Lumbar cumulative load evaluation method, device, and medium based on creep constitutive model

Abstract

The application discloses a kind of based on creep constitutive model's waist cumulative load evaluation method, equipment, medium, the method includes: to lumbar disc sample carries out creep test, obtains the time-strain data of the lumbar disc sample;According to the time-strain data of lumbar disc sample, fitting lumbar disc creep constitutive model;Build waist cumulative load evaluation model;According to the well-fitted lumbar disc creep constitutive model, simulation obtains at least one constant compression load level under time-strain data;With time-strain data as target, fitting nonlinear parameter in waist cumulative load evaluation model;Collecting waist load time series data is input into the well-fitted waist cumulative load evaluation model, and the waist cumulative load estimation value is calculated.Setting reference waist cumulative load threshold, dynamically update waist cumulative load estimation value;When waist cumulative load estimation value reaches or is greater than reference waist cumulative load threshold, generate early warning signal.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of biomechanics, and particularly relates to a lumbar cumulative load evaluation method, device and medium based on a creep constitutive model. BACKGROUND

[0002] Chronic low back pain, as a common occupational health problem, is closely related to the long-term effect of axial load on the lumbar intervertebral disc. The intervertebral disc, as the main load-bearing structure in the spine, is a typical viscoelastic tissue. In static behaviors such as sitting, the intervertebral disc continuously bears axial load, which can cause creep behavior of the tissue, resulting in time-dependent deformation, reduced intervertebral disc height, and internal stress concentration, thereby increasing the risk of cumulative tissue damage. Therefore, reasonable evaluation of lumbar load has important practical significance for the risk identification and intervention of low back pain in sedentary occupational groups.

[0003] At present, the evaluation of lumbar load based on biomechanics has made certain progress:

[0004] Chinese patent CN114419676A determines the stress of each segment of the spine at a specific moment by collecting sitting posture data and substituting it into the spine stress model. Although this method can quantitatively evaluate the instantaneous mechanical load and focuses on the static evaluation of lumbar or muscle load level, it cannot quantify the cumulative effect caused by the continuous action of load over time, making it difficult to evaluate the risk of chronic cumulative damage caused by low-intensity, long-time load.

[0005] Chinese patent CN118749800A determines sedentary fatigue by monitoring the duration of pressure exceeding a preset duration. This method simplifies the complex biomechanical cumulative process into a single "time duration-threshold" comparison, focusing on the time dimension, and fails to consider the coupling effect of different load intensities and time. For example, the holding time of high intensity should be shorter than that of low intensity.

[0006] At present, existing technical solutions also attempt to quantify the cumulative effect of lumbar load by introducing "load-time" integration, and some studies give higher exponential weight (>1) to the load based on this, indicating that high load contributes more to cumulative damage. Such models generally assume a simple linear relationship between cumulative damage effect and time (the exponent of time is 1), ignoring the nonlinear characteristics of the time dimension in the cumulative damage process.

[0007] In summary, the existing technology faces the following two challenges:

[0008] 1. In model construction, there is a lack of nonlinear cumulative load evaluation model that can accurately describe the real mechanical response and damage development trend under the long-term action of static load, and existing methods are difficult to match the basic biomechanical properties of the intervertebral disc.

[0009] 2. At the application level, the existing evaluation method depends on static and fixed time threshold or load threshold. Such a "one-size-fits-all" method only considers the influence of a single dimension and cannot dynamically adjust the intervention time according to different load intensity, so it is difficult to realize dynamic intervention of cumulative damage risk. SUMMARY

[0010] To overcome the deficiencies of the prior art, the embodiments of the present application provide a lumbar cumulative load evaluation method based on a creep constitutive model, a device and a medium.

