Biomechanical analysis of press-extension technique on degenerative lumbar with disc herniation and staggered facet joint

Validation and Estimation of Obesity-Induced Intervertebral Disc Degeneration through Subject-Specific Finite Element Modelling of Functional Spinal Units

(1) Background: Intervertebral disc degeneration has been linked to obesity; its potential mechanical effects on the intervertebral disc remain unknown. This study aimed to develop and validate a patient-specific model of L3-L4 vertebrae and then use the model to estimate the impact of increasing body weight on disc degeneration. (2) Methods: A three-dimensional model of the functional spinal unit of L3-L4 vertebrae and its components were developed and validated. Validation was achieved by comparing the range of motions (RoM) and intradiscal pressures with the previous literature. Subsequently, the validated model was loaded according to the body mass index and estimated stress, deformation, and RoM to assess disc degeneration. (3) Results: During validation, L3-L4 RoM and intradiscal pressures: flexion 5.17° and 1.04 MPa, extension 1.54° and 0.22 MPa, lateral bending 3.36° and 0.54 MPa, axial rotation 1.14° and 0.52 MPa, respectively. When investigating the impact of weight on disc degeneration, escalating from normal weight to obesity reveals an increased RoM, by 3.44% during flexion, 22.7% during extension, 29.71% during lateral bending, and 33.2% during axial rotation, respectively. Also, stress and disc deformation elevated with increasing weight across all RoM. (4) Conclusions: The predicted mechanical responses of the developed model closely matched the validation dataset. The validated model predicts disc degeneration under increased weight and could lay the foundation for future recommendations aimed at identifying predictors of lower back pain due to disc degeneration.

Analysis of biomechanical characterization of the thumb rubbing method

BACKGROUND

Thumb rubbing is one of the widely accepted massage techniques, owing to its simple and effective operation. Exploring the biomechanical characteristics of the thumb rubbing method can assist the understanding of the operating characteristics of manipulation, thereby improvising the therapeutic role of manipulation.

OBJECTIVE

To study the kinematic and kinetic characteristics of the thumb kneading method from the biomechanical point of view, and to quantitatively analyze the key points of thumb kneading operation.

METHODS

We explored the biomechanical characteristics of the thumb kneading operation by an analysis of the parameters scored by the experts and students using the "thumb kneading data glove and data collection system".

RESULTS

(1) Force trajectory: The expert group showed a regular force trajectory compared to the student group, with a stable thumb suction position, small drift and concentrated force. (2) Force value: The average force value of the expert group was concentrated in the range 0.614 ± 0.041 kg, while the average force value of the student group was concentrated in the range 0.650 ± 0.146 kg and the difference was not statistically significant. (3) Frequency: The frequency of the expert group was mainly concentrated in the range 134.280 ± 39.106 times/min, while that of the student group was 66.04 ± 23.651 times/min, (P< 0.05). (4) Period: The operation cycle during the thumb kneading of the expert and student groups was mainly concentrated in the range of 0.476 ± 0.117 s and (0.990 ± 0.259) s, respectively, and the difference was statistically significant (P< 0.05).

CONCLUSION

The present study revealed that the technical operation of the expert group was more stable and standardized than that of the student group. It was found that the force value was inversely proportional to the frequency of the operation. In the "circular rotation" operation of the thumb rubbing method, the force value conversion degree of different parts of the thumb reflected the motion trajectory. Furthermore, the "circular rotation" operation performed by the expert group was better than the student group. The study of the parameters, including the angle of frequency, period and force value can reflect the biomechanical characteristics of thumb rubbing method to a significant extent.

Traditional Chinese Manual Therapy (Tuina) reshape the function of default mode network in patients with lumbar disc herniation

Purpose

Investigating the changes of regional homogeneity (ReHo) values and both static and dynamic functional connectivity (FC) before and after Traditional Chinese Manual Therapy (Tuina) in patients with lumbar disk herniation (LDH) through resting-state functional magnetic resonance imaging (RS-fMRI). Based on this, we observe the effect of Tuina on the above abnormal changes.

Methods

Patients with LDH (n = 27) and healthy controls (HCs) (n = 28) were recruited. The functional magnetic resonance imaging (fMRI) scanning was performed two times in LDH patients, before Tuina (time point 1, LDH-pre) and after the sixth Tuina (time point 2, LDH-pos). And for one time in HCs which received no intervention. The ReHo values were compared between LDH-pre and HCs. The significant clusters detected by ReHo analysis were selected as seeds to calculate static functional connectivity (sFC). We also applied the sliding-window to perform dynamic functional connectivity (dFC). To evaluate the Tuina effect, the mean ReHo and FC values (both static and dynamic) were extracted from significant clusters and compared between LDH and HCs.

