CN112535481B - A method and device for measuring joint contact force based on near-infrared light - Google Patents

Abstract

The invention belongs to the field of human body measurement, and particularly discloses a joint contact force measuring method and device based on near infrared light. The measuring method specifically comprises the following steps: near infrared light is emitted to the joint to be detected, reflected light is generated after the near infrared light interacts with cartilage tissues, and the change of the joint contact force is detected through the light intensity change of the reflected light. The method utilizes the characteristic that near infrared light has penetrability in biological tissues to interact with cartilage tissues and generate reflected light, realizes real-time monitoring on the joint contact force by measuring the intensity of the radiated light in real time, can avoid harm to a human body compared with a direct measurement method of implanting a prosthesis, and has the advantages of good real-time performance, small calculated amount and simple processing process. Meanwhile, the device can measure the contact force inside the joint under the condition that a wearer bears a load only by simple wearing and calibration.

Description

A method and device for measuring joint contact force based on near-infrared light

technical field

The invention belongs to the field of anthropometry, and more specifically relates to a method and device for measuring joint contact force based on near-infrared light.

Background technique

In people's daily activities, joints will form joint contact force when bearing load, generating torque, and transmitting body weight. Therefore, the information of joint contact force has important reference significance in the diagnosis of joint diseases and biomechanical analysis.

In the history of the development of joint contact force measurement methods, the direct measurement of joint contact force is often invasive, such as implanting a tibial prosthesis with a load cell unit into the knee joint through surgery to achieve joint Real-time accurate detection of contact force. However, the cost of this method is high, and the application scenarios are relatively limited due to the characteristics of intrusive measurement.

Non-invasive joint contact force measurement methods include methods based on dynamics, methods based on optimization, methods based on muscle electrical signals, etc., all of which require more sensor information as input, such as combining motion capture systems, ground contact Force measurement systems, muscle electrical signal sensors and other measurement methods obtain relevant dynamic information of the limbs, and process and analyze such information to indirectly estimate joint contact forces and their changes. These non-invasive measurement methods rely heavily on the individual's accurate musculoskeletal system model and limb dynamics model, and often require a more complex sensor system with high computational complexity, making it difficult to achieve portable real-time measurement.

Contents of the invention

In view of the above defects or improvement needs of the prior art, the present invention provides a method and device for measuring joint contact force based on near-infrared light, wherein the method utilizes the penetrating characteristics of near-infrared light in biological tissues, making it It interacts with cartilage tissue and generates reflected light, and realizes real-time monitoring of joint contact force by measuring the intensity of reflected light in real time, so it is especially suitable for anthropometric applications.

In order to achieve the above object, according to one aspect of the present invention, a method for measuring joint contact force based on near-infrared light is proposed. After the interaction occurs, reflected light is generated, and the change of joint contact force is detected through the change of light intensity of the reflected light.

As a further preference, the near-infrared wavelength is 850nm-1000nm.

As a further preference, a laser diode or a light emitting diode is used to emit the near-infrared light.

As a further preference, an avalanche photodiode, a photodiode or a photomultiplier tube is used to detect the light intensity change of the reflected light.

According to another aspect of the present invention, a kind of joint contact force measuring device based on near-infrared light is proposed, and the measuring device includes a wearing unit, a light source unit and a photosensitive unit, wherein:

The wearing unit is used to fix the measuring device on the outside of the joint to be measured;

The light source unit is fixed on the wearing unit, and is used for emitting near-infrared light to the joint to be tested, and the near-infrared light interacts with cartilage tissue and generates reflected light;

The photosensitive unit is fixed on the wearing unit and located on one side of the light source unit, and is used to detect the light intensity change of the reflected light, so as to complete the joint contact force measurement.

As a further preference, the light source unit adopts a laser diode or a light emitting diode.

As a further preference, the photosensitive unit adopts an avalanche photodiode, a photodiode or a photomultiplier tube.

As a further preference, the distance between the light source unit and the photosensitive unit is greater than 8mm.

Generally speaking, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:

1. The present invention provides a method for measuring joint contact force based on near-infrared light. This method utilizes the penetrating characteristics of near-infrared light in biological tissues to make it interact with cartilage tissue and generate reflected light. Real-time measurement of the intensity of radiated light realizes real-time monitoring of joint contact force. Compared with the direct measurement method of implanting prostheses, it can avoid harm to the human body, and has the advantages of good real-time performance, small calculation amount, and simple processing process;

2. In particular, by optimizing the wavelength of near-infrared light in the present invention, it can penetrate deeply into biological tissues and effectively improve the detection accuracy of joint contact force;

3. In addition, the present invention also provides a joint contact force measurement device based on near-infrared light. The device only needs simple wearing and calibration to measure the internal contact force of the joint under the load-bearing condition of the wearer; different from Traditional non-invasive devices such as optimized iterative estimation and indirect estimation using surface electromyography require a large number of sensors. The present invention only needs a pair of photosensitive units and light source units to measure joint contact force, which greatly reduces the number of sensors. , which simplifies the complexity of data analysis and processing.