[0011] In a first aspect, the embodiments of the present application provide a lumbar cumulative load evaluation method based on a creep constitutive model, the method comprising:

[0012] Performing a creep test on a lumbar disc sample to obtain time-strain data of the lumbar disc sample;

[0013] Fitting a lumbar disc creep constitutive model according to the time-strain data of the lumbar disc sample;

[0014] Constructing a lumbar cumulative load evaluation model; simulating to obtain time-strain data under at least one constant compression load level according to the fitted lumbar disc creep constitutive model; fitting nonlinear parameters in the lumbar cumulative load evaluation model with the time-strain data as the target;

[0015] Collecting lumbar load time series data and inputting it into the fitted lumbar cumulative load evaluation model to calculate a lumbar cumulative load estimate.

[0016] In a second aspect, the embodiments of the present application provide an electronic device, comprising:

[0017] At least one processor; and

[0018] A memory in communication connection with the at least one processor; wherein

[0019] The memory stores one or more computer programs executable by the at least one processor, and the one or more computer programs are executed by the at least one processor to enable the at least one processor to execute the above-mentioned lumbar cumulative load evaluation method based on a creep constitutive model.

[0020] In a third aspect, the embodiments of the present application provide a computer-readable storage medium having a computer program stored thereon, the computer program being executed by a processor to implement the above-mentioned lumbar cumulative load evaluation method based on a creep constitutive model.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] The application provides a lumbar cumulative load evaluation method based on a creep constitutive model. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0024] Figure 1 An implementation flowchart of the lumbar cumulative load evaluation method based on the creep constitutive model provided by the embodiments of the present application is shown in the figure.

[0025] Figure 2 A standard linear solid model provided by the embodiments of the present application is shown in the figure.

[0026] Figure 3 A L4-L5 segment time-strain result graph provided by the embodiments of the present application is shown in the figure.

[0027] Figure 4 A change trend graph of the cumulative load under three working conditions provided by the embodiments of the present application is shown in the figure.

[0028] Figure 5 A schematic diagram of an electronic device provided by the embodiments of the present application is shown in the figure. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0030] It should be noted that the features in the following embodiments and implementation manners can be combined with each other without conflict.

[0031] For example, Figure 1As shown, the embodiment of the present application provides a method for evaluating the cumulative load of the lumbar spine based on a creep constitutive model, which comprises the following steps:

[0032] Step S1, performing a creep test on the intervertebral disc sample to obtain the time-strain data of the intervertebral disc sample.

[0033] Specifically, a constant load is applied to the intervertebral disc sample of the target lumbar segment for a period of time, and the change in disc height during this period of time is measured to obtain the time-strain data of the intervertebral disc sample. In this embodiment, the target lumbar segment is preferably L4-L5 or L5-S1 segment.

[0034] Step S2, fitting the creep constitutive model of the intervertebral disc according to the time-strain data of the intervertebral disc sample.

[0035] Specifically, the creep constitutive model, as a theoretical model for describing the mechanical behavior of viscoelastic materials, has been proven by multiple studies to be able to describe the viscoelastic properties of human intervertebral discs. The principle is that the intervertebral disc is essentially a viscoelastic material with significant time dependence, composed of a liquid matrix (water) and a solid matrix (collagen and proteoglycans). The solid matrix makes it have an instantaneous elastic response, while the liquid matrix makes it have a delayed viscous response. Under the continuous action of compression load, this dual-phase property causes the deformation of the intervertebral disc to exhibit typical nonlinearity and time dependence, which macroscopically manifests as a continuous decrease in disc height, i.e., creep behavior.

[0036] Based on this principle, the creep constitutive model describes the nonlinear relationship between the duration of the load and the strain of the disc tissue from a mechanistic perspective, thereby ensuring that the cumulative load evaluation method is based on biomechanical principles.

[0037] In some embodiments, the creep constitutive model of the intervertebral disc adopts a viscoelastic constitutive model, which includes standard linear solid model, Kelvin model, generalized Kelvin model, or generalized Maxwell model, etc. Those skilled in the art can select an appropriate viscoelastic constitutive model according to the complexity of the experiment and the application purpose.

