INSTITUTE OF PHYSICS PUBLISHING
Physiol. Meas. 26 (2005) 951–963
Can mechanical myotonometry or electromyography
be used for the prediction of intramuscular pressure?
R K Korhonen1,2, A Vain4, E Vanninen3, R Viir5and J S Jurvelin1,3
1Department of Applied Physics, University of Kuopio, POB 1627, 70211 Kuopio, Finland
2Human Performance Laboratory, Faculty of Kinesiology, University of Calgary,
2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
3Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital and
University of Kuopio, POB 1777, 70211 Kuopio, Finland
4Institute of Experimental Physics and Technology, University of Tartu, T¨ ahe 4, 51010 Tartu,
5Rheumatism Foundation Hospital, Pikij¨ arventie 1, 18120 Heinola, Finland
Received 8 December 2004, accepted for publication 31 August 2005
Published 17 October 2005
Online at stacks.iop.org/PM/26/951
The aim of the study was to characterize the electromechanical properties
of skeletal muscle during isometric loading as well as to assess the
potential of estimating intramuscular pressure by electrical and mechanical
methods. Simultaneous electromyography (EMG), mechanical myotonometry
(MYO, frequency and decrement of decay) and intramuscular pressure (IMP)
measurements were conducted at rest and during short-term and long-term
isometric contractions in patients with chronic pain in the anterior leg or dorsal
forearm. The EMG amplitude and MYOfreqaccounted significantly (24–73%,
p < 0.0001) for the variations in the IMP under short-term isometric loading.
The IMP, EMG and MYOfreqincreased linearly with the relative muscle load
(r = 0.868–0.993, p < 0.05).
contraction levels of 75% and 100% maximum voluntary contraction (MVC)
and MYOfreqvalues at all contraction levels (0–100% MVC) were higher for
subjects with pathological values of IMP than for those with IMP values in
the normal range. Total changes in IMP and EMG amplitude during 1 min
isometric contraction were linearly interrelated (r = 0.747, p < 0.0001). We
conclude that both surface electromyography and myotonometry parameters
are indicative of intramuscular pressure, but neither of these methods can be
used alone to diagnose non-invasively chronic compartment syndrome with
Mean values of EMG amplitudes at the
myography, isometric contraction
intramuscular pressure, biomechanics, myotonometry, electro-
0967-3334/05/060951+13$30.00© 2005 IOP Publishing LtdPrinted in the UK951
952R K Korhonen et al
Intramuscular pressure (IMP) of healthy skeletal muscle is linearly related to isometric
muscle load (J¨ arvholm et al 1989, 1991, Parker et al 1984, Sejersted and Hargens
1995). Mechanical loading of the muscle increases IMP, which may subsequently decrease
muscle perfusion (J¨ arvholm et al 1988, Sadamoto et al 1983, Styf et al 1987).
critical level of loading, the muscle membrane may not be able to stretch to allow the
increase in the muscle volume, and as a result capillary flow can decrease significantly.
At this point, muscle fatigue impairs the normal functioning of the tissue.
associated with pain, fatigue and disability, this exercise-induced state is called the chronic
compartment syndrome (CCS) (Renemann 1975, Styf et al 1987). IMP also depends on
other factors such as muscle geometry (Bourne and Rorabeck 1989, J¨ arvholm et al 1989,
Sejersted and Hargens 1995). At present, CCS is clinically diagnosed by invasive IMP
Electromyography (EMG) is a physiological measure of muscle activity and fatigue.
EMG can exhibit a linear (Aratow et al 1993, Perry and Bekey 1981) or nonlinear (Lawrence
and De Luca 1983, Solomonow et al 1986) relationship with isometric muscle force. It
has been suggested that EMG amplitude (Krogh-Lund and Jorgensen 1991, 1992), as well
as IMP (Crenshaw et al 1997), increase during sustained submaximal isometric contraction
to fatigue. Possibly, the changes in EMG are due to metabolic alterations in the muscle,
especially if the contraction level is greater than 45% of the maximal voluntary contraction
(MVC) (Brody et al 1991, Crenshaw et al 1997).
the changes in EMG are mainly attributable to neural changes (Crenshaw et al 1997,
Krogh-Lund and Jorgensen 1991, 1992).Even though the relationships between IMP
and EMG have been widely studied, it is still poorly understood whether EMG variations
are consistent with those of IMP when investigating subjects with pathological values
After electric activation of the skeletal muscle, its functional state is reflected by the
muscle tone, an indicator of the mechanical stiffness of muscle (Vain 1993, 1995, 1999).
