Static Flexion Research Articles

Structural design and biomechanical analysis of a combined titanium and polyetheretherketone cage based on PE-PLIF fusion.

In lumbar spinal fusion, the titanium cage tends to cause stress shielding due to their high elastic modulus, which can lead to degenerative lesions in adjacent spinal segments. Furthermore, polyetheretherketone (PEEK) cages have certain material characteristics that do not promote bone ingrowth and fusion stability. In this study, a new cage was designed, and its biomechanical performance in percutaneous endoscopic posterior lumbar interbody fusion (PE-PLIF) was analyzed using the finite element (FE) method. A complete model of the L4-L5 lumbar spine was established, and static and harmonic vibration FE analysis models were developed based on it. The biomechanical properties of titanium, PEEK, and combined cage in PE-PLIF fusion were compared. The strain capacity of the combined fusion increased by 9.5% when compared to the titanium fusion. The surgical model under the combined fusion reduces the L5 endplate stress by 12% in the forward flexion condition and the fusion stress by 17% in the vibration condition compared to the model supported by the titanium fusion, and the differences in screw stress and mobility among the three models are not significant in multiple conditions. Consequently, the combined cage demonstrates a certain reduction in the stress-shielding effect when compared to the titanium cage; it has better fusion effect and provides theoretical support and guidance for the design of the clinical fusion cage.

Comparison of the Effects of a Roller Massager Intervention on the Rectus Femoris Between Lengthened and Slack Positions.

Kasahara, K, Konrad, A, Murakami, Y, Thomas, E, and Nakamura, M. Comparison of the effects of a roller massager intervention on the rectus femoris between lengthened and slack positions. J Strength Cond Res 38(11): 1879-1884, 2024-A roller massager (RM) is a type of foam rolling device, which previous studies have shown to be effective for acutely decreasing tissue hardness and increasing range of motion (ROM). However, these effects may differ with the RM intervention position (i.e., knee flexion or knee extension). Therefore, this study aimed to compare the acute effects of an RM intervention on the rectus femoris (RF) in the knee flexed and extended positions. The subjects were 14 healthy male college students (age, 22.6 ± 0.8 years). The RF of the dominant leg was tested. Three conditions were compared: a control condition with no intervention (CON), an RM intervention in knee extension (i.e., RM_extension), and a RM intervention in knee flexion (i.e., RM_flexion). The measurements were tissue hardness in the proximal (TH_pro), middle (TH_mid), and distal (TH_dis) portions of the RF, knee flexion ROM, pain pressure threshold (PPT), maximal voluntary isometric contraction (MVC-ISO) torque, and maximal voluntary concentric contraction (MVC-CON) torque in the RF before and immediately after the intervention. There were significant interaction effects of TH_mid and knee flexion ROM. Both RM_extension and RM_flexion conditions showed a significant ( p < 0.01) decrease in TH_mid and an increase in knee flexion ROM, but there were no significant differences between conditions. There was a main effect for TH_pro and PPT ( p < 0.05) but no significant interaction effect or main effect for TH_dis, MVC-ISO torque, and MVC-CON torque. The results showed that the RM intervention can effectively decrease tissue hardness and increase ROM, regardless of limb position (i.e., knee extension or flexion).

The Effect of Kinesio Taping on Lumbar Kinematic After Static Lumbar Flexion in Healthy Subjects

Introduction: The application of Kinesio taping (KT) is a rehabilitation technique used to provide muscle and joint support and stability, without limiting the range of motion (ROM). No study evaluated the effects of KT on lumbar flexion relaxation phenomenon and kinematic details after static flexion. This study aims to find out the results of KT on erector spinae (ES) muscle activity, flexion relaxation pattern, and trunk, lumbar, and hip range of motion in healthy subjects during static flexion Materials and Methods: This study used a two-factor within-group design. Twenty-two healthy female students participated in this study. We used surface electromyography (EMG) to assess ES muscle activity and measured kinematic information with data from the camera. Variables related to muscle activity and angles in forward bending movement before and after creep were investigated. The test was performed in two situations with and without the use of KT. Results: KT reduced the time of muscle activity during bending. Also, KT increased trunk, and hip angles at the end of forward flexion. In the lumbar extension phase, the ES muscles were activated later Conclusion: KT can prevent the increase of lumbar spine flexion angle due to the creep effect. It can be used to protect the strained viscoelastic structures and increase the involvement of cutaneous receptors. KT can act as a protector in the dynamic stabilization system of lumbar joints in flexion positions in healthy people.

