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Foot-placement analysis in the elderly-practical considerations
FOOT-PLACEMENT ANALYSIS IN THE. ELDERLY-PRACTICAL CONSIDERATIONS U.S.L. Nayak
and A. Gabell
ABSTRACT Assessment of old people in a gait laboratory requires consideration of certain problems which in younger people either do not arise or are of lesser importance. The problems
Keywords:
Feet, gait analysis,
elderly,
relate to the apparatus used, the footwear worn gait to be observed, These matters are discussed tions offered.
footwear
INTRODUCTION In the Department of Geriatric Medicine we have assessed the gait of 100 elderly persons, using FootPlacement Analysis (FPA), and shall be continuing to use this technique both for research and for clinical purposes. Despite the fact that our Department’s assessment systems were all designed with older people in mind’, we have met with certain difficulties; and we submit our observations in the hope that others may benefit from our experience. It is not our intention to give much detail concerning the technicalities of the apparatus and methods we use or to give results obtained; rather, we shall stress the practical problems which affect the design and performance of assessment procedures in elderly subjects.
APPARATUS We wished to avoid the need for subjects to undress or to have gadgets attached to them or wires trailing behind them, so that their walking could be as normal as possible. We wished also to avoid introducing any abnormal lighting conditions, so photographic methods were excluded. Therefore a walkway was designed (USLN) w h’lc h re q uires only that flexible metallized conducting strips to be affixed to the sole of the subjects’ footwear.
The first two and the last one are the dummy mats, the remaining mats giving a testing surface of 4.2 m in length. The walkway surface is made of brass rods (diameter 2mm) which are secured in troughs (pitch 3mm) of ribbed rubber mat, using loctite glue. The rods are connected in series with electrical resistors and a 4.5V stabilised d.c. power source. There are four individua1 electrical circuits on each mat and one such circuit is shown in Figure 1. Conducting strips of self-adhesive aluminium or copper-coated tape affixed under the subject’s shoes result in two adjacent rods being shorted out when the foot is placed on the walkway during walking. Thus an electrical circuit is completed and a current will flow. A typical voltage variation across a reference resistor (RO) during a stance phase is shown in Figure 2. This voltage signal is fed into our PDP 11/34 digital computer for an on-line data logging (Figure 3). The computer program we have developed processes the data at the end of each walk and presents the footplacement parameters in a form suitable for transfer to clinical report sheets (Figure 4). This form of presentation makes it easy to compare various gait results, e.g. in a before and after treatment situation. Brass
The walkway, which in some ways is similar to and that of Wall et al.*, is modular in construction is made of ten ribbed rubber mats, each 600 x 700 mm. Each mat is glued onto a separate plywood sheet in order to achieve a stable base to the walkway surface. of Geriatric Medicine, B29 SJD, UK.
University
0 1983 Butterworth & Co (Publishers) 0141-5245/83/010069-04 $03.00
rods
(2mmdtol
Alumlnium
1
L.5 V d c stabllised
Design of the walkway
Department Birmingham
and the and solu-
7
of Birmingham,
Figure 1
Walkway
circuit
Ltd J. Biomed.
Eng. 1983, Vol. 5, January
69
U.S.L. Nayak and A. Gabell
Gait analysis:
Heel 4.0 r
Difficulties
off
(a)
r----l
F I o.ot J
“9.0
Heel
t
I----
Toe off
contact
(Touch
(Lift
down)
L
0
1
1
I
o-o
I
I
1
off) a
1
0.5
I
1.0
Time-set Figure 2
inherent
in use of the walkway
The surface, being made of brass rods, could be thought slippery and does appear slippery (although it is ridged). The psychological effect of this is more evident in some subjects than in others. The sense of slip could be increased by the metallised contacts under the shoes. We have to agree with subjects who remark that the surface does not resemble anything on which they have ever walked. The shine of the brass rods was reduced by dipping the rods in a weak solution of chromic acid for a very short duration. However, there were some complaints of glare from the surface, to which reflection from white-painted walls and light-coloured floor-tiles contributed, An attempt was made to reduce the glare by surrounding the walkway with carpeted areas, but this had to be abandoned; although it did reduce glare, loose surface fibres under the sole reduced the efficiency of electrical contact.
