RU2271147C2 - Method for recording biomechanical properties of the vertebral column - Google Patents

Abstract

FIELD: medical engineering.

SUBSTANCE: method involves acting upon testee in sitting position with rectangular acceleration pulse by removing support member for a short time in throwing mechanism usable for treating testee sitting still thereon. Complex mechanical action is applied under these conditions including stretching, dosed quasi-static action and vertebral column compression. Next, mechanical responses are received, amplified and analyzed by means of measuring apparatuses arranged in points under test and compared to each other and to reference values. Both own patient mass brought to known height and body mass reduced to given reference values with loads arranged on patient body. Differences between the obtained parameters and the reference values are interpreted in terms of biomechanical vertebral column properties. The device design is also described.

EFFECT: high accuracy in recording biomechanical properties; wide range of functional applications.

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Description

The invention relates to medicine, namely to vertebrology, and may find application in the diagnosis of diseases of the spine.

A known method for the study of bone tissue based on ultrasonic echoostometry is that the mechanical properties of bone tissue are examined by measuring the speed of propagation of ultrasound in it in different parts of the bone, for which signals are received by several sensors located at a certain distance from each other (a. S. USSR No. 1159556, A 61 B 8/00, 1983).

The ultrasonic echoostometry method has a number of disadvantages, including:

- diagnostic information is largely dependent on the impedance of paraossal tissues;

- ultrasonic vibrations for bone tissue are subthreshold and decay quickly, which does not allow the study of multilink kinematic structures;

- do not cause the appearance of a reflex response to a mechanical stimulus.

There is a method of determining the biomechanical properties of the spine by conducting x-ray functional tests, which consists in the study of the structures of the spinal column by performing x-ray in various functional positions [1].

The disadvantages of the method are:

- the inability to conduct a quantitative analysis of the biomechanical properties of the spine in various segments at a standard selected load;

- locality of the examination associated with a specific anatomical zone of the spine;

- high radiation load associated with the need to perform a series of images;

- the high cost of the study, which complicates its use when observing patients in dynamics, including with preventive examinations in outpatient practice.

There is a method of posthumously determining the strength properties of the cancellous bone of the vertebrae by forming fragments of the spongy bone from the vertebral body, followed by determining the maximum force required to compress the samples in the horizontal or vertical direction, with determining the amount of compression deformation. After that, the elastic modulus of bone tissue samples was determined [2].

The disadvantages of the method is that it cannot be used in relation to a living person, since the sample must be removed from the bone tissue of the vertebral bodies, and after the study, the sample is destroyed.

Closest to the proposed is the "method of determining the depreciation properties of the human support apparatus", which consists in the fact that the depreciation properties of the musculoskeletal system are determined by mechanical action, followed by registration of reflected changes from the bone tissue with the installation of sensors over bone landmarks minimally covered with soft tissues and as far as possible from the tendons, the sensors are oriented along the shortest distance from the distal to the proximal the point of propagation of body vibrations on the studied segment with the determination of the amortization properties by the degree of damping of the vibrations of the body under study between the two seismic sensors, and the vibrations are excited by lifting on socks and then abruptly lowering them on the heels.

The disadvantages of the method are:

- during its implementation, it is impossible to ensure the accuracy and repeatability of exposure conditions;

- shock impact on the musculoskeletal system of the proposed method is weak and quickly fades;

- the impact is transmitted to the spine through the belt of the lower extremities and the pelvic bone, which creates a large number of interference and artifacts, since it is known that heel fat, capsule-ligamentous apparatus of the joints of the lower limb, sacroiliac joints have pronounced damping properties;

- the acoustic characteristics of the right and left lower limbs differ due to various anatomical parameters, so the mechanical impulse does not reach the spine symmetrically, which reduces the information content of the method;

- spinal stretching and the reflex component of the body's response to the impact are not analyzed, while these are important diagnostic parameters.

Thus, the use of this method is not very informative with respect to the spine, since the impact is not dosed, it is very weak and is not symmetrical from the right and left lower extremities to the spine.

An analogue of the proposed device is an ultrasonic, frequency-scanning echoosteometer based on recording the propagation velocity of mechanical vibrations in bone tissue. The echoosteometer contains: an analog-to-digital converter, the input of which is connected to the amplifier output, a control computing device, the group of inputs of which is connected to the group of information outputs of the ADC, the information from which is supplied to the permanent storage device. The echoosteometer is highly sensitive, since an amplifier, ADC and read-only memory are inserted into it, which allows a quantitative assessment of the state of bone tissue (AS USSR No. 2076635, A 61 V 8/08, 1984).

The disadvantage of this device is that it is difficult to use in the study of biomechanical properties of the spine, since emitters are difficult to adapt with uneven contours of the apophyses of the vertebrae. The use of the device is limited by the locality of the study, is very energy intensive, requires the presence of a doctor. In addition, the device is expensive.

