Effects from Extramedullary Design of Femoral Stem on Hip Contact Force: A Musculoskeletal Multi-Body Dynamic Study / 医用生物力学

Objective To investigate the effects of design parameters such as neck-shaft angle, femoral offset and anteversion angle of total hip arthroplasty ( THA) prosthesis on contact forces of the hip. Methods A musculoskeletal multi-body dynamic model of THA was established based on AnyBody software. The effects of single or multiple factors on hip contact force were studied when the neck-shaft angle, eccentricity and anteversion angle varied within ±10°, ±20 mm and ±10°, respectively. Results The maximum hip contact force increased by 26. 08% when femoral offset was reduced by 20 mm. The maximum hip contact force increased by 5. 99% when the neck-shaft angle increased by 10°. When the anteversion angle increased by 10°, the hip contact force decreased at 0% -24% of gait cycle, with the peak decreasing by 19. 16% . However, the hip contact force was significantly increased at 38% -70% of gait cycle, with the peak increasing by 67. 78% . Conclusions In extramedullary design of the femoral stem, based on reconstruction of the patient’s anatomical parameters, the offset of the femoral stem can be appropriately increased, and the neck-shaft angle and anteversion angle can bereduced to avoid increasing forces on the hip.

Musculoskeletal multibody dynamics investigation for the different medial-lateral installation position of the femoral component in unicompartmental knee arthroplasty / 生物医学工程学杂志

The surgical installation accuracy of the components in unicompartmental knee arthroplasty (UKA) is an important factor affecting the joint function and the implant life. Taking the ratio of the medial-lateral position of the femoral component relative to the tibial insert (a/A) as a parameter, and considering nine installation conditions of the femoral component, this study established the musculoskeletal multibody dynamics models of UKA to simulate the patients' walking gait, and investigated the influences of the medial-lateral installation positions of the femoral component in UKA on the contact force, joint motion and ligament force of the knee joint. The results showed that, with the increase of a/A ratio, the medial contact force of the UKA implant was decreased and the lateral contact force of the cartilage was increased; the varus rotation, external rotation and posterior translation of the knee joint were increased; and the anterior cruciate ligament force, posterior cruciate ligament force and medial collateral ligament force were decreased. The medial-lateral installation positions of the femoral component in UKA had little effect on knee flexion-extension movement and lateral collateral ligament force. When the a/A ratio was less than or equalled to 0.375, the femoral component collided with the tibia. In order to prevent the overload on the medial implant and lateral cartilage, the excessive ligament force, and the collision between the femoral component and the tibia, it is suggested that the a/A ratio should be controlled within the range of 0.427-0.688 when the femoral component is installed in UKA. This study provides a reference for the accurate installation of the femoral component in UKA.

Force Transmission Mode of Foot Ankle in Children with Down’s Syndrome During Standing / 医用生物力学

Objective To explore the joint contact force, ligament tensile force and force transmission mode of foot internal structure in Down’s syndrome child (DSC) during standing. Methods The finite element models of foot were constructed based on CT image data from one DSC and one typically developing child (TDC). The models were validated by plantar pressure measurement during static standing. To simulate foot force during standing, the ground reaction force and the triceps surae force were applied as the loading condition. Contact pressure of the tibiotalar, talonavicular and calcaneocuboid joints, tensile force of the spring and plantar calcaneocuboid ligaments, and force transmission mode in transverse tarsal joints were calculated and analyzed. Results The finite element models of foot were validated to be reliable. Compared with the TDC, the DSC showed higher contact pressure at the tibiotalar joint and lower contact pressure at the talonavicular joint. The tensile force of spring and plantar calcaneocuboid ligaments of DSC was 10 times and 58 times of TDC, respectively. The forces transmitted through both mediate and lateral columns in DSC were lower than those in TDC. Conclusions Abnormal contact pressure of the tibiotalar joint, larger tensile force of midfoot ligaments and smaller force of the transverse tarsal joint were found in DSC during standing. The abnormal alteration of stress patterns in foot internal structure of DSC should be fully considered in clinical rehabilitation, so as to provide theoretical references for screening and making intervention plans for early rehabilitation, as well as designing individualized orthopedic insoles.