Signal generated during a stance phase Walkway
Eventually we checked the level of lighting to which elderly people are accustomed in their own homes and adjusted our lighting accordingly. Their preferred light intensity, measured in the horizontal plane at eye-level, was 7.5 exposure value, which is considerably lower than the intensity found in many areas of the hospital. (b)
m
Figure 3
Layout of walkway
dummy
The level of the walkway is slightly raised (18 mm) above the level of the surrounding floor. Therefore we have raised the ‘floorlevel’ around the walkway by wooden boards and ramps, so that subjects are not required
mats
facility
Birmingham University Department of Geriatric Mediclne Age* (' 70 - 79
BASIC ANALYSIS OF GAIT
NAME
)
.................................................
209 Computer CODE Number ................................. ..1-?9. m Height .............................
S.L. (m.)
76 Age ..................................................
S.T.R.
Velocity (V) .........................l_1c. r&,.-l
S.L.R.
2.00 steps/s Stepping Frequency (S.F.) ................. 0.5
0.58 ill. Step Length (S.L.) ........................
1.5
1.0.
2.0
2.5
2 24 ... %(cOY*r.) Step Length Variability (S.L.V.) ......\ 16.40 q . Step Width (S.W.) ......................... ...90 ... %(Co"ar.) Stride Width Variability (S.W.V.) ...90 O.Y8 s. Stride Time (S.T.) ........................ 0.11 5. Double Support Time .......................
S.L.V. (%) S.W.V. (%)
I
i
D.S.S.T. (%) D.S.V. (%)
I
7-t
Double Support/Stride Time (D.S.S.T.)L~:?!. % 1
10
Step Time Ratio R/I. (S.T.R.) .........?.??. ... Step Length Ratio (S.L.R.) ...........0..98 ...03 ... %(Covar.) Double Support Variability (D.S.V.) .38
Foot contact
:
heel
first/flat foot/toes first/toes only
Clinical report sheet
irp J.Biomrd.Eng.
1983,
Vol. 5,January
30
40
50
60
70
80
* for age. Normal Gait profiles( -*range) Subject's values shown by vertical line.
g:
Check the height chart attached before that
Figure 4
20
step-length
is abnormal.
deciding
90
Gait analysis: U.S.L. Nayak and A. Gabell
to step up onto and down from the walkway. Such a procedure is particularly unwise for those who wear bifocals, which add to the difficulty of changing levels. (Eight-five per cent of the subjects whom we have assessed were wearing bifocals). Some subjects still felt as if they were walking on top of a wide wall, possibly because of the clear line of demarcation between the walkway and the surrounding floor. A sub-floor or inset system would probably be preferable.
(4
The space required by the walkway results in the subjects having to move through a large area without furniture near at hand. This makes some people feel insecure. The spaciousness of a gait laboratory is very different from the size of their living-room. Guidelines for old people’s accommodation, state that a person should not have to move more than three steps before being able to touch a firm object. In theory, parallel bars to serve as grab-rails would help. but they are not familiar objects to most old people, so could actually add to their uncertainty and adversely affect their gait. Also they could hinder an assistant’s approach to a subject who got into difficulties on the walkway.
FOOTWEAR We wish to assess subjects in their own usual footwear as the results so obtained represent how they normally walk. However, some problems have arisen in connection with soles and heels. Soles
contacts; i.e. adhesion does not occur. So subjects have to be asked to brmg a second pair of shoes. Slippery smooth plastic soles will not adhere to any form of contact, and have been worn by several subjects. Soles with metal studs could lead to confusion in recordings of electrical contact; so when these are encountered, masking tape has to be applied to the studded area. Heels Female subjects may present problems with highheeled shoes which have a surprisingly small heelbase area (Figure 5). The increased force per unit area may cause shear-slip of the contacts; therefore these must be checked frequently when multiple tests are being performed. The wearing of high heels usually leads to an increased frequency of stepping (Figure 6). When a general survey is being done, subjects wearing high heels have to be treated as a separate group; and when an individual (of any age) is being assessed, heel-height must be taken into account when results are being interpreted. We were not expecting to find that elderly people wore high-heeled shoes. Gait The two main characteristics of gait which have presented problems may be termed “crossover” and “scuffing”. Crossouer. In 1974, Chodera3 pointed out that forward progression does not involve walking straight ahead. Rather, it consists of walking in a manner resembling a sine wave pattern. Thus alternate steps do not necessarily land on alternate
These sometimes get wet en route to the laboratory, and are then unsuitable for use with adhesive
Groups
2.4 .