Biomechanical analysis of the tandem spinal external fixation in a multiple-level noncontiguous lumbar fractures model: a finite element analysis.

This study aimed to investigate the biomechanical characteristics of the tandem spinal external fixation (TSEF) for treating multilevel noncontiguous spinal fracture (MNSF) using finite element analysis and provide a theoretical basis for clinical application. We constructed two models of L2 and L4 vertebral fractures that were fixed with the TSEF and the long-segment spinal inner fixation (LSIF). The range of motion (ROM), maximum stresses at L2 and L4 vertebrae, the screws and rods, and the intervertebral discs of the two models were recorded under load control. Subsequently, the required torque, the maximum stress at L2 and L4 vertebrae, the screws and rods, and the intervertebral discs were analyzed under displacement control. Under load control, the TSEF model reserved more ROM than the LSIF model. The maximum stresses of screws in the TSEF model were increased, while the maximum stresses of rods were reduced compared to the LSIF model. Moreover, the maximum stresses of L2 and L4 vertebrae and discs in the TSEF model were increased compared to the LSIF model. Under displacement control, the TSEF model required fewer moments (N·mm) than the LSIF model. Compared to the LSIF model, the maximum stresses of screws and rods in the TSEF model have decreased; the maximum stresses at L2 and L4 in the TSEF model were increased. In the flexion condition, the maximum stresses of discs in the TSEF model were less than the LSIF model, while the maximum stresses of discs in the TSEF model were higher in the extension condition. Compared to LSIF, the TSEF has a better stress distribution with higher overall mobility. Theoretically, it reduces the stress concentration of the connecting rods and the stress shielding of the fractured vertebral bodies.

Heartbeat detection from high-density EMG electrodes on the upper arm at different EMG intensity levels using Zephlet

Background and objectivesA significant number of global deaths caused by cardiac arrhythmias can be prevented with accurate and immediate identification. Wearable devices can play a critical role in such identification by continuously monitoring cardiac activity using electrocardiogram (ECG). The existing body of research has focused on extracting cardiac information from the body surface by investigating various electrode locations and algorithm development for ECG interpretation. The present study was designed for heartbeat detection using the signals recorded from the upper arm. MethodsFirstly, optimal electrode locations on the upper arm were identified for Rest and elbow flexion (EF) conditions. Next, a synthesized ECG was generated using the selected electrodes with generalized weights over subjects and trials, and then zero-phase wavelet (Zephlet) was applied for feature extraction. Heartbeat detection was finally performed using the extracted detail coefficients incorporated with a multiagent detection scheme (MDS). ResultsThe F1-score for heartbeat detection was 0.94 ± 0.16, 0.86 ± 0.22, 0.79 ± 0.26, and 0.67 ± 0.31 for Rest and EF with three different levels of muscle contraction (C1 to C3), respectively. Changing the acceptable distance between the detected and actual heartbeats from 50 ms to 20 ms, the F1-score changed to 0.81 ± 0.20, 0.66 ± 0.26, 0.57 ± 0.26, and 0.44 ± 0.26 for Rest and C1 to C3, respectively. ConclusionThese findings make several contributions to the current literature, summarized as precise and consistent electrode localization for various muscle contraction levels and accurate heartbeat detection method development for each of these conditions.