[0038] In some embodiments, the creep constitutive model of the intervertebral disc adopts a standard linear solid model. As shown, the standard linear solid model is composed of a Kelvin model and a second spring connected in series, and the Kelvin model is composed of a first spring and a damper connected in parallel. The standard linear solid model has a simple structure and can simultaneously represent the instantaneous elasticity, delayed elasticity and stable viscous flow of the material, making it an effective model for representing the viscoelastic properties of the intervertebral disc. Further, under the condition of constant compression load Figure 2 , the standard linear solid model can be used to describe the nonlinear relationship between the duration of the load and the strain of the disc tissue.​ The expression of the lumbar intervertebral disc creep constitutive model is as follows:

[0039]

[0040] In the formula, is the total strain, and the damage accumulation effect of the lumbar intervertebral disc is described by the total strain amount; is the time, is the constant compression load, is the Young's modulus of the first spring in the Kelvin model, is the viscosity coefficient of the damper in the Kelvin model, is the Young's modulus of the second spring.

[0041] Further, the Young's modulus of the first spring in the lumbar intervertebral disc creep constitutive model , the viscosity coefficient of the damper , and the Young's modulus of the second spring are fitted according to the time-strain data of the lumbar intervertebral disc sample obtained in step S1, so that the expression of the lumbar intervertebral disc creep constitutive model is obtained.

[0042] In other embodiments, the selection of the constitutive model is not limited thereto, and can also be equivalently replaced according to the following considerations:

[0043] 1) For simpler mechanical response: when the stress relaxation or simple creep is mainly concerned, the Maxwell model (one spring and one damper in series) can be used.

[0044] 2) For more complex mechanical response: when it is necessary to more accurately fit complex data with multiple relaxation times, the generalized Maxwell model or the generalized Kelvin model can be used.

[0045] Exemplarily, the human L4-L5 lumbar segment is taken as the lumbar intervertebral disc sample, which is composed of two complete vertebrae and one intervertebral disc. A constant compression load of 30 minutes is applied to the lumbar intervertebral disc sample, the intervertebral disc height is measured by a scale caliper, and the time-strain data of the sample is obtained. The test data is fitted into unknown parameters according to the constitutive equation form of the standard solid linear model: , and .

[0046] Step S3, constructing a lumbar cumulative load evaluation model; according to the fitted lumbar intervertebral disc creep constitutive model, time-strain data under at least one constant compression load level is simulated and obtained; and the nonlinear parameters in the lumbar cumulative load evaluation model are fitted with the time-strain data as the target.

[0047] Specifically, in the present example, the total cumulative load is approximated by discrete summation based on the principle of integrating load over time, and a nonlinear parameter with respect to time is introduced to establish a lumbar cumulative load assessment model; the lumbar cumulative load assessment model is the sum of the product of the m-th power of the load characteristic and the n-th power of the duration of time in each time interval, expressed as follows:

[0048]

[0049] In the formula, represents the lumbar cumulative load, is a quantity for characterizing the load level in the i-th time interval, , N is the number of time intervals, is a quantity for characterizing the duration of time in the i-th time interval, and are nonlinear parameters determined by the lumbar intervertebral disc creep constitutive model, satisfying , , and . . .

[0050] It should be noted that in the embodiments of the present application, the load represents the axial force of the target lumbar segment. The F_i can be any statistical quantity or characteristic value that can characterize the load level in the time interval, including but not limited to: the arithmetic mean, the root mean square, the median, or the maximum load of the interval of all sampling points in the interval.

[0051] Further, the process of fitting the nonlinear parameters in the lumbar cumulative load assessment model includes:

[0052] According to the fitted lumbar intervertebral disc creep constitutive model, simulate to obtain time-strain data under at least one constant compression load level;

[0053] Set a goodness-of-fit threshold; in the present example, the goodness-of-fit threshold is preferably 0.85;

[0054] With the time-strain data as the target, use a nonlinear least squares fitting algorithm to fit the nonlinear parameters m and n in the lumbar cumulative load assessment model when the determination coefficient is greater than the goodness-of-fit threshold.