Influence of valve height on the opening/closure performance of transplanted aortic valve / 生物医学工程学杂志

Valve transplantation is often used in the treatment of aortic valve insufficiency. However, after surgery, the reconstructed aortic roots have an expansion phenomenon, in which the lack of valve height causes the aortic valve to close again. In this paper, the effects of different aortic valve height design on valve opening and closing performance were studied. The optimal surgical plan was obtained by numerical simulation, providing technical support and theoretical basis. In this paper, six groups of three-dimensional geometric models with a valve height increment of ± 0.5 mm were established with a root diameter of 26.0 mm and a valve height of 14.0 mm. Through the structural mechanics calculation and analysis of the parameters such as maximum stress, valve area and contact force of the model, reasonable geometrical dimensions are obtained. The study found that the maximum stress values of the six groups of models ranged from 640 to 690 kPa, which was consistent with the results of the literature; the three-group models with valve heights of 13.5 mm, 14.0 mm, and 14.5 mm were within a reasonable range. The contact force value of the 6 groups of leaflets increased with the increase of valve height. Studies have shown that the height of the aortic valve has an effect on the aortic valve closure performance. A valve height that is too small or too large will reduce the aortic systolic valve area and affect the aortic function.

Effect of follower load on facet joint contact force of lumbar spine / 医用生物力学

Objective To study the influence of follower load on contact force of facet joints under various postures of lumbar spine. Methods A 3D nonlinear finite element model of lumbar spine (L1-S1) was developed, with consideration of the non-uniform thickness and nonlinear material properties of the cartilage layer in facet joints. The model was then applied with different follower preload (0, 0.5, 0.8, 1.2 kN), under pure moment of 7.5 N•m in different directions (flexion, extension, lateral bending, extension and torsion). The contact forces of facet joints on the two sides of each segment under different loading conditions were compared. The asymmetry influence of follower load on contact force of facet joints was also quantitatively studied. Results The follower preload increased the facet force under flexion-extension and bending (ipsilateral), while decreased the force on the contralateral facet under lateral bending. All the effects of follower load on facet force became weaker with the increase of preload. For torsion loading, the preload had almost no effect on facet force. The greatest asymmetry influence of follower load on facet force was under bending (the ipsilateral side), followed by flexion, bending (contralateral side), extension and torsion. Conclusions The follower load shows obviously different effects on contact force of facet joints with different postures. The asymmetry of facet joints should be fully considered in biomechanical studies of lumbar spine, especially in studies on post-structures of lumbar spine under physiological loads.

Comparative efficacy and safety of contact force-sensing catheter and second-generation cryoballoon ablation for atrial fibrillation: a meta-analysis

This meta-analysis compared the efficacy and safety of the contact force (CF)-sensing catheter and second-generation cryoballoon (CB) ablation for treating atrial fibrillation (AF). Six controlled clinical trials comparing ablation for AF using a CF-sensing catheter or second-generation CB were identified from PubMed, EMBASE, Cochrane Library, Wanfang Data, and China National Knowledge Infrastructure. The procedure duration was significantly lower in the CB group compared with that in the CF group [mean difference (MD)=29.4; 95%CI=17.84-40.96; P=0.01], whereas there was no difference between the groups for fluoroscopy duration (MD=0.59; 95%CI=-4.48-5.66; P=0.82). Moreover, there was no difference in the incidence of non-lethal complications (embolic event, tamponade, femoral/subclavian hematoma, arteriovenous fistula, pulmonary vein stenosis, phrenic nerve palsy, and esophageal injury) between the CB and the CF groups (8.38 vs 5.35%; RR=0.66; 95%CI=0.37-1.17; P=0.15). Transient phrenic nerve palsy occurred in 17 of 326 patients (5.2%) of the CB group vs none in the CF group (RR=0.12; 95%CI=0.03-0.43; P=0.001). A comparable proportion of patients in CF and CB groups suffered from AF recurrence during the 12-month follow-up after a single ablation procedure [risk ratio (RR)=1.03; 95%CI=0.78-1.35; P=0.84]. AF ablation using CF-sensing catheters and second-generation CB showed comparable fluoroscopy duration and efficacy (during a 12-month follow-up), with shorter procedure duration and different complications in the CB group.

