Download Applications in Orthopaedics

FUNCTIONAL ROLE OF EMG
IN ORTHOPAEDICS
Mario Lamontagne, PhD1,2,3
Professor in Biomechanics
1- School of Human Kinetics, Faculty of Health Sciences, U. of Ottawa
2- Dept. of Mechanical Engineering, University of Ottawa, Ottawa, Canada;
3- Let People Move, Biomechanics Laboratory, Perugia, Italy
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
1
Scope of this presentation
Introduction
Background on the Electromyography
Recording Technique
Analysis of the EMG signal
Applications in Orthopaedics
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
2
Introduction
The electromyographic (EMG) signal offers a
great source of information to both clinicians
and researchers
EMG can be used to detect gait or joints
pathologies, to assess a rehabilitation program,
to measure the functionality of sport equipment
and to implement an effective biofeedback
therapy.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
3
Introduction
Surface EMG is also widely used in an effort to
understand a number of research issues:
 Muscles coordination around a joint
 Relationship between muscular force and muscle
electrical activity
 Neuromuscular adaptations after joint surgery
following a rehabilitation program.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
4
Background on the EMG
The muscle unit action potential detected by
electrodes in the muscle tissue or on the surface
of the skin.
Central nervous system (CNS) activity initiates a
depolarisation in the motoneuron.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
5
Background on the EMG
A single axon leading to
a muscle is responsible
for the innervation of as
few as 3 or as many as
2000 individual muscle
fibres.
A neuron and the
muscle fibres are
referred to as motor unit
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
6
Background on the EMG
A neuron and the muscle
fibers are referred to as motor
unit (MU)
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
7
Background on the EMG
The nerve impulse is transmitted in a
nerve axon as schematically shown down
below
Triphasic Signal
A
Mario Lamontagne PhD
School of Human Kinetics
B
Voltage
+
APA 6903 /05
8
Background on the EMG
A dipole +
is moving along a
volume conductor. A differential amplifier
records the difference between the potentials
at point A and B on the conductor.
A
Mario Lamontagne PhD
School of Human Kinetics
B
Voltage
+
Triphasic Signal
APA 6903 /05
9
Background on the EMG
The dipole is moving along the conductor. The
potential A is getting more negative.
+
Triphasic Signal
A
Mario Lamontagne PhD
School of Human Kinetics
B
Voltage
-
APA 6903 /05
10
Background on the EMG
More the dipole is moving between the
potentials more the signal is positive
-
A
Mario Lamontagne PhD
School of Human Kinetics
B
Voltage
+
Triphasic Signal
APA 6903 /05
11
Background on the EMG
Finally, the connector B registers the positive
end of the dipole and the connector A is returning
to zero. The result of the amplification becomes
negative
A
Mario Lamontagne PhD
School of Human Kinetics
B
Voltage
+
Triphasic Signal
APA 6903 /05
12
Background on the EMG
The triphasic curve has some similarity with an
action potential which passes through a nerve
axon.
A
Mario Lamontagne PhD
School of Human Kinetics
B
Voltage
+
Triphasic Signal
APA 6903 /05
13
Background on the EMG
Number of MU varies with the type and
function of muscles.
Muscles Number of muscle’s fibers/Neuron
Platysmus
Long Digital Flexor
Tibialis Anterior
Gastrocnemius
Mario Lamontagne PhD
School of Human Kinetics
25
95
609
1775
APA 6903 /05
14
Background on the EMG
Motor Unit Recruitment
Once an action potential reaches a muscle fiber, it
propagates proximally and distally. This is called
motor action potential (MAP).
A motor unit action potential (MUAP) is
spatiotemporal summation of MAPs for an entire
MU.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
15
Background on the EMG
An EMG signal is the algebraic summation of
many repetitive sequences of MUAPs for all
active motor units in the vicinity of the recording
electrodes
MUAP1
MUAP2
MUAP3
MUAP4
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
16
Background on the EMG
Muscle tension
MU Recruitment
The order of MU
recruitment is according
to their sizes. The
smaller ones are active
first and the bigger ones
are active last.
