PLANTAR

PRESSURE

MEASUREMENTS

ULCERATION T.

DUCKWORTH,

A.

IN J. M.

From

Static

and dynamic

measurements

diabetic patients with neuropathy, and normal

neuropathy subjects

THE

BOULTON,

the Royal

R.

pressure

to hospital

that complications about 20% of (Bessman

least,

patients so that fication previous number

of

problems

those out in in the

perception

feet

skin

be

in

resistance,

the

great

and

the

The

toes, ankle

similar series of non-diabetic

had

the metatarsals, ofdiabetic subjects.

some time developed pressures at the ulcer

have

a in

and those

ulceration sites.

under

© 1985 British 030l-620X/85/1034

VOL.

67-B.

No.

reprints

should

Editorial $2.00

I. JANUARY

be sent

Society

had

perception the occurneuropathy measured

abnormally with

only feet

of a

7% ofa series which had at

and

T. Joint

Duckworth. Surgery

the

use

this

predictive

groups

that

and

high

bedside investigations, vibration perception

useful

dynamic

in identifying

publication

A and

of

41

divided

three

being described with

et al. diabetic

Group A and not dependent

were

more

feet, while no history

the

fully

1983).

in a

Group

A I 3 of foot

the remaining of foot ulceration.

28

who were and type of

any evidence of disease, or foot

Group B each had 20 patients on insulin. Group C consisted

healthy non-diabetic subjects matched with Groups B for age and sex; no subject in this group had

a mean

The

1982).

in

groups,

neuropathy; of neuropathic

a history

22 had

subjects

into

glycosuria or a family history of diabetes. In each group there were 29 men and

under have

into

pressure

METHODS non-diabetic

these patients had peripheral vascular

neuropathy,

ulceration. who were

of foot

of 41 diabetic patients, A for age, sex, duration

consisted with Group none

diabetic

studies

(Boulton

involving (Group A2) B

that pressure the specific areas

to ulceration. an investigation

AND and

investigated. They were criteria for this grouping

Group

those

and

role.

diabetic

ulceration patients

with no areas of

of high pressure better types of measurement

simple of the

be

PATIENTS

of4l

of subjects:

patients detected

spot was detected on of the foot which might

areas both

might

of static

Eighty-two

the been

age

12 women,

of 52 years.

measurement

of the

distribution

of

foot uses an optical method, details fully described elsewhere (Duckworth

Essentially,

the

subject

stands

or walks

pressure of which et al. on a glass

plate which is illuminated at its edges by strip lights and is covered by a sheet of soft white plastic. At the points where

1985

high-pressure all the areas

alone,

diabetes; by high

1 7%

abnormally

to Professor

of Bone

out on three

at risk of foot ulceration, might then be used to identify

previous

index.

T. Duckworth, FRCS, Professor of Orthopaedic Surgery A. J. M. Boulton, MRCP, Senior Lecturer R. P. Betts, M Med Sci, PhD, CEng, MIEE, Principal Physicist C. I. Franks, PhD, CEng, MIEE, Principal Physicist J. D. Ward, MD, FRCP, Consultant Physician Royal Hallamshire Hospital, Sheffield 510 2JF. England. for

WARD

the foot which were prone The present paper describes

with

Requests

carried

consisted of 41 patients these (Group A 1) had

Valsalva

the

compared

controls All

J. D.

It was concluded as measurement

such

OF

Sheffield

been

matched

technique,

under

if those

pressure

In a series of 41 patients with diabetic et al. 1983) 5 1 % of the feet, when

pedobarographic

case some,

motor conduction nerves, vibration

(Boulton pressures

I. FRANKS,

Hospital,

patients studies

investigations

the vibration significantly with

these investigations threshold correlated most rence of foot ulceration.

Of

a

the that

avoided

at risk.

that study included median and peroneal

threshold

response,

are

C.

threshold

recognised

et al. 1983) described which might be helpful

(Boulton factors which

the of

at risk could be identified, measures, such as modibe taken in good time. A

are particularly appropriate preventive of footwear, could publication of predictive

It was

is particularly It is possible

could

who

detecting carried velocity

these

BETFS,

tended to show multiple the importance of making the foot from ulceration.

be produced by deformity in the pattern of weight-

bearing (Treves I 884), and this when the sensibility is disturbed. at

affecting all admissions

1982).

long ago that ulceration could of the foot causing changes

P.

