Comprehensive diagnosis of lower extremity

pathologies requires assessment of the contractile capaci�

ty of muscles. The literature on joint mobility diagnosis

and dynamometry of the femur and crus muscles is enor�

mous [1�3]. There is a correlation between muscle force

and cross�sectional area [4]. This correlation is charac�

terized by age� and gender�dependent factor of

force/cross�sectional area of muscle [5]. This factor

increases twofold from 6 to 20 years of age without gen�

der�related variation and does not depend on sex hor�

mones [6]. In diagnostic practice, it is methodologically

difficult to interpret the results of hand dynamometry.

The physiological basis of this test and test methodology

as well as exact interpretation of test results are the main

problems. Femoral dynamometry is particularly impor�

tant in the case of femur pathology. The methodology of

the test and interpretation of its results require additional

study. In addition to practical purposes, the results of the

test are of considerable theoretical significance [7]. The

literature about functional incompetence of femoral mus�

cles in postural and locomotor behavioral stereotypes is

scarce and scattered.

The femoral dynamometer was constructed at the

Ilizarov Scientific Center for Restorative Traumatology

and Orthopedics, Ministry of Health of the Russian

Federation [8]. The femoral dynamometer (Fig. 1) con�

tains a platform 1, frame 2 with a seat 3 with back holder

5 attached to the seat plank 4 and dynamometer 6, which

is connected to cuff 8 by cord 7. In addition, the frame

racks 9 are arranged as tubes with mobile plank 10 and

arm holders 11. The frame plank 12 is attached to guide�

way 13 with plate 14, which is fixed with screw 15.

The femoral dynamometer is used as follows. The

crus flexor is tested in the sitting patient. The height of

Biomedical Engineering, Vol. 48, No. 1, May, 2014, pp. 30�32. Translated from Meditsinskaya Tekhnika, Vol. 48, No. 1, Jan.�Feb., 2014, pp. 27�30.

Original article submitted October 26, 2013.

300006�3398/14/4801�0030 © 2014 Springer Science+Business Media New York

Ilizarov Scientific Center for Restorative Traumatology and

Orthopedics, Ministry of Health of the Russian Federation, Kurgan,

Russia; E�mail: rjik532007@rambler.ru

* To whom correspondence should be addressed.

A Femoral Muscle Dynamometer

V. A. Shchurov*, T. I. Dolganova, and D. V. Dolganov

A dynamometer for measuring the strength of the femoral muscles (crus and femur flexors and extensors) was

developed. Dynamometric parameters of femoral muscles in the norm and their dependence on age (7�40 years

old) were determined. Two working modes of the muscles of the hip joint in patients with ankylosis were highlight�

ed. The pathognomonic symptoms include the lack of hip joint mobility and fixed abnormal position of the extrem�

ity. Any extremity motion is performed at the expense of the healthy part of the hip joint. The results of the tests

allowed therapy tactics to be elucidated and corrected.

Fig. 1. Femoral dynamometer.

Femoral Muscle Dynamometer 31

platform 1 is 20 cm. Cuff 8 is attached to the ankle joint

above the crus. If knee contracture is absent, the crus is

bent at an angle of 90о. If knee contracture is present, the

angle is increased as much as possible. Unit 7 is used to

regulate the length of the cord. The muscle force is meas�

ured by the Tokar dynamometer with cord connected to

the dynamometer (certificate No. 86/1027�68) attached

to plank 4. The maximal force is tested for the standing

patient. The patient faces frame 9, while his/her knee

contacts plate 14. The total force of the crus flexor is

measured. Plate 14 is extracted from cylinder 13 and fixed

using screw 15.

The crus–extensor force moment is calculated by the

formula:

М = F·L·cos(α – 90°).

The crus–flexor force moment is calculated as:

М = F·L·cos(180° – α).

The parameters of the femur extensor and flexor as

well as femur adductors and abductors were determined.

Plate 14 is inserted into cylinder 13. The patient’s hip is

attached to plank 10. The standing patient contacts plank

10 and the dynamometer. The distance from the patient’s

hip to cuff 8 determines the lever length L. The hip cen�

ter is 1 cm above femoral artery, close to the trochanter.

The force moment is calculated from the absolute

force F measured using the dynamometer and distance L

from hip to cuff 8, as well as knee joint angle α other than

90°.

The force moment is calculated as:

М = F·L.

The femoral dynamometer provides comfortable

testing conditions. The goal of this work was to test

dynamometric parameters of femur and crus flexor and

extensor as well as femoral adductors and abductors.