[0055] Exemplarily, taking L4-L5 as the target lumbar segment, according to the lumbar intervertebral disc creep constitutive model, calculate the time-strain results of L4-L5 segment under the constant compression load within one hour, as shown in Figure 3 Use a nonlinear least squares method to fit the time-strain data to determine the nonlinear parameters of the lumbar cumulative load assessment model. The finally obtained parameter values are and The coefficient of determination R for the fit 2 The value is 0.86. The expression for the cumulative load assessment model of the lumbar region is obtained as follows:

[0056]

[0057] Step S4: Collect lumbar load time series data and input it into the fitted lumbar cumulative load assessment model to calculate the lumbar cumulative load estimate.

[0058] Specifically, time-series data of lumbar load is collected. This time-series data of lumbar load is a data sequence that varies over time and includes load values ​​and their corresponding timestamps, represented as follows:

[0059]

[0060] in, Indicates the first The timestamp of each sampling point Indicates the first The amount of load level of the target lumbar segment at each sampling point. This indicates the total number of sampling points within that time period.

[0061] Extract load characteristics for each time interval from the waist load time series data. With duration This includes: dividing the total time period into N consecutive time intervals. ,generally And calculate the duration of each time interval. For each time interval, the load characteristics are calculated based on the load values ​​corresponding to all sampling points within the current time interval; the load characteristics are the mean, root mean square, median, or maximum value of the load within the current time interval.

[0062] Load characteristics in each time interval With duration The data is input into a fitted lumbar cumulative load assessment model to obtain an estimated lumbar cumulative load. This estimated cumulative load is an assessment index that comprehensively reflects the risk of cumulative tissue damage caused by load intensity and duration.

[0063] For example, targeting the L4-L5 lumbar segments, lumbar load information under three working conditions was collected over an 8-hour period, i.e., the compressive loads borne by the L4-L5 segments were 500 N, 700 N, and 900 N, respectively. The total time period was a continuous time interval [0, 8 h], with sampling in seconds. The arithmetic mean of the load values ​​at all sampling points was taken as the load level. The trend of the estimated cumulative lumbar load under the three working conditions over 8 hours was output as follows:Figure 4 The results show that the introduction of the nonlinear parameter about time makes the change trend of the cumulative load estimation value closer to the creep curve, which indicates that the waist cumulative load evaluation method of the present application can more accurately reflect the influence of the actual creep behavior on the cumulative load.

[0064] Further, the method further comprises:

[0065] setting a reference waist cumulative load threshold value; including: defining a reference behavior; collecting the waist load time series data under the reference behavior and inputting into the fitted waist cumulative load evaluation model, taking the waist cumulative load estimation value output by the waist cumulative load evaluation model under the reference behavior as the reference waist cumulative load threshold value;

[0066] real-time collection of the waist load time series data and inputting into the fitted waist cumulative load evaluation model, thereby dynamically updating the waist cumulative load estimation value;

[0067] generating a risk prompt signal when the waist cumulative load estimation value reaches or is greater than the reference waist cumulative load threshold value.

[0068] Exemplarily, the following two scenarios are compared to specifically show the dynamic evaluation effect of the present example.

[0069] In the user sitting scenario, "sitting for no more than 1 hour" is defined as the reference behavior of the sitting scenario. It is measured that the load borne by the L4-L5 intervertebral disc under the sitting posture is low, and the average load is about 500 N. The data of the reference behavior is substituted into the waist cumulative load evaluation model. The waist cumulative load evaluation model calculates that the cumulative load index corresponding to the behavior is 0.25. Therefore, the reference waist cumulative load threshold value is set to 0.25. This value represents the risk threshold value of dynamic risk assessment.

[0070] Scenario one: the user adopts a high-load lazy sitting posture.