PREVENTION

FOOT

but in some cases a particularly methods were needed to reveal

be considered to be at risk. The dynamic measurements than the static measurements. Our results indicate when seeking to devise suitable means of protecting

diabetics

DIABETIC

Hallamshire

of foot

THE

(with and without a history of ulceration), diabetic as confrols. In many cases both techniques of measurement

abnormally high pressure under the foot, only one of the tests and sometimes both

It has been estimated foot now account for

AND

the

plastic

sheet

is pressed

into

contact

with

the 79

80

T. DUCKWORTH,

glass

plate

within

by the foot,

the

glass

light

by total

A.

which

internal

J.

M.

BOULTON,

is normally

R.

contained

reflection

escapes

from

The grey image of the sole is detected television camera and the pressure

by a at any

point under measuring

the foot can be determined automatically the intensity of the image at that

by point;

causing

the image

the foot make contact. image, the analogue alternate converted

frame from to digital

stored

in

Table

as the various

In order information

to analyse the contained

the television camera form. The digitised

microcomputer

the

I. Results

level in the output from stand on the plate to or may walk across the

to change

of the foot

pressure

studies

parts

of

changing in every

and

for the four

may

groups

I. FRANKS,

through

are

J.

the

be

indicating

D.

WARD

footstep

calculated

for

and

then

each

area

all the pressure/time

are

moment.

On

combining

the

right

10 sample frames from each showing a series of for the footprint at that

is a composite

all the recorded

frame

frames.

Below

this,

and

the

the ability

graphs

form, in this

colour-coded illustration

are

normally

graphs

have

been

to detect

abnormal

numbered

feet

using

static

and/or

dynamic

Normal on static but abnormal on dynamic tests

Abnormal dynamic test

1

6

21

A2: neuropathy no ulcers

56

19

14

7

12

26

B: no neuropathy

81

23

22

7

7

30

C:

82

10

11

5

3

15

Static results the table on

from two patients the basis of having

continuously an image

of

in Group B and I 2 in Group C were not an abnormal dynamic result, although

displayed on a colour television the foot with 16 colour

corresponding

to a given

plantar

Duckworth 1983). The system is currently vertical-force transducers,

pressure

monitor as levels, each (Franks,

Betts

and

corner

of the

ments sum

glass

calibration of the

During

dynamic

achieved

studies

by

transducer output.

outputs

For

by outputs of

the

sum

with

the

integrated

by the use ofa simple “joystick” of interest selected are the heel, toe

and

the

with frame

comparison

other

toes.

measure-

comparison

by

In the dynamic studies, information go to make up a complete

great

static

a frame

combined to form a composite whole foot; areas ofinterest may

the

by the use of four one under each

plate.

transducer

performed

which

pressure is

force

calibrated mounted

of

body calibration

of

the

from footstep

pressure

is

force

the frames can be

on this

of the image

control. The usual areas the five metatarsal heads, The

variation

of peak

such was

patient available

from

each

of these

two

on either or static

groups

is included

in

RESULTS measurements the horizontal

for the line at

I .75 kgcm These results

2

point results,

the forefoot. Table I summarises these two from Group B and 1 2 from Group C

under but

were

not

2 shows

the threshold peak pressure

the

for

the four

groups

points

recorded

on

ments the

representing are of the

pressure reached at any this case, at any time

results the

dynamic

line

by

above

line

this

at All

show

peak

2

remained Table

THE

JOURNAL

above this I summarises OF BONE

AND

peak

and, in a single

represents represented

pressures

the foot greater than this threshold, and the upper the diagram has been used to illustrate the length that the pressure during one footstep.

Again, the

the forefoot course of

I 0 kgcm the patients

had

measure-

diagram.

diagram

point under during the

horizontal of normality.

points

of

as a scatter

footstep. The the threshold the

of normality. recorded at any

available.

Figure

(light)

image

One result

Figure 1 shows the results of static four groups as a scatter diagram,

weight.

pressure

be defined

the

available. no static

methods

abnormalities

Normal on dynamic but abnormal on static tests

on

in

by hand.

