Variability of Minimum Toe Clearance in ramp walking using Echelon, Esprit, and Elan

CATALFAMO FORMENTO, PAOLA; RIVERAS, MAURICIO; MUÑOZ LARROSA, EUGENIA

2019-09-02/2019-11-29

Biomédica

Tecnol.sanit.y curativa-Protesis

Background: Minimum Toe Clearance (MTC) is defined as the minimum vertical distance between the lowest point under the front part of the foot and the ground, occurring during mid-swing. Low values of MTC (and/or high values of variability) in lower limb amputees are related to higher probability of tripping and falling. Incline walking represents a falling risk for amputees and affects MTC. Hence, increasing the values of MTC (and/or reduce variability), especially on ramps, is an objective of new prosthetic designs. The aim of this study was to evaluate the effect of different prosthetic designs on MTC variability in inclined walking.Methods: Thirteen transtibial amputees walked on a ramp using three different prostheses: energy storage and return (Esprit), hydraulic ankle (Echelon), and hydraulic ankle with microprocessor (Elan). Median MTC, coefficient of variation (CV), and interquartile range (iqr) were compared across ankle type in ascent and descent.Findings: When using Elan, larger (hence safer) MTC median values for ascending (P≤0.001, W=0.58) and descending the ramp (P=0.003, W=0.47) were found in the prosthetic limb. Also significantly lower CV was found on the prosthetic limb for both types of adaptive feet (Echelon and Elan) when compared to Esprit for descending the ramp (P=0.014, W=0.45). No significant differences in iqr were found between prostheses in the ground conditions studied. However, when the prosthetic limb is in stance phase, acting as the supporting leg, both the median and variability of MTC of the intact limb are either in between the values obtained for Esprit and Echelon or present the worst value of CV for ascending the ramp.Interpretation: Elan produced the safer results in terms of MTC for the prosthetic limb both in ascending and descending the ramp. Still, results show an increase in the variability of MTC of the sound limb when using Elan for ascending the ramp. This effect may be due to some instability of the prosthetic limb in stance phase when using Elan.