[0071] Specifically, the user adopts a lazy sitting posture, which causes the lumbar load to increase, and the actually measured average load is about 1000 N, and the cumulative load index accumulates at a significantly accelerated speed. When the user has only sat for 15 minutes, the real-time cumulative load index has reached the reference waist cumulative load threshold value. The system immediately generates a risk prompt signal to prompt the user to adjust the posture. This scenario shows that in the high-load case, the safe duration allowed by the system (15 minutes) issues an intervention signal in advance before the reference time (60 minutes) is reached.

[0072] Scenario two: the user adopts a low-load leaning-back sitting posture.

[0073] The user maintains a good supported upright sitting posture, the lumbar spine load is low, the average measured load is about 400 N, and the cumulative load index cumulative speed is slower. When the user sits for 95 minutes, the real-time cumulative load index is slowly accumulated from 0 to 0.25, reaching the reference lumbar cumulative load threshold. The system generates a risk prompt signal at this time, prompting the user to adjust the posture. This scenario shows that in the low load case, the system allows the safe duration (95 minutes) to exceed the reference time (60 minutes), avoiding unnecessary disturbance and achieving personalized and humanized risk assessment.

[0074] In summary, the present application provides a lumbar cumulative load evaluation method based on a creep constitutive model, which confirms the nonlinear parameters in the lumbar cumulative load evaluation model through the lumbar disc creep constitutive model, considers the nonlinear influence of the lumbar disc load level and duration, more accurately reflects the influence of the actual creep behavior on the cumulative load, and more accurately reflects the time-dependent characteristics of the lumbar disc injury accumulation under continuous load, so that the lumbar cumulative load evaluation model is more accurate and has clear physical meaning for the evaluation of the long-term effect of static load on the lumbar disc injury, thereby providing a more reliable quantitative basis for the risk assessment of low back pain.

[0075] Correspondingly, the present application also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the lumbar cumulative load evaluation method based on the creep constitutive model as described above. As shown in Figure 5 The lumbar cumulative load evaluation method based on the creep constitutive model provided by the embodiment of the present application is a hardware structure diagram of any device with data processing capability. In addition to the processor, memory and network interface shown in Figure 5 In addition to the processor, memory and network interface shown in

[0076] Correspondingly, the application further provides a computer readable storage medium, which stores computer instructions, and the instructions are executed by a processor to implement the method for evaluating the waist cumulative load based on the creep constitutive model. The computer readable storage medium can be an internal storage unit of any device with data processing capability, such as a hard disk or a memory. The computer readable storage medium can also be an external storage device, such as a plug-in hard disk, a smart media card (SMC), an SD card, a flash card, etc. Further, the computer readable storage medium can include both the internal storage unit of any device with data processing capability and the external storage device. The computer readable storage medium is used to store the computer program and other programs and data required by the device with data processing capability, and can also be used to temporarily store data that has been output or will be output.

[0077] The above embodiments are only used to illustrate the design ideas and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the present application and implement it, and the protection scope of the present application is not limited to the above embodiments. Therefore, any equivalent changes or modifications made according to the disclosed principles and design ideas of the present application are within the protection scope of the present application.

Claims

1. A method for evaluating a lumbar cumulative load based on a creep constitutive model, characterized by, The method comprises: Performing a creep test on a lumbar intervertebral disc sample to obtain time-strain data of the lumbar intervertebral disc sample; Fitting a lumbar intervertebral disc creep constitutive model according to the time-strain data of the lumbar intervertebral disc sample; Constructing a lumbar cumulative load evaluation model; the lumbar cumulative load evaluation model is a sum of products of m-th powers of load characteristics in each time interval and n-th powers of durations, m>0, n>0, and n≠1, the load characteristics being a mean value, a root mean square value, a median or a maximum value of the load in each time interval; simulating to obtain time-strain data under at least one constant compression load level according to the fitted lumbar intervertebral disc creep constitutive model; fitting nonlinear parameters m and n in the lumbar cumulative load evaluation model with the time-strain data as a target; Inputting the lumbar load time series data into the fitted lumbar cumulative load evaluation model to calculate a lumbar cumulative load estimation value.

