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Department
of Podiatry
Tissue
Stress Model & Other Theories: B
The Tissue
Stress Model in the Literature
McPoil TG & Hunt GC: Evaluation and Management of Foot and
Ankle Disorders: Present Problems and Future Directions. JOSPT
21(6)381-388 1995 (in course manual)
McPoil TG & Hunt GC: An Evaluation and Treatment Paradigm
for the Future. In Hunt GC & McPoil (eds): Physical Therapy
of the Foot and Ankle 2nd Ed 199?. Churchill Livingstone
Citations only include - Payne, 1997 & 1998 and Menz 1997 - Why
so few?
The Tissue
Stress Model
McPoil and Hunt, in their two papers on the tissue stress model, start
by discussing some of the problems with the traditional/classical
approach to foot biomechanics
They then provide what they refer to as an overuse injury model based
on excessive tissue stress
However the model does not necessarily 'grow' out of the critique
Principles
it is based on:
excessive stress can occur to the various tissues
the goal is to reduce tissues stress to a tolerable level
need to determine if the symptoms reported are mechanical or nonmechanical
in nature
Protocol
for Evaluation and Management
1) Identify the involved tissues being stressed based on symptoms
and other subjective information obtained from the history
2) The application of various stresses to the involved tissues in
an attempt to replicate symptoms through the use of non-weightbearing
and weightbearing tests as as well as palpation
3) Based on the findings of the evaluation, determine if the patient's
complaint is related to excessive mechanical loading of tissues or
if it is a non-mechanical problem. If it is a determined that the
patient's complaint is caused by excessive mechanical loading of tissues,
then ascertain whether the patients problem is related to:
&endash;
a) excessive foot pronation
&endash;
b) lack of foot mobility
&endash;
c) limitation in flexibility
&endash;
d) decrease in muscle strength
&endash;
(any others?)
4) A management protocol that emphasizes;
a) Reducing
tissue stress to a tolerable level through rest, activity modification,
footwear and/or orthoses
b) Healing
the involved tissues through medications and physical therapeutic
mechanisms
c) The
restoration of lower extremity flexibility and muscle strength
d) A
plan for the gradual resumption of activity
Is this
consistent with the approach put forward by Fuller?
For example:
Plantar fasciitis
1. What are the symptoms that the patient will complain off?
2. What is the key point in the history that indicates that it is
of mechanical origin?
3. What are the weightbearing and non-weightbearing tests?
4. What are the key points in the management protocol based on the
tissue stress model?
5. What are the purposes of the orthoses in this model?
Is this
an alternative model or a protocol that puts orthoses management in
the appropriate place in the management of patients?
Other
Theories: B
Can we
integrate it all and make clinical decisions?
Will there ever be one theory or many theories?
abnormal function in any body plane can interfere with function
so must we assess alignment and function in all three body planes
Prior (unpublished, 1998) has suggested an approach based on this:
Transverse
Plane
For normal
function need:
A sufficient low gear axis angle in relation to the long axis of the
foot and angle of gait to allow supinaton at heel lift
A sufficient high gear axis angle in relation to the long axis of
the foot and the angle of gait to allow transfer and facilitate the
windlass effect
The angle of gait and the angle of the high gear axis should be of
the same magnitude in relation to the long axis of the foot to allow
this axis to function in the line of progression
The axis of the subtalar joint in relation to the sagittal plane should
pass through the first and second interspace
The perpendicular
bisections of each axis show the longer radial arm from the heel to
the transverse axis (Btr) versus the shorter radial arm to the oblique
axis (Bobl). The greater the radial arm length, the greater the ability
to develop greater thrust, hence high versus low gear push. Once the
medial arm becomes engaged by weight shift to the transverse axis,
it causes the 'closed packing' of the calcaneo-cuboid joint and secondary
tarsal and midtarsal joint stability. (FBM, 1979)
Frontal
Plane
For normal
function need:
The NCSP will be slightly inverted
STJ eversion occurs at heel strike
STJ remains everted while calcaneus unweights
STJ inversion at heel lift to accommodate external limb rotation,
to assist ankle joint plantarflexion an facilitate sagittal plane
motion
Adequate forefoot to rearfoot alignment to facilitate axes transfer
Sagittal
Plane
For normal
function need:
Adequate first MPJ and ankle ROM
Equal limb length
At heel strike the ankle must plantarflex
During midstance the ankle must dorsiflex
Must be a transfer from the low gear to high gear axis just prior
to heel off
Following heel lift the ankle must plantarflex, the first MPJ must
dorsiflex with first ray plantarflexion
References
see
above
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