Biomechanical analysis of bone mesoscopic structure and mechanical properties of vertebral endplates of degenerated intervertebral discs in rabbits

In previous studies of disc degeneration,the structural and mechanical properties of the endplate were often neglected.In this paper,the station legislation was used to construct an animal model of minor trauma disc degeneration,and the mechanism of disc degeneration was further investigated by observing the changes of mesoscopic structure and developing the mechanical properties of endplate bone.Twenty-eight 6-month-old Japanese white rabbits were divided into two groups:control group and experimental group.An animal model of intervertebral disc degeneration was established by upright experiment in the experimental group.The bone mesoscopic structures in different areas of each endplate were observed by histological and imaging methods,and the mechanical properties of the endplates were measured by indentation method.The two groups of data were compared by one-way ANOVA.After the experimental animals stood for 17 weeks,The experimental group showed the characteristics of early disc degeneration.The microstructure of the degenerative group showed that the end plate mineralization degree was higher,the bone mass was larger,and the number and thickness of bone trabeculae were larger.The results of indentation test showed that the mechanical properties of the degeneration group were enhanced,and the lower endplate was obviously enhanced.We successfully established a model of human disc degeneration with non invasive trauma and more consistent with the process of human disc degeneration through the standing experiment.In the experimental group,the internal structure of the endplate was dense and pore distance was reduced.The change of bone mesoscopic structure further affects the endplate,resulting in the enhancement of the mechanical properties of the endplate after intervertebral disc degeneration.The reduction of the pore distance and the narrowing of the internal channel structure of the endplate also hinder the nutrition supply of the intervertebral disc,which may be the key reason affecting the degeneration of the intervertebral disc.A biomechanical method for investigating the mechanism of intervertebral disc degeneration can be provided in this paper.

Investigation into the analysis method for assessing contact stress in joint prosthesis

Contact stress is the important cause of wear and failure of knee joint prostheses implanted in the human body during movement.The calculation of contact stress on joint prostheses is often inaccurate due to the deviation of joint position during activity.This paper proposes a correction method for contact stress based on finite element results.Firstly,the contact stress and contact radius between femoral and tibial prostheses of knee joint were calculated and analyzed by Hertz contact theory.Then,individualized finite element models based on the individualized geometry of the joint prosthesis and individualized loading were constructed,and the finite element contact stress was analyzed.The finite element results were calibrated utilizing the Hertz contact theory.Additionally,this study investigated the impact of three gait patterns(normal gait,medial thrust gait,and bouncing gait)on the contact stress experienced by the tibial insert.The research methods and results can provide ideas for theoretical analysis and finite element simulation of prosthetic joint contact,as well as offer theoretical support and analysis methods for evaluating the lifespan of prosthetic joints.

Automatic quantification of morphology on magnetic resonance images of the proximal tibia

The morphological quantification of the proximal tibia of the knee joint is important in knee replacement.Accurate knowledge of these parameters provides the basis for design of the tibial prosthesis and its fixation.Ideally,a prosthesis that is suitable for the morphological characteristics of Chinese knees is needed.In this paper,a deep learning automatic network framework is designed to achieve automatic segmentation and automatic quantitative analysis of magnetic resonance images of the tibia.An enhanced feature fusion network structure is designed,including high and low-level feature fusion path modules to create accurate segmentation of the tibia.A new method of extracting feature points and lines from outline contours of the proximal tibia is designed to automatically calculate six clinical morphological linear parameters of the tibia in real-time.The final result is an automatic visualisation of the tibial contour and automated extraction of tibial morphometric parameters.Validation of the results from our system against a gold standard obtained by manual processing by expert clinicians showed the Dice coefficient to be 0.97,the accuracy to be 0.98,and the correlation coefficients for all six morphological parameters of the automatic quantification of the tibia are above 0.96.The gender-specific study found that the values of the proximal tibial linear parameters of internal and external tibial diameter,anterior and posterior diameter,lateral plateau length,lateral plateau width,medial plateau length,and medial plateau width in male patients are significantly greater than in female patients(all P values<0.01).The results enrich the use of deep learning in medicine,providing orthopaedic specialists with a valuable and intelligent quantitative tool that can assess the progression and changes in osteoarthritis of the knee joint.

DETERMINATION OF QUADRICEPS FORCES IN SQUAT AND ITS APPLICATION IN CONTACT PRESSURE ANALYSIS OF KNEE JOINT

While the quadriceps muscles of human body are quite important to the daily ac-tivities of knee joints,the determination of quadriceps forces poses significant challenges since it cannot be measured in vivo.Here,a novel approach is presented to obtain the forces in squat through the combination of motion photography,force transducers measuring,multi-rigid-body theory and finite element analysis.Firstly,the geometrical and angular data of human for squat process were obtained through the analysis of photographed pictures for human squat with cam-era.At the same time,force transducers were used to measure the reaction forces from feet and to determine the center of gravity for identical squat process.Next,based on the multi-rigid-body dynamics,a mathematical model for human right leg and foot was established in order to determine the quadriceps torques under different squat angles.Then,so as to determine the quadriceps forces along with varied squat angles,a simplified three-dimensional finite element model was built,including tibia,fibula,patella,patella ligament and quadriceps tendon.Finally,the contact pressure of knee joint was analyzed for the squat with the established model of knee joint involving the obtained quadriceps forces from finite element analysis.And it showed that in the 0-90 degree squat process,the peak value of contact pressure of articular cartilages and menisci is increased with the increased squat angle.This study can be referenced for further un-derstanding of the biomechanical behaviors of knee,contact pressure effects of daily activities on knee,and is significantly instructive for sports rehabilitation.