MU 4
MU 3
MU 2
MU 1
MU 1
MU
2
MU 3
MU 4
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
17
Background on the EMG
MUAP vs. Force
– For a voluntary contraction, muscle’s force
depends on the number of MU and the
frequency of activation
– Muscle’s force is proportional of the crosssectional area of the active muscle fibers.
– Muscle force during isometric action is
around 30 N/cm2
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
18
Recording Techniques
The
differential
increases
the amplitude
A
wide
variety preamplifier
of electrodes
are available
to
of the difference signal between each of detecting
measure
the the
electrical
muscle
output
electrode and
common
ground.
The advantage of
microelectrode
and needleiselectrode
(notthe
practical
for
the
differential preamplifier
to improve
signalto-noise
ratio studies)
of the measurement.
movement
Surface electrodes (SE) and Intramuscular wire
electrodes (IWE) are commonly used in movement
studies
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
19
Recording Techniques
EMG Signal Detection Summary
• Bipolar electrodes (active electrode rather than
passive electrodes
• Distance between electrodes 10 to 20 mm
apart
• Bandwidth of 20-500 Hz
• CMRR greater than 100 dB
• Noise less than 2mV
• Electrode located on the midline of the muscle
belly
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
20
Analysis of the EMG signal
In the time domain:
RAW
• the root-mean squared (RMS)
value or also called Linear
Envelop)
• the average rectified value
Onset
Peak
• Both are appropriate and
provide useful measurements of
the signal amplitude
• Muscle onset (time)
• Peak amplitude of RMS
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
21
Analysis of the EMG signal
In the Frequency domain:
• Spectral Density
–Median Frequency
–Mean Frequency
• Wavelet
This represents the
frequency contents of
EMG signal.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
22
Interpretation of the EMG signal
EMG is a tool not without its hidden
weaknesses
These problems have the potential to
mask any benefit obtained from the
recorded information.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
23
Anecdotal Demonstration
Adrian R. M. Upton conducted
an anecdotal demonstration of
the difficulty of documenting
brain death by placing EEG
electrodes in an upside-down
bowl of lime Jell-O (reported in
The New York Times, March 6,
1976, p. 50).
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
24
Interpretation of EMG
 As with EEG traces, the interpretation of the
recorded EMG should be conducted with care.
 However, with proper use, the surface
electromyogram is a powerful and effective tool
for both clinical evaluation and research.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
25
Applications in Orthopaedics
Recent
technological
Most
of the
applicationsdevelopment
of sEMG and in sEMG
moved
research
from
imEMG
are based
on:the laboratory to the
field
applications.
Muscle
activation and timing
Muscle contraction profile
Muscle strength of contraction
Muscle fatigue.
Few orthopaedic applications will be
presented in sports, rehabilitation
and sport medicine.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
26
APPLICATIONS IN SPORT MEDICINE
Muscle Activation and Timing1
Objective:
 Examine the neuromuscular response to
functional knee bracing relative to anterior tibial
translations.
Design:
 During randomized brace conditions,
electromyographic data with simultaneous
skeletal tibiofemoral kinematics and GRF were
recorded from four ACL deficient subjects to
investigate the effect of the functional brace
during activity.
Ramsey, D. K., Lamontagne, M., Wretenberg, P., Valentin, A., Engström, B., & Németh, G.
(2003). Electromyographic and biomechanics analysis of anterior cruciate ligament deficiency and
functional knee bracing. Clin Biomech (Bristol, Avon). 2003 Jan;18(1):28-34
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
27
Rectus femoris (mV)
APPLICATIONS IN SPORT MEDICINE
Muscle Activation and Timing1
1
A1
A2
A3
0
Methods:
Mario Lamontagne PhD
School of Human Kinetics
A1
A2
A3
Semitendinosus (mV)
0
1
A1
A2
A3
Gastrocnemius (mV)
0
1
A1
A2
A3
0
Vertical & posterior
ground reaction force (BW)
 Kinematic and kinetic measure-ments
were synchronously recorded with the
EMG signal. The EMG data from the
RF, S, BF, and LG were integrated for
each subject in three separate time
periods: 250 ms preceding foot-strike
and two consecutive 125 ms time
intervals following foot-strike.
