Study on differentiation factors for main disease identification ofintermittent claudication
Tetsuyou Watanabe1 , Takeshi Yoneyama1 , Yasumitsu Toribatake2 , Hiroyuki Hayashi3 and Noriaki Yokogawa2

Abstract— Intermittent Claudication [1] is a walking symptom. After a short time walking, patients suffer from pains
at lower limbs. But if taking a rest, the pains can be relieved
and they can walk again. Unfortunately, it arises from not one
but mainly two kinds of diseases: LSS (lumber spinal canalstenosis) and PAD (peripheral arterial disease). Additionally,
it is reported that symptom is similar and LSS groups isfurthermore divided into two main groups: L4 and L5 groups.
Therefore, it is clinically very important to differentiate which
diseases the patients suffer from, PAD, L4 or L5. We aims
at developing the system to differentiate them from shortwalking motion data. In our previous paper [2], we derived
differentiation factors, but did not consider the difference
between L4 and L5 and the results are limited. This paper
focuses on biarticular muscles associated with the diseases, andderive new and effective differentiation factors. The results
supports their effectiveness and validity.

I. INTRODUCTION
Intermittent Claudication [1] is a walking symptom. Aftera short time walking, patients suffer from pains at lower
limbs. But if taking a rest, the pains can be relieved andthey can walk again. Recently there has been a marked
increase in the number of patients who consult a doctorof orthopedic surgery due to the intermittent claudication[3], since the intermittent claudication is one of walking
symptoms. Unfortunately, intermittent claudication comesfrom not one but mainly two types of diseases: LSS (lumber
spinal canal stenosis) and PAD (peripheral arterial disease).
Additionally, LSS can be divided into two groups: L4 andL5 radiculopathies based on the area where stenosis occurs.
It is clinically very important to identify the main disease
for intermittent claudication.
Toribatake at al. [1]–[3] pointed out that PAD and LSSgroups have similar symptoms and emphasized the significance of their differential diagnosis. There are mainly two
types of examination methods for differentiation. The one issimple but poorly precise and often fails to differentiate. The
examples are touching or observing standing posture. The
other is precise but invasive and high cost. The examples
are angiography, myelography, MRI (magnetic resonance*This work was not supported by any organization
1 T. Watanabe and T. Yoneyama are with the School of MechanicalEngineering, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192,
Japan (corresponding author to provide phone: +81-76-234-4682; fax: +8176-234-4682; e-mail: twata@t.kanazawa-u.ac.jp)
2 Y. Toribatake and N. Yokogawa are with the Department of Orthopedic
surgery, Koseiren takaoka Hospital
3 H. Hayashi is with the Department of Orthopedic surgery, Kanazawa
red cross Hospitalimaging), ABI (ankle brachial index) [4]. Furthermore, these
examinations require high professionals and precision instruments. It is difficult to conduct such a high cost examination
at small hospitals. If we can differentiate with minimum required simple instruments, it would be very useful, and evennon-professionals can easily use at small hospitals. With thisin mind, we developed another examination method in whichanalyzing 2D walking motion measured by commerciallyavailable cameras [2]. However, the difference between L4and L5 was not considered and the obtained results are still
limited. The derived differentiation factors were only withregard to one angle corresponding to uniarticular muscles.
However, the muscles associated with PAD, L4 and L5 are
not only uniarticular but also biarticular. It indicates thepossibility of existence of factors associated with biarticular
muscles, or combination of multiple angles. Then, this paper
tries to extract another differentiation factors related withcombination of multiple angles. In half a century, there areseveral researches concerning with walking motion analysis[5]–[8]. However, the differentiation of intermittent claudication by walking motion analysis has not been researchedvery well.
A. Participants
The participants are 13 normal healthy persons (5 males
and 8 females), 10 PAD patients (9 males and 1 females), 10
LSS (L4) patients (6 males and 4 females), and 13 LSS (L5)patients (4 males and 9 females). Medical doctors among
the authors comprehensively considered clinical features,radiological examinations, surgical findings, MRI, MRA,
ABI, contrast enhanced CT, and effects of selective nerve
root blocks and diagnosed the patients. Since patients with
LSS mainly suffers from L5 or L4 radiculopathies, this paper
focuses on L5 and L4.
B. Motion capture
Fig.1 shows the walking motion measuring system. We
constructed the measurement system as much as simply
such that at small hospitals, even a few non-professional
medical staffs can use. Note that we do not aim at developing
measurement systems with high accuracy, but extracting
clinically convinced and useful differentiation factors fromlimited information (from simple instruments). We also suppose that measurement is conducted in narrow space and at
not-controlled environment. Then, we measured gait patternof participants with LED markers who walk on the treadmill

