27: Biomechanics III - Mahoney

Question 1

10° eversion and 25° inversion

STJ neutral =

Answer 1

2 varus

STJ neutral = 1/3 of total range of STJ motion – maximum eversion (1/3 of 35°)-10° = +2° (varus)

OR just put the STJ in neutral and measure

Question 2

describe different heel positions base on rearfoot compensation

Answer 2

A fully compensated rearfoot varus moves to heel vertical

A partially compensated rearfoot varus moves some degree of eversion, but does not get to heel vertical

An uncompensated rearfoot varus has no STJ eversion available

Question 3

10° of eversion at the STJ
3° of rearfoot varus deformity

what will the heel position be?

Answer 3

Need 3° of eversion to get the heel vertical, and we have 10° available

So, we get to heel vertical and we have a fully compensated RF varus deformity

we can use another 7° of eversion if we need the heel to evert past vertical to accommodate for any additional deformities (like FF varus, equinus, genu valgum, etc.) we may measure

If there is no other deformity, our RCSP will then be heel vertical

Question 4

NCSP is the sum of …

Answer 4

Tibial stance position + STJ neutral

Question 5

if forefoot varus is 3, then heel must …

Answer 5

evert 3 degrees to compensate

Question 6

forefoot varus 2 through 5 with a flexible plantarflexed 1st ray — the RCSP will be …

Answer 6

vertical

- STJ does not have to evert past vertical (1st met does the job)

Question 7

Compensation for a FF valgus of 7° or greater will occur by ..

Answer 7

MTJ longitudinal axis not enough so ..

STJ supination followed by supination of oblique axis of MTJ

Question 8

where will compensation for ankle equinus occur?

Answer 8

• By knee extension
• By knee flexion and hip flexion
• By STJ pronation to unlock the oblique axis of the MTJ to attempt to gain ankle dorsiflexion

Question 9

genu valgum –>

genu varum –>

Answer 9

RCSP of increased vlagus, prontation

RCSP of increased varus

• • However, the foot will be medial to the midline of the leg and, hence, will be in a relatively pronated position to the leg even if the heel is vertical or in varus
• • medial position will cause symptoms of pronation in spite of the heel’s position

Question 10

compensate increased external hip rotation –>

compensate increased internal hip rotation –>

Answer 10

• RCSP of increased valgus

- RCSP of increased varus or valgus (supination or pronation)

Question 11

limb length inequality
supination on long side if …
supination on short side if …

Answer 11

Supination of the foot on the long leg side and pronation of the foot on the short leg side, IF the pelvis tilts down on the short side (most common)

Supination of the foot on the short side and pronation of the foot on the long side, IF the pelvis does NOT compensate

Cannot determine the exact amount of RCSP change

Question 12

Which are not true?

A Pelvis tilts down on the short side

B Pelvis tilts down on the long side

C Shoulder tilts down on the short side

D Shoulder tilts down on the long side

E Foot pronates on the long side if there is no pelvic compensation, and on the short side if there is pelvic compensation

F Foot supinates on the short side if there is no pelvic compensation, and on the long side if there is pelvic compensation

Answer 12

A, D, E, F

Question 13

After a patient has fully compensated for a rearfoot varus deformity, there is 6° of calcaneal eversion left. The patient has 4° of forefoot varus. The resting calcaneal position is most likely to be

Answer 13

4-6 degrees valgus

Question 14

Determine the resting calcaneal stance position of the following patient who has:
5° of rearfoot varus
10° of STJ eversion
5° of forefoot valgus

Answer 14

heel is vertical

forefoot valgus doesn’t usually compensate at STJ