Dexterous hand movement is possible due to closed loop control dependent on efferent motor output and afferent sensory feedback. This control strategy is significantly altered in those with upper limb amputation as sensations of touch and movement are inherently lost. For upper limb prosthetic users, the absence of sensory feedback impedes efficient use of the prosthesis and is highlighted as a major factor contributing to user rejection of myoelectric prostheses. Numerous sensory feedback systems have been proposed in literature to address this gap in prosthetic control; however, these systems have yet to be implemented for long term use. Methodologies for communicating prosthetic grasp and touch information are reviewed, including discussion of selected designs and test results. With a focus on clinical and translational challenges, this review highlights and compares techniques employed to provide amputees with sensory feedback. Additionally, promising future directions are discussed and highlighted.

Force Sensitive Resistors (FSRs) are commercially available thin film polymer sensors commonly employed in a multitude of biomechanical measurement environments. Reasons for such wide spread usage lie in the versatility, small profile, and low cost of these sensors. Yet FSRs have limitations. It is commonly accepted that temperature, curvature and biological tissue compliance may impact sensor conductance and resulting force readings. The effect of these variables and degree to which they interact has yet to be comprehensively investigated and quantified. This work systematically assesses varying levels of temperature, sensor curvature and surface compliance using a full factorial design-of-experiments approach. Three models of Interlink FSRs were evaluated. Calibration equations under 12 unique combinations of temperature, curvature and compliance were determined for each sensor. Root mean squared error, mean absolute error, and maximum error were quantified as measures of the impact these thermo/mechanical factors have on sensor performance. It was found that all three variables have the potential to affect FSR calibration curves. The FSR model and corresponding sensor geometry are sensitive to these three mechanical factors at varying levels. Experimental results suggest that reducing sensor error requires calibration of each sensor in an environment as close to its intended use as possible and if multiple FSRs are used in a system, they must be calibrated independently.

A tubular braided composite bone cast for improving the efficiency and quality of bone fracture treatment is investigated. Finite element analysis was used to evaluate stress concentrations in fracture sites supported with plate and tubular casts. The stress in a plated bone is 768 % of that in a whole bone at the same location, while it is only 47 % in a bone with a tubular cast. Three unbroken synthetic humeri were mechanically tested using an in-vitro long bone testing procedure developed in-house to find their stiffness at 20° and 60° abduction; these were found to be 116.8 ± 1.5 N/mm and 20.63 ± 0.02 N/mm, respectively. A 2 cm gap osteotomy was cut through the diaphysis in each bone. The bones were casted with a Kevlar/Cold cure composite, with calculated braid angles and thicknesses that Closely matched bone propoerties. The stiffness tests were repeated, and the results were within 10 % of the unbroken bone. This novel method of bone casting is promising if other clinical challenges can be minimized.

Hip protectors are often prescribed to the elderly who are at risk of falling, with the goal of preventing hip fractures. However, determining the effectiveness of hip protectors has been hampered by unreliable compliance data. This study reports a reliable objective method of measuring compliance and the developed method could be used in any climate, regardless of temperature. Custom compliance monitors were built and embedded inside hip protectors. An algorithm was developed to utilize both temperature and acceleration to determine compliance. Seven young volunteers (age 24.6 ± 4.2 years old) wore the protectors for a total of 667 h while closely recording their compliance. One female (77 years old) who had hip fracture history wore the compliance monitors for 91.6 % of the time during a 1-week stay in a hospital. From the volunteers' trial, using temperature alone overpredicted compliance by 1.2 % and using acceleration alone overpredicted by 5.4 %, but using a combination of the two methods plus a correction factor only underestimated by 0.6 %. From the elderly data, the average compliance recorded from the temperature, acceleration, and combined methods with correction was 94.6, 88.9, and 90.2, respectively. The high accuracy of temperature sensors in this study will not be attainable in hot climates where most of the worldwide increase in hip fractures is occurring. The developed monitor with the algorithm provided high accuracy in determining compliance and was able to determine both the longitudinal and cross-sectional compliance at any time.

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