Objective To investigate the effect of orthosis design parameters on correction of scoliosis and orthosis-trunk interface pressure.Methods A finite element model of scoliosis was constructed to simulate the assembly effect of the orthosis.The orthosis was divided into four loading areas(left rib,right rib,anterior-left and posterior-right area)to simulate six modification conditions.In Models 1,2 and 3,a fixed modification of 20 mm was applied on the anterior left and posterior right areas,while the displacement loads of 20,25 and 30 mm were applied on both the left rib and right rib areas.In Models 4,5 and 6,a fixed modification of 25 mm was applied on left rib and right rib areas,with the displacement loads of 15,20 and 25 mm applied on both anterior left and posterior right areas.The Cobb angle,apical vertebral rotation(AVR)and interface pressure were calculated.Results The correction of Cobb angle in Models 1,2 and 3 was 8.94°,15.62° and 17.91°,respectively,with AVR correction of 7.53°,6.69° and 5.87°,respectively.In Models 4,5 and 6,the correction of Cobb angle was 14.55°,15.62° and 16.09°,with AVR correction of 5.25°,6.69° and 8.63°,respectively.In Model 6,the correction rate of Cobb angle and AVR was 45.48%and 41.22%,respectively,with a maximum pressure of 26.51 kPa on orthosis-trunk interface,achieving the most significant outcome.Conclusions The modification of orthosis has a significant effect on the correction of Cobb and AVR angles.The loading on the left rib and right rib areas mainly affect the Cobb angle,while the loading on the anterior left and posterior right areas mainly affect the spinal axial-rotation.A modification of 25 mm on all loading areas achieves the optimal spinal correction.This study provides the quantitative data for orthosis design.

Objective To investigate the effect of orthosis design parameters on correction of scoliosis and orthosis-trunk interface pressure.Methods A finite element model of scoliosis was constructed to simulate the assembly effect of the orthosis.The orthosis was divided into four loading areas(left rib,right rib,anterior-left and posterior-right area)to simulate six modification conditions.In Models 1,2 and 3,a fixed modification of 20 mm was applied on the anterior left and posterior right areas,while the displacement loads of 20,25 and 30 mm were applied on both the left rib and right rib areas.In Models 4,5 and 6,a fixed modification of 25 mm was applied on left rib and right rib areas,with the displacement loads of 15,20 and 25 mm applied on both anterior left and posterior right areas.The Cobb angle,apical vertebral rotation(AVR)and interface pressure were calculated.Results The correction of Cobb angle in Models 1,2 and 3 was 8.94°,15.62° and 17.91°,respectively,with AVR correction of 7.53°,6.69° and 5.87°,respectively.In Models 4,5 and 6,the correction of Cobb angle was 14.55°,15.62° and 16.09°,with AVR correction of 5.25°,6.69° and 8.63°,respectively.In Model 6,the correction rate of Cobb angle and AVR was 45.48%and 41.22%,respectively,with a maximum pressure of 26.51 kPa on orthosis-trunk interface,achieving the most significant outcome.Conclusions The modification of orthosis has a significant effect on the correction of Cobb and AVR angles.The loading on the left rib and right rib areas mainly affect the Cobb angle,while the loading on the anterior left and posterior right areas mainly affect the spinal axial-rotation.A modification of 25 mm on all loading areas achieves the optimal spinal correction.This study provides the quantitative data for orthosis design.

Objective To study the effects of prosthetic alignment on internal contact mechanical characteristics of intact knee joint for transfemoral amputees. Methods The gait experiment of transfemoral amputees was performed under different alignment conditions, and the differences of lower limb motion and ground reaction force (GRF) were analyzed and compared with those of the non-amputees. The three-dimensional （30） finite element model of knee joint was build and used to analyze the effect of alignments of socket adduction and abduction on internal contact mechanical characteristics between femur cartilage, tibia cartilage and meniscus. Results For knee joint of the non-amputees, contact force was mainly concentrated on the medial sides at the moment of the first GRF peak, while contact force was mainly concentrated on the lateral sides at the moment of the second GRF peak. However, for intact knee joint of the transfemoral amputees, contact force was mainly concentrated on the medial side at the moment of two GRF peaks. The stress of the medial meniscus, contact force and contact area between the medial meniscus and cartilage all obviously increased under the alignment of 6° socket adduction. Conclusions Compared with non-amputees, the incidence of knee osteoarthritis (OA) in amputees was higher, which was related to the long-term overload of the medial knee joint. The alignment of socket adduction may increase the risk of knee OA in the intact side of transfemoral amputees. In clinic, excessive adduction of the socket should be avoided during prosthetic alignment.

We observed the effect of vibration parameters on lumbar spine under different vibration conditions using finite element analysis method in our laboratory. In this study, the CT-images of L1-L5 segments were obtained. All images were used to develop 3D geometrical model using the Mimics10. 01 (Materialise, Belgium). Then it was modified using Geomagic Studio12. 0 (Raindrop Geomagic Inc. USA). Finite element (FE) mesh model was generated by Hypermesh11. 0 (Altair Engineering, Inc. USA) and Abaqus. Abaqus was used to calculate the stress distribution of L1-L5 under different vibration conditions. It was found that in a vibration cycle, tensile stress was occurred on lumbar vertebra mainly. Stress distributed evenly and stress concentration occurred on the left rear side of the upper endplate. The stress had no obvious changes under different frequencies, but the stress was higher when amplitude was greater. In conclusion, frequency and amplitude parameters have little effect on the stress distribution in vertebra. The stress magnitude is positively correlated with the amplitude.
Biomechanical Phenomena ; Finite Element Analysis ; Humans ; Lumbar Vertebrae ; physiology ; Vibration

This study was aimed to estimate the effect of different ProDisc-C arthroplasty designs after it was implanted to C5-C6 cervicalspine. Finite element (FE) model of intact C5-C6 segments including the vertebrae and disc was developed and validated. Ball-and-socket artificial disc prosthesis model (ProDisc-C, Synthes) was implanted into the validated FE model and the curvature of the ProDisc-C prosthesis was varied. All models were loaded with compressed force 74 N and the pure moment of 1.8 Nm along flexion-extension and bilateral bending and axial torsion separately. The results indicated that the variation in the curvature of ball and socket configuration would influence the range of motion in flexion/extension, while there were not apparently differences under other conditions of loads. The method increasing the curvature will solve the stress concentration of the polyethylene, but it will also bring adverse outcomes, such as facet joint force increasing and ligament tension increasing. Therefore, the design of artificial discs should be considered comprehensively to reserve the range of motion as well as to avoid the adverse problems, so as not to affect the long-term clinical results.
Arthroplasty ; Biomechanical Phenomena ; Finite Element Analysis ; Humans ; Intervertebral Disc ; Pressure ; Prostheses and Implants ; Range of Motion, Articular ; Spine ; Zygapophyseal Joint