Results

A total of 200 persons without orthopedic patholo�

gies (7�40 years old, 102 males and 98 females) were test�

ed (Table 1). The age dependence of the force of flexors

and extensors was observed. The total increase in muscu�

lar force was due to increase in body weight. In children

7�11 years old, the index of muscle antagonists was gen�

der�independent (1.3�1.4). During the pubertal period,

the increment of relative and absolute parameters of crus

extensors was larger than in crus flexors. The index of

muscle antagonists increased. This index in girls 11�13

years old or in boys 15�17 years old was 1.6�1.8. In adults,

the maximal force of extensors was 1.5�2 times greater

TABLE 1. Dynamometric Parameters of Femoral Muscles in the Norm (N·m)

M

n = 17

48.2 ± 3.11

34.4 ± 2.55

72.7 ± 5.61

75.6 ± 5.44

50.2 ± 3.29

54.4 ± 3.23

69.9 ± 4.21

(28.6%)

F

n = 13

43.7 ± 2.29

31.6 ± 3.58

58.2 ± 5.98

56.5 ± 5.41

37.5 ± 3.44

40.6 ± 3.88

55.8 ± 4.11

(37.6%)

M

n = 11

71.7 ± 3.09

51.6 ± 2.66

90.2 ± 5.11

101.6 ± 6.72

68.6 ± 4.12

70.9 ± 4.09

99.8 ± 5.23

(40.9%)

F

n = 13

77.3 ± 4.55

44.5 ± 4.34

77.8 ± 4.98

96.2 ± 5.14

65.3 ± 4.31

71.7 ± 5.34

99.1 ± 5.763

(38.2%)

M

n = 12

120.6 ± 6.42

76.3 ± 4.64

150.6 ± 6.51

158.3 ± 6.85

113.8 ± 6.61

114.5 ± 6.53

151.7 ± 5.92

(32.5%)

F

n = 18

84.8 ± 6.04

64.3 ± 5.56

90.9 ± 5.70

103.9 ± 7.11

71.6 ± 5.51

76.9 ± 5.82

105.5 ± 5.16

(37.2%)

M

n = 26

141.2 ± 6.33

86.8 ± 5.98

187.7 ± 6.74

182.4 ± 6.97

146.9 ± 5.99

150.7 ± 6.08

183.4 ± 7.02

(21.7%)

F

n = 18

91.2 ± 6.04

69.1 ± 5.06

96.9 ± 6.70

96.4 ± 6.12

65.2 ± 6.51

77.1 ± 7.01

103.5 ± 6.45

(34.3%)

7�11 years 12�13 years 14�15 years 16�17 years 18�40 years

Crus

extensor

Crus flexor

Femur flexor

Femur

extensor

Femur

adductors

Femur

abductors

Abduction at

maximal

adduction

(%)

M

n = 36

154.5 ± 6.76

122.7 ± 5.99

198.7 ± 6.82

196.3 ± 6.34

157.0 ± 5.89

163.8 ± 5.69

194.9 ± 6.44

(19%)

F

n = 36

111.7 ± 5.55

79.5 ± 4.79

94.2 ± 5.38

104.8 ± 6.72

71.6 ± 5.56

81.5 ± 4.88

101.5 ± 6.21

(24.6%)

32 Shchurov et al.

than the maximal force of flexors, which was training�

dependent [9].

Seventy patients with pathologies of the proximal

segment of the femoral bone were observed. In patients

with dysplasia of the hip joint, there was a significant

decrease in the parameters of femoral flexor dynamome�

try (m. psoas and m. iliac), as well as femoral adductor

(gluteus minimus and gluteus medius muscles). Femoral

extensors prevent kyphosis of the hip. One�year�long

therapy completely restored parameters of muscle

dynamometry. This provided for the recovery of the

femoral muscular apparatus. Nevertheless, 6 months after

the Ilizarov apparatus was removed, the femoral dynamo�

metric parameters remained constant. One year after the

Ilizarov apparatus was removed, the parameters were at

the level of 79% of the initial value. Crus flexors and

femoral abductors recovered more slowly [3].

In 20 patients with hip ankylosis (18�34 years old)

the movement of the pathological extremity was imple�

mented at the expense of the healthy hip part [10].

The intact extremity muscles operate in two modes:

1) femur movement at the expense of hip movement; 2)

intact extremity movement. In mode 1, the ankylosed leg

was tested using the dynamometer plank 10 set at various

heights. In mode 2, the intact leg was tested using

dynamometer plank 10.

In patients with hip ankylosis, there was a 20�40%

decrease in the muscular force of the intact extremity in

mode 1 before therapy relative to mode 2. The index of

antagonists was constant in the intact extremity in the two

modes. This index for femoral adductors/abductors was

96�105%, while for extensors it was 75�85%.

Conclusion

1. The femoral muscle dynamometer suggested in

this work allows the functional state of femoral muscles to

be tested quantitatively in adequate units and their

dynamics to be measured objectively.

2. The tests of the dynamometer in healthy subjects

and patients with locomotor pathologies demonstrated

that there are age and gender variations in the force

parameters of the tested muscles. Their recovery dynam�

ics were also studied.

3. Compensatory mechanism was observed in

patients with hip ankylosis. Any pathological extremity

motion was performed at the expense of the healthy part

of the hip joint.

4. The mathematical expectation of the force

moment of the muscles given in Table 1 with regard to the

age and gender can be used as a measure of pathology

severity.

5. The dynamometric parameters of the tested mus�

cles are additional diagnostic symptoms and allow reha�

bilitation tactics to be corrected.

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