Closest to the proposed device is a device for studying the effects of vibration loads on biological objects. The device includes: a vibration exciter on the base, seismic sensors, matching and measuring amplifiers, an analog-to-digital converter (ADC), which has communication lines with a computer. The device allows you to transmit vibrational effects on the human body in a sitting position, subsequently measuring the mechanical impedance of the body using seismic sensors located at the point of contact of the body with the support, on the head and upper limb of the subject [4].

The disadvantages of the closest analogue of the device is that the mechanical impedance and complex frequency functions described by the researchers characterize only the distribution of vibrational effects in the body and do not have a physiological interpretation, since vibrational effects are not an adequate load for the musculoskeletal system with which a person is found only in technologically created conditions. The dependence of the amplitude and phase of oscillations of various parts of the body on the frequency of the vibrational effect, analyzed by the authors, varies widely, therefore, it cannot be interpreted as a source of diagnostic information. Using the described device, it is impossible to stretch the spine and fix the reflex component of the body's response.

Thus, none of the considered methods and devices for the formation of test samples on the human spine implements the required adequate effects, none of them provides synchronization of effects and recording of responses, which does not allow the constancy of testing conditions and the complete extraction of information. An additional problem is the restoration of standard conditions for bringing the device into working condition before the next test breakdown.

The aim of the invention is to provide a method for improving the accuracy of diagnosis of biomechanical properties of the spine.

This goal is achieved by the fact that in the known method of recording the biomechanical properties of the supporting apparatus of a person, which consists in the fact that mechanical effects are carried out with subsequent registration of reflected changes from the bone tissue, using seismic sensors located on the spinous processes of the vertebrae and bones of the skull, according to the method of excitation mechanical vibrations in the spine is performed by instantly removing support using a dropping mechanism designed for motionless about the patient sitting on it, and as the test effect, they use both the patient’s own mass, cocked to a certain height, and the patient’s mass, brought to the standard selected values using additional loads hung on the patient, and then the mechanical responses located at the test points are compared between themselves and with the reference, whereby they judge the biomechanical properties of the spine.

To implement the method, a device was developed, consisting of a base, made with the possibility of placing the examinee on it in a seated position, with seismic sensors placed on it, connected to measuring equipment, according to the invention, movable and fixed flaps connected by a hinge between the flaps are located on the base there is a limiter of mobility and magnets connected to flexible rods and a synchronizer for recording data of measuring equipment.

Figure 1 presents the proposed device in an unassembled form. Figure 2 presents the device in assembled form. Figure 3 - the device is in the active state. Figure 4 - the device after removing the support of the resetting mechanism. 5, 6, 7 - resetting mechanism. Fig - the location of the patient on the device before the examination. Figure 9 - mechanical response from a seismic receiver located on the movable shutter of the device: A is the moment of removal of the support, B is the free fall phase, C is the restoration of the support reaction, D is the phase of the quasistatic effect. FIG. 10 is a diagram of a device.

The device comprises a movable leaf 1, a metal disk (leaflet limiter) 2, a rod 3 (hinge), a fixed leaf 4, a base 5 (Fig. 1), permanent magnets 6, a synchronizer 7, flexible rods 8 (Fig. 6). Seismic sensors located on the skin in the projection of the parietal bones of the skull 9, seismic sensors located on the skin in the projection of the spinous processes of the vertebrae 10, the seismic sensor located on the movable leaf of the device - 11, amplifier 12, analog-to-digital converter 13, electronic computer 14.