6-
matched
for and height
age,sex n=9,
pc
O-01
.
s-
Heel
4-
height
3-
cm.
2-
. . . .
1 -
12
34 females
5
6
1
males
T
60
.
Heel base
.
1.8
40
area
I
I
, .
14 i females
high-heeled
males
Figure 5 Heel height and heel base area of shoes worn by some pilot-study subjects, showing the inverse relationship between these factors
group Figure 6 height,
Variation age 65-85
in frequency
I&-heeled group of stepping
with heel-
J. Biomed. Eng. 1983, Vol. 5, January
71
Gait analysis:
U.S.L. Nayak and A. Gabell
recorded
as
recorded
as
I . line of progression
Figure 7
sides of the mid-line of a walkway (Figure 7). This undulating mode of progression is exaggerated in some older subjects, particularly when vestibular function is impaired; when such impairment is unilateral, the gait often shows a marked veer to one side, so that a subject may spend most of his time on only one side of the walkway. So there are disadvantages in planning circuitry or programming in the assumption that feet will land alternately on the right and left side of the walkway. Our original computer program required modification to accommodate this characteristic. Scuffins. Reduced foot-clearance, which is common in the elderly, results in heel-contact occurring and being recorded part-way through the swing phase, long before any weight is taken on the scuffing foot (scuffing gait type 1, Figure 8). Thus a very long double-support time may be recorded; this is really a double- ‘contact’ time, as the scuffing foot is not usually giving any support during its scuff. A second type of scuffing gait, in which the ‘scuffing’ foot does not maintain contact, presents further problems (Figure 9). In either case, visual observation is also needed in order that computer print-outs can be correctly interpreted, and should be adopted for this. recorded as suppor,t phase
-
true
support
Figure 9 Contact pattern on walkway of bilateral scuffing gait: -, Type 2
CONCLUSIONS From this discussion it will have become clear that, in designing any facility for assessment of the elderly, thought must be given to very basic and simple matters such as avoidance of undressing, maintenance of glare-free lighting at a level lower than is usual in hospital surroundings, avoidance of white walls and light floor-tiles, avoidance of changes in floor-level and of large bare expanses. For foot placement analysis it can be supposed that an inset or sub-carpet walkway system would be preferable for elderly people, possibly one sensitive to pressure rather than contact. However, despite the practical difficulties, our present technique for FPA has proved to be generally acceptable to elderly subjects. ACKNOWLEDGEMENTS The construction of the walkway was commissioned by Professor Bernard Isaacs of the Birmingham University Department of Geriatric Medicine and funded by the West Midlands Regional Health Authority; the computer was generously supplied by the Hayward Foundation; contact material was supplied by Rexham (UK) Limited, and technical assistance was given by Mr E Whateley.
1
---
___
2
----scuff
scuff
REFERENCES
----
L R
---
Normal forward progression in gait
-true
support
Figure 8 Contact pattern on walkway of bilateral scuffing gait:-, Type 1
72 J. Biomed. Eng. 1983, Vol. 5, January
3
.Nayak, U.S.L. Gabell, A., Simons, M.A. and Isaacs, B Measurement of gait and balance in elderly subjects, J. Am. Geriatrics Sot. 1982, 8, 516-520. Wall, J.C., Dhanedran, M., and Klenerman, L., A method for measuring the temporal and distance factors of gait, J. Biomed. Eng. 1976, 11 409-412. Chodera, J.D., Analysis of gait from footprints, Physiotherapy 1974,60,179-181.
