The Effect of Prosthetic Alignment on Prosthetic and Total Leg Stiffness While Running With Simulated Running-Specific Prostheses.

Ashley Groothuis,Han Houdijk

doi:10.3389/fspor.2019.00016

Ashley Groothuis, Han Houdijk

Open Access

https://doi.org/10.3389/fspor.2019.00016

Copy DOI

Abstract

Running-specific prostheses (RSP) are designed to replicate the spring-like behavior of the biological leg in people with a lower limb amputation. Running performance strongly depends on stiffness of the RSP. The aim of this study was to investigate the effects of angle of alignment of the RSP on its stiffness, and how this affects total leg stiffness and the gait pattern during running. Ten able-bodied athletes performed eight trials on a treadmill with running-specific prosthetic simulators, while the alignment of the blades relative to the socket was set in four different angles (0, 5, 10, and 15°) during two different step frequency conditions (free and imposed). RSP stiffness, total leg stiffness, residual leg stiffness, and spatiotemporal parameters were measured. In both step frequency conditions, the RSP stiffness decreased linearly with increasing angle of alignment. Able bodied athletes were able to compensate for the decreased RSP stiffness, and keep total leg stiffness almost invariant, by increasing residual leg stiffness through a more straight the knee at initial contact. This study confirms that alignment is an important factor to take into account when optimizing the RSP. Whether the observed compensations are feasible in amputee athletes needs further investigation.

Highlights

Athletes with a lower limb amputation use prostheses that mimic the spring-like behavior of the biological human leg
We investigated the effect of alignment of the blade relative to the socket on prosthetic stiffness and total leg stiffness during actual running on a treadmill
We explored whether runners would adapt angle of attack during running and/or whether runners would adapt residual leg stiffness to mitigate the potential change in prosthetic stiffness with changing alignment during running

Summary

Introduction

Athletes with a lower limb amputation use prostheses that mimic the spring-like behavior of the biological human leg. Human running is seen as a bouncing gait for which the body can be modeled as a simplified spring-mass model (Blickhan, 1989; Farley et al, 1993). The spring-mass model consists of a mass equivalent to the body mass supported by a single linear spring (Figure 1). This model can give insight into the relation between properties or behavior of the leg and running performance (i.e. running velocity and efficiency). Step frequency of a spring mass system depends on the stiffness of the leg and the angle of attack of the leg with the ground (Blickhan, 1989; Farley et al, 1998; Morin et al, 2007). To improve running performance, leg stiffness and landing angle are important parameters that could be manipulated

Objectives

Methods

Results

Conclusion