RU2180517C2 - Orthopedic diagnostic complex - Google Patents

Abstract

FIELD: medical equipment, in particular, orthopedic diagnosis, applicable in diagnostic examination of patients. SUBSTANCE: a three-dimensional image of the contour of the subplantar part of both feet in the loaded condition (at standing) and the chart of distribution of pressure on the loaded sections of the feet with simultaneous indication of the quantitative information reflecting both the geometric characteristics of the lower surface of the feet and the local pressures on their separate sections are obtained in real time. The position of the longitudinal axes of both feet and the angle between them, the distance between the centers of both feet, the position of the projections of the centers of gravity of each leg and the common center of the body masses on the supporting plane, and the dynamic characteristics of their deviations (amplitude and period of vibrations averaged for the preset time interval) in the quiet state of the patient are automatically calculated and displayed. The result is attained due to the use of combined transducers of vertical displacement and pressure grouped in rectangular matrices forming the supporting platforms for each feet. The combined transducers of vertical displacement and pressure of the inductive-transformer type have a single ferromagnetic core in the form of a cylindrical rod with a rounded upper head spring-loaded by two springs: the upper one with a wide range of deformation and a low stiffness, and the lower one with a narrow range of deformation and a high stiffness separated by a washer, and a single frame of dielectric material that accommodates two geometrically separated windings, and in whose axial plane the movable core can freely move. EFFECT: enhanced efficiency. 2 cl, 4 dwg

Description

 The invention relates to the field of medical diagnosis, namely to orthopedic diagnosis.

 For orthopedic diagnostics, information about the relief of the sole of the feet in the loaded (when standing) and unloaded conditions, the distribution of pressure on the surface of the foot on a support flat surface, the angle of rotation of the longitudinal axes of the foot, the projection of the centers of gravity of each foot and the whole body on the support surface is important. and the dynamics of variations of all of the above parameters when standing.

 Meanwhile, the authors are not aware of devices that would allow simultaneously in real time to receive all the specified information.

 Known devices [1], which allow to obtain a model of the plantar area of the foot, containing a stand, a flask filled with a loose filler and covered with an airtight elastic film, a vacuum pump, a vacuum wire connecting the vacuum pump to the flask made in the form of a rectangular (or close) pipeline to it) a section, the cavity of which, with the help of a fitting, is connected to a vacuum wire, and on the inner wall of the flask there are holes through which the elastic is tightened by the flask and tightens it filled with a film and filled with loose filler, air is pumped out. So that the bulk filler does not get into the vacuum system, the holes of the flask are closed by an air-permeable filter.

 The device allows you to get a negative footprint and works as follows. At atmospheric pressure in the vacuum system, the patient becomes on an elastic film covering the flask with bulk material, and the subsoil surface of the granular filler under the pressure of the foot acquires a negative relief of the sole of the foot. Next, a vacuum pump is turned on, pumping air from the inner space of the flask, as a result of which the particles of the loose filler adhere tightly to each other and the surface of the loose filler retains a negative imprint of the sole of the foot.

 All necessary measurements are carried out using manual measuring tools (ruler, vernier caliper), either directly from this negative print, or from the plaster cast received from it — models of the plantar surface of the foot.

 Also known is a method and device [2] for examining the support function of the foot, consisting of a sock made of an elastic airtight material worn on the patient’s leg, in the center of the sole of which there is a pipe for subsequent pumping of air, a foot made of transparent material (glass) with a hole for the sock pipe, vertically mounted measuring tube and a scale, which through the elbow filled with tinted liquid, can be connected to the sock pipe. When putting the sock on the patient’s foot, the nozzle is open and due to the elasticity of the material of the sock when the foot is placed on the foot (the toe nozzle passes through the corresponding holes in the foot) without load (the patient is sitting), the lower surface of the toe is flat and its contour corresponds to the contour of the foot. This contour can be drawn on the bottom surface of the transparent footrest. Then the nozzle is connected to the syringe and the air is sucked out from underfoot space until the lower surface of the toe is firmly pressed against the surface of the foot. The volume of air in the syringe determines the amount of underfoot space in an unloaded state. Then the nozzle is disconnected from the syringe (the air again fills the pit) and through the elbow filled with tinted liquid, it is connected to the measuring tube. After this, the patient becomes on his feet, the underwater space under load decreases, as a result of which the fluid from the knee rises along the measuring tube by an amount corresponding to the volume of air squeezed out of the underfoot space under load. Knowing its initial volume (in an unloaded state), it is possible to determine the remaining volume of underwater space in a loaded state. And from the foot prints on the foot (for this the outer surface of the sole of the sole can be covered with coloring matter), you can find the area of the supporting surface of the foot in both loaded and unloaded states.