Description of drawings

Fig. 1 is the schematic diagram of the joint contact force measurement method based on near-infrared light provided by the present invention;

Fig. 2 is a schematic diagram of measurement when the knee joint is stressed in a preferred embodiment of the present invention, wherein (a) is a schematic diagram of knee joint stress, and (b) is a schematic measurement diagram;

Fig. 3 is a structural schematic diagram of a joint contact force measurement device based on near-infrared light constructed according to a preferred embodiment of the present invention;

Fig. 4 is a schematic structural view of a fixture in a preferred embodiment of the present invention, wherein (a) is a front view, and (b) is a cross-sectional view;

Fig. 5 is a schematic diagram of the drive and modulation part of the LED used in the preferred embodiment of the present invention;

6 is a schematic diagram of the drive and acquisition part of the avalanche photodiode used in the preferred embodiment of the present invention;

Fig. 7 is a graph showing the deformation of knee articular cartilage and the variation of reflected light intensity in a preferred embodiment of the present invention;

Fig. 8 is a data diagram of changes in reflected light intensity signals caused by changes in joint pressure to be measured in a preferred embodiment of the present invention.

Throughout the drawings, the same reference numerals are used to designate the same elements or structures, wherein:

1-wearing unit, 2-photosensitive unit, 3-light source unit, 4-fixing piece.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

As shown in Figures 1 and 2, the embodiment of the present invention provides a method for measuring joint contact force based on near-infrared light. Reflected light is generated after the action, and the change of joint contact force is detected through the change of the light intensity of the reflected light.

Specifically, when a person stands and bears weight, the knee joint will bear the pressure generated by the body weight. This pressure will be transmitted by the articular cartilage on the femur and tibia in the form of joint contact force. When the person moves, the knee joint needs to generate Joint moments, under the action of muscle forces, also generate contact forces on the articular cartilage. Such joint contact force is the pressure acting on the articular cartilage. Under such compressive stress, the articular cartilage will be deformed to a certain degree. Therefore, by measuring the deformation degree of the articular cartilage, real-time detection of the joint contact force can be realized. .

Near-infrared light (with a wavelength of 780nm to 1000nm) can penetrate deeply in biological tissue. By measuring the intensity of reflected light emitted after the interaction of near-infrared light in biological tissue, such as absorption and scattering, the changes in biological tissue can be monitored. . Therefore, when the articular cartilage deforms due to changes in the joint contact force, the near-infrared light absorption and scattering intensity will also change, and the measurement of the joint contact force can be realized through the change in the reflected light intensity at the joint to be measured. Due to the difference of light intensity signals in different areas, it can be processed by calibration or multi-channel signal analysis to achieve accurate measurement of joint contact force.

Further, the near-infrared wavelength is 850nm-1000nm, and the near-infrared light penetration in this wavelength range is better, and the near-infrared wavelength is preferably about 850nm or about 950nm; use laser diodes or light-emitting diodes to emit near-infrared light; use avalanche Photodiodes, photodiodes, or photomultiplier tubes detect changes in the intensity of reflected light.

As shown in Figures 3 and 4, according to another aspect of the present invention, a joint contact force measurement device based on near-infrared light is provided, the measurement device includes a wearable unit 1, a light source unit 3 and a photosensitive unit 2, wherein:

The wearing unit 1 is used to fix the measuring device on the outside of the joint to be measured so that it is close to the joint to be measured, and the wearing unit 1 preferably adopts a strap structure;

The light source unit 3 is fixed on the wearing unit through the fixing part 4, and is used for emitting near-infrared light of a certain intensity to the joint to be tested, and the near-infrared light interacts with the cartilage tissue and generates reflected light;

The photosensitive unit 2 is fixed on the wearing unit through the fixing piece 4, and is located on one side of the light source unit, and is connected with the light source unit 3 by a wire to detect the light intensity change of the reflected light, thereby completing the joint contact force measurement.