Muscle tone increases as a function of contraction force. Myotonometry (MYO) represents
a noninvasive way to characterize the viscoelastic properties, i.e. frequency (MYOfreq) and
decrement of decay (MYOdec), of skeletal muscle in vivo (Vain et al 1992, Veldi et al
2000). The interrelationships between the viscoelastic properties of muscle and IMP are
not clarified but should be assessed to improve the understanding of their mechanical
In the present study, simultaneous IMP, EMG and MYO measurements were conducted
at rest as well as during short-term and long-term isometric loading for subjects with
pain in the dorsal forearm or anterior leg (possibly due to chronic CS). The objective of
this study was to establish if there is a relationship between IMP, EMG and MYO, and
whether EMG or MYO could be used to estimate IMP non-invasively in the diagnosis
of chronic CS. Differences in the measured parameters during two maximal voluntary
contractions, and the capabilities of EMG and MYO to estimate IMP under short-term
loading were evaluated.The potential of EMG and MYO to differentiate subjects
with pathological values of IMP from those with normal values was investigated under
short-term isometric loading.Finally, EMG and IMP changes during long-term loading
were interrelated.We hypothesized that EMG and MYO could be useful in predicting
clinically significantly increased IMP. Possibly, with the aid of these non-invasive
methods, some of the current invasive tests for patients with normal IMP may be
At levels below 30% of the MVC,
Electromechanical characteristics of the muscle 953
Table 1. Description of the study subjects (mean ± SD).
Blood pressure (kPa)
Age (years) Height (cm)Weight (kg) BMIa(kg m−2) Systolic Diastolic
45.8 ± 10.0
40.3 ± 11.5
177.8 ± 5.2
163.8 ± 4.2
86.0 ± 7.6
64.5 ± 10.3
27.2 ± 2.9
24.9 ± 4.0
18.0 ± 0.9
18.4 ± 2.4
9.9 ± 1.1
10.1 ± 1.5
aBody mass index.
Materials and methods
Measurements were carried out in 37 subjects (37 IMP, 30 EMG and 26 MYO subjects,
table 1) who had pain in the dorsal forearm (extensor compartment) or anterior leg (anterior
compartment). First, the interrelationships between IMP, EMG and MYO were studied.
Second, the subjects were divided into two groups: (1) high values of IMP indicative of
chronic CS and (2) low values of IMP suggesting no chronic CS, based on clinically used
IMP in the dorsal forearm and anterior leg, respectively, at rest, (b) >0.2 kPa/% intramuscular
pressure during contraction of 0–100% MVC, (c) >3.3 kPa IMP 1 min after loading or >2.7
kPa IMP 5 min after loading, and (d) pain associated with decrease of muscle force during
contraction. Subsequently, the diagnostic performances of EMG and MYO to differentiate
these groups were determined.
Before the measurements, the IMP catheter and EMG electrodes were positioned in
the muscle compartment and on the skin surface above the muscle, respectively (figure 1).
For the measurements, the subjects were lying in a supine position and the limb under
investigation was loaded with a loadmeter (Digitest force, Digitest OY, Finland) using a
standardized protocol for short-term (5 s, 0%, 100%, 75%, 50%, 25% and 100% MVC)
and long-term (60 s, 40% and 20% MVC) isometric loading of the muscle (Jurvelin and
Mussalo 2003).6The foot or arm was lying on the bed in a natural position without any extra
stretch. Loading of the dorsiflexed wrist or ankle was used (figure 2). Since the loading
force can be influenced by the angle of the hand or foot and by the position of the strap
relative to the joint center, the hand and foot were always held at the angles of ∼20◦and ∼0◦,
respectively. Displacements a and b in figure 2 were ∼8 cm and ∼15 cm, respectively. The
reason for the differences in the angle and displacement was purely anatomical. Furthermore,
due to the differences in the measurement geometries, the analyses were made separately for
hand and foot. During loading IMP, EMG and load signals were continuously recorded for
4 min, while myotonometric measurements were conducted at rest and during isometric
loading periods (figure 3).