Biceps femoris (mV)
1
4
0
APA 6903 /05
Time (s)
28
Group means
0.04
Brace
21%
*
0.03
APPLICATIONS IN SPORT MEDICINE
0.02
0.01
1
Muscle Activation and Timing
0.00
1
2
Time interval
Results:
Rectusfemoris
femoris
Biceps
Semitendinosus
Rectus femoris
0.03
0.02
Mario Lamontagne PhD
School of Human Kinetics
Group
means
Groupmeans
means
Group
0.05
0.05
0.05
0.04
0.04
0.04
0.03
0.03
No brace
No brace
Brace
Brace
17%
21%
44%
*
*
*
11
22
interval
Time interval
No brace
Brace
0.02
0.02
0.01
0.01
0.00
0.00
333
Semitendinosus
Lateral
gastrocnemius
0.05
0.05
roup
roupmeans
means
roup means
Group means
 With
0.05 brace, ST activity
No brace
significantly
decreased 17%
0.04
Brace
21%
prior to footstrike*
0.03
 whereas BF significantly
0.02
decreased
44% during A2,
0.01
(P<0.05).
 RF0.00activity
significantly
1
2
3
increased 21%
A2 (P<0.05).
Timein
interval
 No consistent
reductions in
Semitendinosus
0.05
anterior translations were
No brace
Brace
0.04
evident. *17%
3
0.04
0.04
*17%
No brace
No brace
Brace
Brace
0.03
0.03
APA 6903 /05
0.02
0.02
29
APPLICATIONS IN SPORT MEDICINE
Muscle Activation and Timing1
Conclusion:
 Joint stability may result from proprioceptive feedback
rather than the mechanical stabilising effect of the
brace. As a result of bracing, we observed decreased
S and BF activity but increased RF activity. We suggest
increased afferent input from knee proprioceptors and
brace-skin-bone interface modifies EMG activity.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
30
Applications in Orthopaedics
PURPOSES
To better understand the neuromuscular
control of the hamstrings to protect the
ACL strain using an in vivo
experimentation.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
31
Applications in Orthopaedics
METHODS: Participants
Five healthy males (mean: age;
25yrs; height: 167cm; weight:
71.5kg)
No previous knee joint injuries.
Prior the in vivo data collection,
participants was instructed to the
implantation procedure and testing
protocol including training of the
tasks
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
32
Applications in Orthopaedics
METHODS: Surgical Procedure
DVRT arthroscopically
implanted on the anteromedial band of the intact ACL
under local anesthesia.
The barbed ends of the DVRT
are inserted into the ligament
bundle and fixed in place.
The surgical instruments were
removed and the wounds
were closed and sutured
around the exiting instrument
wire.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
33
Applications in Orthopaedics
METHODS: Testing Protocol
Kinematics was recorded
with 4 H-S cameras (50
Hz) using SIMI Motion
System.
EMG, force plate, and
DVRT signals was
collected for 8 s at
1000Hz synchronously
with kinematic data
A total of five trials per
movements were
collected
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
34
Applications in Orthopaedics
METHODS: Data Analysis
Rectified EMG signals were
normalised by peak amplitude for
the dynamic contractions of the
three manoeuvres using the
stopping motion EMG data as
normalisation basis.
The data from all five trials was
ensemble averaged over the cycle
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
35
Applications in Orthopaedics
RESULTS: IN-VIVO ACL STRAIN
1
MEAN KNEE ANGLE
5000
NORMALISED MEAN STRAIN
MEAN Fz
140
120
100
80
60
Knee Angle
40
0.8
4000
GRF (N)
% of Maximum Value
Knee Angle (Degrees)
160
0.6
0.4
DVRT
0.2
3000
2000
GRF
1000
20
21
41
61
1
81
20
39
58
77
% of Maximum Value
0.8
0.6
0.4
Vastii
20
39
58
77
96
96
1
1
MEAN VL
MEAN VM
0.2
1
1
MEAN BF
MEAN ST
0.8
0.6
0.4
Hamstrings
0.2
MEAN GL
MEAN GM
0.9
% of Maximum Value
1
% of Maximum Value
0
0
0
0.8
0.7
0.6
0.5
0.4
Gastroc.