Biomechanical investigation of the hybrid lumbar fixation technique with traditional and cortical bone trajectories in transforaminal lumbar interbody fusion: finite element analysis

ObjectiveTo compare the biomechanical performance of the hybrid lumbar fixation technique with the traditional and cortical bone trajectory techniques using the finite element method.MethodsFour adult wet lumbar spine specimens were provided by the Department of Anatomy and Research of Xinjiang Medical University, and four L1–S1 lumbar spine with transforaminal lumbar interbody fusion (TLIF) models at L4–L5 segment and four different fixation techniques were established: bilateral traditional trajectory screw fixation (TT–TT), bilateral cortical bone trajectory screw fixation (CBT–CBT), hybrid CBT–TT (CBT screws at L4 and TT screws at L5) and TT–CBT (TT screws at L4 and CBT screws at L5). The range of motion (ROM) of the L4–L5 segment, von Mises stress of cage, internal fixation, and rod were compared in flexion, extension, left and right bending, and left and right rotation.ResultsCompared with the TT–TT group, the TT–CBT group exhibited lower ROM of L4–L5 segment, especially in left-sided bending; the CBT–TT group had the lowest ROM of L4–L5 segment in flexion and extension among the four fixation methods. Compared with the CBT–CBT group, the peak cage stress in the TT–CBT group was reduced by 9.9%, 18.1%, 21.5%, 23.3%, and 26.1% in flexion, left bending, right bending, left rotation, and right rotation conditions, respectively, but not statistically significant (P > 0.05). The peak stress of the internal fixation system in the TT–CBT group was significantly lower than the other three fixation methods in all five conditions except for extension, with a statistically significant difference between the CBT–TT and TT–CBT groups in the left rotation condition (P = 0.017). In addition, compared with the CBT–CBT group, the peak stress of the rod in the CBT–TT group decreased by 34.8%, 32.1%, 28.2%, 29.3%, and 43.0% under the six working conditions of flexion, extension, left bending, left rotation, and right rotation, respectively, but not statistically significant (P > 0.05).ConclusionsCompared with the TT–TT and CBT–CBT fixation methods in TLIF, the hybrid lumbar fixation CBT–TT and TT–CBT techniques increase the biomechanical stability of the internal fixation structure of the lumbar fusion segment to a certain extent and provide a corresponding theoretical basis for further development in the clinic.

Stress analysis of the screw of atlantoaxial posterior screw fixation C1LM-C2PS and C1LM-C2PARS with and without rod: A FEM based study

Human cervical spine consists of three vertebrae C0-occiput, C1-atlas, & C3-axial in its upper part. The atlantoaxial complex is the most portable segment of the cervical spine and is accountable for half of the flexion, extension, and axial rotation movements of the neck. Atlantoaxial cervical spine injuries are serious injuries since there is a likely risk of harm to the spinal cord. Sustaining stability of the atlantoaxial joint following a neck injury is a difficult task because both vertebrae have complicated anatomy. Thus, the strength of a bone screw is especially significant in the early post-operative stages. Different stabilization procedures have been accounted for C1-C2 injury fixation, out of which fixation with transarticular screws is considered as the gold standard procedure. But screw malposition and high riding transverse foramen of the C2 vertebra are some limitations of this fixation technique. Current FE-based study provides a comparison of the biomechanical stability of the two different atlantoaxial posterior screw fixation techniques (C1Lateral Mass-C2 Pedicle screws, C1Lateral Mass-C2PARS screws).In this work, a C1-C2 cervical spine model of a male patient is developed using MRI CT scan data using a 3-d slicer software and biomechanical stability comparison is done for C1LM-C2PS & C1LM-C2PARS screws fixed once with a supporting posterior screw fixation rod and once without rod under the physiological loading conditions of flexion, extension, lateral bending, and axial rotation using ANSYS WORKBENCH 16.2. The effects of the engaging supporting rod on the cervical spine were evaluated in the form of von-mises stresses induced in screws. Result shows reduction in screw stress values when implanted with supporting rods. C1LM-C2PS screw fixation with rod might be thought of as the best fixation solution for fractured C1-C2 vertebrae as it showed minimum stress values in the analysis as compared to C1LM-C2PARS with and without rod.

Combined flexion and compression negatively impact the mechanical integrity of the annulus fibrosus.

