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Department
of Podiatry
Digital
Deformities
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Biomechanical
basis of forefoot and digital derangement
Forefoot derangements include:
HAV
Hallux rigidus/limitus
Adductovarus digits
Mallet/Hammer/Claw toes
Tailor's bunions
1st MT/C exostosis
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Treatment
orthoses
changes to footwear, Sx ...
Contracted toes
Three
principal types of digital contracture
Mallet toe
PF at the DIPJ only
Hammer toe
DF at the MTPJ and DIPJ, and PF at the PIPJ
Claw toe
DF at the MTPJ and PF at the PIPJ and DIPJ
digital deformities can lead to:
HK, HD, HM development
dystrophic and mycotic nail changes
problems with shoe fitting
Can often occur in conjunction with other FF changes (eg. HAV)
As the toes contract, the MTPJ are DF and produces a retrograde PF
is placed on the MT's
interossei
important stabilisers in stance
lumbricales
function primarily in the swing phase
both help stabilise the toes without buckling
these muscles are important in that they:
extend the IPJ's
PF the MTPJ's
With
XS pronation (and a lack of normal resupination at propulsion)
the intrinsics and the long flexors excessively fire
... but the intrinsic m.'s lack the strength to stabilise the foot,
and they fatigue in the attempt to do so
The pull of the long flexors can lead to the development of a hammer
toe
because the prox. and middle phalanges are no longer stabilised
Flexor stabilisation
most common cause of hammertoes
occurs during late midstance and propulsion
FDL & FDB fire earlier, creating DF at the lesser MTPJ's
FDL/FDB overpower the plantar force exerted here by the interossei
can also lead to the development of adductovarus digits
Hammertoes
As well as flexor stabilisation, there are other aetiological entities
that can cause hammertoes ...
a plantarflexed ray
loss/weak lumbricale function
loss/weak digital extensors
short MT
Trauma
Idiopathic ...
Pathologies
digital lesions, bursae
Treatment
Palliative podiatry
correct shoe fitting
functional orthoses
silicon devices
Surgery (fusion of IPJ's, removal of phalanxes' ...)
Adductovarus digits
deformity in which the lesser digits rotate into a position of adduction
and varus
5th toe most common > 4th > 3rd
extremely common deformity
Brief pathomechanics
excessively STJ pronation at late midstance/propulsion
forefoot abduction, FDL pull shifts medially
leads to an abnormal medial pull on the lesser digits which cannot be
counteracted by QP
can lead to the development of dorso-lateral HD's on the affected digit,
as well as HM
Treatment
orthotic control of XS STJ pronation rarely sees a regression of this
condition
however, controlling the FF hypermobility should help reduce the lesions,
as will well fitted shoes
Silicone devices
Sx
Tailor's bunion
A digital deformity in which there is an abnormal prominence of the
5th MT head
Aetiology
often seen with partially compensated RF/FF varus deformities
PF/DF 5th ray
Idiopathic
the 5th MT has a larger ROM than the adjacent MT's - it can easily DF,
abd, and evert in an unstable pronated foot
This deformity can become fixed as soft tissue adapts
May become symptomatic due to the development of a lateral 5th MT bursa
Management
palliative podiatry
wider fitting shoes
pressure-relieving devices
functional orthoses to relieve shearing of the MT head - not always
successful
Sx (bumpectomy, osteotomy ...)
Other contributors
HAV can contribute to toe deformities
as the hallux drifts laterally, it tends to push the lesser toes laterally,
then it may override or underride the second toe
the 2nd toe often can become hammered and can dislocate
 References
McGlamry,
E D (1987) Comprehensive textbook of foot surgery, Volume 1, Williams
and Wilkins p.547
Sgarlato, T E (1971) A compendium of podiatric biomechanics. CCPM
San Francisco
Moore, K L (1992) Clinically oriented anatomy, Third Edition. Williams
& Wilkins Baltimore
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