 A device [3] is also known for determining the distribution of the pressure of the human body on the supporting surfaces, which consists of a multi-contact body pressure sensor, an adjustable air source with an air pressure sensor, a switch and a measuring unit. The body pressure sensor consists of elastic membranes forming a closed cavity (support pad), while there are metallized contact pads on the inner surfaces of the membranes. On the lower membrane they are point-like and form a measuring matrix, and on the upper one they are zigzag-shaped, arranged in such a way that when the membranes are fully pressed against each other, the upper contact system completely covers all contact areas of the lower membrane (without closing the taps from them). The device operates as follows. The patient sits down or stands on a support pillow. In this case, of course, all contacts are closed. The switch is turned on, which alternately connects to the measuring unit all the contact pads of the lower membrane and the air pressure sensor. Then, compressed air from the compressor is pumped into the support pad. As the air pressure rises in the intermembrane space, contacts begin to open (first where the body pressure is weaker, then where it is stronger). In cyclically repeated polls, all contacts remaining closed and the air pressure corresponding to this cycle are simultaneously recorded. By the air pressure corresponding to the breaking of the contact, it is possible to determine the pressure of the body at a given point.

 Also known [4] are tensometric devices that allow measuring pressure on local sections of the plantar area of the foot both in statics (when standing) and in dynamics (when walking). Such devices contain miniature strain gauges mounted on a support platform (when standing) or in shoes (when walking). The signal from the sensors is measured with a pointer device (in statics, i.e. when standing) or fed to a loop or electronic oscilloscope (for studies in dynamics, i.e. when walking). However, the number of installed sensors does not exceed 3-5, which makes it possible to measure pressure at only a few points of the foot.

 Also known are devices called stabilographs [4, 5], which make it possible to determine the position of the projection of the patient’s common center of mass (OCM) on a horizontal plane when standing. The device is a horizontal support platform on which the patient becomes both feet. The platform is based on three (located in the form of an isosceles triangle) or four (located at the corners of a rectangular platform) elastic elements with strain gauges attached to them, the signals from which are fed to the loop oscilloscope and recorded. Then these records are jointly processed and for each moment of time the projection of the JCM on the reference horizontal plane is calculated. The method requires a very long and laborious mathematical processing of the obtained signal records, carried out manually.

 Thus, although there are certain methods and devices that can identify some of the above orthopedic diagnostic signs, however, firstly, they cannot be combined to simultaneously obtain information about all these signs, and secondly, none of these devices allows receive information in real time in real time (after the experiment, painstaking and time-consuming processing of its results is required to extract useful information), thirdly, not all diagnostic signs can be measured by these devices and, fourthly, measuring the dynamic characteristics of changes in these parameters when standing still is of great difficulty (in particular, the dynamics of changes in the topography of the foot with existing devices cannot be determined).

 The technical problem to which the invention is directed is the creation of a device (complex) that provides simultaneous real-time measurement of such orthopedic diagnostic signs, such as: relief of the sole of the foot; pressure distribution over the foot support area; the position of the projections of the centers of gravity of each leg and the common center of mass of the body on a horizontal plane relative to the projections of the feet; turning angle between the longitudinal axes of the feet in a natural state in a comfortable position; as well as the dynamic characteristics of variations of these parameters when standing still. At the same time, all the specified information should be presented to the doctor in the final visual and convenient form for direct use, without requiring any additional manual processing, and be automatically registered.