***

Subject***

800~900mm
TripodFig. 1.

Angle [degree]

CameraTreadmill*140

5 LED Markers

130** : P<0.05* : P<0.1120
1102300~3000mm

100

Walking measurement systemyyFig. 3.

Acromion(Marker 1)(x1,y1)

Normalxx

Femur angle

Head of fibula (Marker 3)(x3,y3)

L4

*

180

L5

* : P<0.1**

175
Angle [degree](x2,y2)=(0,0)

PAD

Average of ankle angle

Upper body angle

Anterior superior
iliac (Marker 2)**** : P<0.01

170
165
160

Knee angle

Lateral malleolus (Marker 4)(x4,y4)(x ,y )
5

Ankle angle

Normal

PAD

L4

L5

5

Fifth metatarsal head (Marker 5)(a) Marker positions

Fig. 2.

155

Fig. 4. Knee angle at stance phase start time (The dash lines show thecase when conducting t-test for every pair)(b) Angles

Coordinate frame, marker positions, and angles

in semidarkness such that LED marker positions can easily
captured. Semi-darkness can transform not-controlled environment into controlled environment. Another purpose is todifferentiate the groups with minimum required information.
If the instruments are a few and simple, non-professionals
can easily handle them and we can reduce measurement time,
which is also comfortable for patients. Concerning this, weused the simple 2 dimensional motion capture system.
We put handmade LED markers on acromion, anterior
superior iliac, head of fibula, lateral malleolus and the 5th
metatarsal head of participant. Fig.2 (a) shows the definitionof the coordinate frame and the marker positions. Note thatthe right side is forward in Fig.2. The LED markers wereattached on the disordered leg. Before the experiment, theparticipants took a practice of walking on the treadmill. Its
purposes are safety, calibrations, and setting of the treadmill
speed.
We decided the speed so that the participant can normallywalk. If the participant felt pain, we stopped the measurement. For the safety, medical doctors stand by watching theparticipant such that the medical doctors can immediately
stop the treadmill and help the participant at accidents.
The length per pixel of image was calibrated according tomarker length attached on the treadmill. The used camera
is commercially available product, and its frame rate was30[frame/sec].
C. analysis
The used angles for analysis are shown in Fig.2 (b). We
detected the marker positions by our own algorithm [2] based
on LK filter [9]. From the marker positions, we derived theangles. Note that the angles do not identical to real ones
since they are mapped on the sagittal plane, and then wecall them with our own names. Analysis was conducted withregard to average one cycle data. The accuracy of this systemdepends on the resolution of camera and the distance between
treadmill and camera. It was 2.97±0.23 [mm/pixcel].
II. D IFFERENTIATION FACTORS
Frist, we describe the previously derived differentiation
factors [2], in order to see how they change when considering
L4 and L5 groups separately. Next we describe about new
differentiation factors corresponding to biarticular muscles.
Here, we focus on gastrocnemius muscle where is criticalpart for PAD group and quadriceps muscle where L4 grouphas sensation disturbance. After showing the results, we will
discuss the results.
A. Previously derived differentiation factors [2]
Fig.3 and Fig.4 respectively show the results for previously
derived differentiation factors. Let stance phase start time
be the time when the x component of the marker positionon the 5th metatarsal head is the largest. At the time thefoot reaches its most forward position, and then the time
is not always identical to the time when real stance phasestarts (which is possibly before the stance phase start time).
Therefore, we picked up knee angles at 4 frames before thestance phase start time and at the stance phase start time,and calculated their average, which is the knee angle atstance phase start time. From Fig.3, it can be seen that PAD
group has large values while L5 group has small values,
and there are statistical significant differences between PAD
and L5 groups. Note that we used tukey-kramer method forstatistics analyses. From Fig.4, it can be seen that the values

