Uneven terrain exacerbates the deficits of a passive prosthesis in the regulation of whole body angular momentum in individuals with a unilateral transtibial amputation

Abstract

BackgroundUneven ground is a frequently encountered, yet little-studied challenge for individuals with amputation. The absence of control at the prosthetic ankle to facilitate correction for surface inconsistencies, and diminished sensory input from the extremity, add unpredictability to an already complex control problem, and leave limited means to produce appropriate corrective responses in a timely manner. Whole body angular momentum, L, and its variability across several strides may provide insight into the extent to which an individual can regulate their movement in such a context. The aim of this study was to explore L in individuals with a transtibial amputation, when challenged by an uneven surface. We hypothesized that, similar to previous studies, sagittal plane L would be asymmetrical on uneven terrain, and further, that uneven terrain would evoke a greater variability in L from stride to stride in individuals with amputation in comparison to unimpaired individuals, due to a limited ability to discern and correct for changing contours beneath the prosthetic foot.MethodsWe examined sagittal plane L in ten individuals with a unilateral transtibial amputation and age- and gender- matched control participants walking on flat (FT) and uneven (UT) treadmills. The average range of L in the first 50% of the gait cycle (LR), the average L at foot contact (LC) and their standard deviations (vLR, vLC) were computed over 60 strides on each treadmill.ResultsOn both surfaces we observed a higher LR on the prosthetic side and a reduced LC on the sound side (p < 0.001) in the amputee cohort, consistent with previous findings. UT invoked an increase in LC (p = 0.006), but not LR (p = 0.491). vLR, and vLC were higher in individuals with amputation (p < 0.001, p = 0.002), and increased in both groups on UT (p < 0.001).ConclusionsThese findings support previous assertions that individuals with amputation regulate L less effectively, and suggest that the deficits of the prosthesis are exacerbated on uneven terrain, potentially to the detriment of balance. Further, the results indicate that a greater demand may be placed on the unaffected side to control movement.Electronic supplementary materialThe online version of this article (10.1186/s12984-019-0497-9) contains supplementary material, which is available to authorized users.

Development of a Length-Actuated Lower Limb Prosthesis: Functional Prototype and Pilot Study

“…The qualitative complaints of subjects on their current microprocessor prostheses aligned with the quantitative shortcomings published in literature. Prosthesis users in the study stated that walking up stairs and inclines is strenuous, which agrees with studies done on both passive and microprocessor prostheses 13–16 . The studies have shown muscular asymmetry during stair ascent possibly attributed to a knee extension deficiency and an increased incidence of plane slips on slopes attributed to a high whole-body angular momentum 13–15 .…”

“…Prosthesis users in the study stated that walking up stairs and inclines is strenuous, which agrees with studies done on both passive and microprocessor prostheses. [13][14][15][16] The studies have shown muscular asymmetry during stair ascent possibly attributed to a knee extension deficiency and an increased incidence of plane slips on slopes attributed to a high whole-body angular momentum. [13][14][15] With a more sophisticated length-actuated prosthesis, the limb could shorten to enable stair clearance and vertical propulsion during stair ascent, and hyper leg lengthening and force-assisted shortening during stair descent.…”

Uneven Terrain Recognition Using Neuromorphic Haptic Feedback

“…So far, most of the relevant studies have been devoted to promoting postural and balance control [19][20][21][22], improving gait symmetry [12,[23][24][25] and enhancing walking performance [26]. Less evidence has been reported about the perception of the floor conditions, although the identification of the properties of a terrain to walk on is crucial for the dynamic stability of a person with amputation [27]. As a matter of fact, the uneveness of the ground is one of the most significant environmental factors affecting the risk of falls [28][29][30].…”