15

controls

selected

produced

20

+

by

but for the purpose of photographic paper they are shown in black only

22

Al: neuropathy ulcers

produced

areas of interest are outlined. Below this are the peakpressure/time curves for the selected areas of interest. The iso-pressure contour lines, the areas of interest and

Abnormal dynamic

Group

curves

studies. On the left there the total number recorded, isopressure contour lines

Total number of feet

Abnormal static test

is

on the monitor. The raw and on a floppy disc system and for the patients’ records. plotter outputs for dynamic

“Missed”

on test

of interest

displayed together analysed data are recorded plotted in a form suitable Figures 3 and 5 are typical

the peak-pressure/time

signal is first information is

memory

C.

automatically

that point. monochrome

plate,

BETTS,

pressure

the glass and is scattered by the plastic sheet, producing an image of the foot which can be seen from below. The greater the applied pressure, the brighter the image at

this is represented as a voltage the camera. The patient may produce a static pressure profile,

P.

under part of of time

threshold level these results. JOINT

SURGERY

PLANTAR

PRESSURE

MEASUREMENTS

AND

THE

PREVENTION

OF

ULCERATION

IN

Figure 1-Scatter recorded in the

5. .

Figure recorded Above

THE

DIABETIC

diagram three groups

showing from

81

FOOT

the peak pressures static measurements.

2-Scatter diagram showing the peak pressures in the three groups from dynamic measurements. 10 kgcm2 the results represent the length of time during which the pressure exceeds this level.

4.

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A1

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A2 Fig.

VOL.

67-B.

No.

I. JANUARY

1985

C I

A1

A2

B Fig.

2

C

82

T. DUCKWORTH,

Table methods indicating and/or

I also

shows

of pressure the ability dynamic

A.

J. M.

a comparison

BOULTON,

between

recording for to detect abnormal

the

R.

P.

the two

BET1’S,

sole

of the

slightly

four groups, feet using static

on

foot,

longer

testing

was

circulation

Case an

I. A 45-year-old

for two of

white

insulin-dependent years.

male

diabetic

There

examination

deformities

CASE

was he

and

police

for

no history

had

no callosities.

no

officer,

I 1 years,

was

the

weight with

ofthe referable

no obvious

level.

of pressure

At the time

metatarsal

the

prominence

feet,

no

Case history

in the

The

J. D.

WARD

it was

noted

that

There

was

cotton-wool 25

and

units

(the

pin-prick normal

studies head

static

(Fig. of

studies

under

2. A 45-year-old

the

(Fig.

the

metatarsal

sensory the is

was

disturbance

vibration 2 to

3) showed

that

right

reached

foot

4) also

right

white

of insulin-dependent

foot,

showed

but

housewife, diabetes

1.2

perception 10

units).

The

the an

in this

pressure an

under

abnormally

abnormally

case

under

72 kg,

had

high the

fifth

B.4

weight and

at

symptoms

as

i.

a 30-year

of neuropathy

.2

CCS)

3

Case k/

but range

TI*

0

second

head.

5.S

Fig.

the

no detectable

normal.

pressure

level

been

usual.

metatarsal

high

feet. to

second

neuropathy

91 kg. had

diabetic

ofulceration

symptoms There

REPORTS

although

appeared

Dynamic ILLUSTRATIVE

I. FRANKS,

than

with

threshold

methods.

C.

,

1 a diabetic patient with neuropathy no history of ulceration (Group A2).

Figure 3-Dynamic the right foot: metatarsal head

pressure pressure exceeded

but

measurements in under the second the normal range.

Figure 4-Static measurements in both feet: pressure under the fifth metatarsal head in the right foot has exceeded the normal range reaching a value of 2.3 kgcm2.

Fig.

4

THE

JOURNAL

OF BONE

AND

JOINT

SURGERY

for

PLANTAR four

years.

There

examination and

feet.

the

sole.

The

were

were was

head

to pin-prick

no history

complained

feet

There

metatarsal 27 units.

was

she

PRESSURE

undeformed a slight

on the

foot.

on

Dynamic

pressure

studies

high

level,

first which

metatarsal was

head not

prominent

callosity

There

was

right

under

lower

ankle

(Fig.

5) showed

that

right

foot

reached

in the

static

the

pressure

peak

6)

tendency

in

ULCERATION

where for

all the

IN

pressure

greatest

THE

levels

DIABETIC

were

loading

to

normal.

be

on

the

83

FOOT Figure lateral

6 shows border

DISCUSSION It is hardly

pulses

possible,

and

out pedobarographic those

pressure

patients

identified,

an abnormally

test

measurement

Fig.

of

who

are

for example vibration

probably

ofall

diabetic

particularly

by means

perception

to carry

not necessary,

screening

at

patients. risk

of the simple

threshold,

then

S

Case

2. also

from

Group

A2.