To observe the effect of static flexion, in combination with compression, on the intralamellar and interlamellar matrix properties of the annulus fibrosus. C3/C4 cervical functional spinal units of porcine specimens were selected. Following preloading, all specimens were loaded under 1200N axial compression in either a neutral or static end range flexion posture (15º) for 2h. Following loading, six annulus samples were dissected from each disc: four single-layer and two multi-layer samples. The multi-layer samples underwent peel tests to quantify the mechanical properties of the interlamellar matrix while the single-layer samples underwent tensile tests to quantify the mechanical properties of the intralamellar matrix. Statistical comparisons between properties were performed to determine differences between postural condition, extraction location, and extraction depth. Flexion elicited a decrease in lamellar adhesive strength (p = 0.045) and in single-layer failure strain (p = 0.03) when compared to a neutral posture. Flexion also had extraction depth-specific effects namely increased intralamellar matrix stiffness in the inner annulus when compared to neutral (p = 0019). Flexion also resulted in a significant decrease in toe region strain for the inner region of the annulus (p = 0.035). The inner region of the annulus was shown to have a significant increase in stress at 30% strain when compared to the outer region after flexion (p = 0.041). The current findings suggest that the mechanical properties of the interlamellar and intralamellar matrices are sensitive to flexion, creating an environment that promotes an increased potential for damage to occur.

Biomechanical characterization of bilateral pedicle screw internal fixation combinations on lumbar vertebrae

Purpose Pedicle screw fixation has been considered a suitable surgical intervention for addressing a diverse range of indications involving the lumbar spinal segments, but the impact of bilateral pedicle screw internal fixation combinations on the stability and flexibility of vertebral body motion has been limited. This study aimed to the effect of pedicle screw internal fixation on the mechanical characterization of lumbar multi-segmental vertebra under various loading conditions. Methods Porcine lumbar multi-segmental vertebral samples were tested with three pedicle screw fixation groups including rigid fixation, mixed fixation and dynamic fixation under four loading conditions of flexion, posterior extension, left-side bend, and right-side bend at bending moments of 3 N⋅m, 4 N⋅m, 5 N⋅m and 6 N⋅m, respectively. The stability and flexibility of the segmental motion were statistically analysed. Results The flexibility of joint activities increased using one-way dynamic pedicle screws with the range of motion for mixed fixation and dynamic fixation increased by 30% and 47% in left side bend and by 25% and 73% in right side bend, respectively. The range of motion for lumbar vertebra increased with higher moments. Conclusions The flexibility of joint activities was improved using one-way dynamic pedicle screws and the mixed fixation was considered moderate providing larger flexibility in right and left side bend without compromising stabilization. The results of this study are useful for providing theoretical reference for clinical selection of surgical plans.

Effects of plantar flexion angle during falling on rebound jump height

Introduction: Rebound jumps (RJs), successive vertical jumps performed as quickly as possible with a brief foot-ground contact duration, are often used as part of plyometric training. Since RJs incur high mechanical outputs of the ankle joint, it was hypothesized that RJ height would be affected by the degree of plantar flexion angle prior to each landing. In this study, RJ heights were compared between two distinct plantar flexion conditions. Ankle joint kinematics, ground reaction force (GRF) and ground-contact duration were measured to identify factors that determined the difference in RJ height, if observed, resulting from the alteration of the plantar flexion angle.

Robotic ankle control can provide appropriate assistance throughout the gait cycle in healthy adults.

Ankle foot orthoses are mainly applied to provide stability in the stance phase and adequate foot clearance in the swing phase; however, they do not sufficiently assist during the entire gait cycle. On the other hand, robotic-controlled orthoses can provide mechanical assistance throughout the phases of the gait cycle. This study investigated the effect of ankle control throughout the gait cycle using an ankle joint walking assistive device under five different robotic assistance conditions: uncontrolled, dorsiflexion, and plantar flexion controlled at high and low speeds in the initial loading phase. Compared with the no-control condition, the plantar flexion condition enhanced knee extension and delayed the timing of ankle dorsiflexion in the stance phase; however, the opposite effect occurred under the dorsiflexion condition. Significant differences in the trailing limb angle and minimum toe clearance were also observed, although the same assistance was applied from the mid-stance phase to the initial swing phase. Ankle assistance in the initial loading phase affected the knee extension and ankle dorsiflexion angle during the stance phase. The smooth weight shift obtained might have a positive effect on lifting the limb during the swing phase. Robotic ankle control may provide appropriate assistance throughout the gait cycle according to individual gait ability.

