Leprosy Mailing List – September 18th, 2007
Ref.: Main factors
contributing to foot ulcers in leprosy
From: Cross H., Greenville, SC, U.S.A.
Dear Dr Noto,
I too have been following with interest
the discussion on the foot ulceration and would like to respond to
some of the issues raised by Wim Theuvenet (LML September 4th,
2007).
I am very glad that he raised the issue of
the paucity of evidence regarding the affects of self care advice on
the recurrence of plantar ulceration and hope that it will stimulate a more
concerted effort to study the topic.
As later considered in Wim
Theuvenet's correspondence and also that of Drs Salafia and Warren,
the causes of ulceration are multi-factorial so it is very difficult
to attribute ulceration or its recurrence to any one factor. However evidence from China
and Nepal are currently being prepared for publication that will show
that where people were following essential self-care advice (soaking,
oiling and scraping) they were remarkably successful in healing or
improving plantar ulceration and that the effects could be sustained
(3 year evaluation period in China). In Guizhou (China) this was
accomplished without any modifications to commercial canvas shoes (not
even the addition of soft insoles).
The extent to which activity adjustment could have been a
contributing factor in China was not measured, but it may have been
significant.
I am also particularly interested in
kinematic variables associated with plantar ulceration and continue to
investigate these (a paper based on the outcomes of a recent study I
conducted is currently being considered for publication). Wim Theuvenet's hypothesis
that unsteadiness due to intrinsic paralysis may lead to high peak
pressure merits further investigation, although it should be
considered that a great number of people who do present with
ulceration do not have intrinsic muscle paralysis. Cavangah et al. ascertained
that people with diabetic neuropathy did demonstrate a significant
increase in sway during standing that was not compensated for by other
sensory systems. However
they also recorded that study of the sagittal plane movements of the
same individuals walking on a treadmill showed little effect on the
kinematic control of gait when compared to age matched non-neuropathic
control groups and they suggested that the observation may have been
due to a dominance of efferent input over afferent feedback during
gait.
I recently studied the feet of 144 individuals from the
Philippines and Nepal. I
only accepted feet that had normal skeletal architecture (no bone
loss) and did not have extrinsic or intrinsic muscle paresis or
paralysis (n = 263). For
brevity in this correspondence I will not give precise sample details,
but approximately half the subjects had leprosy related insensibility
and half were normal, half of those with plantar insensibility also
had simple ulcers or scars from previous ulceration.
All feet were categorized according to a
simple semantic classification based on the posture of the subtalar
joint during stance. Feet
were either categorized as "Supinated", "Pronated",
"Hyperpronated" or "Neutral" (neither supinated or
pronated). Forefoot peak
pressures were significantly higher among subjects classified as
either "Pronated" or "Hyperpornated"
compared with subjects classified as "Neutral".
I also studied feet with
ulceration independently and found that the relative risk that
ulceration would present on “Hyperpronated” or “Pronated” feet
was high (5.3 and 2.8 respectively) but “Supinated” feet were not
at greater risk of presenting with ulcers than “Neutral”.
When compared on semantic
classification the "Normal" group was not significantly
different from the "Insensible" group. In both groups it was found
that approximately 70% of subjects could be categorized as
Hyperpronated or Pronated and that the remaining 30% could be divided
about equally between "Neutral and "Supinated".
Pronation of the subtalar
joint is a very common compensation for minor anatomical
aberrations including tibial varum and femoral exorotation. It
does cause instability at joints, some of which will allow
greater mobility than others. This
leads to an uneven distribution of forces across the forefoot resulting
in localization of pressure beneath bones that are less
mobile (typically 2nd or 3rd metatarsals) and shearing stress beneath
mobile bones (the first metatarsal).
Regards,
Hugh Cross
1.
Cavanagh
PR, Simoneau GG, Ulbrecht JS. Ulceration,
unsteadiness, and uncertainty: the biomechanical consequences of
diabetes mellitus. J.Biomech.
1993;26 Suppl 1:23-40
