Showing papers by "David Howard published in 2012"

Stance phase mechanical characterization of transtibial prostheses distal to the socket: a review.

Abstract: Achieving the required functionality of a trans-tibial prosthesis during the stance phase of gait (e.g., shock absorption, close to normal roll-over characteristics, and smooth transition into swing) depends on the “Amputee Independent Prosthesis Properties” (AIPPs), defined here as the mechanical properties of the prosthesis that directly influence the performance of the amputee. Accordingly, if research studies are to advance the design of prostheses to achieve improved user performance, AIPPs must be a primary consideration. However, the majority of reported studies can be categorized as either human performance testing of commercial prosthetic components or AIPP characterization; and only in a few notable cases have authors reported studies in which these two approaches are combined. Moreover, very little consistency exists in the current methods used for AIPP characterization, thus making comparisons between the results of such studies very difficult. This paper introduces a framework for studying prosthesis design, which includes AIPP characterization, human performance and/or gait simulation studies, and detailed design. This framework provides a structure for reviewing previous approaches to AIPP characterization, discussing both their merits and shortcomings, and their use in previous experimental and simulation studies. For the purposes of this review, stance phase AIPP models have been categorized as either lumped parameter or roll-over shape based.

The effects of transverse rotation angle on compression and effective lever arm of prosthetic feet during simulated stance

Abstract: Background and Aim: Unlike sagittal plane prosthesis alignment, few studies have observed the effects of transverse plane alignment on gait and prosthesis behaviour. Changes in transverse plane rotation angle will rotate the points of loading on the prosthesis during stance and may alter its mechanical behaviour. This study observed the effects of increasing the external transverse plane rotation angle, or toe-out, on foot compression and effective lever arm of three commonly prescribed prosthetic feet. Technique: The roll-over shape of a SACH, Flex, and single-axis foot was measured at four external rotation angle conditions (0°, 5°, 7°, and 12° relative to neutral). Differences in foot compression between conditions were measured as average distance between roll-over shapes. Discussion: Increasing the transverse plane rotation angle did not affect foot compression. However, it did affect the effective lever arm, which was maximised with the 5° condition, although differences between conditions were small.

In vivo measurement of the biomechanical properties of plantar soft tissues under simulated gait conditions

Abstract: Background In vivo biomechanical properties of plantar soft tissues have been assessed via manual indentation using simplified loading profiles [1], or in gait, with low image resolution/capture rates [2]. Since plantar soft tissue properties are highly rate dependent [3] these methods are potentially inadequate. The Soft Tissue Response Imaging Device (STRIDE) permits functionally relevant loading profiles to be applied to the plantar tissues.