Design and evaluation of a hydraulic mechanism with available components for passive knee prostheses.

BACKGROUND: Hydraulic knee prosthesis can provide stance phase control and swing phase control suitable for active persons with an amputation. However, typical commercial hydraulic knees are costly and require frequent maintenance making them inaccessible for persons with an amputation in low-income countries. The objective of this article is to present a new design for a low-cost hydraulic knee prosthesis. METHOD: The prototype hydraulic knee is made of simple hydraulic components. The hydraulic system was designed to provide flexion locking during the stance phase and damping during the swing phase of gait. RESULTS: The prototype was tested and results show that the hydraulic knee can prevent flexion of the knee at stance phase when the highest external knee flexion moment in the gait cycle occurs. The prototype mechanism is capable of resisting flexion torque of 60 N-m. CONCLUSIONS: The prototype hydraulic knee can be assembled from available hydraulic components for low cost and ease of maintenance which is feasible for persons with an amputation in low-income countries.IMPLICATIONS FOR REHABILITATIONA new design hydraulic knee which assembled from simple hydraulic components which provide both stance control and swing control.The use of simple hydraulic components makes the knee feasible for low-income country where service and maintenance staff is inadequate.

Curved versus straight-cut hinges for open-door laminoplasty: A finite element and biomechanical study.

In this study, the stabilities of the hinge sides of plate-augmented open-door laminoplasties based on cutting in a curved or straight line were compared using a finite element (FE) model and an experimental assessment. Using FE models generated from CT scans of a human subject, straight and curved techniques for cutting the hinge side were evaluated. Compressive forces were applied to both simulated models, and the stress distributions on the respective hinge sites were evaluated by comparing the maximum von Mises stresses. Biomechanical testing procedures were then carried out on porcine cervical vertebrae, with straight- and curved-cut groups loaded to failure, and the corresponding reaction forces on the hinge sites were recorded using a loading cell. The FE analysis results revealed no significant differences between the straight- and curved-cut groups in terms of maximum stress forces on the superior, middle, or inferior portions of the hinge sites. In the experimental study, the curved-cut group withstood higher loads to failure at the hinge site than the straight-cut group. The ability of the curved-cut laminoplasty hinges to withstand higher compressive loading to failure than straight-cut hinges suggests the potential of the proposed technique to reduce the risk of hinge fracture and displacement.

An EMG-CT method using multiple surface electrodes in the forearm.

Electromyography computed tomography (EMG-CT) method is proposed for visualizing the individual muscle activities in the human forearm. An EMG conduction model was formulated for reverse-estimation of muscle activities using EMG signals obtained with multi surface electrodes. The optimization process was calculated using sequential quadratic programming by comparing the estimated EMG values from the model with the measured values. The individual muscle activities in the deep region were estimated and used to produce an EMG tomographic image. For validation of the method, isometric contractions of finger muscles were examined for three subjects, applying a flexion load (4.9, 7.4 and 9.8 N) to the proximal interphalangeal joint of the middle finger. EMG signals in the forearm were recorded during the tasks using multiple surface electrodes, which were bound around the subject's forearm. The EMG-CT method illustrates the distribution of muscle activities within the forearm. The change in amplitude and area of activated muscles can be observed. The normalized muscle activities of all three subjects appear to increase monotonically with increases in the load. Kinesiologically, this method was able to estimate individual muscle activation values and could provide a novel tool for studying hand function and development of an examination for evaluating rehabilitation.