 The solution to this problem is achieved by creating an orthopedic diagnostic complex consisting of a measuring support platform and an electronic system. The measuring support platform contains two (under each of the feet) support pads formed by combined vertical displacement and pressure transducers grouped into rectangular matrices, which are placed on turntables equipped with rotation angle sensors and can be rotated in a horizontal plane by a certain angle, and rotary platforms are based on basic support platforms, one of which is stationary, and the second is made with the possibility of linear movement in horizontal plane whith respect to the fixed platform and is provided with a linear displacement sensor. The electronic system contains an analog switch unit, a generator of exciting signals of the primary converters, a measuring unit, an interface module and a personal computer, the power inputs of the combined vertical and pressure transducers, their information outputs and the information outputs of the rotation angle and linear displacement sensors through the analog switch unit are connected respectively with the output of the generator of exciting signals and the information input of the measuring unit, the output of the measuring The unit is connected to the digital input of the interface module, which is connected via a standard communication channel to a personal computer, the outputs of which are connected through the interface module to the control inputs of the analogue switch unit and the measuring unit. The information received from the sensors is processed by a personal computer using special programs; it is displayed on a computer screen in a visual and convenient for the doctor form and can be recorded in a long-term memory.

 The invention is illustrated by the structural-functional diagram of an orthopedic diagnostic complex (Fig. 1), schematic drawings of a measuring support platform (Fig. 2) and a diagram of a combined transducer of vertical displacement and pressure (Fig. 3).

 Orthopedic diagnostic complex (figure 1) consists of a measuring support platform 1, an electronic system 2 and a personal computer 3.

 The measuring support platform 1 comprises two support platforms 4 formed by combined vertical displacement and pressure transducers grouped into rectangular matrices, rotation angle sensors 5 located in each support platform, and a distance sensor 6 between the centers of the support platforms.

 The electronic system 2 consists of a block of analog switches 7, a generator 8 of exciting signals of the primary converters, a measuring unit 9 and an interface module 10 that provides communication with a personal computer 3.

 The measuring platform (Fig. 2) contains two support platforms 4, in which combined vertical displacement and pressure transducers 11 are arranged in rectangular matrices. The support platforms are rigidly mounted on rotary platforms 12 with the possibility of free rotation by some angle in the horizontal plane. Sensors 5 of the rotation angle are combined with the vertical axis of each turntable. Above the surfaces of the supporting platforms are covered with a removable elastic film 13. The rotary platforms are supported by the basic supporting platforms 14, one of which (left - in Fig. 2) is stationary, and the second can move linearly relative to the basic fixed platform. To measure the magnitude of this displacement, a linear displacement transducer 6 is installed, which is a multi-turn potentiometric transducer connected via a pulley mounted on its axis with a cable 15, one end of which is fixed to a movable base platform, and the other end to a block 16 with a coil spring, which provides constant tension of cable-block transmission. A linear displacement transducer of any other type can be used, providing a measuring range of 250-300 mm with an error of not more than ± 5 mm.

 Combined transducers of vertical movement and pressure can be implemented in various ways. The linear displacement measuring range should be at least 20 mm, and pressure (weight) - up to 0.5 kg with permissible errors not exceeding 5%. The transverse dimensions of the combined transducer should not exceed 8 mm (so that it would be possible to compose a matrix from them with a step of no more than 10 mm). In addition, an important pressure requirement is a high pressure overload capacity, including impact loads.

 Figure 3 shows a possible variant of the combined transducer of vertical displacement and pressure of the inductive type, satisfying all the requirements. It consists of a ferromagnetic cylindrical rod 17, which can freely move in the axial hole of the sensor frame 18 made of a dielectric. The frame contains windings 19 and 20, the first of which is sensitive to the vertical movement of the ferromagnetic rod 17, and the second to pressure. Rod 17 is spring-loaded with two springs: cylindrical 21 with low stiffness and a range of vertical compression of up to 20 mm and conical 22 with great stiffness and a compression range of up to 3 mm. The springs are separated by a washer 23. The sensor frames are fixed between the supporting metal plates 24 and 25, between which there is a printed circuit board 26, to which the terminals of the windings of all the sensors of the matrix are soldered and integrated circuits of the analog switch are placed on it.

 The upper ends of the ferromagnetic rods have a rounded head and on top of the entire sensor matrix is covered with an elastic film 13, which can be easily replaced and disinfected.

 To reduce friction, the rotary platforms roll on balls placed in the grooves in the support and base platforms, having the form of circular arcs with a center coinciding with the center of rotation of the rotary platform. Similarly, on balls placed in longitudinal grooves made in the movable base platform and at the base of the support platform, linear movement of the movable base platform occurs.

 Orthopedic diagnostic complex works as follows.

 The patient stands with both feet on the supporting pads 4 so that the feet do not protrude beyond the edges of the pads, and takes a natural position, pushing the pads to a convenient distance and turning them to a convenient angle for standing (these parameters can be forced by the doctor if necessary).

