Adam K. Arabian

Perception of socket alignment perturbations in amputees with transtibial prostheses

A person with amputations subjective perception is the only tool available to describe fit and comfort to a prosthetist. However, few studies have investigated the effect of alignment on this perception. The aim of this article is to determine whether people with amputation could perceive the alignment perturbations of their prostheses and effectively communicate them. A randomized controlled perturbation of angular (3 and 6 degrees) and translational (5 and 10 mm) alignments in the sagittal (flexion, extension, and anterior and posterior translations) and coronal (abduction, adduction, and medial and lateral translations) planes were induced from an aligned condition in 11 subjects with transtibial prostheses. The perception was evaluated when standing (static) and immediately after walking (dynamic) using software that used a visual analog scale under each alignment condition. In the coronal plane, Friedman test demonstrated general statistical differences in static (p < 0.001) and dynamic (p < 0.001) measures of perceptions with angular perturbations. In the sagittal plane, it also demonstrated general statistical differences in late-stance dynamic measures of perceptions (p < 0.001) with angular perturbations, as well as in early-stance dynamic measures of perceptions (p < 0.05) with translational perturbations. Fisher exact test suggested that people with amputations perceptions were good indicators for coronal angle malalignments but less reliable when defining other alignment conditions.

Socket Pressure and Discomfort in Upper-Limb Prostheses: A Preliminary Study

ABSTRACT The appropriate fit and comfort while wearing prosthetic sockets are critical factors that contribute to the successful use of upper-limb prostheses. The prevailing metric in current clinical practice for measuring socket fit is self-reported patient discomfort or pain. This can be problematic because of the subjective nature of self-report and possible insensate portions of the residual limb. Objective methods for measuring socket fit would provide prosthetists with more reliable information needed to minimize discomfort and injury due to tissue breakdown associated with localized pressure and shear. The objectives of this study were 1) to develop a method for quantifying upper-limb socket fit condition by measuring the socket-skin interface pressure distribution and 2) to detect any potential correlation between this pressure and patient discomfort in the residual limb. A total of nine upper-limb prosthetic users participated: three in transradial (TR) group, three in transhumeral (TH) group, and three in shoulder disarticulation (SHD) group. Socket interface pressure was measured with thin-film pressure-mapping sensor system, whereas discomfort score was self-recorded using a visual analog scale (VAS). Pressure and discomfort were measured in 68 arm-weight configurations for the subjects with TR or TH amputation and 70 arm-weight configurations for the subjects with a SHD. The accuracy error of the sensors ranged from 5% to 17%, with posttest errors ranging from 7% to 35%. When testing the repeatability of the same arm-weight configurations, pressure was less variable than discomfort in the TR group, slightly less variable than discomfort in the TH group, and more variable than discomfort in the SHD group. Correlations between pressure and discomfort ranged from no correlation to a strong correlation (r = 0.36, p < 0.001) depending on the subject. Discomfort did not correlate with pressure in any of the three subjects with SHD. The results show that more reliable methods are needed for determining socket fit using socket pressure measurement for clinical application.

Low-cost backpack-portable robot system for mine and UXO detection and identification

The Johns Hopkins University Applied Physics Laboratory (JHU/APL) has developed a prototype backpack-portable robot system for mine and unexploded ordnance (UXO) detection and identification. The robot system is compact, lightweight and is estimated to be inexpensive to construct. The robot has been designed with an inexpensive, highly accurate, wide bandwidth time-domain electromagnetic induction (EMI) sensor for the detection and identification of metal components in mines and UXO. The robot can be configured for autonomous or person-in-the-loop control. The robot system can be configured with additional light-weight and low-cost mine and UXO sensors such as ground penetrating radar (GPR) and chemical explosive detectors.

Synergy in Green Power Production Methods and Siting

Unreliability of power production from green sources is a significant hindrance to implementation. This study investigates a dual-synergistic approach to alternative power; the dual synergies being (a) multiple energy sources and (b) multiple locations. Generation simulations were conducted for notional combined systems in two California coastal locations: one in the northern portion and one in the southern. These combined systems consisted of offshore wave, offshore wind, and onshore solar generation. Estimated production was compared hourly with demand. Treating the two locations as a single entity showed the synergistic behavior superior by 40% to the production when viewing the two sites independently.