2. The creep constitutive model-based evaluation method of the waist cumulative load according to claim 1, characterized by, The process of fitting the lumbar intervertebral disc creep constitutive model according to the time-strain data of the lumbar intervertebral disc sample comprises: Fitting a time-strain curve according to the obtained time-strain data of the lumbar intervertebral disc sample to determine Young's modulus and a viscous coefficient in the lumbar intervertebral disc creep constitutive model, thereby obtaining an expression of the lumbar intervertebral disc creep constitutive model; The lumbar intervertebral disc creep constitutive model adopts a viscoelastic constitutive model.

3. The creep constitutive model-based evaluation method of the waist cumulative load according to claim 2, characterized by, The process of fitting the lumbar intervertebral disc creep constitutive model according to the time-strain data of the lumbar intervertebral disc sample comprises: The lumbar intervertebral disc creep constitutive model is composed of a Kelvin model in parallel connection of a first spring with Young's modulus E1 and a damper with a viscous coefficient η1, and a second spring in series connection with Young's modulus E2; Fitting a time-strain curve according to the obtained time-strain data of the lumbar intervertebral disc sample to determine Young's modulus E1 of the first spring, the viscous coefficient η1 of the damper, and Young's modulus E2 of the second spring in the lumbar intervertebral disc creep constitutive model, thereby obtaining an expression of the lumbar intervertebral disc creep constitutive model.

4. The creep constitutive model-based evaluation method of a lumbarspinal cumulative load according to claim 1, characterized by, The process of fitting the nonlinear parameters in the lumbar cumulative load evaluation model comprises: Simulating to obtain time-strain data under at least one constant compression load level according to the fitted lumbar intervertebral disc creep constitutive model; Setting a goodness-of-fit threshold; Fitting the nonlinear parameters m and n in the lumbar cumulative load evaluation model with the time-strain data as a target by using a nonlinear least squares fitting algorithm, when a determination coefficient is greater than the goodness-of-fit threshold.

5. The creep constitutive model-based evaluation method of the waist cumulative load according to claim 1, characterized by, The process of inputting the lumbar load time series data into the fitted lumbar cumulative load evaluation model to calculate a lumbar cumulative load estimation value comprises: Collecting lumbar load time series data, the lumbar load time series data being a data sequence containing load values and corresponding time stamps changing over time; Extracting load characteristics and durations in each time interval from the lumbar load time series data, comprising: dividing a total time period into a plurality of continuous time intervals and calculating a duration of each time interval; for each time interval, calculating a load characteristic according to load values corresponding to all sampling points in the current time interval; The load characteristics and the duration of each time interval are input into the fitted waist cumulative load evaluation model to obtain a waist cumulative load estimation value.

6. The creep constitutive model-based evaluation method of a lumbarspinal cumulative load according to claim 1, characterized by, The method further comprises: setting a reference waist cumulative load threshold value; including: defining a reference behavior; collecting waist load time series data under the reference behavior and inputting the data into the fitted waist cumulative load evaluation model; and taking the waist cumulative load estimation value output by the waist cumulative load evaluation model under the reference behavior as the reference waist cumulative load threshold value; real-time collection of waist load time series data and inputting the data into the fitted waist cumulative load evaluation model to dynamically update the waist cumulative load estimation value; when the waist cumulative load estimation value reaches or is greater than the reference waist cumulative load threshold value, a risk prompt signal is generated.

7. An electronic device, comprising: comprise: at least one processor; and a memory in communication with the at least one processor; wherein the memory stores one or more computer programs executable by the at least one processor, and the one or more computer programs are executed by the at least one processor to enable the at least one processor to perform the waist cumulative load evaluation method based on the creep constitutive model according to any one of claims 1-6.

8. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program, when executed by the processor, implements the waist cumulative load evaluation method based on the creep constitutive model according to any one of claims 1-6.

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