IMP was measured using a slit catheter method (Stryker, Intra-Compartmental Pressure
Monitor System, Indwelling Slit Catheter Set, USA) (Bourne and Rorabeck 1989). First, the
patient’s skin was cleaned carefully and the saline-filled catheter of 1.6 mm in outer diameter
was inserted in the proximal direction into the muscle compartment through a needle. Since
IMP is influenced by the depth of the catheter in the muscle (Sejersted et al 1984), care was
taken to position the catheter tip at the same depth in all patients. The depth varied between
6IMP measurements were conducted according to the clinical protocol in use in the Kuopio University Hospital.
954R K Korhonen et al
intramuscular pressure (IMP) measurements, the catheter tip was positioned in the muscle
compartment of interest, 2–4 cm under the active EMG electrodes.
measurements using myotonometry (MYO) was on the muscle surface between the active
Electrode placements in the electromyography (EMG) measurements.In the
Test location for the
Figure 2. A schematic representation for the isometric loading of dorsal forearm (a) and anterior
leg (b) muscle compartments with description of the measurement geometries (c). The wrist and
ankle joints were dorsiflexed. The hand and the foot was always held at an angle of α ≈ 20◦and
α ≈ 0◦, respectively. Displacements a and b were ∼8 cm and ∼15 cm, respectively.
2 and 4 cm, depending on the amount of subcutaneous fat and the muscle compartment. The
needle was pulled out and the catheter was attached to an external pressure transducer7
(AE-840, Sensonor, Horten, Norway) connected to a pressure amplifier (Mingograph 4,
Siemens-Elema, Solna, Sweden). After amplification, the pressure and loadmeter signals
were relayed to a PC through a 12-bit AD-converter board. To avoid the artificial effect
7Transducer specifications—resonant frequency: 300 Hz, sensitivity: 50 µV V−1cmHg−1, pressure range:
−20···+300 mmHg, nonlinearity and hysteresis: max 0.5% of full scale.
Electromechanical characteristics of the muscle 955
Figure 3. Intramuscular pressure (IMP) and electromyography (EMG) at rest and during short
((a): 100%, 75%, 50%, 25% and 100% MVC) and long ((b): 40% and 20% MVC) term isometric
of gravity, the pressure transducer was kept at the same height as the catheter tip. The
pressure transducer was calibrated against a mercury sphygmomanometer (Erkameter, Erka,
Bad Toelz, Germany). The IMP analysis was performed using custom-made software. In
addition to pressure-time data, the IMP values, corresponding to each short-term load, were
systematically quantitated from the measurements.
Quantitative surface EMG
Simultaneously with IMP measurements, EMG of the muscle was recorded using bipolar
Ag/AgCl electrodes, attached to the skin surface above the muscle of interest (figure 1). The
skin contact size of the electrodes was 48 mm in diameter. The EMG signal was preamplified
and sent to a ME3000P Muscle Tester unit with a 2 MB SRAM-card (Mega Electronics
Ltd, Kuopio, Finland). The signal was amplified and filtered in the ME3000P unit. The
frequency band for the measurement was 15–500 Hz with a sampling frequency of 1000 Hz.
Simultaneous IMP and load signals were also relayed to the ME3000P unit through a ME3000
ISO isolation unit. After registration of EMG, IMP and load signals, the data from the
SRAM-card were downloaded to a PC with an appropriate software (Multi Signal System
ME3000P V2.05 software, Mega Electronics Ltd, Kuopio, Finland). The raw EMG signal
was subsequently rectified and averaged by the software using an averaging time of 10 ms
(figure 3). EMG amplitudes were quantitated during each (0–100% MVC) short-term muscle
load. To describe the time-dependent behavior of the EMG (and IMP) during long-term
loading (figure 3(b)) curve-fitting was performed using y = A0+ Aexp(–kt), where A0is the
amplitude of EMG (µV) or IMP (Pa) at equilibrium, A is the change of the amplitude, k (s−1)
is the time constant and t (s) is time. This exponential best-fit could describe accurately the
time-dependent behavior of both EMG and IMP.
Simultaneously with IMP and EMG measurements, the mechanical characteristics of the
muscle were determined at rest and during isometric contractions using myotonometry (Vain
et al 1992, 1996, Vain 1999, Veldi et al 2000). In this method, the viscoelastic response of the
muscle due to the constant mechanical impact (duration ∼10 ms) on the skin surface above
the muscle is recorded as a damped harmonic oscillation (figure 4). Each myotonometry
956R K Korhonen et al
measurement, the test probe of the instrument is positioned against the muscle of interest and
after a short mechanical impact released at the point a. Frequency and decrement of decay are
calculated from the curve to estimate the elastic and viscous properties of tissue.
