CN112535481B - Joint contact force measuring method and device based on near-infrared light - Google Patents
Joint contact force measuring method and device based on near-infrared light Download PDFInfo
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- CN112535481B CN112535481B CN202011324643.3A CN202011324643A CN112535481B CN 112535481 B CN112535481 B CN 112535481B CN 202011324643 A CN202011324643 A CN 202011324643A CN 112535481 B CN112535481 B CN 112535481B
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- A61B5/22—Ergometry; Measuring muscular strength or the force of a muscular blow
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
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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
Technical Field
The invention belongs to the field of human body measurement, and particularly relates to a joint contact force measuring method and device based on near infrared light.
Background
In the daily activities of people, the joints can form joint contact force when bearing loads, generating torque and conducting body weight, so that the information of the joint contact force has important reference significance in the aspects of diagnosis of joint diseases, biomechanical analysis and the like.
In the development history of the joint contact force measuring method, direct measurement of the joint contact force is often invasive, for example, a tibial prosthesis with a force transducer unit is implanted into a knee joint through surgery, so that real-time accurate detection of the joint contact force is realized. However, this method is costly and the application scenario is greatly limited due to its invasive measurement features.
Non-invasive joint contact force measurement methods include a dynamics-based method, an optimization-based method, a muscle electrical signal-based method and the like, which all require more sensor information as input, for example, the relevant dynamics information of the limb is obtained by combining measurement means such as a motion capture system, a ground contact force measurement system, a muscle electrical signal sensor and the like, and the information is processed and analyzed to indirectly estimate the joint contact force and the change condition thereof. These non-invasive measurement methods rely heavily on the accurate musculoskeletal system model and the limb dynamics model of the individual, often require more complex sensor systems, are computationally complex, and are difficult to implement in a portable and real-time manner.
Disclosure of Invention
In view of the above drawbacks and needs of the prior art, the present invention provides a method and an apparatus for measuring a joint contact force based on near-infrared light, wherein the method utilizes the characteristic of penetrability of the near-infrared light in biological tissues to interact with cartilage tissues and generate reflected light, and the intensity of the reflected light is measured in real time to monitor the joint contact force in real time, so that the method and the apparatus are particularly suitable for applications of body measurement.
In order to achieve the above object, according to one aspect of the present invention, a method for measuring a joint contact force based on near infrared light is provided, the method specifically includes: and emitting near infrared light to the joint to be detected, generating reflected light after the near infrared light interacts with the cartilage tissue, and detecting the change of the joint contact force through the light intensity change of the reflected light.
More preferably, the wavelength of the near infrared is 850nm to 1000nm.
As further preferred, the near-infrared light is emitted using a laser diode or a light emitting diode.
Further preferably, the change in light intensity of the reflected light is detected using an avalanche photodiode, a photodiode, or a photomultiplier tube.
According to another aspect of the present invention, there is provided a near-infrared light-based joint contact force measuring apparatus including a wearing unit, a light source unit, and a 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 finish the joint contact force measurement.
Further preferably, the light source unit employs a laser diode or a light emitting diode.
Further preferably, the photosensitive cell employs an avalanche photodiode, a photodiode, or a photomultiplier tube.
As a further preference, the distance between the light source unit and the light sensitive unit is greater than 8mm.
Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:
1. the invention provides a joint contact force measuring method based on near infrared light, which utilizes the characteristic that the near infrared light has penetrability in biological tissues to interact with cartilage tissues and generate reflected light, realizes real-time monitoring of 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 measuring method of implanting a prosthesis, and has the advantages of good real-time performance, small calculated amount and simple processing process;
2. particularly, the invention can ensure that the near infrared light penetrates deeper in biological tissues by optimizing the wavelength of the near infrared light, thereby effectively improving the detection precision of the joint contact force;
3. in addition, the invention also provides a joint contact force measuring device based on near infrared light, and the device can realize the measurement of the contact force in the joint under the condition that a wearer bears load only by simple wearing and calibration; different from the defects that non-invasive devices such as traditional optimization iterative estimation, surface myoelectricity indirect estimation and the like need a large number of sensors, the joint contact force measurement method can measure the joint contact force by only one pair of photosensitive units and light source units, greatly reduces the number of the sensors, and simplifies the complexity of data analysis and processing.