 Under the influence of the patient’s weight, the ferromagnetic movable rods 17 of the combined sensors forming the measuring matrix move in accordance with the relief of the sole of the foot. Moreover, due to the low stiffness of the springs 21, the conical springs 22 are not deformed in the unloaded sections of the foot, and therefore, the corresponding pressure sensors give zero readings, since the lower ends of the movable core 17 are outside the sensitivity zone of the winding 20. Under the loaded sections of the foot, the springs 21 are compressed to of the limit, after which stiffer springs 22 begin to compress. In this case, the lower end of the rod 17 enters the sensitivity zone of the winding 20, as a result of which the inductive coupling between EMF is induced by winding 20 and winding 19 and in winding 20, approximately proportional to the further movement (approximation) of the ferromagnetic rod 17 to winding 20. The entire sensitivity range of winding 20 to changing the position of the rod 17 should correspond to the deformation range of the conical spring 22 (2-3 mm). Due to the large difference between the stiffness of the springs 21 and 22, the entire weight of the patient will be distributed only to the supporting areas of the foot.

 The winding 19 is connected to a sinusoidal current generator, the frequency of which is selected in such a way as to ensure maximum sensitivity of the winding 19 to the vertical movement of the ferromagnetic rod 17 in the unloaded sensors and the winding 20 to the further movement of the rod 17 in the loaded sensors. Experimental studies have shown that the optimal excitation frequency of displacement sensors is 5-8 KHz with a rod diameter of 2-2.5 mm. The coil of the displacement sensor operates in the set current mode, and the coil 20 is the secondary winding of the air transformer, the primary winding of which is the winding 19. In this case, while the ferromagnetic rod 17 is far from the winding 20, the inductive coupling between the windings is very weak and the signal induced in the winding 20 is close to zero. But when the spring 21 is fully compressed, the end face of the ferromagnetic rod 17 enters the sensitivity zone of the winding 20, the inductive coupling between the windings begins to increase and the signal induced in the winding 20 increases in proportion to the further movement of the ferromagnetic rod 17.

 The sensor windings using the block 7 of the analog switches are alternately connected to the sinusoidal current generator 8 and the measuring unit 9, containing an amplifier, detector and analog-to-digital converter. The performance of the ADC, analog switches and all other elements is selected so that the polling cycle of all sensors of both matrices, as well as the sensors of angular and linear displacements of reference sites, does not exceed 1 s.

 Further, these signals are already in digital form through the interface module 10 enter the personal computer 3.

 All further processing of the obtained measurement information is performed by the computer programmatically.

The applied software of the orthopedic diagnostic complex should provide:
1. The construction of a three-dimensional image of the relief of the surface of the feet and the profiles of its sections with an arbitrary arrangement of vertical cutting planes in a given scale with a simultaneous indication of digital values of the clearance between the reference plane and the arch of the foot at the cursor location.

 2. The construction of large-scale images of the supporting sections of the surfaces of the feet with contours of equal pressure and coloring them in 10 gradations (with a pressure change step of 10% of the maximum value).

 3. Calculation and image on the constructed pressure maps of each foot of the projections of the geometric centers of pressure of each leg and the total center of mass (GCM) of the whole body.

 4. The construction and image of the longitudinal axes of the feet and the indication of the numerical value of their angles, as well as the distance between the centers of rotation of the feet.

 5. Calculation and indication (in digital form) of the dynamic parameters of the deviation of the projections onto the supporting plane of the centers of gravity of each leg and the JMC (amplitude and period of oscillations averaged over a given time interval).

 6. Memorization and short-term (for visual analysis on the screen) or long-term storage (archiving) of any image frames and additional information (patient data) entered from the keyboard.

 In addition, the software includes a module for controlling the hardware of the complex (block of analog switches and measuring unit).

 An enlarged block diagram of a package of special software for the complex is presented in figure 4.

 Obviously, this complex makes it easy to fix and measure the numerical values of the characteristics of an unloaded foot.

 Measurement of the characteristics of unloaded feet (in this case, only the profile of the lower surface of the foot is measured) provides additional diagnostic information. Of particular interest is the identification of changes in the foot profile under load, which is easy to obtain by comparing the profiles of the foot without load and under load.