Finite Element Analysis and Comparative Study of 4 Kinds of Internal Fixation Systems for Anterior Cervical Discectomy and Fusion in Children.

Background Spinal injury in children usually occurs in the cervical spine region. Anterior fixation of the lower cervical spine has been applied in treating pediatric cervical spine injury and disease due to its stable and firm mechanical properties. This study performed finite element analysis and comparison of four different anterior cervical internal fixation systems for children to explore more standard methods of anterior cervical internal fixation in children and seek more effective and safe treatment for children's cervical spine diseases. Methods A finite element model of 6-year-old children with lower cervical spine C4/5 discectomy was established, and the self-designed lower cervical spine anterior locking internal fixation system ACBLP and the children's anterior cervical internal fixation system ACOP, ACVLP, and ACSLP plate screws were fixed and loaded on the model. 27.42 N·m torque load was applied to each internal fixation model under six working conditions of anteflexion, backward flexion, left flexion, right flexion, left rotation, and right rotation, to simulate the movement of the cervical spine. The activity and stress distribution cloud diagram of each finite element model was obtained to explore the optimal method of anterior cervical fixation in children. Results In the four internal fixation models of ACOP, ACVLP, ACSLP, and ACBLP, the mobility of the C4/5 segment showed a decreasing relationship, and the mobility of adjacent segments increased significantly. In the Mises stress cloud diagram of the cervical spine of the four models, the vertebral body and accessories of the ACBLP model born the least stress, followed by ACSLP. The steel plate and screws in the ACVLP internal fixation model were the most stressed. The stress of the internal fixation system (plate/screw) in all models increased in the order of ACBLP, ACSLP, ACVLP, and ACOP. Conclusions ACBLP internal fixation system had obvious advantages in anterior internal fixation of the lower cervical spine in children, C4/5 had the smallest degree of movement, relative displacement was minimal, and the stress on the centrum and pedicle was the least, while the stress on the plate screw was relatively the smallest.

Finite Element Analysis of Spinal Cord Stress in a Single Segment Cervical Spondylotic Myelopathy.

BackgroundSpinal cord ischemia is largely caused by cervical spondylotic myelopathy (CSM), which has a corresponding biomechanical basis. Finite element analysis of spinal cord stress in diseased segments of CSM was performed to provide a biomechanical basis for the pathogenesis of CSM.MethodsA single segment (C4-5) in a patient with CSM was selected for mechanical simulation of three-dimensional (3D) computed tomography scanning, and a 3D finite element model of the cervical vertebra was constructed. Based on the patient's age, sex, height, weight, and other parameters, a finite element analysis model of an individual with healthy cervical vertebrae in our hospital was selected as the control to compare the stress changes between the patient and control groups in the analysis of the cervical vertebrae under anterior flexion, posterior extension, lateral flexion, and rotating load in the diseased spinal cord segment.ResultsIn the CSM patient, the diseased segment was C4-5. Under loading conditions of forward flexion, posterior extension, left flexion, right flexion, left rotation, and right rotation, the maximum stress on the spinal cord in the control group was 0.0044, 0.0031, 0.00017, 0.00014, 0.0011, and 0.001 MPa, respectively, whereas those in the spinal cord in the CSM group were 0.039, 0.024, 0.02, 0.02, 0.0194, and 0.0196 MPa, respectively.ConclusionThe maximum stress on the diseased segments of the spinal cord in the CSM group was higher than that in the control group, which contributed to verifying the imaging parameters associated with spinal cord compression stress.

Three-Dimensional Biomechanical Finite Element Analysis of Lumbar Disc Herniation in Middle Aged and Elderly.

Lumbar intervertebral disc protrusion disease refers to the degeneration of intervertebral disc, rupture of fibrous ring, nucleus pulpous protrusion and stimulation or compression of nerve root. The import command in Mimics medical 3D reconstruction software was used to erase the irrelevant image data and obtain vertebral body images. The original 3D model of each vertebral body was built by 3D computing function. A three-dimensional finite element model was established to analyze the effect of different surgical methods on the mechanical distribution of the spine after disentomb. The stress distribution of the spine, intervertebral disc, and left and right articular cartilage at L4/L5 stage and the position shift of the fourth lumbar vertebra were analyzed under 7 working conditions of vertical, forward flexion, extension, left and right flexion, and left and right rotation. The results showed that the established model was effective, and the smaller the area of posterior laminar decompression was, the lesser the impact on spinal stability was. The PELD treatment of lumbar disc herniation had little impact on spinal biomechanics and could achieve good long-term biomechanical stability. Combining the clinical experiment method and finite element simulation, using the advantages of finite element software to optimize the design function can provide guidance for the design and improvement of medical devices and has important significance for the study of clinical mechanical properties and biomechanics.