Drawings
FIG. 1 is a schematic diagram of a near-infrared light-based method for measuring contact force of a joint according to the present invention;
FIG. 2 is a schematic diagram of measurement of knee joint stress in a preferred embodiment of the present invention, wherein (a) is a schematic diagram of knee joint stress and (b) is a schematic diagram of measurement;
FIG. 3 is a schematic diagram of a near-infrared light-based articular contact force measurement device constructed in accordance with a preferred embodiment of the present invention;
FIG. 4 is a schematic structural view of a fixing member in a preferred embodiment of the present invention, in which (a) is a front view and (b) is a sectional view;
FIG. 5 is a circuit schematic of the driving and modulating portions of the LED used in the preferred embodiment of the present invention;
FIG. 6 is a schematic circuit diagram of the drive and acquisition portion of an avalanche photodiode used in a preferred embodiment of the present invention;
FIG. 7 is a diagram of the cartilage deformation of the knee joint and the change of the reflected light intensity in the preferred embodiment of the present invention;
fig. 8 is a data diagram of the change of the reflected light intensity signal caused by the pressure change of the joint to be measured in the preferred embodiment of the present invention.
The same reference numbers will be used throughout the drawings to refer to the same elements or structures, wherein:
1-a wearing unit, 2-a photosensitive unit, 3-a light source unit and 4-a fixing piece.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the respective embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
As shown in fig. 1 and 2, an embodiment of the present invention provides a joint contact force measuring method based on near-infrared light, and the measuring method specifically includes: 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.
In particular, when a person stands and bears a load, the knee joint is subjected to a pressure generated by the body weight, which is transmitted by the articular cartilage on the femur and the tibia in the form of an articular contact force, and when the person moves, the knee joint needs to generate an articular moment, and under the action of muscle force, a contact force is also generated on the articular cartilage. The joint contact force is the pressure acting on the articular cartilage, the articular cartilage deforms to a corresponding degree under the action of the compressive stress, and the joint contact force can be detected in real time by measuring the deformation degree of the articular cartilage.
Near infrared light (with the wavelength of 780 nm-1000 nm) can penetrate through a biomass tissue deeply, and the change condition of the biological tissue can be monitored by measuring the intensity of reflected light emitted after interaction of absorption, scattering and the like of the near infrared light in the biological tissue. Therefore, when the articular cartilage deforms due to the change of the articular contact force, the absorption and scattering intensity of the near infrared light also changes, and the measurement of the articular contact force can be realized through the change of the intensity of the reflected light at the joint to be measured. Due to the difference of light intensity signals of different areas, the light intensity signals can be processed in a calibration mode or a multi-path signal analysis mode, so that the accurate measurement of the joint contact force is realized.
Further, the wavelength of the near infrared is 850nm to 1000nm, the near infrared light penetrability in the wavelength range is good, and the wavelength of the near infrared is preferably about 850nm or about 950 nm; emitting near infrared light by using a laser diode or a light emitting diode; the change in the intensity of the reflected light is detected using an avalanche photodiode, or photomultiplier tube.
As shown in fig. 3 and 4, according to another aspect of the present invention, there is provided a near-infrared light-based joint contact force measuring apparatus including a wearing unit 1, a light source unit 3, and a light sensing unit 2, wherein:
the wearing unit 1 is used for fixing the measuring device on the outer side of the joint to be measured so as to enable the measuring device to be close to the joint to be measured, and the wearing unit 1 preferably adopts a bandage structure;
the light source unit 3 is fixed on the wearing unit through the fixing piece 4 and is used for emitting near infrared light with certain intensity to the joint to be measured, and the near infrared light interacts with cartilage tissues and generates reflected light;
the photosensitive unit 2 is fixed on the wearing unit through the fixing piece 4, is positioned on one side of the light source unit, is connected with the light source unit 3 through a lead, and is used for detecting the light intensity change of reflected light so as to complete the joint contact force measurement.