and A. Gabell
ABSTRACT Assessment of old people in a gait laboratory requires consideration of certain problems which in younger people either do not arise or are of lesser importance. The problems
Keywords:
Feet, gait analysis,
elderly,
relate to the apparatus used, the footwear worn gait to be observed, These matters are discussed tions offered.
footwear
INTRODUCTION In the Department of Geriatric Medicine we have assessed the gait of 100 elderly persons, using FootPlacement Analysis (FPA), and shall be continuing to use this technique both for research and for clinical purposes. Despite the fact that our Department’s assessment systems were all designed with older people in mind’, we have met with certain difficulties; and we submit our observations in the hope that others may benefit from our experience. It is not our intention to give much detail concerning the technicalities of the apparatus and methods we use or to give results obtained; rather, we shall stress the practical problems which affect the design and performance of assessment procedures in elderly subjects.
APPARATUS We wished to avoid the need for subjects to undress or to have gadgets attached to them or wires trailing behind them, so that their walking could be as normal as possible. We wished also to avoid introducing any abnormal lighting conditions, so photographic methods were excluded. Therefore a walkway was designed (USLN) w h’lc h re q uires only that flexible metallized conducting strips to be affixed to the sole of the subjects’ footwear.
The first two and the last one are the dummy mats, the remaining mats giving a testing surface of 4.2 m in length. The walkway surface is made of brass rods (diameter 2mm) which are secured in troughs (pitch 3mm) of ribbed rubber mat, using loctite glue. The rods are connected in series with electrical resistors and a 4.5V stabilised d.c. power source. There are four individua1 electrical circuits on each mat and one such circuit is shown in Figure 1. Conducting strips of self-adhesive aluminium or copper-coated tape affixed under the subject’s shoes result in two adjacent rods being shorted out when the foot is placed on the walkway during walking. Thus an electrical circuit is completed and a current will flow. A typical voltage variation across a reference resistor (RO) during a stance phase is shown in Figure 2. This voltage signal is fed into our PDP 11/34 digital computer for an on-line data logging (Figure 3). The computer program we have developed processes the data at the end of each walk and presents the footplacement parameters in a form suitable for transfer to clinical report sheets (Figure 4). This form of presentation makes it easy to compare various gait results, e.g. in a before and after treatment situation. Brass
The walkway, which in some ways is similar to and that of Wall et al.*, is modular in construction is made of ten ribbed rubber mats, each 600 x 700 mm. Each mat is glued onto a separate plywood sheet in order to achieve a stable base to the walkway surface. of Geriatric Medicine, B29 SJD, UK.
University
0 1983 Butterworth & Co (Publishers) 0141-5245/83/010069-04 $03.00
rods
(2mmdtol
Alumlnium
1
L.5 V d c stabllised
Design of the walkway
Department Birmingham
and the and solu-
7
of Birmingham,
Figure 1
Walkway
circuit
Ltd J. Biomed.
Eng. 1983, Vol. 5, January
69
U.S.L. Nayak and A. Gabell
Gait analysis:
Heel 4.0 r
Difficulties
off
(a)
r----l
F I o.ot J
“9.0
Heel
t
I----
Toe off
contact
(Touch
(Lift
down)
L
0
1
1
I
o-o
I
I
1
off) a
1
0.5
I
1.0
Time-set Figure 2
inherent
in use of the walkway
The surface, being made of brass rods, could be thought slippery and does appear slippery (although it is ridged). The psychological effect of this is more evident in some subjects than in others. The sense of slip could be increased by the metallised contacts under the shoes. We have to agree with subjects who remark that the surface does not resemble anything on which they have ever walked. The shine of the brass rods was reduced by dipping the rods in a weak solution of chromic acid for a very short duration. However, there were some complaints of glare from the surface, to which reflection from white-painted walls and light-coloured floor-tiles contributed, An attempt was made to reduce the glare by surrounding the walkway with carpeted areas, but this had to be abandoned; although it did reduce glare, loose surface fibres under the sole reduced the efficiency of electrical contact.