The MRI-based 3D morphologic changes of knee meniscus under knee weight-bearing and early flexion conditions

There are few studies investigate morphologic changes of knee meniscus in vivo mechanical loading and three-dimensions (3D) deformation and displacement of the whole meniscus between in vivo mechanical loading and unloading conditions are still unclear. To investigate the displacements and 3D morphological changes of the menisci under knee weight-bearing and early flexion conditions in healthy adults using a Magnetic Resonance Imaging (MRI)-compatible loading device (a 3.0 T MR imaging system) combined with a newly developed 3D comparison technique. Fifteen healthy volunteers were recruited in this cross-sectional observational study. Each subject underwent MRIs of their dominant right knee in eight different scanning conditions using a 3.0-T MRI scanner with a custom-made MRI-compatible loading device. The knee meniscus images were 3D reconstructed, and dimensional comparisons were made for each meniscal model with baseline (0°-unloaded model). The morphologic changes of the meniscal-anterior horn (AH), body (BD), and posterior horn (PH) regions were expressed as mean positive and negative deviations. The displacements were further investigated, and the meniscal extrusions of different subregions were measured. The morphologic changing patterns of human meniscus under loading and flexions were presented using 3D chromatic maps. The bilateral menisci were generally shifting laterally and posteriorly in most flexion angles and were changing medially and anteriorly under fully extended knee loading conditions. The mean deviations were more significant with loading at 0° of knee flexion, while the PH region in the lateral side changed further posteriorly with loading in 30° flexion. Most of the differences were not significant in other flexion angles between loading conditions. The extrusion of meniscus’s medial body was greater in full extension compared to any other flexing angles. Mechanical loading can significantly deform the menisci in knee extension; however, this effect is limited during knee flexion. Current study can be used as a reference for the evaluations of the integrity in meniscal functions.

Study on the mechanical differences between single-row belt rivets and double-row suture bridge in repairing rotator cuff injury

To compare and analyze the mechanical differences between single-row suture anchor fixation for repairing rotator cuff injuries and double-row suture bridges for repairing rotator cuff injuries from a biomechanical perspective. The CT scan data of healthy adult shoulder joint were imported into Mimics, Geomagics and Hypermesh to carry out reverse reconstruction of two repair models, material assignment and mesh division, and the tearing of supraspinatus muscle was designed. After treatments, the load and boundary conditions were applied to the shoulder joint in ABAQUS software. The shoulder joint was fixed with four working conditions including flexion 15 °, flexion 30 °, internal rotation 15 ° and internal rotation 30 ° after anchor fixationand repair. The stress changes of the upper rotator cuff muscle and the anchor with thread were compared under these four conditions. Under the two flexion conditions, the stress of the supraspinatus in the double row suture bridge fixation model was 8.3% and 12% less than that in the single-row suture anchor fixation, respectively. Under the two internal rotation conditions, the stress of supraspinatus in the double row suture bridge fixation model was 47% and 48% less than that in the single row fixation repair model, respectively. The "load sharing" effect between the two rows of four anchors makes the stress distribution more dispersed, increases the contact area between the supraspinatus muscle and the humerus, reduces the stress of the anchor, avoids the serious stress concentration phenomenon, and explains the advantages of the fixation method of the double row suture bridge from the biomechanical angle.