Contact force-guided catheter ablation for the treatment of atrial fibrillation: a meta-analysis of randomized, controlled trials

Contact force (CF) sensing technology allows real-time monitoring during catheter ablation for atrial fibrillation (AF). However, the effect of CF sensing technology on procedural parameters and clinical outcomes still needs clarification. Because of the inconsistent results thus far in this area, we performed a meta-analysis to determine whether CF sensing technology can improve procedural parameters and clinical outcomes for the treatment of AF. Studies examining the benefits of CF sensing technology were identified in English-language articles by searching the MEDLINE, Web of Science, and Cochrane Library databases (inception to May 2015). Ten randomized, controlled trials involving 1834 patients (1263 males, 571 females) were included in the meta-analysis (681 in the CF group, 1153 in the control group). Overall, the ablation time was significantly decreased by 7.34 min (95%CI=-12.21 to -2.46; P=0.003, Z test) in the CF group compared with the control group. CF sensing technology was associated with significantly improved freedom from AF after 12 months (OR=1.55, 95%CI=1.20 to 1.99; P=0.0007) and complications were significantly lower in the CF group than in the control group (OR=0.50, 95%CI=0.29 to 0.87; P=0.01). However, fluoroscopy time analysis showed no significantly decreased trend associated with CF-guided catheter ablation (weighted mean difference: -2.59; 95%CI=-9.06 to 3.88; P=0.43). The present meta-analysis shows improvement in ablation time and freedom from AF after 12 months in AF patients treated with CF-guided catheter ablation. However, CF-guided catheter ablation does not decrease fluoroscopy time.

The application of contact force sensing catheter in catheter ablation of atrial fibrillation / 中国医师进修杂志

Atrial fibrillation (AF) is one of the common arrhythmias. Catheter radiofrequency ablation is a only effective therapeutic method of AF currently. Contact force sensing catheter like SMART TOUCH can real time monitoring the pressure of catheter tip, which can help operators to understand the contact force between atrial and ablation points, and guide the atrial fibrillation ablation. It is significantly improved the effectiveness and safety of the atrial fibrillation. This article will focus on the current situation of radiofrequency ablation for AF by contact force catheter, in order to provide guidance for clinical work.

Micro-frictional contact force properties of articular cartilage / 医用生物力学

Objective To study the frictional contact force properties of articular cartilage by modified silicon probes of the atomic force microscopy (AFM). Methods Modification was conducted on the silicon nitride probes of AFM by the micromanipulator, and the glass microsphere was glued on the probe by glass adhesive as the pinhead. Micro-tribology properties of human and bovine articular cartilage were then investigated by using the modified AFM probes. Results With the increase of load, the friction force of human and bovine cartilage also increased gradually. When the sliding speed increased from 0 to 100 /s, the friction force between specimens and probes increased quickly; when the sliding speed increased from 100 /s to 300 /s, the friction force increased slowly. Conclusions Articular cartilage had an obvious fibrous structure in its surface. There was a direct relationship between the surface roughness of articular cartilage and the measuring range. When the load or sliding speed increased, the friction forces of human and bovine cartilage show an increase with the same variation range. The investigation on mechanical and tribological properties of articular cartilage in micro-frictional experiment will contribute to understanding the injury mechanism of articular cartilage and developing wear-resistant materials for medical artificial joints.

Musculoskeletal multi-body dynamic simulation on patient-specific total knee replacement during right-turn gait / 医用生物力学

Objective To develop a musculoskeletal multi-body dynamic model of the patient-specific total knee replacement (TKR), and to simulate knee joint biomechanical characters of the patient during right-turn gait. Methods Based on the musculoskeletal dynamic software AnyBody and the method of force-dependent kinematics as well as the related data from a patient with TKR, the corresponding patient specific lower extremity musculoskeletal multi-body dynamic model was constructed and then used to simulate the right-turn gait of the patient. The knee contact forces, motion, muscle activations and ligament forces were predicted simultaneously by inverse dynamics analysis on such right-turn gait. ResultsThe root mean square error of the predicted average tibiofemoral medial contact force and lateral contact force were 285 N and 164 N, respectively, and the correlation coefficients were 0.95 and 0.61, respectively. The predicted average patellar contact force was 250 N. The predicted contact forces and muscle activations were consistent with those in vivo measurements obtained from the patient. In addition, the model also predicted the average range of tibiofemoral rotations of flexion-extension, internal-external, varus-valgus as 3°-47°, -3.4°-1.5°, 0.2°--1.5°, and the average range of tibiofemoral translations of anterior-posterior, inferior-superior, medial-lateral as 2.6-9 mm, 1.6-3.2 mm, 4.2-5.2 mm, respectively. The predicted average peak value of the medial, lateral collateral ligament force and posterior cruciate ligament force were 190, 108, 108 N, respectively. Conclusions The developed model can predict in vivo knee joint biomechanics, which offers a robust computational platform for future study on the failure mechanisms of knee prosthesis in clinic.

