A novel physiological testing device to study knee biomechanics in vitro

Background To properly study knee kinetics, kinematics and the effects of injury and surgical treatment in vitro, the knee should be constrained as little as possible, while imposing physiological loads. A novel dynamic biomechanical knee system (BKS) is presented here. The aim of this study was to test the feasibility and reproducibility of the system and demonstrate its features with an Anterior Cruciate Ligament (ACL) lesion model. Methods Six goat knees were used in the current study. Flexion and extension simulating gait was imposed by a servo-motor, while normal joint load was applied by two artificial muscles. Intra-class correlation coefficients (ICCs) were assessed for inter-test measures, while paired t-tests were performed for comparison between intact knees and knees with ACL-lesion. Results The ICC's for inter-test measures based on all six goat knees were excellent: varus/valgus: ICC = 0.93; rotation: ICC = 0.94 (all p < 0.01), and translation in frontal (x)-, side (y)- and upward (z)-direction (ICC = 0.90, 0.88 & 0.94) (all p < 0.01). A significant increase in joint center movement was found in knees after creating an ACL-lesion (p = 0.018): translation increased more than two-fold in frontal (p = 0.016), side (p = 0.004) and upward (p = 0.018) direction. Conclusions Five degrees of motion were reproducibly assessed in the intact joint, suggesting that the goat knee may find its natural pathway when loaded in the BKS. The novel five-degrees-of-freedom knee system allows a detailed study of the effect of a diversity of defects and surgical treatments on knee biomechanics under physiological loading conditions

Implementation of emg- and force-based control interfaces in active elbow supports for men with duchenne muscular dystrophy: a feasiblitity study

While there is an extensive number of studies on the development and evaluation of electromyography (EMG)- and force-based control interfaces for assistive devices, no studies have focused on testing these control strategies for the specific case of adults with Duchenne muscular dystrophy (DMD). This paper presents a feasibility study on the use of EMG and force as control interfaces for the operation of active arm supports for men with DMD. We have built an experimental active elbow support, with a threefold objective: 1) to investigate whether adult men with DMD could use EMG- and force-based control interfaces; 2) to evaluate their performance during a discrete position-tracking task; and 3) to examine users' acceptance of the control methods. The system was tested in three adults with DMD (21-22 years). Although none of the three participants had performed any voluntary movements with their arms for the past 3-5 years, all of them were 100% successful in performing the series of tracking tasks using both control interfaces (mean task completion time EMG: 6.8 ± 4.8 s, force: 5.1 ± 1.8 s). While movements with the force-based control were considerably smoother in Subject 3 and faster in Subject 1, EMG based-control was perceived as less fatiguing by all three subjects. Both EMG- and force-based interfaces are feasible solutions for the control of active elbow supports in adults with DMD and should be considered for further investigations on multi-DOF control