Gastrocnemius stop position=(xh1 , yh1)

Gastrocnemius start position=(xh2 , yh2)

Rectus femoris stop position=(Xd1 , Yd1)
knee

Knee
K
Kn
ee angle = θ 3

440mm

Gastrocnemius
180° - θ4

180° - θ3

Femur////////////////////////////////////////////////////////////////////////////////////////////////
/ ///
/ ///
/ ///
/ ///
/ ///
/ ///
/ ///
/ ///
//

Tibia
Ankle

40mm

Knee

Ankle angle = θ 4

∟

foot

50mm

m
40m

370mm

(b) quadriceps muscle
Reference models for biarticular muscle muscles********* : P<0.01

*

***

***

** : P<0.05

400* : P<0.1

390

380

370
Normal

PAD

L4

L5

Fig. 6. Maximally relaxed muscle length of gastrocnemius muscle at thereference model
***
**

40

*** : P<0.01***

Motion range (mm)180° + θ1(Upper body angle) + θ2 (Femur angle)

Rectus femoris passage position=(Xd3 , Yd3)

Fig. 5.

410

Rectus femoris
P
Patella(a) gastrocnemius muscle

Maximally Expanded muscle length(mm)

Rectus femoris start position=(Xd2, Yd2)** : P<0.05* : P<0.130

20reference model regarding the knee and ankle angles for theparticipant as the knee and ankle angles for the model. Let
the derived length be the muscle length for the participant. It
is different from the real muscle length for the participant, but
directly comparable. The comparable muscle length can besaid to be normalized muscle length. Hereafter, we abbreviate
normaized unless otherwise noted.
Utilizing this model and angle data, we calculated maximum relaxed and contracted muscle lengths, and motion
range (See Fig.6 and Fig.7. Relatively effective factors are
only shown). For maximum relaxed length, the value getslarger with the order of PAD, L4 and L5 groups except forNormal group. The difference was vivid and there are statistical significant differences between many groups. For motion
range, the values for Normal groups are only large and there
are statistical significant differences between Normal and theother groups.
C. Factors associated with quadriceps muscle

10
Normal

PAD

L4

L5

for L4 group is only large, although we did not get any
significant differences. Note that if we conducted t-test forevery pair, we got significant differences between L4 and theother groups, shown in Fig.4 with dash lines. The difficultyof differentiating L4 groups can be seen.

With the same way as gastrocnemius muscle, we createdthe reference model (Fig.5 (b) for quadriceps muscle associated with critical part for L4 group and derived comparable
and normalized muscle length. Utilizing this model and angle
data, we calculated maximum relaxed and contracted muscle
lengths, and motion range (Fig.8 and Fig.9). For maximum
contracted length, the value for L4 is small, although vivid
differences could not be gotten. For motion range, the valuesof normal and L4 groups are large and there are statisticalsignificant differences between L5 and the other groups.