Preliminary analysis of knee stress in Full Extension Landing

OBJECTIVE: This study provides an experimental and finite element analysis of knee-joint structure during extended-knee landing based on the extracted impact force, and it numerically identifies the contact pressure, stress distribution and possibility of bone-to-bone contact when a subject lands from a safe height. METHODS: The impact time and loads were measured via inverse dynamic analysis of free landing without knee flexion from three different heights (25, 50 and 75 cm), using five subjects with an average body mass index of 18.8. Three-dimensional data were developed from computed tomography scans and were reprocessed with modeling software before being imported and analyzed by finite element analysis software. The whole leg was considered to be a fixed middle-hinged structure, while impact loads were applied to the femur in an upward direction. RESULTS: Straight landing exerted an enormous amount of pressure on the knee joint as a result of the body's inability to utilize the lower extremity muscles, thereby maximizing the threat of injury when the load exceeds the height-safety threshold. CONCLUSIONS: The researchers conclude that extended-knee landing results in serious deformation of the meniscus and cartilage and increases the risk of bone-to-bone contact and serious knee injury when the load exceeds the threshold safety height. This risk is considerably greater than the risk of injury associated with walking downhill or flexion landing activities. .

The Effect of Tibial Posterior Slope on Contact Force and Ligaments Stresses in Posterior-Stabilized Total Knee Arthroplasty-Explicit Finite Element Analysis

PURPOSE: The purpose of this study is to evaluate the effect of change in tibial posterior slope on contact force and ligament stress using finite element analysis. MATERIALS AND METHODS: A 3-dimensional finite element model for total knee arthroplasty was developed by using a computed tomography scan. For validation, the tibial translations were compared with previous studies. The finite element analysis was conducted under the standard gait cycle, and contact force on ultra-high molecular weight polyethylene (UHMWPE) and stresses on lateral and medial collateral ligaments were evaluated. RESULTS: The tibial translations showed similarity with previous studies. As the tibial posterior slope angle increases, the contact stress area increased and was well distributed, and the contact force on UHMWPE decreased overall. However, the maximum contact force in the case for 10degrees case was greater than those for others. The stresses on ligaments were the greatest and smallest in 0degrees and 10degrees cases, respectively. CONCLUSIONS: The higher tibial posterior slope angle leads to the lower contact stress and more extensive stress distribution overall in posterior-stabilized total knee arthroscopy. However, it does not absolutely mean the smallest contact force. The stresses on ligaments increased with respect to the smaller tibial posterior slope angle.

Determination of contact force at facet joint with different sagittal orientation under shearing loads:a finite element analysis / 中国矫形外科杂志

[Objective] The efleet of sagittal orientations of articular facet on the contact force and contact regions of a lumbar spine segment was evaluated.[Methods] [Results]Three-dimensional geometrical and mechanical accurate finite element models of the lumbar L4、5 motion segment representing three sagittal-orientations articular facet were generated and invalidated by an effective CAD method.Contact force and contact regions of the articular facets of three finite element models were predicted under the pure shearing loads.[Result] Under anterior shear condition,the contact force on the facet decreased with the increase of sagittal 0rientation of articular facet.however.in posterior shear load,the contact force on the facet increased with the increase of sagittal orientation.Meanwhile,under both pure shear loading,the percentages of the sagittal and the transversal components are increased with the dectease of the sagittal angle.However,under the salne load condition,there are no difference between the contact regions of the three models with different facet joint angle.[Conclusion]The spatial orientation and geometric forms of the coronal facet articular surfaces are more effective in restricting motion in transversal and sagittal planes while assuming a minor role in resisting axial force or motion than sagittal facet articular surface.It Was presumed that anterior shear force play a more prominent contribution on the degeneration of the facet joint with coronal articular surface compared with posterior shear force.