Typical damped oscillation curve, as measured with myotonometry. During the
measurement took ∼250 ms including five oscillations. From these data, the oscillation
frequency (MYOfreq(Hz)) and logarithmic decrement of decay (MYOdec) can be calculated
to quantify the functional state of the muscle (Bader et al 1992, Vain et al 1992, Veldi et al
2000, Fung 1993). MYOfreqcharacterizes the elastic properties of the muscle and reflects
the tissue ability to resist the force that changes its shape. MYOdeccharacterizes the viscous
properties of the muscle and reflects the ability of the tissue to restore its initial shape. Three
values of MYOfreqand MYOdecwere calculated from these measurements.
The mean values and standard deviations (±SD) were calculated for the IMP, EMG and MYO
values. Linear regression analysis and Bland and Altman analysis (Bland and Altman 1986)
were utilized to describe the relationships between recorded parameters and best-fit equations,
Software, Inc, Northampton, MA, USA). The Wilcoxon signed ranks and Mann–Whitney
U-tests were used for statistical comparisons.
The mean values of the recorded parameters in the dorsal forearm and anterior leg for the
subjects with high (group 1) and low IMP (group 2) values at rest and at maximum load are
shown in table 2. The IMP values of group 1 were statistically higher (p < 0.05, Mann–
Whitney U-test) than those of group 2 at 100% MVC both in the arm and the leg. EMG values
of group 1 in the arm at rest and at 100% MVC, as well as MYOdecvalues of group 1 in the
leg at 100% MVC, were significantly different (p < 0.05, Mann–Whitney U-test) than those
of group 2. All parameter values were statistically (p < 0.05, Wilcoxon signed ranks test)
higher (except MYOdec) at the maximum load than at rest. At the 100% MVC, the loading
force correlated significantly with IMP, EMG and MYOfreqin the anterior leg (r = 0.628,
r = 0.617, r = 0.680, respectively, p < 0.05), whereas in the dorsal forearm only IMP
correlated significantly with force (r = 0.654, p < 0.05).
A Bland and Altman plot shows agreement between the values of registered parameters
during the first and last 100% MVC (figure 5). The measured parameters, except MYOdec
(r = 0.273, p = 0.178, data not shown), during the first and last 100% MVC correlated
Electromechanical characteristics of the muscle
Table 2. Mean (±SD) values of the intramuscular pressure (IMP) elecromyography (EMG) and myotonometry (MYO) parameters (MYOfreqand MYOdec) in the dorsal forearm and
anterior leg for subjects with high IMP (possible chronic CS, group 1) and subjects with low IMP (no chronic CS, group 2) at rest and at 100% maximal voluntary contraction.
Dorsal forearm Anterior leg
Group 1 Group 2Group 1 Group 2
∗0.92 ± 0.41
∗#3.25 ± 1.27
∗15.7 ± 2.0
1.14 ± 0.27
#17.2 ± 8.1
#318 ± 119
25.5 ± 2.5
1.02 ± 0.13
∗0.74 ± 0.57
∗7.05 ± 1.26
∗15.7 ± 1.2
1.01 ± 0.34
3.09 ± 1.88
183 ± 84
26.7 ± 4.5
1.09 ± 0.34
∗2.48 ± 0.95
∗3.79 ± 1.97
∗23.4 ± 2.8
0.94 ± 0.32
#17.2 ± 7.7
335 ± 252
33.8 ± 7.5
#0.80 ± 0.14
∗1.78 ± 1.72
∗4.60 ± 3.91
21.8 ± 4.3
4.23 ± 1.48
317 ± 193
27.0 ± 6.1
1.00 ± 0.11
∗p < 0.05, as compared with the value at 100% maximal voluntary contraction (Wilcoxon signed ranks test).
#p < 0.05, as compared with the value of group 2 (Mann–Whitney U-test).
