Biomechanic research on short-segment posterior pedicle screw fixation / 中华创伤杂志

Objective To compare the stability effect of the fixation segment using the new test system based robotics to simulate the complex human movement at natural state about the three-level fixa-tion by using four, five or six pedicle screws in treatment of thoracolumbar burst fractures. Methods Six human cadaveric spines were dissected from T_(11)-L_3. The inferior half part of L_1 vertebral bodies and L_1-L_2 dises were resected to mimie an unstable L_1 burst fracture with loss of anterior column support. Specimens were tested in accordance with the following order:intact, 4,5 and 6 pedicle screws fixation at the three-level fixation. The range of motion (ROM) of the fixation segment (T_(11)-L_3) was measured with the six-freedom degree robotics system controlled by mixed force and displacement during flexion, exten-sion, lateral bending and axial torsion, when the stiffness was calculated. One-way statistieal analysis was used for analyzing the collected data. Results With increased number of screws, the ROM of the fixa-tion segment (T_(11)-L_3) was gradually decreased and the stiffness gradually increased. The ROM under ax-ial rotation of six and five screws group became smaller than four screws group (P < 0.05). The stiffness under axial rotation of six screws group was higher than four screws group (P < 0.05). There was no sta-tistical difference between five screws group and four screws group in regard of the stiffness in axial rota-tion (P > 0.05). There were no significant differences in ROM and stiffness under six different loading directions between six screws group and five screws group (P > 0.05). No statistical difference was observed for three fixation modes in aspects of ROMs and stiffness under flexion-extension or lateral ben-ding (P > 0.05). Conclusions Three-level fixation of burst fractures with five or six screws offers im-proved biomechanical stability compared with traditional four screws fixation. But the difference is insig-nificant between six and five screws fixations.

On evaluating the robot-based experimental system for biomechanical experiment of human knee / 生物医学工程学杂志

This is a report on how we use the hybrid force-displacement control method to load the human knee and analyze the effect and value of our robot experimental system through the biomechanical experiments of total meniscal resection of human knee. The whole robot control system can load continuously on the specimens, thus overcoming the shortcomings of the traditional loading methods which can only load discretely. In the meantime, by using the robot-based testing system, the force (torque) of the specimens and the spatial position under the force can be measured in real-time, which overcomes the shortcomings caused by the separation of force (torque) measurement from displacement measurement and so greatly improves the measurement accuracy.

Research of joint-robotics-based design of biomechanics testing device on human spine / 生物医学工程学杂志

This paper introduces the hardware and software of a biomechanical robot-based testing device. The bottom control orders, posture and torque data transmission, and the control algorithms are integrated in a unified visual control platform by Visual C+ +, with easy control and management. By using hybrid force-displacement control method to load the human spine, we can test the organizational structure and the force state of the FSU (Functional spinal unit) well, which overcomes the shortcomings due to the separation of the force and displacement measurement, thus greatly improves the measurement accuracy. Also it is esay to identify the spinal degeneration and the load-bearing impact on the organizational structure of the FSU after various types of surgery.