Biomechanics of HAV Flashcards
abduction and adduction of the lesser toes caused by the interossei uses what as a reference line?
utilizes 2nd toe as midline reference point
the lumbricals use what as their reference point fo rmidline?
midline of the body
in which direction does the great toe move if it were abducting?
moves away from the midline of the body (but towards the 2nd toe)
what does the great toe utilize as its midline?
midline of the body
which muscle causes abduction of the great toe?
adductor hallucis
in which direction does the great toe move if it were adducting?
towards the midline (or away from the 2nd toe)
which muscles causes adducting of the great toe?
abductor hallucis
therefore the names of abductor hallucis and adductor hallucis utilize what reference ilne?
2nd toe as midline
what is the primary etiology of HAV?
STJ pronation
how does pronation lead to HAV?
-as the arch lowers and cuboid dorsiflexes, it loses its ability to act as a fulcrum for peroneus longus to plantarflex the 1st met
what is a Lapidus procedure?
fusion of 1st met-cueniform joint
what movement does the 1st met have when it is dorsiflexing?
it also inverts
in which planes of deformity is HAV?
frontal plane (valgus) ; transverse plane (abduction)
what action does the 1st lumbrical have?
adducts the 2nd toe
what is Stage 1 of a bunion deformity characterized by?
lateral subluxation of base of proximal phalanx away from the 1st metahead
*and 1st met dorsiflexes and inverts
What is the hallux doing in stage 1 of a bunion deformity?
it is plantarflexing and everting
What is the order in which muscles act in a bunion deformity?
- EHB- pulls laterally
- bowstringing of EHL and FHL tendons as longitudinal axis of 1st met moves medially
- ABH loses its medial stabilizing force as 1st met dorsiflexes
- FHB contributes to lateral abductory force
what effect does EHB have in stage 1 of bunion deformity?
pulls the big toe laterally as the 1st met moves more medially
which muscle action is seen in stage 1 of bunion deformity/
EHB
what muscle action is seen in stage 2 of bunion deformity?
(EHL and FHL tendons bowstring)
*ABH loses its medial stabilizing force as 1st met dorsiflexes
what is stage 2 of bunion deformity characterized by?
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
which way does the long axis of the 1st met move in stage 2?
moves more medially –> which causes bowstringing of EHL and FHL tendons
where does ABH lie in relation to transverse axis of 1st MPJ?
lies below transverse axis –> causing it to lose its medial stabilizing force and balance of adductor hallucis
what effect does FHB have in stage 2 of bunion deformity?
contributes to the lateral abductory force as the sesamoids drift more laterally
what is stage 3 of bunion deformity characterized by?
(joint changes)
- increased IM angle
- widening of the foot
how does the long axis of the 1st met change in stage 3 of bunion deformity?
-moves more medially and becomes oriented proximal/plantar/lateral to distal/dorsal/medial
how does the transverse axis of motion of 1st MPJ change in stage 3?
-no longer level with the transverse plane and orients from proximal/lateral/DORSAL to distal/medial/PLANTAR
what is stage 4 of bunion deformity characterized by?
subluxation or dislocation of 1st MPJ (and overriding of 2nd toe)
how effective are orthotics in treating HAV?
may slow the progression of HAV and are most effective in the early stage (from stage 3 on, orthotics are useless)
