Predictors of cervical myelopathy and hydrocephalus in young children with achondroplasia

Background Cervical myelopathy and hydrocephalus occasionally occur in young children with achondroplasia. However, these conditions are not evaluated in a timely manner in many cases. The current study presents significant predictors for cervical myelopathy and hydrocephalus in young children with achondroplasia. Methods A retrospective analysis of 65 patients with achondroplasia who visited Seoul National University Childrens Hospital since 2012 was performed. The patients were divided into groups according to the presence of cervical myelopathy and hydrocephalus, and differences in foramen magnum parameters and ventricular parameters by magnetic resonance imaging between groups were analyzed. Predictors for cervical myelopathy and hydrocephalus were analyzed, and the cut-off points for significant ones were calculated. Results The group with cervical myelopathy showed foramen magnum parameters that indicated significantly lower cord thickness than in the group without cervical myelopathy, and the group with hydrocephalus showed significantly higher ventricular parameters and Posterior indentation grade than the group without hydrocephalus. Cord constriction ratio (OR 5199.90, p = 0.001) for cervical myelopathy and Frontal horn width (OR 1.14, p = 0.001) and Posterior indentation grade (grade 1: OR 9.25, p = 0.06; grade 2: OR 18.50, p = 0.01) for hydrocephalus were significant predictors. The cut-off points for cervical myelopathy were Cord constriction ratio of 0.25 and FM AP of 8 mm (AUC 0.821 and 0.862, respectively) and Frontal horn width of 50 mm and Posterior indentation grade of 0 (AUC 0.788 and 0.758, respectively) for hydrocephalus. Conclusion Cord constriction ratio for cervical myelopathy and Frontal horn width and Posterior indentation grade for hydrocephalus were significant predictors and may be used as useful parameters for management. Posterior indentation grade may also be used to determine the treatment method for hydrocephalus

Range Sensor-Based Efficient Obstacle Avoidance through Selective Decision-Making

In this paper, we address a collision avoidance method for mobile robots. Many conventional obstacle avoidance methods have been focused solely on avoiding obstacles. However, this can cause instability when passing through a narrow passage, and can also generate zig-zag motions. We define two strategies for obstacle avoidance, known as Entry mode and Bypass mode. Entry mode is a pattern for passing through the gap between obstacles, while Bypass mode is a pattern for making a detour around obstacles safely. With these two modes, we propose an efficient obstacle avoidance method based on the Expanded Guide Circle (EGC) method with selective decision-making. The simulation and experiment results show the validity of the proposed method

Exploring Multimodal Watch-back Tactile Display using Wind and Vibration

A tactile display on the back of a smartwatch is an attractive output option; however, its channel capacity is limited owing to the small contact area. In order to expand the channel capacity, we considered using two perceptually distinct types of stimuli, wind and vibration, together on the same skin area. The result is a multimodal tactile display that combines wind and vibration to create "colored" tactile sensations on the wrist. As a first step toward this goal, we conducted in this study four user experiments with a wind-vibration tactile display to examine different ways of combining wind and vibration: Individual, Sequential, and Simultaneous. The results revealed the sequential combination of wind and vibration to exhibit the highest potential, with an information transfer capacity of 3.29 bits. In particular, the transition of tactile modality was perceived at an accuracy of 98.52%. The current results confirm the feasibility and potential of a multimodal tactile display combining wind and vibration

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opening control using the multi-fingered roboti

Compact Hip-Force Sensor for a Gait-Assistance Exoskeleton System

In this paper, we propose a compact force sensor system for a hip-mounted exoskeleton for seniors with difficulties in walking due to muscle weakness. It senses and monitors the delivered force and power of the exoskeleton for motion control and taking urgent safety action. Two FSR (force-sensitive resistors) sensors are used to measure the assistance force when the user is walking. The sensor system directly measures the interaction force between the exoskeleton and the lower limb of the user instead of a previously reported force-sensing method, which estimated the hip assistance force from the current of the motor and lookup tables. Furthermore, the sensor system has the advantage of generating torque in the walking-assistant actuator based on directly measuring the hip-assistance force. Thus, the gait-assistance exoskeleton system can control the delivered power and torque to the user. The force sensing structure is designed to decouple the force caused by hip motion from other directional forces to the sensor so as to only measure that force. We confirmed that the hip-assistance force could be measured with the proposed prototype compact force sensor attached to a thigh frame through an experiment with a real system

Shoes with active insoles mitigate declines in balance after fatigue

Fatigue can induce postural instability and even lead to falls. However, most current methods to delay or reduce fatigue require long preparatory time, or large and expensive equipment. We propose a convenient method to alleviate postural instability due to fatigue. We paid attention to that fatigue and aging share similar neurophysiological deterioration of sensory-motor function. Considering that stochastic resonance via sub-sensory mechanical vibration increases postural stability in the elderly, we propose that sub-sensory insole vibration reduces the negative effect of fatigue on postural control. We performed experiments with 21 young and healthy adult participants, and demonstrated that insole vibration compensates for the loss of balance ability due to fatigue. The sub-sensory insole vibration restored both the area of center of pressure and the complexity of the time series of the motor output after fatigue to the pre-fatigue levels. The insole units generating the vibration were completely concealed in shoes and controlled by a smart phone. This compact implementation contrasts with the cumbersome procedure of current solutions to fatigue-induced postural instability.Y