 To measure the profile of an unloaded foot, the patient must transfer the entire weight of his body to one leg, without removing the second from the supporting platform. To make sure that the second leg is not loaded, it is possible according to the readings of the pressure sensors of the corresponding supporting platform, which should be zero. In this case, obviously, only vertical displacement sensors will work, fixing the profile of the lower surface of the unloaded foot, because in this case, only the upper springs of low stiffness will be compressed (in accordance with the profile of the foot). To simultaneously measure the profiles of both feet without the patient's load, you can sit on a chair located next to the support platform without removing his legs from the support platforms.

Salient features of the proposed device are:
- the use under each foot of the combined transducers of vertical displacement and mechanical pressure grouped into rectangular matrices, which are alternately interrogated using a program-controlled block of analog switches;
- the use of rotary (in the horizontal plane) bearing pads with angle sensors;
- providing the possibility of linear movement of one of the reference sites and the installation of a sensor for its movement;
- providing automatic input of all measured information into a computer with a polling cycle of all sensors that provide information in real time.

 All this provides the ability to automatically calculate and visualize on a computer display three-dimensional images of the relief of the feet, maps of the pressure distribution on the supporting sections of the surface of the feet, combined with the latest images of the projections on the supporting plane of the centers of gravity of each leg and the common center of mass of the body, images of the profiles of the relief of the feet for an arbitrary the location of the vertical secant plane, the digital indication of the dynamic parameters of the projections onto the supporting plane of the centers of gravity of each leg and common center of mass and other digital data; automatic digital measurement of the distances between any two arbitrarily located points on stop images marked with cursors arbitrarily moved across the screen by the operator.

 Literature.

 1. Sitenko A.N., Prozorovsky V.F., Zarudny S.S., Mayevsky B.C. Device for manufacturing a negative model of the plantar area of the foot. Auth. testimonial. USSR, 1509037, 1987.

 2. Nagibin V.I., Dyusenbaev K.A. A method for examining the support function of the foot and a device for its implementation. Auth. testimonial. USSR 1814877, 1991, publ. B.I. 18, 1993.

 3. Volkovitsky V. R., Sokolovsky M. I., Ageev A. F., Eremina E. S. A device for determining the pressure of the human body on supporting surfaces. Auth. testimonial. USSR, 1507327, 1987. Publ. B.I. 34, 1989.

 4. Clinical Biomechanics / Ed. IN AND. Filatova. - L .: Medicine, 1980 .-- 200 p.

 5. Volkov S.V., Mitrofanov O.P., Vasiliev A.A. Stabilizer. Auth. testimonial. USSR 1457896, 1987. Publ. B.I. 6, 1989.

Claims (2)

 1. An orthopedic diagnostic complex comprising a measuring support platform and an electronic system, characterized in that the measuring support platform contains two, under each of the feet, support platforms formed by combined vertical displacement and pressure transducers grouped into rectangular matrices and mounted on rotary platforms, equipped with rotation angle sensors, and the rotary platforms rest on the basic support platforms, one of which is stationary, and the second is made with with the possibility of linear movement relatively stationary in the horizontal plane and equipped with a linear movement sensor, the electronic system complex contains a block of analog switches, an excitation signal generator, a measuring unit, an interface module and a personal computer, the power inputs of the combined transducers of vertical movement and pressure, their information outputs and information the outputs of the angle sensors and linear displacement through the block of analog switches are connected respectively but with the output of the exciting signal generator and the information input of the measuring unit, the output of the measuring unit is connected to the digital inputs of the interface module, which is connected via a standard communication channel to a personal computer, the outputs of which through the interface module are connected to the control input of the block of analog switches and measuring unit.  2. The orthopedic diagnostic complex according to claim 1, characterized in that the combined transducers of vertical displacement and pressure are structurally uniform transducers of inductive transformer type having a movable ferromagnetic core in the form of a cylindrical rod with a rounded upper head, spring-loaded with two springs separated by a washer moreover, the upper spring has a large deformation range and low stiffness, and the lower has a small deformation range and high stiffness, the lower part of the movable core is located in the axial cavity of a single frame of dielectric material, on which two geometrically separated windings are placed, the upper one with a winding length equal to the maximum deformation of the upper spring, and the lower, short one, which is the secondary winding of the air transformer formed by these windings, the distance between the windings is selected so that with maximum compression of the upper spring, the ferromagnetic core falls into the sensitivity zone of the lower winding.

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