GROUND REACTION FORCE IN
MORTON’S FOOT
MORTON’S SYNDROME
Maclean Graydon
The root of all foot problems?
Supervisor: Dr. Pat Costigan
WHY YOUR FEET REALLY HURT
MORTON’S FOOT VS. “NORMAL” FOOT
“After 35 years of treating these problems as a
foot doctor, I absolutely believe that military
men/women, who get March fractures, also have
a Morton’s Toe, (Long Second Toe) the vast
majority of time.”
“I would bet anything that if the x-rays were reexamined of the men, who got a March fracture it
would show that the majority of them also had a
Morton’s Toe. It would be of great benefit to our
armed forces for the military doctors to consider
this relationship between the first metatarsal
bone and march fracture, and treat it before it
happens”
1st metatarsal head behind
3rd (short 1st met shaft)
1st metatarsal head slightly
behind 2nd
www.whyyourfeetreallyhurt.com
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THE GREEK FOOT
MORTON’S THEORIES
MORTON’S THEORIES
MORTON’S THEORIES
The “Greek” foot was believed to be beautiful and
desirable (Greek and Roman art and sculpture)
Morton challenged belief that this type of foot
was anatomically preferable
Relative shortness of the first metatarsal
leads to a multitude of foot problems and
poor mechanics
One of the requirements of ideal foot function is
an equidistance of the head of the first and
second metatarsals from the heel
axis of
leverage
He called this the
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MORTON’S THEORIES
The centre of transmitted weight runs from the
heel to an area between the 2nd and 3rd
metatarsals
He called this the
STATICOMETER
axis of balance
MORTON’S EQUIPMENT
Staticometer (2 platforms, each with 3 sections
that measured load under heel, medial FF and
lateral FF)
Roentgenogram (x-ray)
MORTON’S THEORIES
The first metatarsal is the inner pillar of support
A short or hypermobile first would allow the foot
to pronate and pressure would increase under the
2nd metatarsal head
This would cause 2nd metatarsal hypertrophy
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CRITICAL ANALYSIS
Of Morton’s Theories
CRITICAL ANALYSIS
THEORIES
OF
MORTON’S
Morton relied on intuition
Rudimentary measurements
Didn’t have the benefit of digital equipment
Small sample sizes
Studies performed on healthy college students
CRITICAL
ANALYSIS OF
MORTON’S
THEORIES
Measurement of metatarsal length:
Measured from talonavicular joint to end of 2nd
metatarsal bone on radiograph. Transverse line
drawn at right angle from this point and then
distance to 1st metatarsal bone measured
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CRITICAL ANALYSIS OF MORTON’S
CRITICAL
THEORIES
THEORIES
Morton’s measurement
AND
CLAPHAM
MORTON’S
This technique does not allow for divergence of
the 1st and 2nd metatarsals (large intermetatarsal
angle a.k.a. metatarsus primus varus)
Hardy and Clapman (1951) showed that
metatarsus primus varus distorted Morton’s
method of transverse line measurement
Morton’s x-ray measurement
MORTON VS. HARDY
ANALYSIS OF
METHOD
Hardy&Clapham’s
measurement
CLINICAL IMPLICATIONS
Difficult
to apply the measurement for
determining Morton’s foot to the clinic as
it requires an x-ray machine
Various methods in the literature have
been unreliable
Measuring metatarsal length by palpation
is more difficult than one might think
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MORTON’S THEORIES: WHAT THE
LITERATURE SAYS
Few studies have substantiated Morton’s
hypotheses on second metatarsal hypertrophy
and stress
In fact, most studies that have used proper
scientific methods and large enough sample sizes
have contradicted his findings
However …
MORTON’S THEORIES
What the literature says
IN SUPPORT OF MORTON’S THEORIES
IN SUPPORT OF MORTON’S THEORIES
Cavanagh & Rogers (1987)
107 barefoot subjects on capacitance mat
Forefoot peak pressures were usually located
under the second metatarsal head
Higher peak magnitude of pressure under the 2nd
metatarsal head in feet with Morton’s syndrome
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IN SUPPORT OF MORTON’S THEORIES
Davitt et al (2005)
An association between functional second
metatarsal length and midfoot arthrosis
Study group: 2nd met 18.6% > 1st met
Control group: 2nd met 4.1% > 1st met
RELATIVE LENGTH OF
(DAVITT ET AL 2005)
1ST METATARSAL
IN SUPPORT OF MORTON’S THEORIES
Chuckpaiwong et al (2007)
Ratio of 1st vs. 2nd metatarsal = .80 in feet with
