten from the infantile position
10
Q

etiology of subtalar varum

A
  • uneven epiphyseal growth
  • wedge shaped talus
  • retention of varus calcaneal torsion at birth
11
Q

etiology calcaneal varum

A
  • improper development

- malaligned calcaneal fracture

12
Q

Rule of Compensation for RF Varus

A
  • 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)
13
Q

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

A

equal

14
Q

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

A

1/3

15
Q

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

A

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

16
Q

RF varus = ________ – __________

A

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

17
Q

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°)

A

uncompensated RF varus

Heel functions in an inverted position

18
Q

Example

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

what type of varus?

A

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

19
Q

s/s uncompensated rearfoot varus or partially compensated RF varus

A

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

20
Q

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

A

partially compensated RF varus

21
Q

Example:

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

what type of RF varus?

A

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

22
Q

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

Heel assumes a vertical position relative to the ground

A

compensated RF varus

23
Q

normal tibial stance

normal total range of STJ

A

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)

24
Q

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

what is RCSP?

A

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

25
Q

what does a compensated RF varus do to gait?

A

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

26
Q

root theory

A

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

27
Q

define rearfoot valgus

A

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

28
Q

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

A

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

Can be due to traumatic injury or congenital deformity

29
Q

the heel cannot go past ____ degrees of eversion

A

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

30
Q

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°

A

RCSP of 3° everted

RCSP of 5° everted to 7° everted

RCSP of 5° everted to 13° everted

31
Q

casting in a “pronated position”

A

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

32
Q

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

A

7-10 valgus

33
Q

WB or NWB to determine rearfoot varus/valgus

A

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

34
Q

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

A

rearfoot deformity will compensate before the forefoot deformity

35
Q

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

A

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.

Decks in Surg+BioMech [all exams] Class (68):