0.3
0.2
0.1
0
1
20
39
58
77
96
0
0
TIME (%)
Mario Lamontagne PhD
School of Human Kinetics
1
20
39
58
77
96
1
20
39
58
77
96
TIME (%)
TIME (%)
APA 6903 /05
36
Applications in Orthopaedics
DISCUSSION
 Almost 80% of ACL injuries are
non-contact in nature.
 Neuromuscular strategy
anticipated the landing impact
during all motions 1-2
 Strategy to position Lower-limb
segment before landing 3
 Joint coordination might play a
role for injury prevention
ACL rupture during the Canadian
badmington Championship:
UO Student
1- Besier, T.F., Lloyd, D.G., Ackland, T.R., 2003. Muscle activation strategies at the knee during running and cutting
maneuvers. Med. Sci. Sports Exerc. 35, 119–127.
2- Cowling, E.J., Steele, J.R., 2001. Is lower limb muscle synchrony during landing affected by gender? Implications for
variations in ACL injury rates. J. Electromyogr. Kinesiol. 11, 263–268.
3- McLean, SG, X. Huang, A. Su, and A. v d Bogert, 2004. Sagittal plane biomechanics cannot injure the ACL during
sidestep cutting. Clinical Biomechanics 19 828-838.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
37
Applications in Orthopaedics
DISCUSSION
 The anticipatory muscle
contraction of the hamstrings
and Gastrocnemius play an
important role of protecting
excessive ACL elongation.
 The Hamstrings and
Gastrocnemius are more
associated with ACL elongation
than Knee joint Torque.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
38
Applications in Orthopaedics
Gender Difference for a cut motion
 Male and Female elite football players
 Control speed
 Cue given at 1.2m from the FP
See EMG Data
Mario Lamontagne PhD
School of Human Kinetics
2
APA 6903 /05
1
C
39
Applications in Orthopaedics
Muscle Fatigue1
Surface EMG can be used as muscle
fatigue indicator
We investigated possible differences in muscle
fatigue and recovery of knee flexor and extensor
muscles in patients with a deficient anterior cruciate
ligament compared with patients with a normal
anterior cruciate ligament.
Tho, K., Németh, G., Lamontagne, M., & Eriksson, E. (1997). Electromyographic Analysis of Muscle Fatigue in
Anterior Cruciate Ligament Deficient Knees. Clinical Orthopaedics & Related Research(340), 142-151.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
40
Applications in Orthopaedics
Muscle Fatigue1
 SEMG of 15 patients with ACL deficiency was
measured while the muscles were under 80% of MVC
for 60 s and remeasured after 1, 2, 3, and 5 minutes
of rest
 Knee joint was at 45 degrees of flexion.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
41
Applications in Orthopaedics
Muscle Fatigue1
Coefficient of MF change and amplitude increase during 80% MVC for 60s
Findings
showed that:
(modified from Tho et al. 1997 ).
Conditions
First 60 s of contraction
• all muscles
recorded
significantlyNormal
decreased
Injured
Knee
Knee
Muscles
MPF
Coefficient of
Amplitude
Change
Coefficient of
Amplitude
Change
MF (SD)
(%) amplitude.
MF (SD)
(SD)
(%)
• an increase
in(SD)
LEEMG
-0.096 (0.073)
125 (172)
42
-0.069 (0.064)
132 (95)
76
Vastus Medialis
femoris
Rate of -0.136*
decrease
MPF was
significantly
greater23 in
(0.086)
64of
(119)
20
-0.100 (0.046)
60 (112)
Rectus
-0.105* quadriceps
(0.087)
89 (141) and29normal
-0.054 (0.073)
165 (184)
67
Vastus Lateralis
the injured
hamstrings.