proximal metatarsal fracture
However ratio was .95 in feet with non-proximal stress
fractures of the 2nd met
Proximal stress fractures have higher risk of nonunion, have longer recuperation period, more often
require surgery than distal fractures (due to higher
load and rate)
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2 PART STUDY
Part 1
Static foot measurements to determine normal
metatarsal length ratios
MORTON’S FOOT STUDY
QUEEN’S UNIVERSITY DEPT. OF
REHABILITATION
Design a clinical tool to be used by pedorthists
Part 2
Dynamic gait study to show differences in gait
between Morton’s feet and normal feet
Gain knowledge of forefoot mechanics during
propulsion and establish whether there are
differences in feet with Morton’s syndrome
MY HYPOTHESES
MY HYPOTHESES
Part 1
Morton’s syndrome will be defined as a 1st
metatarsal that is approximately 80% as long as
the 2nd metatarsal
20-30% of feet will have Morton’s syndrome
Part 2
The lever arm (1st ray) is shortened on the medial
side of the arch
The 1st MTP joint dorsiflexes too early in the gait
cycle
The effect of the windlass mechanism and the
intrinsic foot muscles is reduced in Morton’s feet
The foot will continue to pronate into late-stance
instead of re-supinating causing a medial toe-off
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WINDLASS MECHANISM
PROPULSION
WHAT WE HOPE TO PROVE – AND
GROUND REACTION FORCES
HOW WE HOPE TO PROVE IT
This medial toe-off should be measurable by
increased medial shear force (GRF in m-l
direction) as well as medial deviation of the CofP
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G.R.F. AT HEEL-OFF
Shear force in the propulsion phase is the key to
the study
Other studies with Morton’s feet examine
pressure on the 2nd metatarsal head
They have used pressure mats or insoles, not
force plates
STUDY DESIGN
STUDY DESIGN – PART 1
STUDY DESIGN – PART 1
1st measure – Clinical Tool
Palpate navicular tubercle, distal tip of 1st and 2nd
metatarsal shafts
Place pen mark on skin
Take digital photo from 30cm above foot
Measure distance between points on photo - using
GIMP software
8 subjects – repeat 10 times to acquire stable mean
for error
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STUDY DESIGN – PART 1
STUDY DESIGN – PART 1
Trial 1
Subject
Mac
Dave
Jessie
Lori
GG
Sheila
Meg
Leane
STUDY DESIGN – PART 1
Distance (mm)
1st met
2nd met
246.9
291.8
248.3
198.2
210.7
220.4
247.3
201.6
Ratio
268.7
316.7
281.4
232.1
247.1
242.9
274
228.3
0.918
0.921
0.882
0.853
0.852
0.907
0.902
0.883
STUDY DESIGN – PART 1
Repeat photo measurement on 60 subjects in
clinic
Measure sub-section twice – one week apart to
establish reproducibility
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STUDY DESIGN – PART 2
1st measure
GRF measured on force plate
Measure GRF in all 3 directions (x,y,z) but most
concerned with medio-lateral (x) shear forces
at heel-off (propulsion phase)
GROUND REACTION FORCES
STUDY DESIGN – PART 2
2nd measure
Skin markers: measure kinematics of foot
Basic movements to synchronize with force plate
data
Identifies heel-off
Calculate 1st MTPJt angle during propulsion
phase
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IRED MARKERS
250
1000
900
200
800
700
150
600
100
500
400
50
x-grf
z-force
extension angle
300
200
0
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49
-50
heel height
100
0
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OUTCOME MEASURES
STUDY DESIGN
Metatarsal length ratio
1st MTPJt angle at which max vertical grf is generated
Medio-lateral shear force at heel-off
Medio-lateral shear force at max vertical grf point
Deviation of center of pressure
Regression Analysis
Medial shear force versus length ratios
Centre of pressure versus length ratios
STUDY DESIGN
Regression Analysis
1st MTPJt angles versus length ratios
Will help determine if there are differences in
sagittal plane mechanics
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SUMMARY
DISCUSSION
Take several clinical foot measurements
Measure points on digital photographs
Measure kinetics and kinematics of gait
Use statistics to show whether different foot
types have similar characteristics at various
points in the gait cycle
Can we easily identify Morton’s syndrome in a
clinical setting?
Do feet with Morton’s syndrome have different
gait characteristics?
Can footwear, orthotics or surgery correct these
differences?
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