Kinematics and Plantar Pressure Analysis of Varus Femur and Varus Tibia / 医用生物力学

Objective To compare the differences in kinematic parameters and plantar pressures for two types of knee varus with tibial and femoral origins in gait analysis, so as to provide biomechanical theoretical basis for different types of genu varus. Methods Twenty-six patients with unilateral knee osteoarthritis (KOA) varus genu were enrolled, with 13 from femoral and 13 from tibial sources. Using Noraxon MyoMotion three-dimensional (3D) motion capture system and Footscan plantar pressure test system, the gait of the subjects during natural walking was measured, the temporal and spatial parameters of the gait, the kinematics parameters of lower limb joints and plantar pressures were collected, to make comparative analysis between the two groups. Results The range of knee flexion and extension of tibial varus, the peak of hip abduction, the range of motion (ROM) of hip adduction and abduction and the peak of ankle pronation were larger than those of femoral lateral genu varus. The peak of knee flexion and hip adduction was smaller than that of femoral lateral genu varus. Compared with femoral varus, subjects with tibial varus had increased stress time and peak pressure on the plantar of the 4th and 5th metatarsals (P<0.05). In the 3rd metatarsal region, the impulse of healthy femoral limb was greater than that of healthy limb with tibial deformity. While in the medial calcaneal region, the impulse of healthy femoral limb was smaller (P<0.05). Conclusions There are some differences in kinematic parameters and plantar pressures between two different types of unilateral genu varus patients. The results of this study are helpful to understand the abnormal gait caused by genu varus, and provide reliable reference for postoperative rehabilitation and limb exercise for different types of genu varus.

Gait Analysis of Hip Disarticulation Amputees Based on Kinematic Parameters and Plantar Pressure Measurement / 医用生物力学

Objective To analyze the gait characteristics of hip disarticulation amputees, and analyze the reasons for their differences from normal gait, so as to assist clinical diagnosis and evaluation. Methods Through the portable human motion capture device and plantar pressure analysis system, the kinematics and plantar pressure information of 5 hip amputees were collected and compared with 15 healthy volunteers in control group. Gait differences between the amputees and normal subjects and between the affected leg side and the healthy leg side of the amputees were compared. Results The proportion of double-support period for hip amuptees was higher than that of normal gait. Step length, step time, loading response period, mid support period, pre-swing period, proportion of the swing period for the affected leg side and healthy leg side of hip amputees showed significant differences with those of control group. The relative symmetry index of the gait for hip amputees was 0.60±0.05. Compared with the affected leg side, the support period of the healthy leg side was extended, the step length was shortened, the ground reaction force was greater than that of the affected leg side, and the center of pressure trajectory shifted to the affected leg side. Conclusions The gait of hip amputees is significantly different from that of normal people. Hip amputees have weak walking ability, poor gait symmetry, and they lack of continuity in the body’s center of gravity. The results provide experimental basis and theoretical analysis for the design of mechanical structure and control system of novel hip prosthesis.

Variable Quasi-circular Gait Planning with Smooth Angular Acceleration for Lower Limb Rehabilitation / 中国康复理论与实践

Objective:To solve the problem of leg shaking caused by the sudden change of angular acceleration at the joint of periodic motion during circular gait training of lower limb rehabilitation robot. Methods:A kind of quasi-circular gait was proposed, which divided the periodic motion into three phases: start phase, middle phase and end phase. The time was equal in the start phase and the end phase, and could be adjusted with the parameter ratio. The joint trajectories of the two phases were planned by quintic polynomial, and the middle phase was still the circular gait joint trajectory. The trajectory of the proposed quasi-circular gait was simulated. Results:The angular velocity was continuously differentiable and 0, the angular acceleration was continuous and 0, and the end-effector trajectory became flat with the increase of ratio. The results on the physical prototype of the lower limb rehabilitation robot were principally consistent with the simulation, and the machine worked smoothly. Conclusion:The proposed variable quasi-circular gait had smooth angular acceleration at the junction of periodic motions, which effectively solved the jitter problem when using circular gait for lower limb rehabilitation training and avoided secondary injury to the patients.

Solution for Movement Mode of Lower Limb Rehabilitation Robot Adapted to Individual Differences / 中国康复理论与实践

Objective:To solve the movement mode adapting to individual differences for the trajectory planning of lower limb rehabilitation robots. Methods:After summarizing the six movement modes of the lower limb rehabilitation robot, according to the multi-rigid body theory of the human body, the exoskeleton of the lower limb rehabilitation robot was simplified into a two-bar linkage mechanism, the inverse kinematics analysis of the motion mode was performed, and the motion pattern solving system was designed based on C#. Results:The motion mode joint angle value calculated based on the C# motion mode solving system was transmitted to the upper computer, and the six motion modes were successfully applied to the lower limb rehabilitation robot. Through the inversion kinematics analysis of the motor model, the C#-designed motion mode solving system could solve the motorized joint angle values that adapted to individual of different leg lengths with lower extremity motor dysfunction. Through physical prototype experiments, the lower limb rehabilitation robot could drive the human body model for rehabilitation training according to the planned exercise mode. The actual joint angle curve and the theoretical joint angle curve were basically coincident, the joint angle error was small. Conclusion:The individual difference motion pattern solution is valid and feasible.

Design Optimization, Function Analysis and in vitro Experiments of an Electric Stapler for Minimally Invasive Surgery / 医用生物力学

Objective To develop a new type of electric stapler, so as to solve the problems of insufficient rotation angle, inconvenient operation and difficulty in controlling the pressing strength of existing products. Methods An electric stapler was designed and manufactured. The motion trajectory curve of the prototype was measured by using the three-coordinate imaging instrument to build functional test platform of the prototype, and the goodness of fit was used to evaluate consistency between the theoretical curve and the measured curve. The small intestine tissues of fresh pig were anastomosed at different bending angles of the front end, and the forming rate of the anastomotic stoma was measured. Results The goodness of fit between the test curve and the theoretical curve for both turning motion and shooting motion was ideal, while the goodness of fit between the test curve and the theoretical curve for pressing motion was not ideal when the turning joint was bent at 0°-30°, and was ideal when it was bent at 45°-60°. In performance test, the deformity rate of the nail was smaller than 1.14%, indicating that the bending angle had no significant impacts on the anastomotic effect. Conclusions The kinematics curves of shooting motion and turning motion are consistent with the theoretical curves. The pressing motion curves fluctuate at different bending angles, which will not affect the anastomotic effect, and the effect of the electric stapler meets the clinical requirements.

Design of surgical manipulator for peritoneal surgery in nuclear magnetic environment / 医疗卫生装备

Objective To merge the traditional magnetic imaging technology with emerging robotics and to create a new surgical model that replaces human eyes with robotic arms instead of manpower.Methods Structural compatibility analysis was executed with Monte Carlo method. According to the theory of magnetic field compatibility, the mechanical arm components were classified, the magnetic field compatibility of the manipulator was discussed, the key components of the manipulator were selected,and the finite element analysis was performed to verify its reliability.The positive and negative kinematics models of robotic arms were constructed by matrix transformation and robotics toolbox. The polynomial interpolation of five times was used to plan the trajectory of the end of the manipulator.Results The work space of the robot arm solved by Monte Carlo method was found to envelop completely the inner ring aperture of the NMR,and thus the spatial accessibility of the robot arm was verified.Finite element analysis proved that the structural strength of the manipulator was well-designed and the kinematics model of the manipulator was successfully constructed.The trajectory planning found that the joints rotated uniformly and the desired requirements were met.Conclusion The robot arm developed gains advantages in configuration and nuclear magnetic compatibility.