Biomechanics of HAV

Question 1

abduction and adduction of the lesser toes caused by the interossei uses what as a reference line?

Answer 1

utilizes 2nd toe as midline reference point

Question 2

the lumbricals use what as their reference point fo rmidline?

Answer 2

midline of the body

Question 3

in which direction does the great toe move if it were abducting?

Answer 3

moves away from the midline of the body (but towards the 2nd toe)

Question 4

what does the great toe utilize as its midline?

Answer 4

midline of the body

Question 5

which muscle causes abduction of the great toe?

Answer 5

adductor hallucis

Question 6

in which direction does the great toe move if it were adducting?

Answer 6

towards the midline (or away from the 2nd toe)

Question 7

which muscles causes adducting of the great toe?

Answer 7

abductor hallucis

Question 8

therefore the names of abductor hallucis and adductor hallucis utilize what reference ilne?

Answer 8

2nd toe as midline

Question 9

what is the primary etiology of HAV?

Answer 9

STJ pronation

Question 10

how does pronation lead to HAV?

Answer 10

-as the arch lowers and cuboid dorsiflexes, it loses its ability to act as a fulcrum for peroneus longus to plantarflex the 1st met

Question 11

what is a Lapidus procedure?

Answer 11

fusion of 1st met-cueniform joint

Question 12

what movement does the 1st met have when it is dorsiflexing?

Answer 12

it also inverts

Question 13

in which planes of deformity is HAV?

Answer 13

frontal plane (valgus) ; transverse plane (abduction)

Question 14

what action does the 1st lumbrical have?

Answer 14

adducts the 2nd toe

Question 15

what is Stage 1 of a bunion deformity characterized by?

Answer 15

lateral subluxation of base of proximal phalanx away from the 1st metahead
*and 1st met dorsiflexes and inverts

Question 16

What is the hallux doing in stage 1 of a bunion deformity?

Answer 16

it is plantarflexing and everting

Question 17

What is the order in which muscles act in a bunion deformity?

Answer 17

1. EHB- pulls laterally
2. bowstringing of EHL and FHL tendons as longitudinal axis of 1st met moves medially
3. ABH loses its medial stabilizing force as 1st met dorsiflexes
4. FHB contributes to lateral abductory force

Question 18

what effect does EHB have in stage 1 of bunion deformity?

Answer 18

pulls the big toe laterally as the 1st met moves more medially

Question 19

which muscle action is seen in stage 1 of bunion deformity/

Answer 19

EHB

Question 20

what muscle action is seen in stage 2 of bunion deformity?

Answer 20

(EHL and FHL tendons bowstring)

*ABH loses its medial stabilizing force as 1st met dorsiflexes

Question 21

what is stage 2 of bunion deformity characterized by?

Answer 21

true abduction deformity of the hallux, with hallux pressing against second toe
*joint space widens and first signs of lateral joint deviation may be noted

Question 22

which way does the long axis of the 1st met move in stage 2?

Answer 22

moves more medially –> which causes bowstringing of EHL and FHL tendons

Question 23

where does ABH lie in relation to transverse axis of 1st MPJ?

Answer 23

lies below transverse axis –> causing it to lose its medial stabilizing force and balance of adductor hallucis

Question 24

what effect does FHB have in stage 2 of bunion deformity?

Answer 24

contributes to the lateral abductory force as the sesamoids drift more laterally

Question 25

what is stage 3 of bunion deformity characterized by?

Answer 25

(joint changes)

• increased IM angle
• widening of the foot

Question 26

how does the long axis of the 1st met change in stage 3 of bunion deformity?

Answer 26

-moves more medially and becomes oriented proximal/plantar/lateral to distal/dorsal/medial

Question 27

how does the transverse axis of motion of 1st MPJ change in stage 3?

Answer 27

-no longer level with the transverse plane and orients from proximal/lateral/DORSAL to distal/medial/PLANTAR

Question 28

what is stage 4 of bunion deformity characterized by?

Answer 28

subluxation or dislocation of 1st MPJ (and overriding of 2nd toe)

Question 29

how effective are orthotics in treating HAV?

Answer 29

may slow the progression of HAV and are most effective in the early stage (from stage 3 on, orthotics are useless)