Figure 5-Dynamic pressure measurements in the right foot: pressure under the first metatarsal head has exceeded the normal range. Figure 6-Static measurements the peak of pressure (right fifth metatarsal head but limits.

Fig.

VOL.

67-B,

No.

I, JANUARY

1985

6

a

during

standing.

loss was

side.

(Fig.

OF

second

threshold the

of legs

sensory

perception although

PREVENTION

areas the

no detectable

ofthe

reflected

THE

At the time

no obvious

normal,

the

feet.

in both

the vibration

appeared

to palpate

the

with

but

circulation

ofthe

AND

sensation

non-tender

right

difficult

under

ofulceration of a burning

or cotton-wool, The

MEASUREMENTS

in both feet: foot) is under the is within normal

can

clinical pressure

If be

84

T.

measurements the feet which

DUCKWORTH,

A.

J. M.

may be useful in identifying are specially vulnerable and,

more

are

pathy

and

common

that

in patients

all

almost

with

patients

diabetic

of

which correlate well The present paper is analysis, and to is likely to give the

most useful information. The equipment is sophisticated so that its use can only be justified if it can be shown to have advantages over simple clinical judgement. Similarly,

the

more

complicated

pressure measurement were proved to have less-complicated The

technique

have been

for

of static

the

static

I. FRANKS,

and

A

dynamic

were

not

case Even

in the when

obvious

on clinical

two there

ment

of the level

could

be made

likely

the site of previous heads were at risk,

abnormal, published

of patients

who

should

because the distribution series were somewhat

upper levels, suggesting individuals were in fact symptom-free of 10 kgcm

at the 2 for

curves in skewed towards

that some not normal,

time the

of the although

of testing. dynamic

similarly been chosen on the basis lished results (Betts et al. I 980b). Using patients

with

these thresholds, neuropathy

and

be considered Betts’ the

“normal” all were

dynamic. “missed”

the

static

the

of

pub-

may fail revealed

in Group a history

measurement

Similarly, in Group 12 of the 19 feet

previously

Al, that is those of ulceration, 20

but

dynamically and the dynamic “missed” detected statically. Reference to Table every group there were a number of

of

Group

C who had abnormally both of the measurement

allocated

to Group

on the

measurement be abnormal

7 of the 14 feet I shows that in feet which were

the dynamic were only

abnormal by one of the two techniques It is noticeable that there were or

normal

A2 the static indicated to

abnormal on both the static and ments but also some feet which

measuredetected as

of measurement. some subjects

in

high pressures on either techniques. Patients were

C if they

denied

having

any

symp-

toms related to their feet and if they had never had any operative procedure on the feet. Subsequent examination of the Group C subjects showed a number to have marked callosities and these showed as abnormal on the scatter

diagrams.

If these

patients

failed

were

excluded

from

site

patients, under the

reason

therefore,

areas in the feet of no history of ulcera-

sites

the site metatarsal

sometimes in addition

showed to those

ulceration. the dynamic so;

of previous

The

the

perhaps,

foot

with a with

at which

ulceration

in the future.

demonstrated failed to do to demonstrate

often

level has

these 20, only 14 were found to be abnormal on the static measurements, ie the static method “missed” six abnormal feet. On the other hand, one foot was found to be on

always

The threshold measurements

of the total of 22 feet were found to have an abnormally high pressure level on the dynamic measurements;

abnormal

measurements to be at risk

maps

It may

to represent

mate

number

contour

the

reached

points in the group ulceration correlated

ulceration.

most was

the

pressure

be inferred that similar high-pressure those patients with neuropathy but are

reports. no assess-

of the

In pressure

level

was

case

of the

the site ofprevious

tion

measurements

of a threshold

This

be

abnormality of 1.75 kgcm2. The justification for this lies in previously published results in the form of distribution curves for normal patients (Betts et al. l980a). This threshold level may indeed slightly underesti-

basis

and

of pressure which might purely on clinical grounds.

to occur

the

examination.

patients illustrated in the was an obvious prominence,

is likely

on

WARD

No attempt was made in this study to correlate the results of pedobarographic measurement with clinical judgement of “high spots”, although it was frequently noted that high-pressure points detected by the system

of

tabulated

J. D.

group, the contrast between this group B would of course be more marked.

