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JOURNAL, VOLUME 1, ISSUE 2, 2018; ABSTRACT, POSTER PRESENTATION AT THE AOPA’S 101ST NATIONAL ASSEMBLY, SEPT. 26-29, VANCOUVER, CANADA, 2018.  DOI: 
https://doi.org/10.33137/cpoj.v1i2.32013     

1 

 
OPEN  ACCESS 

 

AOPA’S 101 ST NATIONAL ASSEMBLY ABSTRACTS, SEPTEMBER 26-29, VANCOUVER, CANADA, 2018 
 

ABSTRACT (POSTER PRESENTATION) 

HOW REPRODUCIBLE ARE THE EFFECTS OF A MICROPROCESSOR FOOT? 

Michael McGrath*1, Nadine Stech1, Piotr Laszczak1, Alan Kercher2, Saeed Zahedi1, David Moser1 

1Endolite Technology Centre, Basingstoke, UK  
2Endolite North America, Miamisburg, OH, USA 
*Email: mike.mcgrath@blatchford.co.uk 

DOI: https://doi.org/10.33137/cpoj.v1i2.32013  

 

INTRODUCTION 

Using microprocessor-control to dynamically adapt 

hydraulic ankles, by changing the resistances to 

dorsiflexion and plantarflexion (DF/PF) movements, has 

been shown to have beneficial biomechanical effects 

during slope descent1. Another, more recent case study 

also showed that the level walking biomechanical effects 

of microprocessor-feet (MPF) persist, and the same 

trends can be observed in repeated gait analysis sessions, 

over a year apart2. This work looks to expand on both of 

these concepts, analysing repeated gait analysis sessions 

to see if the biomechanical changes of MPF during slope 

descent are reproducible over time. 

METHODS 

A mixed cohort of trans-tibial and trans-femoral, K3 

amputees participated in this study. Each was fitted with 

a microprocessor-controlled hydraulic ankle-foot (Elan, 

Endolite), which dynamically varies the resistances to 

dorsi-/plantarflexion (DF/PF) depending on the gradient 

of the walking surface. Two prosthetic conditions were 

tested, in a randomised order. These included one with 

the dynamic resistance variation active (MPF-on) and 

one without (MPF-off), so that the device behaved like a 

regular hydraulic ankle, with constant resistance to 

DF/PF. Each participant was asked to descend a 5° slope 

at their comfortable walking speed. A 5° slope was 

selected as this aligns with the ADA regulations 

regarding disability access ramps – a common real-life 

environmental barrier. Kinematic and kinetic 

measurements were recorded using a gait analysis system 

and a force plate embedded in the sloped surface. Each 

participant was recorded for two different data collection 

sessions, at least a month apart. 

RESULTS 

The findings showed a number of gait parameter changes 

that were reproduced in the different testing sessions. 

While quantitative changes were different, even within 

participants, the observable changes were in the same 

direction each time. The most consistent changes 

occurred at the prosthetic ‘ankle’. The transition from DF  

moment to PF moment at the prosthetic ‘ankle’ 

consistently occurred earlier in the gait cycle with the 

MPF-on. This implied that there was less resistance to PF 

movement, so a stable ‘foot flat’ position was achieved 

sooner and so did the change from ‘heel rocker’ to ‘ankle 

rocker’. The earlier transition meant that there was an 

increased resistance to DF movement, implying a 

braking effect to control momentum build up. This effect 

was also seen as increased negative ‘ankle’ work done. 

These same trends were observed for both trans-tibial 

and trans-femoral amputees, showing reproducibility 

regardless of amputation level. 

 
Figure 1: The prosthetic ‘ankle’ moment plots for a trans-tibial 

amputee with MPF-off (black) and MPF-on (green), for test 

sessions four months apart. 

CONCLUSION 

It is not simply the function of a prosthetic device that is 

important but also the consistency of that function. A 

mailto:mike.mcgrath@blatchford.co.uk
https://doi.org/10.33137/cpoj.v1i2.32013


 

 

McGrath M, Stech N, Laszczak P, Kercher A, Zahedi S, Moser D. HOW REPRODUCIBLE ARE THE EFFECTS OF A MICROPROCESSOR FOOT? CANADIAN PROSTHETICS & ORTHOTICS 
JOURNAL, VOLUME 1, ISSUE 2, 2018; ABSTRACT, POSTER PRESENTATION AT THE AOPA’S 101ST NATIONAL ASSEMBLY, SEPT. 26-29, VANCOUVER, CANADA, 2018.  DOI: 
https://doi.org/10.33137/cpoj.v1i2.32013     

2 

 
OPEN  ACCESS 

 

AOPA’S 101 ST NATIONAL ASSEMBLY ABSTRACTS, SEPTEMBER 26-29, VANCOUVER, CANADA, 2018 
 

ABSTRACT (POSTER PRESENTATION) 

consistent performance will improve user confidence in 

a prosthetic device and highlights the potential to 

influence long term health problems, such as 

osteoarthritis and back pain, both of which are common 

among the amputee population3. 
 

SIGNIFICANCE 

Showing reproducibility of the effects of MPFs indicates 

that there will be an influence on the long term 

biomechanics of the user. 

REFERENCES 

1.Struchkov et al. Biomechanics of ramp descent in unilateral 

trans-tibial amputees: Comparison of a microprocessor 

controlled foot with conventional ankle-foot mechanisms. Clin 

Biomech. 2016;32:164–170. DOI: 

10.1016/j.clinbiomech.2015.11.015 

2.De Asha et al. Which Prosthetic Foot to Prescribe?: 

Biomechanical Differences Found during a Single-Session 

Comparison of Different Foot Types Hold True 1 Year Later. 

J Prosthet Orthot. 2017;29(1):39–43. 

DOI:10.1097/JPO.0000000000000119  

3.Gailey. Review of secondary physical conditions associated 

with lower-limb amputation and long-term prosthesis use. J 

Rehabil Res Dev. 2008;45(1):15-29. DOI: 

10.1682/JRRD.2006.11.0147 

DISCLOSURE 

The Authors are employees of Endolite North America or 

Blatchford (the parent company of Endolite North America); 

the manufacturer of the ankle-foot devices used in this study. 

 

 

 

 

https://doi.org/10.1016/j.clinbiomech.2015.11.015

