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Electromagnetic phenomena in bone
Electromagnetic
phenomena
in bone
Dear Sir, Attempts have been made to understand the physical properties of bone, both in uitro and in rho. These studies have concluded that bone is a heterogeneous, viscoelastic, complex fibrous, anisotropic tissue, its properties depending upon geometry and dimensions and also on density, rigidity, fluidity, mineral and ash content, crystallinity, microhardness, position and orientation of the fibres, hydration, temperature and anisotropy I-3 . The growth and remodelling pattern of bone as a coniequence of the application of electrical and magnetic fields has been studied in detai14,“. Fukada and Yasuda5 first reported that bone, in both its wet and dry states, is piezoelectric in the classic sense, i.e., an application of mechanical stress produces polarization and application of an electric field produces strain in the bone. This piezoelectric stimulation is used by orthopaedic surgeons for the treatment of non-unions and congenital pseudarthrosis4. Although the mechanism of electrical stimulation of bone is still unknown, accurate information on its electrical properties is essential. We have studied the electrical properties of fresh wet bone with and without a magnetic field. The bone samples were sliced from the mid-diaphysis of the bone wall to give cuboid shapes (15 x 12 x 5 mm). Electrical connections were made by painting colloidal air-curing silver paint on either side of the samples. A schematic diagram of the arrangement of the connections is shown in Figure I. A voltage of
O-250 V was applied from a commercial Dimmerstat (Model 150 IP, Automatic Electric Ltd, Bombay) across electrodes R and S and the electrical potential generated in the bone with the application of this a.c. field was measured on a calibrated oscilloscope screen. The strain developed in the bone due to the applied electrical stress is taken as the ratio of the change in potential due to the electrical stress to its initial value. A magnetic field of 159 x 10” A rn-’ was applied perpendicular to the electrical field using a horseshoe type permanent magnet. The electrical strain in the bone was determined with and without the magnetic field. The stress-strain curves are plotted m Figures 2 and 3. The piezoelectric effect does not interfere with the Hall voltage developed in the bone with the application of the magnetic field. The superimposition of the stress-strain curves with and without the magnetic field clearly shows this behaviour. The potential generated due to stress is found to increase in the presence of the magnetic field. The data reported in Table 2 reflect the effect of the magnetic field in the a.c. stress generated potentials at room temperature (30 f 0.1 “C). As expected, a linear stress-strain relationship is found up to 220 V (within the elastic limit) and irregularity is observed beyond the elastic limit, (within the plastic range) for both electric and magnetic fields. When current is passed between electrodes R and S (Figure I) in the presence of a magnetic field, which is caused to pass through the bone sample at right angles to the plane of the sample, the moving charges in the bone are deflected towards the top and bottom of the sample, depending upon the directions of the magnetic field and the electric field. Deflection of the charge carriers causes a potential to appear across electrodes P and Q, the
1000
output voltage
t
900
Electrical
F
mz
800
I
X
700 1
.c
voltage
F
500
‘; ro .u ;;L
300
2 w
200
-
400
600 I 100
t
OV’ 0
v Figure 1 Schematic circuit magnetic effects in hone
diagram
c) 1989 Butterworth & Co (Publishers) 0141-5425/89/060525~2 $03.00
for the study
20
’
40
’
60
’
80
’
100
’
120
Electrical
of clcctroFigure
2
Electrical
stress-strain
’
140
’
160
’
180
stress
hehaviour
’
200
’
220
’
240260
’
(VI
of hone
Ltd
J. Biomed.
Eng. 1989, Vol.
I11November
525
Table 1
Effect of magnetic
field
on
stress generated
Stress generated
Electrical stress without magnetic field (V)
potential
in bone
Electrical stress under magnetic field (V)
potentials
(mV)
Stress generated under magnetic
potential field
(mV) 0 20 40 60 80 100 120 140 160 200 220 240
T" x _
210 190 175 156 142 120 100 86 67 49 32 II
0 20 40 60 80 100 120 140 160 200 220 240
voltage in the bone results from the increase in biopotential. It is expected from this study that the stress generated potential (in this case electromagnetic stress) may be investigated as a possible stimulus for bone formation and regeneration in artificial defects.