Results

In comparison to HCs, LDH patients displayed decreased ReHo in the left orbital part middle frontal gyrus (LO-MFG). For sFC analysis, no significant difference was found. However, we found decreased dFC variance between LO-MFG and the left Fusiform, and increased dFC variance in the left orbital inferior frontal gyrus and left precuneus. Both ReHo and dFC values revealed after Tuina, the brain activities in LDH patients were similar to HCs.

Conclusion

The present study characterized the altered patterns of regional homogeneity in spontaneous brain activity and those of functional connectivity in patients with LDH. Tuina can reshape the function of the default mode network (DMN) in LDH patients, which may contribute to the analgesic effect of Tuina in LDH patients.

Biomechanical modelling of the facet joints: a review of methods and validation processes in finite element analysis

There is an increased interest in studying the biomechanics of the facet joints. For in silico studies, it is therefore important to understand the level of reliability of models for outputs of interest related to the facet joints. In this work, a systematic review of finite element models of multi-level spinal section with facet joints output of interest was performed. The review focused on the methodology used to model the facet joints and its associated validation. From the 110 papers analysed, 18 presented some validation of the facet joints outputs. Validation was done by comparing outputs to literature data, either computational or experimental values; with the major drawback that, when comparing to computational values, the baseline data was rarely validated. Analysis of the modelling methodology showed that there seems to be a compromise made between accuracy of the geometry and nonlinearity of the cartilage behaviour in compression. Most models either used a soft contact representation of the cartilage layer at the joint or included a cartilage layer which was linear elastic. Most concerning, soft contact models usually did not contain much information on the pressure-overclosure law. This review shows that to increase the reliability of in silico model of the spine for facet joints outputs, more needs to be done regarding the description of the methods used to model the facet joints, and the validation for specific outputs of interest needs to be more thorough, with recommendation to systematically share input and output data of validation studies.

Simplifying the human lumbar spine (L3/L4) material in order to create an elemental structure for the future modeling

The human lumbar spine incorporates the best joints in nature due to its optimal static and dynamic behavior against the internal and external loads. Developing an elemental structure based on this joint requires simplification in terms of the materials employed by keeping the mechanical and anatomical behaviors of the human lumbar spine. In the present study, the finite element (FE) of two motion segments of the human lumbar spine (L3/L4) was developed based on the CT scan data as the base for vertebrae geometry, verified geometry properties for another part of two motion segments, and combination of materials and loads obtained from the validated resources. Then, simplification occurred in four continuous steps such as omitting the annual fibers of annual matrix, representing the material of the annual matrix to the nucleus, demonstrating the material of annual matrix to the endplates too, and omitting the trabecular part of vertebrae. The present study aimed to propose the method for developing the basic structure of the human lumbar spine by simplifying its materials in the above-mentioned steps, analyzing the biomechanical effects of these four steps in terms of their internal and external responses, and validating the data obtained from the FE method. The validated simplified way introduced in this study can be used for future research by making implants, prosthesis, and modeling based on the human lumbar spine in other fields such as industrial design, building structures, or joints, which results in making the model easier, cheaper, and more effective.

Biomechanical Effects of Lateral Bending Position on Performing Cervical Spinal Manipulation for Cervical Disc Herniation: A Three-Dimensional Finite Element Analysis

Background

Most studies report that the common position of cervical spinal manipulation (CSM) for treating symptomatic cervical disc herniation (CDH) is lateral bending to the herniated side. However, the rationality of lateral bending position on performing CSM for CDH is still unclear.

Objective

The purpose of this study is to investigate the biomechanical effects of lateral bending position on performing CSM for CDH.

Methods

A finite element (FE) model of CDH (herniated on the left side) was generated in C5-6 segment based on the normal FE model. The FE model performed CSM in left lateral bending position, neutral position, and right lateral bending position, respectively. Cervical disc displacement, annulus fiber stress, and facet joint stress were observed during the simulation of CSM.

Results

The cervical disc displacement on herniated side moved forward during CSM, and the maximum forward displacements were 0.23, 0.36, and 0.45 mm in left lateral bending position, neutral position, and right lateral bending position, respectively. As the same trend of cervical disc displacement, the annulus fiber stresses on herniated side from small to large were 7.40, 16.39, and 22.75 MPa in left lateral bending position, neutral position, and right lateral bending position, respectively. However, the maximum facet stresses at left superior cartilage of C6 in left lateral bending position, neutral position, and right lateral bending position were 6.88, 3.60, and 0.12 MPa, respectively.

Conclusion

Compared with neutral position and right lateral bending position, though the forward displacement of cervical disc on herniated side was smaller in left lateral bending position, the annulus fiber stress on herniated side was declined by sharing load on the left facet joint. The results suggested that lateral bending to the herniated side on performing CSM tends to protect the cervical disc on herniated side. Future clinical studies are needed to verify that.