The implementation of the method is as follows: the patient is explained the meaning of the study, after which he is seated on the movable leaf of the device 1, which is in the activated state, shown in Fig. 8. A motionlessly seated patient is “dumped” from a certain safe height, for example, 1-2 cm, as a result of which, from the moment the support reaction disappears, while the body is still in contact with the surface, until its recovery, a multicomponent mechanical effect on the spine occurs. The nature of the impact shown in Fig.9. After the support is removed, the pelvis with the lower half of the trunk and lower extremities, under the action of gravity, rushes down, while the inertia of rest still acts on the head, as a result of which the spinal column lengthens like a spring - the stretching phase. In the second phase, the reaction force of the support of the mobile shutter of the device is restored. At the moment of contact of the movable leaf of the device on which the subject is placed, a metered quasistatic ascending, mechanical effect is applied to the surface. The impact energy is transmitted along the structures of the spinal column. The third phase is due to the fact that the head and upper body, which continues to move under the influence of gravity, after restoring body weight, cause compression of the spine in all departments, as a result of which its length becomes shorter than at rest. In this case, the patient’s contact with the surface of the movable sash remains during the entire exposure time, therefore, the effect of the second phase carried out using the proposed method is not shock, but quasistatic. At the time of the restoration of the support, the mechanical effect is transmitted directly to the movable leaf of the device, which in turn transfers it to the branches of the ischial bones of the pelvis in contact with it. The impact is transmitted to both sciatic bones at the same time with the same strength, which is difficult to implement in any other way. The mechanical responses received by seismic sensors located on the spinous processes of the vertebrae and bones of the skull record the processes of transmission of the effect on the structures of the spinal column. Subsequently, amplification and analysis of signals received from the sensors is carried out, followed by processing of the received signals using an analog-to-digital converter connected to a computer. The biomechanical properties of the spine are judged on the basis of data obtained in the process of deciphering the mechanical responses by the time of appearance and their amplitude characteristic (Fig. 11-14). Such complex movements of the spine occur during walking, so the proposed method is closest to physiological stress. Human body mass is an “adequate” load for the spine, and that is why it is used as a source of test exposure (Figure 10). After the test with its own weight, the body weight is brought to a certain standard value, for example 80 kg, if the adult population is examined. By placing additional weights on the subject at certain points on the body, which allows us to analyze the biomechanical properties of the spine under conditions of additional load and, if necessary, standardize the impact. In this case, the mass of additional cargo is Σm = 80kg-m _rev (m _rev is the mass of the subject). After that, the obtained parameters are compared with each other and with the reference ones. The reference indicator is the data obtained during the examination of healthy individuals of the corresponding gender, age and constitution.

We give an example of mechanical responses obtained during examination of an adult patient who does not have a history of injuries and diseases of the spine. The start of recording parameters from seismic sensors is the signal received from the synchronizer. Figure 11 presents the mechanical response from the seismic sensor located on the parietal bones of the skull of the subject. The mechanical response contains 3 phases: phase A - the extension phase, which characterizes the elastoelastic properties of the ligamentous apparatus and is 0.07 ± 0.005 s; phase B - registers a mechanical impulse transmitted along the spine, characterizes the mechanical properties of bone structures, duration 0.15 ± 0.005 s, amplitude (Dmax) 25 ± 2 mV. Phase C is the reflex component of the response, the time of occurrence is 0.08 s, the duration is 0.02 s, the amplitude is 10 ± 2 mV.

12-14 show the mechanical responses from seismic sensors located on the skin in the projection of the spinous processes of the 4 lumbar, 12 thoracic and 6 cervical vertebrae, respectively. The responses were analyzed by appearance time, maximum and average amplitude.

On Fig presents the mechanical response from the seismic sensor located on the skin in the projection of the spinous process 4 of the lumbar vertebra. The appearance time is 0.01 ± 0.005 s, the maximum amplitude is 460 ± 5 mV, and the average amplitude is 200 mV. In FIG. 13-12 thoracic vertebra: appearance time 0.03 = 1 = 0.005 s, maximum amplitude 170 ± 5 mV, average amplitude 50 mV. On Fig presents the mechanical response from the seismic sensor located on the skin in the projection of the spinous process 6 of the cervical vertebra. The time of occurrence is 0.06 ± 0.005 s, the maximum amplitude is 45 ± 5 mV, and the average amplitude is 15 mV.

The described complex mechanical action can be accurately dosed only in the case when it is possible to reproduce with a given accuracy the law of the reaction of support. In a specific case, the reaction of the support must be eliminated instantly (stepwise) and then instantly restored after a delay time. The prototypes of the method and device considered do not include the means of implementing the specified exposure requirements. As such a means of manipulating the support, a device is needed that almost instantly eliminates the reaction of the support. The most effective as switching devices are mechanical systems with “disasters” of assembly type [5]. An example is a bending rod, loaded along the axis. If at a certain moment the rod is at least slightly bent, then it instantly loses stability. Equally important is the accurate restoration of the initial conditions of the experiment and the exact synchronization of the recording of response signals with the moment of switching the reaction of the support, to ensure the repeatability of the conditions of the impact.