Signal generated during a stance phase Walkway
Eventually we checked the level of lighting to which elderly people are accustomed in their own homes and adjusted our lighting accordingly. Their preferred light intensity, measured in the horizontal plane at eye-level, was 7.5 exposure value, which is considerably lower than the intensity found in many areas of the hospital. (b)
m
Figure 3
Layout of walkway
dummy
The level of the walkway is slightly raised (18 mm) above the level of the surrounding floor. Therefore we have raised the ‘floorlevel’ around the walkway by wooden boards and ramps, so that subjects are not required
mats
facility
Birmingham University Department of Geriatric Mediclne Age* (' 70 - 79
BASIC ANALYSIS OF GAIT
NAME
)
.................................................
209 Computer CODE Number ................................. ..1-?9. m Height .............................
S.L. (m.)
76 Age ..................................................
S.T.R.
Velocity (V) .........................l_1c. r&,.-l
S.L.R.
2.00 steps/s Stepping Frequency (S.F.) ................. 0.5
0.58 ill. Step Length (S.L.) ........................
1.5
1.0.
2.0
2.5
2 24 ... %(cOY*r.) Step Length Variability (S.L.V.) ......\ 16.40 q . Step Width (S.W.) ......................... ...90 ... %(Co"ar.) Stride Width Variability (S.W.V.) ...90 O.Y8 s. Stride Time (S.T.) ........................ 0.11 5. Double Support Time .......................
S.L.V. (%) S.W.V. (%)
I
i
D.S.S.T. (%) D.S.V. (%)
I
7-t
Double Support/Stride Time (D.S.S.T.)L~:?!. % 1
10
Step Time Ratio R/I. (S.T.R.) .........?.??. ... Step Length Ratio (S.L.R.) ...........0..98 ...03 ... %(Covar.) Double Support Variability (D.S.V.) .38
Foot contact
:
heel
first/flat foot/toes first/toes only
Clinical report sheet
irp J.Biomrd.Eng.
1983,
Vol. 5,January
30
40
50
60
70
80
* for age. Normal Gait profiles( -*range) Subject's values shown by vertical line.
g:
Check the height chart attached before that
Figure 4
20
step-length
is abnormal.
deciding
90
Gait analysis: U.S.L. Nayak and A. Gabell
to step up onto and down from the walkway. Such a procedure is particularly unwise for those who wear bifocals, which add to the difficulty of changing levels. (Eight-five per cent of the subjects whom we have assessed were wearing bifocals). Some subjects still felt as if they were walking on top of a wide wall, possibly because of the clear line of demarcation between the walkway and the surrounding floor. A sub-floor or inset system would probably be preferable.
(4
The space required by the walkway results in the subjects having to move through a large area without furniture near at hand. This makes some people feel insecure. The spaciousness of a gait laboratory is very different from the size of their living-room. Guidelines for old people’s accommodation, state that a person should not have to move more than three steps before being able to touch a firm object. In theory, parallel bars to serve as grab-rails would help. but they are not familiar objects to most old people, so could actually add to their uncertainty and adversely affect their gait. Also they could hinder an assistant’s approach to a subject who got into difficulties on the walkway.
FOOTWEAR We wish to assess subjects in their own usual footwear as the results so obtained represent how they normally walk. However, some problems have arisen in connection with soles and heels. Soles
contacts; i.e. adhesion does not occur. So subjects have to be asked to brmg a second pair of shoes. Slippery smooth plastic soles will not adhere to any form of contact, and have been worn by several subjects. Soles with metal studs could lead to confusion in recordings of electrical contact; so when these are encountered, masking tape has to be applied to the studded area. Heels Female subjects may present problems with highheeled shoes which have a surprisingly small heelbase area (Figure 5). The increased force per unit area may cause shear-slip of the contacts; therefore these must be checked frequently when multiple tests are being performed. The wearing of high heels usually leads to an increased frequency of stepping (Figure 6). When a general survey is being done, subjects wearing high heels have to be treated as a separate group; and when an individual (of any age) is being assessed, heel-height must be taken into account when results are being interpreted. We were not expecting to find that elderly people wore high-heeled shoes. Gait The two main characteristics of gait which have presented problems may be termed “crossover” and “scuffing”. Crossouer. In 1974, Chodera3 pointed out that forward progression does not involve walking straight ahead. Rather, it consists of walking in a manner resembling a sine wave pattern. Thus alternate steps do not necessarily land on alternate
These sometimes get wet en route to the laboratory, and are then unsuitable for use with adhesive
Groups
2.4 .