B. Factors associated with gastrocnemius muscle

D. Discussion

Here we derive new differentiation factors associated withgastrocnemius muscle where is critical part for PAD group.
There is individual difference for body size, and directcomparison of muscle lengths does not make sense. Then, weused reference model. We made it based on the bone sizeof the real human skeleton model in our lab. We decided
the connecting positions between muscles and bones for thereference model based on the data of anatomia [10], [11].
Fig.5(a) shows the created reference model. If consideringcertain participant data, we calculated muscle length at the

From Fig.3, previous factor [2], namely average angleof ankle is considered to be effective to differentiate PAD
and L5 groups. From Fig.6, it can be seen that maximallyrelaxed muscle length of gastrocnemius muscle are effective
to differentiate PAD and the other groups. Comparing withthe previously derived factors, its high effectiveness can be
seen.
Soleus muscle associated with ankle angle and gastrocnemius muscle belong to triceps surae muscle which is critical(the area where problems appear) for PAD group. PAD

Fig. 7.

Motion range of gastrocnemius muscle at the reference modelMaximally contracted muscle length
(mm)

565
* : P<0.1*’ : P<0.105
*’
*

560

555

550
Normal

PAD

L4

L5

Fig. 8. Maximally contracted muscle length of quadriceps muscle at thereference model***

III. C ONCLUSION

*
*

***

25

Motion range (mm)*** : P<0.01** : P<0.05* : P<0.1

20

15

10
NormalFig. 9.

PAD

range similar to Normal group might be due to the unexpected bending/flexion (If they could avoid the unexpected
bending/flexion, motion range might be small). Note that thereason for small motion range at L5 group is considered tobe the same as the case mentioned before.
Summarizing, by considering differentiation factors associated with biarticular muscles (combination of multiple
angles), we got stronger differentiation factors for differentiating Normal, PAD, L4 and L5 groups (comparing withpreviously derived factors).

L4

L5

Motion range of quadriceps muscle at the reference model

patients have to prevent collapse and stenosis of blood vessel
inside the muscles. They would like to keep the radius of theblood vessel large in order to deliver the blood minimizing
the loss of the blood flow, especially at the knee joint inspite of the decrease of the blood flow at the upstream
due to stenosis, and keep enough large blood flow at cruralmuscle. Then, they keep the length of the gastrocnemius
muscle large, and ankle angle large at any time. In reality, thefactor associated with gastrocnemius muscle is related withthe soleus and gastrocnemius muscles and then this might
be the reason why this factor was more effective.
On the other hand, L5 group has sensation disturbance attibialis anterior muscle and bottom side of foot. This causes
the increase of risk of collisions between (tip area of) footand ground. In order to decrease the risk, L5 patients tend
not only to keep ankle angle small but also not to lift up
their legs, which indicates their walking is close to shuffling.
Small ankle angle, large maximally relaxed muscle lengthand small motion range support the hypothesis.
From Fig.9, it can be seen that motion range of quadriceps
muscle are effective to differentiate L5 and the other groups.
But, if seeing both Fig.8 and Fig.9, it can be seen that
this factor is important for differentiation of L4 groups.
From both figures, we can see that motion range for L4
group is similar to Normal group, but the contraction amountis largest. It indicates that L4 group walks keeping thequadriceps muscle contracted. For L4 group, quadriceps
muscle is critical and there is sensation disturbance. This
causes large unexpected bending/flexion of knee angle justafter landing. In order to get smooth walking in spite of theunexpected bending/flexion, they tend to keep the quadriceps
muscle contracted (small upper body, small femur and large
knee angles), especially at the landing (see Fig.4). Motion

Intermittent claudication mainly comes from two kindsof diseases: LSS (lumber spinal canal stenosis) and PAD(peripheral arterial disease). LSS is also subdivided into
L4 and L5 groups. The medical treatments for them aretotally different, and then their differentiation is very important problem. In our previous paper [2], we derived
differentiation factors related with unit angle. However, theobtained results were still limited. This paper presented
new differentiation factors associated with combination ofmultiple angles, focusing on biarticular muscles. The results
support the effectiveness of new factors. We also discussed
why we got effective factors taking into account diseases
characteristics. The derived factors are effective but a little
bit large variances can be seen. The differentiation system
concerning the variance might be our future work.
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