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Department
of Podiatry
First
Ray Pathomechanics
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First ray function
- first ray normally sits parallel to
the plane of the lesser rays
- equal amounts of dorsiflexion and plantarflexion ('thumbs
breadth')
- require plantarflexion to enable 65° of MPJ dorsiflexion
during propulsion
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First
ray function
- first
ray normally sits parallel to the plane of the lesser rays
- equal amounts of dorsiflexion and plantarflexion ('thumbs breadth')
- require plantarflexion to enable 65° of MPJ dorsiflexion during
propulsion
Abnormal variations
- plantarflexed first ray
- acquired and congenital
- flexible / hypermobile or rigid
- dorsiflexed first ray
- acquired and congenital
Plantarflexed
1st ray
- osseus
deformity in which the first ray lies in a plantarflexed position
relative to the lesser rays when the STJ in the neutral position and
the MTJ is locked around the oblique axis
- present in 15% of the population (McPoil et al, 1988)
- may be congenital or acquired
- weak gastrocnemius
- hypertonicity of peroneus longus
- weak tibialis anterior
- secondary to uncompensated rf or ff varus
- weak intrinsics - hallux dorsiflexion
- each category may be:
rigid (no motion available)
flexible / hypermobile (can dorsiflex above plane of lesser metatarsals)
semi-flexible / semi-rigid (can only dorsiflex to plane of lesser
metatarsals)
Differentiation
- congenital:
equal amounts of dorsi- and plantarflexion from plantarflexed position
- acquired: asymmetrical range of motion, due to muscle contracture,
limited plantarflexion from resting position, large range of dorsiflexion
- may be quite difficult to differentiate due to age-related decreases
in first ray motion
Pathomechanics
- as
for forefoot valgus
- rigid ff valgus = rigid PF 1st
- flexible ff valgus = flexible PF 1st
Features
and pathology
Flexible / hypermobile
- medium to high MLA non-WB, lowers on WB
- HK sub 2nd MPJ
- HAV
- plantar fasciitis
- Morton's neuroma
Rigid
- high MLA non-WB and WB
- HK sub 1st and 5th MPJs
- tailor's bunion
- digital deformities
- pathologies associated with rigid FF valgus
Orthotic
management
- lateral
posting / balancing
- 'bring ground up to the foot'
- prevents supinatory (MTJ or STJ) compensation
- may dorsiflex flexible PF1st to neutral position before casting
- first ray cutout may be required for rigid PF1st
Dorsiflexed
1st ray
- osseus
deformity in which the first ray lies in a dorsiflexed position relative
to the lesser rays when the STJ in the neutral position and the MTJ
is locked around the oblique axis
- also called metatarsus primus elevatus
- may be congenital or acquired
- congenital is generally larger
- acquired due to: contracture of tibialis anterior, or may be associated
with FF supinatus
Pathomechanics
- first ray unable to plantarflex sufficiently during propulsion
- prevents normal MPJ dorsiflexion
- dorsal jamming of MPJ
- commonly associated with hallux limitus and rigidus
- Rx: metatarsal osteotomy with plantarflexion
Summary
- plantarflexed
first ray
- congenital / acquired
- flexible / rigid
- function as per ff valgus
- dorsiflexed first ray
- congenital / acquired
- cannot plantarflex during propulsion
- restricts MPJ dorsiflexion
- hallux limitus / rigidus
 References
Michaud
TC (1993) Foot orthoses and other forms of conservative foot care.
Williams and Wilkins, Baltimore, pp.93-105.
Root ML, Orien WP and Weed JH (1971) Clinical biomechanics: normal
and abnormal function of the foot. Clinical Biomechanics Corp,
Los Angeles, Chapter 10.
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