Anthropometrics, flexibility and training history as determinants for bicycle configuration

Intrinsic factors such as leg length, arm length, flexibility and training history are factors that may be relevant to the optimisation of the individual bicycle configuration process. Bike fitting methods do not always take all these variables into account, and as yet there have been limited studies examining how these variables can affect the cyclist's position on the bicycle. The main aims of this study were to establish how individual anthropometrics, training history and flexibility may influence cyclists' freely chosen bicycle configuration, and to determine the full-body static flexion angles chosen by cyclists on the bicycle.Fifty well-trained male cyclists were recruited for the study. A multivariate linear regression analysis was performed to predict the four main configurations of a bicycle (saddle height, saddle setback, handlebar reach and handlebar drop) based on individual anthropometrics, flexibility and training history. Average joint kinematic ranges for the knee (36°±7°) and elbow (19°±8°) joint supported previous recommendations. Hip (77°±5°) and shoulder (112°±7°) joint angles should be determined as true clinical joints.Trochanteric leg length (p < 0.01), Knee Extension Angle test (p < 0.01) and mSchober test (p = 0.04) were significant predictors for determining saddle height. Hamstring flexibility can be used to predict handlebar drop (p = 0.01).A cyclist who wishes to adopt a more aerodynamic position with an increased handlebar drop should aim to improve their hamstring flexibility.

Finite element analysis on stress concentration improvement in patellofemoral joint by releasing lateral patellar retinaculum with stiletto needle based on the theory of Jinshugu()

To study mechanism of improvement of stress concentration on patellofemoral joint by stiletto needle releasing lateral patellar retinaculum guided by the theory of Jinshugu() and based on the finite element model of knee joint. and to elucidate the biomechanical mechanism of stiletto needle releasing changing patellar trajectory and reducing patellofemoral joint pressure. CT data of knee joint from a normal male (aged 29, heighted 171 cm, weighted 58 kg) was selected. Starting with construction of three-dimensional model of knee joint by using finite element software, the finite element model of knee joint with complete tendonand bone structures were established through several steps, such as geometric reconstruction, reverse engineering, meshing, material assignment and loading analysis. The loading condition was set as 500 N load on knee joint, and the average tensile stress of quadriceps femoris tendon was about 200 N. To simulate the release of lateral patellar retinaculum by stiletto needle at 30 and 90 position of knee flexion in finite element model separately, and to compare the improvement of stress concentration of patellofemoral joint by stiletto needle intervention under different knee flexion conditions. The peak stress of patellofemoral joint and tibiofemoral joint decreased after stiletto needle releasing of patellofemoral lateral retinaculum compared with before intervention, which was(1) knee flexion at 30 degrees:patellar cartilage decreased by 0.498 MPa (decreased 9.06%), femoral trochlea decreased by 0.886 MPa(decreased 16.27%);(2) knee flexion at 90 degrees:patellar cartilage decreased by 0.558 MPa (decreased 8.6%), femoral trochlea decreasedby 0.607 MPa (decreased 9.94%). Releasing lateral patellofemoral retinaculum with stiletto needle could effectively alleviate the stress concentration of patellofemoral joint and reduce local stress peak value, which it is helpful to improve patellar trajectory and make stress distribution more uniform.

Validation of Lumbar Compressive Force Simulation in Forward Flexion Condition

Safety standard requirements must be implemented for lumbar support robots, which are mainly used for preventing low back pain (LBP) in caregivers. Usually, simulations are used to mimic actions that are not allowed for a real person. However, a comprehensive validation of a simulator in dynamic conditions has not been conducted. In this study, an ergonomic simulator is validated through forward flexion invasive experiments. The correspondence between the simulated and experimental compressive force (CF), as well as the CF obtained using two existing models about the unified angle, is investigated. The results show that the CF error between the measurements and the simulator at a flexion angle of 30∘ is 11.8% and is lower than those obtained for the other two models (16.8% and 20.6%). Linear regression shows that the invasive data and estimated CF are close (slope = 1) in Merryweather’s model and CF simulator but not for Potvin’s model. We evaluate the precision of the simulator by using intraclass correlation coefficient method. Merryweather’s model is moderately consistent with invasive measurements, with R–0.685 and 0.627 at 0 and 30∘, while the CF simulator shows good consistency with Merryweather’s model with R–0.879 and 0836 at 0 and 30∘.

Validation of Lumbar Compressive Force Simulation in Forwarding Flexion Condition

Validation of Lumbar Compressive Force Simulation in Forwarding Flexion Condition