A light-emitting element and a light-sensitive element can be adopted and arranged in parallel to the direction of the cartilage or in perpendicular to the direction of the cartilage; a plurality of light-emitting elements and a plurality of photosensitive elements can be adopted and distributed on the periphery of the joint to be measured, so that multi-path signal acquisition is realized, and the detection light intensity change of cartilage tissues in a plurality of specific areas to different near infrared wavelengths is analyzed simultaneously, so that more accurate joint contact force measurement is realized.
Before the joint contact force measuring device is used, the external load on the joint to be measured and the variation of the light intensity of reflected light before and after the joint to be measured is calibrated in an off-line mode, the corresponding relation between the joint contact force and the light intensity of the reflected light is established, and then the joint contact force can be estimated according to the collected light intensity signals when the joint contact force measuring device is used, so that the real-time measurement of the joint contact force is achieved. The light intensity signal emitted after the interaction of the joint tissue to be measured and the near infrared light is measured in real time and is input into the calibrated data processing module, so that the real-time analysis and processing of the contact force of the joint to be measured can be completed, the real-time performance is good, the calculated amount is small, the wearing structure is simple, a complex analysis processing process is not needed, and the device is suitable for the real-time measurement of the contact force of the joint.
Further, the light source unit 3 adopts a laser diode or a light emitting diode, wherein a driving and modulating part circuit of the Light Emitting Diode (LED) is as shown in fig. 5, and is driven by battery power supply and is modulated and driven by an STM32 single chip microcomputer, so that the modulation of the output light intensity of the LED is realized; the photosensitive unit 2 adopts an avalanche photodiode, a photodiode or a photomultiplier, wherein a driving and modulating part circuit of the Avalanche Photodiode (APD) is shown in FIG. 6, a battery drives an amplifying circuit, a voltage signal is acquired through an AD conversion module and transmitted to a PC for processing and analysis; the distance between the light source unit 3 and the light sensitive unit 2 is greater than 8mm.
In the preferred embodiment of the invention, an LED with the wavelength of 850nm and a Hamamatsu-C12702 type APD module are selected, a driving, modulation and acquisition circuit as shown in figures 5 and 6 is built, a diffuse reflection signal acquired by the APD is LED out from the knee joint to be measured to an APD photosensitive area through an optical fiber, the distance between a wearing part light source and the center of the photosensitive measurement area is fixed to be 10mm, and the diffuse reflection light intensity (namely the number of emitted photons of a diffuse reflection detection area) when the knee joint is stressed and deformed and cartilage occurs is measured.
Analysis by combining the Monte Carlo method to obtain the data chart shown in fig. 7 shows that when the thickness of the articular cartilage is changed due to compression, the diffuse reflection light intensity is increased along with the compression of the articular cartilage.
The wearing device of the wearer carries out experimental data acquisition to obtain the data diagram shown in figure 8, when the knee joint is subjected to pressure change, the change trend of diffuse reflection light intensity shows the same trend as the analysis result of the Monte Carlo method, when the knee joint is subjected to large pressure, the diffuse reflection light intensity can be enhanced, and in the experiment, the change condition of the joint contact force can be analyzed according to the data characteristics. Thereby realizing the real-time detection of the joint contact force.
It will be understood by those skilled in the art that the foregoing is only an exemplary embodiment of the present invention, and is not intended to limit the invention to the particular forms disclosed, since various modifications, substitutions and improvements within the spirit and scope of the invention are possible and within the scope of the appended claims.
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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