One light-emitting element and one photosensitive element can be used to arrange parallel to or perpendicular to the direction of cartilage; multiple light-emitting elements and multiple photosensitive elements can also be used to distribute around the joint to be tested, so as to realize multi-channel signal Acquisition and simultaneous analysis of changes in the detection light intensity of cartilage tissue in multiple specific regions for different near-infrared wavelengths to achieve more accurate measurement of joint contact force.

Before use, through the offline calibration of the external load on the joint to be tested and the change of the reflected light intensity before and after loading, the corresponding relationship between the joint contact force and the reflected light intensity can be established, and then it can be used according to the The collected light intensity signals estimate the joint contact force, so as to realize the real-time measurement of the joint contact force. Real-time analysis and processing of the contact force of the joint to be tested can be completed by measuring the light intensity signal emitted after the interaction between the joint tissue to be tested and the near-infrared light in real time and inputting it into the calibrated data processing module. It is small, has a simple wearable structure, does not require complex analysis and processing, and is suitable for real-time measurement of joint contact force.

Further, the light source unit 3 adopts a laser diode or a light-emitting diode, wherein the driving and modulating part of the circuit of the light-emitting diode (LED) is shown in Figure 5, which is driven by battery power and modulated by the STM32 single-chip microcomputer, so as to realize the control of the output light intensity of the LED. Modulation; the photosensitive unit 2 adopts an avalanche photodiode, a photodiode or a photomultiplier tube, wherein the drive and modulation part of the avalanche photodiode (APD) circuit is shown in Figure 6, the amplifying circuit is driven by a battery, and the voltage signal is collected by an AD conversion module. It is transmitted to a PC for processing and analysis; the distance between the light source unit 3 and the photosensitive unit 2 is greater than 8mm.

In a preferred embodiment of the present invention, the LED and Hamamatsu-C12702 type APD modules with a wavelength of 850nm are used to build the drive, modulation and acquisition circuits shown in Figures 5 and 6, and the diffuse reflection signal collected by the APD passes through the optical fiber from the The distance from the knee joint to the photosensitive area of the APD is fixed at 10mm between the wearing part of the light source and the center of the photosensitive measurement area, and the diffuse reflection light intensity (that is, the number of photons emitted from the diffuse reflection detection area) is measured when the knee joint is subjected to changes in force and cartilage deformation occurs.

Combining the analysis with the Monte Carlo method, the data graph shown in Figure 7 is obtained. It can be seen that when the articular cartilage is compressed and the thickness changes, the diffuse reflection light intensity will become stronger with the compression of the articular cartilage.

The wearer wears the device for experimental data collection, and the data graph shown in Figure 8 is obtained. When the pressure on the knee joint changes, the change trend of the diffuse reflection light intensity presents the same trend as the analysis result of the Monte Carlo method. When the joint is under pressure When the value is larger, the diffuse light intensity will become stronger. In the experiment, the change of joint contact force can be analyzed according to this data characteristic. In this way, real-time detection of joint contact force is realized.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (7)

1. A joint contact force measuring method based on near infrared light is characterized by comprising the following steps: emitting near infrared light to a joint to be detected, generating reflected light after the near infrared light interacts with cartilage tissues, and detecting the change of the joint contact force through the light intensity change of the reflected light, wherein the wavelength of the near infrared light is 850 nm-1000 nm.

2. The near-infrared-based contact force measuring method of claim 1, wherein the near-infrared light is emitted using a laser diode or a light emitting diode.

3. The near-infrared-based contact force measuring method for joints according to claim 1 or 2, wherein the change in light intensity of the reflected light is detected by an avalanche photodiode or a photomultiplier tube.

4. The utility model provides a joint contact force measuring device based on near infrared light, its characterized in that, this measuring device is including wearing unit, light source unit and photosensitive unit, wherein:

the wearing unit is used for fixing the measuring device on the outer side of the joint to be measured;

the light source unit is fixed on the wearing unit and used for emitting near infrared light to the joint to be detected, and the near infrared light interacts with cartilage tissues and generates reflected light;

the photosensitive unit is fixed on the wearing unit, is positioned on one side of the light source unit and is used for detecting the light intensity change of the reflected light so as to complete the measurement of the joint contact force.

5. The near-infrared-based articular contact force measurement device according to claim 4, wherein the light source unit employs a laser diode or a light emitting diode.

6. The near-infrared-based articular contact force measurement device of claim 4, wherein the photosensitive cells employ avalanche photodiodes or photomultiplier tubes.

7. The near-infrared-light-based articular contact force measurement device according to any one of claims 4 to 6, wherein the distance between the light source unit and the light-sensitive unit is greater than 8mm.

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