1000 900 1
7J
5 c
217 202 180 162 148 124 105 90 70 52 35 15
800 t
Tl &
600
iz
500
ACKNOWLEDGEMENTS
k -z
400
The authors are thankful to Professor S.K. Joshi, Director, NPL, New Delhi, for his keen interest in the investigation. Our thanks are also due to Director, BPRD, Ministry of Home Affairs, New Delhi, for the grant of a fellowship to S. Yadav.
3 .u
;
700 1
=F, , , , , , , , , , 0
2 w
20
40
60
80 100 120 140 160 180200
Electrical Figure magnetic
3
Electrical field
stress-strain
stress behaviour
220240260
of bone
in
the
magnitude and polarity of which depend upon the direction and intensity of the magnetic field, the applied electric field, the type of charge carriers and the dimension of the bone sample. The output recorded is in the range of millivolts. The generation of biopotential in fresh wet bone with the application of an electric field is due to piezoelectric and electrokinetic (streaming potential) behaviour of bone. When the magnetic field is applied at right angles to the electric field, the generation of a Hall
526
J. Biomed. Eng. 1989, Vol.
II, November
Sanjay Yadav and V.R. Singh National Physical Laboratory New Delhi 110 012 India
(VI
1. Abendschien W, Hyatt GW. Ultrasonic and selected physical properties of bone. Clin Orthop 1970; 69: 294-301. and anisotropic mechanical 2. Katz JL, Yoon HS. The structure properties of bone. IEEE Tram 1981; BME-31: 878-84, 3. Sanjay Yadav, Seema Singhal, Singh VR, Kagpal KC. Study on variation of ultrasonic propagation parameters of bone by an X-ray diffraction technique. A/@ Acoustics 1988 (in press). 4. Smith RL, Nagel DA. Effect of pulsing electromagnetic field on bone growth and articular cartilage. Clin Orthob 1983; 181:
277-82. 5. Fukada E, Yasuda I. On the piezoelectricity Jpn 1957; 1’2: 1158.
in bone. JP@sSoc
phenomena
in bone
Dear Sir, Attempts have been made to understand the physical properties of bone, both in uitro and in rho. These studies have concluded that bone is a heterogeneous, viscoelastic, complex fibrous, anisotropic tissue, its properties depending upon geometry and dimensions and also on density, rigidity, fluidity, mineral and ash content, crystallinity, microhardness, position and orientation of the fibres, hydration, temperature and anisotropy I-3 . The growth and remodelling pattern of bone as a coniequence of the application of electrical and magnetic fields has been studied in detai14,“. Fukada and Yasuda5 first reported that bone, in both its wet and dry states, is piezoelectric in the classic sense, i.e., an application of mechanical stress produces polarization and application of an electric field produces strain in the bone. This piezoelectric stimulation is used by orthopaedic surgeons for the treatment of non-unions and congenital pseudarthrosis4. Although the mechanism of electrical stimulation of bone is still unknown, accurate information on its electrical properties is essential. We have studied the electrical properties of fresh wet bone with and without a magnetic field. The bone samples were sliced from the mid-diaphysis of the bone wall to give cuboid shapes (15 x 12 x 5 mm). Electrical connections were made by painting colloidal air-curing silver paint on either side of the samples. A schematic diagram of the arrangement of the connections is shown in Figure I. A voltage of
O-250 V was applied from a commercial Dimmerstat (Model 150 IP, Automatic Electric Ltd, Bombay) across electrodes R and S and the electrical potential generated in the bone with the application of this a.c. field was measured on a calibrated oscilloscope screen. The strain developed in the bone due to the applied electrical stress is taken as the ratio of the change in potential due to the electrical stress to its initial value. A magnetic field of 159 x 10” A rn-’ was applied perpendicular to the electrical field using a horseshoe type permanent magnet. The electrical strain in the bone was determined with and without the magnetic field. The stress-strain curves are plotted m Figures 2 and 3. The piezoelectric