958R K Korhonen et al
Figure 5. Differences in intramuscular pressure (IMP) (a), electromyography (EMG) (b) and
myotonometry parameters (MYOfreq= frequency (c), MYOdec= decrement of decay (d)) between
pairs by using a Bland and Altman plot (Bland and Altman 1986). Number of subjects in IMP,
EMG and MYO groups were 37, 25 and 26, respectively.
parameters (frequency (MYOfreq) and decrement of decay (MYOdec)) with the intramuscular
pressure (IMP) in the dorsal forearm and anterior leg. For the correlation analysis parameter
values at different levels (0, 25, 50, 75, 100% MVC) of isometric loading were normalized with
that at 25% MVC.
∗p < 0.0001, n is the number of data points (e.g. n = 70 refers to 14 subjects).
significantly (r = 0.887–0.918, p < 0.0001, data not shown). Only the IMP values during the
last 100% MVC were statistically lower than those during the first 100% MVC (p < 0.05,
Wilcoxon signed ranks test).
EMG and MYOfreqcorrelated positively and significantly (r = 0.487–0.855, p < 0.0001,
table 3) with IMP at rest and during loading periods in the dorsal forearm and the anterior
leg. Mean values of IMP, EMG and MYOfreqcorrelated significantly (r = 0.868–0.993, p =
0.0007–0.06) with the relative (%MVC) muscle load both in group 1 and 2 (figure 6). Mean
values of EMG (75% and 100% MVC) and MYOfreq(0–100% MVC) were higher for patients
with high values of IMP (group 1).
When all subjects were pooled, the IMP and EMG amplitude (A) changes during 1 min
20% and 40% MVC were highly correlated (r = 0.747, p < 0.0001, figure 7). In 25 out of 38
Electromechanical characteristics of the muscle959
Figure 6. Intramuscular pressure (IMP) (a), electromyography (EMG) (b) and myotonometry
parameters (MYOfreq= frequency (c), MYOdec= decrement of decay (d)) (mean±SD) as a
function of relative, isometric muscle load (0%, 25%, 50%, 75%, 100% MVC) for subjects with
high (group 1) and low (group 2) values of IMP. Number of subjects in each group can be seen
from table 2.
electromyography (EMG) amplitudes during 1 min isometric contractions (20% or 40% MVC).
An exponential fit, y = A0 + Aexp(–kt), was made to each IMP and EMG measurement
(figure 3(b)), and the amplitudes (A) were correlated. Group 1 refers to the subjects with high IMP
values (suggesting chronic CS) and group 2 are the subjects with IMP values in the normal range.
Number of successful measurements was 38, which does not indicate the number of subjects as
the measurements for one subject were conducted during 20% and 40% MVC (figure 3(b)).
Linear correlation between the total change in intramuscular pressure (IMP) and
960R K Korhonen et al
the IMP amplitude decreased.
short-term and long-term isometric loading in subjects with pain in the anterior leg or dorsal
forearm. EMG and MYO parameters correlated positively and significantly with the IMP
values and could typically explain 24–73% (r2) of the variation found in IMP at the same time.
The mean values of EMG amplitudes at the contraction levels of 75% and 100% MVC
and MYOfreq values at all contractions levels (0–100% MVC) were higher for subjects
with pathological values of IMP compared to those with IMP values in the normal range.
During 1 min isometric loading, IMP and EMG amplitudes exhibited similar time-dependent
The similar time- and load-dependent behaviors of the IMP and EMG revealed the
interplay between the mechanical and electrical characteristics of skeletal muscle, and suggest
that major changes in the EMG signal may be indicative of chronic compartment syndrome.
et al 1997, K¨ orner et al 1984, Sadamoto et al 1983, Sjogaard et al 1986, 2004) which have
were conducted on healthy subjects, whereas in the present study the subjects suffered from
pain in the leg or arm. Some of the patients had high (pathological) values of IMP, suggesting
possible chronic CS. IMP is influenced by the muscle water content, compartmental volume
as well as the properties of the surrounding muscle fascia (Bourne and Rorabeck 1989).
Isometric loading probably increases transfer of fluid into the compartment leading to the
IMP elevation. However, in most subjects in this study, both the IMP and EMG amplitudes
decreasedduring1minofisometricloading. Possibly, theconstantloadwasnotmaintainedin
subject to transfer the load to other muscles of the arm or leg during recording. Unfortunately,
we were not able to conduct simultaneous EMG measurements on other muscles which
would possibly have revealed if load transfer had taken place. On the other hand, the time-
dependent behavior of the IMP might reflect the dynamic balance of interstitial muscle fluid
and mechanical properties of the muscle and fascia. After the initiation of loading there is an
immediate increase in the interstitial muscle pressure. In response to this increased pressure,
the fascia becomes tensed and extended at a rate controlled by the viscoelastic properties of
the tissue. These changes increase the compartment volume and may reduce IMP. Finally,
a static mechanical equilibrium is achieved between the existing forces from the fluid flow
induced muscle swelling and the tension of the muscle-fascia, after which no further change
in IMP takes place.
