Objective To investigate the biomechanical characteristics of Salto Talaris tibial components with different heights at the bone-prosthesis interface during different gait support phases after total ankle replacement.Methods An ankle joint model was reconstructed using a weight-bearing CT from a 61-year-old female patient with ankle arthritis,and Salto Talaris tibial components with different heights(5,7,9,11 mm)were modelled to simulate the loading of the tibial-prosthesis during four gait support phases,and to analyse the micromotion and stresses at the bone-prosthesis interface.Results The 11 mm and 9 mm models had a poorer prosthesis stability,with the peak micromotion exceeding 50 μm and the peak internal tibial stresses of 30.75 MPa and 29.86 MPa,respectively,which exceeded the yield stress of the cancellous bone.The tibial stresses of the 7 mm and 5 mm models were within reasonable ranges and the average peak micromotions were only 42.66 μm and 40.32 μm.In contrast,the initial stability of the 5 mm model prosthesis was the best.Conclusions For total ankle replacement with Salto prosthesis,the height of the tibial component should be chosen appropriately,and the optimal height was about 5 mm.Excessive flexion and extension activities of the ankle joint should be avoided to maintain the stability of the prosthesis after surgery.This study provides a theoretical basis for the improvement of the structural parameters of the Salto prosthesis,which is valuable for the selection of clinical surgical prostheses and helps to improve the results of total ankle replacement.

Objective To investigate the biomechanical characteristics of Salto Talaris tibial components with different heights at the bone-prosthesis interface during different gait support phases after total ankle replacement.Methods An ankle joint model was reconstructed using a weight-bearing CT from a 61-year-old female patient with ankle arthritis,and Salto Talaris tibial components with different heights(5,7,9,11 mm)were modelled to simulate the loading of the tibial-prosthesis during four gait support phases,and to analyse the micromotion and stresses at the bone-prosthesis interface.Results The 11 mm and 9 mm models had a poorer prosthesis stability,with the peak micromotion exceeding 50 μm and the peak internal tibial stresses of 30.75 MPa and 29.86 MPa,respectively,which exceeded the yield stress of the cancellous bone.The tibial stresses of the 7 mm and 5 mm models were within reasonable ranges and the average peak micromotions were only 42.66 μm and 40.32 μm.In contrast,the initial stability of the 5 mm model prosthesis was the best.Conclusions For total ankle replacement with Salto prosthesis,the height of the tibial component should be chosen appropriately,and the optimal height was about 5 mm.Excessive flexion and extension activities of the ankle joint should be avoided to maintain the stability of the prosthesis after surgery.This study provides a theoretical basis for the improvement of the structural parameters of the Salto prosthesis,which is valuable for the selection of clinical surgical prostheses and helps to improve the results of total ankle replacement.

Objective To study the effects of selecting different fixing segments on biomechanical characteristics of the spine during the treatment of early onset scoliosis（EOS） by growing rod technique. Methods By using finite element method, four spine models (C6-S1 segments) fixed by growing rod were established: preoperative model, T1-L4 fixed model, T2-L4 fixed model, T3-L4 fixed model. Then 7 N·m torque load and 1 rad angular displacement load were applied on superior surface of C6 segment to analyze biomechanical characteristics for adjacent structure of the fixed vertebral body. Results The whole spinal range of motion (ROM) decreased significantly after operation. When the T2-L4 segment was fixed, the spine activity was mostly restricted, the compensatory activity of adjacent vertebrae increased significantly, and the intervertebral disc stress increased significantly. Conclusions When T2 segment is selected as the upper instrumented segment, the risk of proximal junctional kyphosis and spinal degeneration is the highest, which should be avoided in clinical surgery.

Objective To study the effect of vibration environments on patients with posterior lumbar interbody fusion in daily life. Methods Finite element models of an intact lumbar spine and a postoperative model with fixed L4-5 segments were established. Subsequently, a 40-kg mass point was applied to the upper end plate of the L1 segment to perform a modal analysis. Results In comparison with an intact lumbar spine, the resonance frequency for each order of the whole lumbar spine was reduced after posterior lumbar interbody fusion, and the primary movement of the corresponding modes were also changed. The first two inherent frequencies of the modal in the fusion model were 2.94 Hz and 3.81 Hz, which were close to the vibration frequencies in daily life. In the first three order vibrations, the mode amplitudes of the posterior elements for the L2 and L3 segments increased in the fusion model, which could increase the risk of postoperative degeneration at such locations. In addition, the vibration amplitude of the intervertebral disc of the L3-4 segments clearly increased, particularly at the part of the disc near the L3 vertebral body, which could lead to increased stress and strain and further accelerate its degeneration. Conclusion sBased on the modal analysis of a lumbar spine after posterior lumbar interbody fusion, the investigation of the vibration characteristics of the postoperative lumbar spine will provide some theoretical guidance for the recovery and healthy life of the patients after the corresponding surgery.

OBJECTIVETo study the effect of length of cervical anterior fusion on adjacent levels by Biomechanical test.

METHODSSix fresh-frozen human cervical specimens were used in this study. The specimens were tested in flexion, extension, bending and rotation on a spine 3D test system. The specimens were tested intact and then underwent a single-level anterior cervical discectomy and fusion (ACDF) at the C4-5 first, a double-level fusion at the C4-6, and finally extended to triple-level at the C4-7, Based on a hybrid test method. Changes in overall range of motion (ROM), segmental motion and facet joints pressure during flexion, extension, bending and rotation were measured and statistically analyzed.

RESULTSThe overall ROM of the entire spinal construct decreased progressively as the single-level fixation extending to 2-level and 3-level (P < 0.05). A progressive increase in ROM above (C3-4) the fused motion segment units (MSUs) was found during flexion, extension and bending (P < 0.05). In bending and extension, a same result was recorded on the average pressure and max pressure of C3-4 facet joints (P < 0.05).

CONCLUSIONSThis study has demonstrated that the biomechanics at adjacent levels to a cervical spine fusion are altered and that there was progressively increased adjacent segment motion and stress as a single-level ACDF extended to a 3-level fusion, which might lead to the acceleration of adjacent segment degeneration.

Biomechanical Phenomena ; Cadaver ; Cervical Vertebrae ; surgery ; Diskectomy ; methods ; Humans ; Range of Motion, Articular ; Rotation ; Spinal Fusion ; methods

In view of the shortage of medical equipment road transportation simulation platform, we put forward a road transportation simulation method based on 6-DOF parallel robots. A 3D road spectrum model was built by the improvement of the harmonic superposition method. The simulation model was then compared with the standard model to verify its performance. Taking the road spectrum as the excitation, we could get the robot motion data to control the parallel robot through the S-shaped linear interpolation of the absolute position. It can simulate the movement of vehicles with different speed under various road conditions efficiently and accurately.
Equipment Design ; Motor Vehicles ; Robotics ; instrumentation ; Transportation ; instrumentation ; methods

This paper designed a ventilator control system to control proportional valves and motors. It used LabVIEW to control the object mentioned above and design ,validate, evaluate arithmetic, and establish hardware in loop platform. There are two system' s hierarchies. The high layer was used to run non-real time program and the low layer was used to run real time program. The two layers communicated through TCP/IP net. The program can be divided into several modules, which can be expanded and maintained easily. And the harvest in the prototype designing can be seamlessly used to embedded products. From all above, this system was useful in employing OEM products.
Man-Machine Systems ; Software ; Software Design ; Ventilators, Mechanical