effect does not interfere with the Hall voltage developed in the bone with the application of the magnetic field. The superimposition of the stress-strain curves with and without the magnetic field clearly shows this behaviour. The potential generated due to stress is found to increase in the presence of the magnetic field. The data reported in Table 2 reflect the effect of the magnetic field in the a.c. stress generated potentials at room temperature (30 f 0.1 “C). As expected, a linear stress-strain relationship is found up to 220 V (within the elastic limit) and irregularity is observed beyond the elastic limit, (within the plastic range) for both electric and magnetic fields. When current is passed between electrodes R and S (Figure I) in the presence of a magnetic field, which is caused to pass through the bone sample at right angles to the plane of the sample, the moving charges in the bone are deflected towards the top and bottom of the sample, depending upon the directions of the magnetic field and the electric field. Deflection of the charge carriers causes a potential to appear across electrodes P and Q, the
1000
output voltage
t
900
Electrical
F
mz
800
I
X
700 1
.c
voltage
F
500
‘; ro .u ;;L
300
2 w
200
-
400
600 I 100
t
OV’ 0
v Figure 1 Schematic circuit magnetic effects in hone
diagram
c) 1989 Butterworth & Co (Publishers) 0141-5425/89/060525~2 $03.00
for the study
20
’
40
’
60
’
80
’
100
’
120
Electrical
of clcctroFigure
2
Electrical
stress-strain
’
140
’
160
’
180
stress
hehaviour
’
200
’
220
’
240260
’
(VI
of hone
Ltd
J. Biomed.
Eng. 1989, Vol.
I11November
525
Table 1
Effect of magnetic
field
on
stress generated
Stress generated
Electrical stress without magnetic field (V)
potential
in bone
Electrical stress under magnetic field (V)
potentials
(mV)
Stress generated under magnetic
potential field
(mV) 0 20 40 60 80 100 120 140 160 200 220 240
T" x _
210 190 175 156 142 120 100 86 67 49 32 II
0 20 40 60 80 100 120 140 160 200 220 240
voltage in the bone results from the increase in biopotential. It is expected from this study that the stress generated potential (in this case electromagnetic stress) may be investigated as a possible stimulus for bone formation and regeneration in artificial defects.
1000 900 1
7J
5 c
217 202 180 162 148 124 105 90 70 52 35 15
800 t
Tl &
600
iz
500
ACKNOWLEDGEMENTS
k -z
400
The authors are thankful to Professor S.K. Joshi, Director, NPL, New Delhi, for his keen interest in the investigation. Our thanks are also due to Director, BPRD, Ministry of Home Affairs, New Delhi, for the grant of a fellowship to S. Yadav.
3 .u
;
700 1
=F, , , , , , , , , , 0
2 w
20
40
60
80 100 120 140 160 180200
Electrical Figure magnetic
3
Electrical field
stress-strain
stress behaviour
220240260
of bone
in
the
magnitude and polarity of which depend upon the direction and intensity of the magnetic field, the applied electric field, the type of charge carriers and the dimension of the bone sample. The output recorded is in the range of millivolts. The generation of biopotential in fresh wet bone with the application of an electric field is due to piezoelectric and electrokinetic (streaming potential) behaviour of bone. When the magnetic field is applied at right angles to the electric field, the generation of a Hall
526
J. Biomed. Eng. 1989, Vol.
II, November
Sanjay Yadav and V.R. Singh National Physical Laboratory New Delhi 110 012 India
(VI
1. Abendschien W, Hyatt GW. Ultrasonic and selected physical properties of bone. Clin Orthop 1970; 69: 294-301. and anisotropic mechanical 2. Katz JL, Yoon HS. The structure properties of bone. IEEE Tram 1981; BME-31: 878-84, 3. Sanjay Yadav, Seema Singhal, Singh VR, Kagpal KC. Study on variation of ultrasonic propagation parameters of bone by an X-ray diffraction technique. A/@ Acoustics 1988 (in press). 4. Smith RL, Nagel DA. Effect of pulsing electromagnetic field on bone growth and articular cartilage. Clin Orthob 1983; 181:
277-82. 5. Fukada E, Yasuda I. On the piezoelectricity Jpn 1957; 1’2: 1158.
in bone. JP@sSoc