MYO reflects the functional state of skeletal muscle. In particular, MYO reflects the
tension of the muscle fascia and fibers (Vain 1993, 1995, 1999, Vain et al 1992, Veldi et al
2000). In principle, during isometric contraction, the muscle length does not change,
although increased IMP may subject the muscle fascia into tension in a load-dependent
manner. Also, as shown in figure 2, after the measurements at rest, the wrist was set to
dorsiflexion and measurements during 25–100% MVC were taken in this position. Obviously,
this change in the measurement position could cause nonlinearity in the MYO values at
EMG and MYO measurements predicted IMP with similar accuracy. The thickness of
the subcutaneous fat above the muscle varies from patient to patient which may cause some
Electromechanical characteristics of the muscle961
uncertainty in the MYO measurements, though this is more significant if the fat is greater
than 4.0 mm thick (Boiko 1997). Bipolar quantitative surface EMG measurements can also
be influenced by many factors such as the placement of the electrodes. These kinds of
disturbances were minimized by normalizing all the recorded parameters to 25% MVC. With
all relative load levels, MYOfreqwas systematically higher in subjects with pathological values
of IMP as compared to subjects with low IMP values. This finding indicates that high muscle
tonus might be indicative of chronic CS. Myotonometry can therefore be a helpful tool in the
diagnosis of muscle pathology. At high (75–100%) levels of isometric load, there was a trend
to increased EMG amplitudes in subjects with pathological IMP values, as compared to those
with low IMP values.
The positioning of the strap and the angle of the hand or foot can affect the total
force which the subject is able to resist. Therefore, these parameters were standardized
during the measurements as well as possible, even though small patient-to-patient variations
may have slightly influenced the results. In spite of standardization due to the anatomical
differences, the analyses were made separately for the dorsal forearm and the anterior leg.
The significant linear correlations detected between the maximum force and IMP, EMG and
to the next. Furthermore, as the main aim was to characterize the relationships between EMG,
IMP and MYO, the measurement geometry for all the parameters during one measurement
session was invariably the same.
For technical reasons we were not able to successfully conduct all EMG and MYO
measurements but had to neglect some from the final analyses. The IMP-based diagnosis
of chronic compartment syndrome follows the standard clinical protocol established in the
Kuopio University Hospital (Jurvelin and Mussalo 2003). As some of the measurements
were technically unsuccessful, and could not be repeated due to time limits, there are a
different number of patients in the IMP, EMG and MYO groups, and a different number
of EMG measurements during the second 100% MVC (figure 5) and during the long-term
measurements (figure 7). The different number of subjects may slightly affect the mean values
of the measured parameters, but not the correlation analyses. Due to practical limitations, the
consistency of the relationships between the EMG, MYO and IMP could not be determined.
However, the mean differences in the recorded parameters during the first and last 100% MVC
were close to zero indicating no systematic differences between the repeated measurements.
Using the present loading configuration and protocol, it may not be relevant to expect identical
IMP, EMG or MYO values between the measurements. The relatively large magnitude of the
95% confidence intervals, i.e. ±2SDs, in Bland and Altman plots may set some limitations for
the effective diagnostics and monitoring of the patients with small pathological impairments.
We emphasize that more studies are warranted to reveal the true precision of the employed
We conclude that both the surface EMG and MYO are indicative of IMP and could be
used as guiding tools in the diagnosis of chronic CS. However, due to the significant patient-
to-patient variations, we believe that neither of these methods can be used alone to diagnose
Finland (No. 107846); The Kuopio University Hospital (EVO), Kuopio, Finland; The Sigrid
Jus´ elius Foundation, Helsinki, Finland; The Invalid Foundation, Helsinki, Finland; and The
Alberta Heritage Foundation for Medical Research, Alberta, Canada is acknowledged. The
962R K Korhonen et al
authors want to thank Mikko S Laasanen, PhD, University of Kuopio, Finland for technical
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