Inspection

pressures.

pressure

C.

shows that the high-pressure previous history of diabetic

could only be justified if it a significant advantage over the

measurement

results

of

BEll’S,

the “control”

neuro-

a history

P.

Groups

ulceration. It high pres-

with

ulceration show high-pressure areas with the site of previous ulceration. an attempt to refine the pedobarographic define which type of measurement

R.

still further in particular,

which part of the foot is likely to develop has previously been shown that abnormally sures

BOULTON,

of abnormally heads. The other which

high dynamic

metatarsal corresponded

When extra measurements

heads to

metatarsal almost

them, whereas the static system in some cases the static system even those areas which had been

ulceration.

why

either

to demonstrate by the other

one

of the

two

techniques

high-pressure areas which are always clear. During the of static pressures the patient is normally on both feet and may, consciously or subconoff-load one foot, particularly if a high-pressure

measurement

standing sciously,

area is sensitive. problem in those the other hand, of proprioception loading whilst

is not

Clearly, patients

this with

might marked

well be sensory

less of a loss. On

in this latter group of patients, problems and balance may lead to asymmetrical standing. It is also, of course, quite

possible that in the walking foot, changes in shape and relative loading may occur which would not be evident in the standing position. Similarly, the fact that some highpressure areas are not may be due to voluntary part

of

the

foot

picked up on or involuntary

which

would

the

dynamic off-loading

otherwise

be

print of a

taking

an

abnormally high load. This off-loading could take place partly to the other foot or, more likely, within the foot. This phenomenon is certainly seen in some painful conditions ofthe foot when a relatively low pressure area at

a painful

patient normally. way

site

is asked

may to

be try

revealed

as

ignore

the

to

a high pain

It is proposed to use the measurements to design suitable protective footwear,

nary results to equalise

spot and

if the to

walk

made in this and prelimi-

with insoles have suggested that it is possible the loads and redistribute the pressures under THE

JOURNAL

OF

BONE

AND

JOINT

SURGERY

PLANTAR

the

(Boulton

foot

PRESSURE

al.

el

already 1983)

been used in but these tended

dynamic

measurements

example,

spot

under

a static one

Similar

Our

techniques

metatarsal

the

have

would

could lead to dangers. may reveal a high then

be to the

other hand, metatarsals

increasing

others.

might well show are, in fact, already

their

that

It would

that taking

several high

of these loads and

loading

in Case I illustrates sites were different It should be scribed

the

suggest

measures

might prove critical. The patient this point in that the high-pressure on the static and dynamic studies. emphasised that the technique de-

the

reaction

at

the

interface

sole

ULCERATION

of the

consistency the

between

and surgery

foot at the

the

give

dynamic system be made

THE

DIABETIC

a flat

surface.

interface

design

85

FOOT

The

shape

of course,

between

currently the shoe,

some

should

It would determine

and

is therefore within

refine may

IN

of the sole of the shoe will,

pressures

further

to design an orthosis to off-load the pressure other heads. The dynamic measurement, on

under

and

OF

The study measurements

suggest

is

loading

head

PREVENTION

(Reed 1974, either static or

results

system alone measurement

THE

there

no increased logical those

1984).

AND

designing footwear to be based on alone.

that the use ofeither For

MEASUREMENTS

foot

and

being extended in the belief that

of protective indication

as

shoes to

insole. to take this will

and

when

and

modify

insoles

corrective

be considered.

appear fully

from

all

the

these danger

findings areas,

that,

in order

both

static

systems of measurement are required. used here, both types of measurement at the

same

to and

With the can readily

examination.

This work was supported by the Marjorie Parsons Fund. We thank Drs D. R. Cullen and F. J. Flint study patients under their care.

Diabetic Research for permitting us to

REFERENCES Bessman AN. Foot 1982;8( 1): 32-7. Bells

Bells

in

the

diabetic.

RP, Franks CI, Duckworth T, Burke J. Static pressure measurements in clinical orthopaedics. Comput 1980a; I8(5):674-84.

Compr and

dynamic Med Biol

Ther

Duckworth T, Betts pressures under

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