-0.207 (0.124)
125 (132)
58
-0.266* (0.112)
119 (149)
49
Medial Hamstrings

All
muscles
recovered
to
the
initial
MPF
level
after
Lateral Hamstrings
-0.159 (0.155)
204 (178)
80
-0.222 (0.152)
228 (269)
71
1 min of-0.105
rest
but two
muscles
in-0.208**
the(0.146)
injured
and 33
Med. Gastrocnemius
(0.132)
62 (63)
40
52 (53)
normal limb
recorded
of mean
Lat. Gastrocnemius
-0.151 (0.118)
88 (72) an overshoot
63
-0.187 (0.139)
54 (61) power
28
frequency during the recovery phase.
* : p < 0.05 (paired t-test)
** : p < 0.01 (paired t-test)
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
42
Applications in Orthopaedics
Muscle Fatigue1
The findings confirmed
the fatigue state in all the muscles, suggest
recruitment of more Type II fibers as the muscle
fatigue
show the physiological adaptation of the quadriceps
and hamstrings to ACL deficiency.
dissociation between low intramuscular pH and
mean power frequency during the recovery phase.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
43
Applications in Orthopaedics
Muscle Fatigue2
We investigated the possible influence of wearing
functional knee braces on various factors of muscle
fatigue.
 Measured parameters were; MVC, Peak Velocity
(PK), power and number of repetition to muscle
fatigue during isokinetic exercise, and also muscle
fatigue during 50s isometric contraction
Lamontagne, M. & Sabagh-Yazdi, F. (1999). The Influence of Functional Knee Braces on Muscle Fatigue.
Paper presented at the XVIth of the International Society of Biomechanics, Calgary, Canada.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
44
Applications in Orthopaedics
Muscle Fatigue2
 Two groups of healthy and ACL-deficient knee joint
subjects with an average age of 28.8 years and 26,6
years respectively volunteered to this study.
 All tests were performed on an isokinetic device (KinCom 500H) while the EMG signal was collected at
1000 Hz for six muscles (RF), (VL), (VM), (G), (MH)
and (LH).
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
45
Applications in Orthopaedics
Muscle Fatigue2
Analysis of EMG data revealed that
no significant differences were obtained for the EMG
amplitude or the integral of the linear envelope EMG
between the groups and conditions
During the 50s isometric exercise at 80% MVC, the
fatigue state is represented by decline of MF value of
EMG signal greater than 10 Hz
Muscle fatigue state was obtained in all muscles
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
46
Applications in Orthopaedics
Muscle Fatigue2
Average
percentage ofof
decline
of the
 Percentage
decline
ofmedian
MF infrequency.
the Gastrocnemius
was
significantly different between the groups (p<0.05).
ACL
Healthy
 Percentage of decline of median frequency in VM and G of
MusclesACL group
VL RFandVM
LH
VLgroup
RF was
VMfound
G° GMH
G° MH LM
VL and
of healthy
different
9.1 27.6
14.8 (p<0.05)
1.8 35.0 between
27.3 18.4 conditions.
24.9 12.3
1.7
39.3 34.5
Braced statistically
 the outcomes
between
the
12.0 22.4 showed
9.0* 10.6*a high
43.4 correlation
24.0
8.9* 21.2
16.4
9.5* 48.0 28.5
Unbraced
subjective perception of fatigue and percentage of decline of
the MF
(r = 0.64)
VL and
* : significantly
difference
betweenfor
conditions
(p <RF
0.05)muscles during the brace
condition.
° : significantly difference between groups (p < 0.05)
 All other muscles showed very low correlation.
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
47
CONCLUSION
Factors like signal reliability, muscle synergy,
mechanisms of proprioception, muscle fatigue
mechanisms have been a great deal of interest in
movement studies but these topics certainly need
more research in order to understand muscle
function and adaptation for ordinary people and
athletes.
Lamontagne, M. (2000). Electromyography in sport medicine (Chapter 4). In
Rehabilitation of Sports Injuries (Ed. G. Puddu, A. Giombini, A. Selvanetti ),
Springer-Verlag, Berlin, Heidelberg, New York
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
48
Partly funded by:
Natural Sciences and Engineering Council of Canada
and
Let People Move
Mario Lamontagne PhD
School of Human Kinetics
APA 6903 /05
49