6-
matched
for and height
age,sex n=9,
pc
O-01
.
s-
Heel
4-
height
3-
cm.
2-
. . . .
1 -
12
34 females
5
6
1
males
T
60
.
Heel base
.
1.8
40
area
I
I
, .
14 i females
high-heeled
males
Figure 5 Heel height and heel base area of shoes worn by some pilot-study subjects, showing the inverse relationship between these factors
group Figure 6 height,
Variation age 65-85
in frequency
I&-heeled group of stepping
with heel-
J. Biomed. Eng. 1983, Vol. 5, January
71
Gait analysis:
U.S.L. Nayak and A. Gabell
recorded
as
recorded
as
I . line of progression
Figure 7
sides of the mid-line of a walkway (Figure 7). This undulating mode of progression is exaggerated in some older subjects, particularly when vestibular function is impaired; when such impairment is unilateral, the gait often shows a marked veer to one side, so that a subject may spend most of his time on only one side of the walkway. So there are disadvantages in planning circuitry or programming in the assumption that feet will land alternately on the right and left side of the walkway. Our original computer program required modification to accommodate this characteristic. Scuffins. Reduced foot-clearance, which is common in the elderly, results in heel-contact occurring and being recorded part-way through the swing phase, long before any weight is taken on the scuffing foot (scuffing gait type 1, Figure 8). Thus a very long double-support time may be recorded; this is really a double- ‘contact’ time, as the scuffing foot is not usually giving any support during its scuff. A second type of scuffing gait, in which the ‘scuffing’ foot does not maintain contact, presents further problems (Figure 9). In either case, visual observation is also needed in order that computer print-outs can be correctly interpreted, and should be adopted for this. recorded as suppor,t phase
-
true
support
Figure 9 Contact pattern on walkway of bilateral scuffing gait: -, Type 2
CONCLUSIONS From this discussion it will have become clear that, in designing any facility for assessment of the elderly, thought must be given to very basic and simple matters such as avoidance of undressing, maintenance of glare-free lighting at a level lower than is usual in hospital surroundings, avoidance of white walls and light floor-tiles, avoidance of changes in floor-level and of large bare expanses. For foot placement analysis it can be supposed that an inset or sub-carpet walkway system would be preferable for elderly people, possibly one sensitive to pressure rather than contact. However, despite the practical difficulties, our present technique for FPA has proved to be generally acceptable to elderly subjects. ACKNOWLEDGEMENTS The construction of the walkway was commissioned by Professor Bernard Isaacs of the Birmingham University Department of Geriatric Medicine and funded by the West Midlands Regional Health Authority; the computer was generously supplied by the Hayward Foundation; contact material was supplied by Rexham (UK) Limited, and technical assistance was given by Mr E Whateley.
1
---
___
2
----scuff
scuff
REFERENCES
----
L R
---
Normal forward progression in gait
-true
support
Figure 8 Contact pattern on walkway of bilateral scuffing gait:-, Type 1
72 J. Biomed. Eng. 1983, Vol. 5, January
3
.Nayak, U.S.L. Gabell, A., Simons, M.A. and Isaacs, B Measurement of gait and balance in elderly subjects, J. Am. Geriatrics Sot. 1982, 8, 516-520. Wall, J.C., Dhanedran, M., and Klenerman, L., A method for measuring the temporal and distance factors of gait, J. Biomed. Eng. 1976, 11 409-412. Chodera, J.D., Analysis of gait from footprints, Physiotherapy 1974,60,179-181.