The device operates as follows: on a massive base, cylindrical in shape 5, to which the rigid metal sheet 4 is fixedly connected, which is a fixed leaf, with which, in turn, like a book, by means of a hinge, a second metal sheet 1 is joined, having adjustable mobility in the front the plane. Between the flaps 1 and 4 there is a limiter for the mobility of the flaps 2, fixedly connected to the lower flap 4. Figure 2 shows the device in assembled form. The device is brought into active state by cocking the movable flap 1 to a certain height, which is held by a dropping mechanism, which is two magnetic rods 6, which are movably connected to the flaps of the device 1 and 4. Figure 3 shows the device in active form. Figure 4 presents a view of the device after dropping the movable leaf 1. Figure 5, 6, 7 shows a dropping mechanism. 1 - movable leaf, 4 - fixed leaf, 6 - two magnetic rods, 7 - synchronizer, 8 - flexible rods. The device is activated by moving the rods 8, which soon violate the balance of the docked magnets 6, as a result of which the movable leaf 1 loses its support and collapses on the metal disk 2, FIG. 4, 7. The position of the valves 1 and 4 and the resetting mechanism before activation is shown in Fig.6. Final phase - FIG. 7. The pull for the threads 8 is carried out, for example, using a core, an additionally installed electromagnet. After exposure, the movable sash 1 is again cocked to a height exceeding the length of the magnets 6, as shown in Fig. 5, while the ends of the magnets 6 spontaneously and accurately fit, and the sash 1 is carefully lowered, after which the device is ready for exposure again (Fig. 6). To synchronize the operation of the device and measuring equipment at a certain distance from the magnetic rods 6 of the dropping mechanism, a synchronizer 7, for example a reed switch, is closed, the contact closure of which occurs even with a slight change in the position of the magnets 6 from the vertical, which serves as an impulse to start recording parameters of seismic sensors located at the test points on the patient and starts the registration of the signal on the computer. The nature of the effect is monitored using a sensor, which is located on the movable leaf of the device, the mechanical response of which is shown in Fig.9.

Thus, the method improves the accuracy of the diagnosis of biomechanical properties of the spine with the possibility of impact on the spine of the examined complex mechanical effects, which includes tension, quasistatic effects and compression. Such an impact cannot be realized using previously existing methods. The method allows to analyze both the mechanical properties of the bone structures of the spine and the elastoelastic properties of the ligamentous apparatus. The proposed method allows you to register informative parameters of the biomechanical properties of the spine, which allows you to record both morphological and functional abnormalities, before x-ray and instrumental examination, and then, if necessary, already carry out targeted diagnostic measures. The method is non-invasive, harmless to the patient and medical personnel, easy to implement, available and not limited by the number of necessary repeated studies, which can be used both in stationary conditions and in screening, dispensary and preventive examinations.

The device instantly eliminates the reaction of the support, with the formation of a rectangular acceleration pulse. Provides a sufficient strength, dosed multicomponent mechanical impact. The resetting mechanism allows you to restore the standard initial conditions of exposure, which ensures repeatability. The completeness of the extraction of diagnostic information is ensured by synchronizing the onset of exposure with the recording of parameters using measuring equipment.

Information sources

1. Sodofiev V.I. X-ray functional diagnosis of diseases of the musculoskeletal system in children. // © Publishing house "Medicine", Moscow, 1986, pp. 37-43.

2. Lavrukov A.M., Tomilov A.B. Osteosynthesis by external fixation apparatus in patients with spinal injuries and diseases. // Ekaterinburg 2002. © A.M. Lavrukov, A.B. Tomilov, pp. 27-31.

3. Vasin R.A., Bakusov L.M., Nasirov R.V., Malkanov V.V. Method of functional biomechanical tests // Russian journal of biomechanics, No. 1-2: 1998, p. 58-63.

4. Dmitriev A.E., Lyapin V.A., Potemkin B.A., Romanov V.I. Experimental methods for studying the impact of shock and vibration loads on biological objects. Moscow. // Abstracts of the international conference “Achievements of Biomechanics in Medicine” Riga, September 12-15, 1986 Medical Biomechanics in 4 volumes. Volume III, pp. 117-123.

5. Arnold V.I. Catastrophe theory. M .: Publishing. University of Moscow. 1983. 80 p.

Claims (2)

1. A method for studying the biomechanical properties of the spine, including a test mechanical stimulation with excitation of mechanical vibrations in the spine and recording mechanical responses from the bone tissue using seismic sensors located on the skin of the subject in the projection of the spinous processes of the vertebrae and bones of the skull, characterized in that the excitation of mechanical vibrations carried out by instant removal of support in the dropping mechanism, designed for the subject sitting motionless on it, and p the reflex parameters are recorded during stretching of the spinal column, quasistatic impact on it and compression of the spinal column both under the influence of the patient’s own mass and when additional loads are placed on it, after which the registered parameters are compared between themselves and the reference ones, and the morphological and functional properties of the spine. 2. A device for studying the biomechanical properties of the spine, containing a base made with the possibility of placing the subject in a sitting position on it, seismic sensors made with the possibility of their location at the test points and connected to measuring equipment, characterized in that the movable and fixed flaps are located on the base interconnected by means of a metal rod, between the leaves there is a metal disk fixedly connected to the fixed casement, and magnets under izhno connected with valves and connected with flexible rods, adapted to activate the device by moving them, and a synchronizer adapted to start measuring apparatus.

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