Northwestern University Feinberg School of Medicine

Northwestern University Prosthetics-Orthotics Center

Simulation of Ankle Foot Orthotic Joint Misalignment

Principal Investigator: Stefania Fatone, PhD, BPO(Hons)

Co-investigators: Kerice-Ahmun Tucker, BS, William Brett Johnson, PhD

Funded by: National Institute on Disability and Rehabilitation Research (NIDRR)

Status:Completed

Introduction

During fabrication, an AFO’s joint axis must be aligned with the anatomical ankle axis to ensure that the AFO provides the desired function.  However, sometimes, the two axes aren’t properly aligned, and the AFO fails to achieve the desired outcome. In an attempt to gain greater insight into the consequences of misalignment, a program called AFO3D was developed to simulate the likely result of both rotational and translational misalignments.

The following assumptions apply to the simulation:

1. The ideal AFO joint angle is the angle that minimizes the total potential energy of the system.
2. The AFO is rigid.
3. The AFO foot shell remains fixed relative to foot.
4. Ankle rotations take place about a single axis through the lateral and medial malleoli.
5. The AFO ankle joint is a single axis that rotates freely.
6. There is no slippage between the AFO and the leg.
7. The AFO does not alter the leg’s kinematics.

AFO3D Simulation of AFO Joint Misalignment Program

We have created an AFO3D-Installation Folder located outside this web page. The Folder contains: 1) the AFO3D Installer (an executable file); 2) the AFO 3D Installation Instructions; and 3) the AFO3D User's Manual. Everyone is welcome to access, view, download and use this program. Prior to leaving this web page, you may preview the AFO 3D Installation Instructions and the AFO 3D User's Manual or download from the off-site AFO 3D Installation Folder.  Access the AFO 3D Installation Instructions for information and screen shots about the installation and extraction of the included MatLab compiler.

The program consists of two main windows: a command window where the simulation is setup and run, and a Plot Window where the results of the simulation are displayed. Open the AFO 3D-Installation Folder to access all resources.

  1. Download the AFO3D_install program to your computer (Windows 7 compatible).
  2. Double click the icon to open a black DOS prompt window and the program will download the MatLab Compiler.
  3. Continue to follow the prompts for the MRTC installer.
  4. After installation, click on the AFO3D icon to open and run the AFO3D app.
Publications

Fatone S, Johnson WB, Kwak S (2016) Using a Three-Dimensional Model of the Ankle-Foot Orthosis to Explore the Effects of Combinations of Axis Misalignments. Prosthetics Orthotics International, 40(2)247-252. DOI: 10.1177/0309364614556839. The online version of this article is available at: http://poi.sagepub.com/content/early/2014/11/11/0309364614556839

Fatone S, Johnson WB, Tucker K (2016) A 3D Model to Assess the Effect of Ankle Joint Axis Misalignments in Ankle-Foot Orthoses. Prosthetics Orthotics International, 40(2):240-246. DOI: 10.1177/0309364614543551. The online version of this article is available at: http://poi.sagepub.com/content/early/2014/07/30/0309364614543551.