Research Papers

Development of a Portable Knee Rehabilitation Device That Uses Mechanical Loading

[+] Author and Article Information
Daric Fitzwater

Department of Mechanical Engineering,
Indianapolis, IN 46202
e-mail: defitzwa@iupui.edu

Todd Dodge

Department of Biomedical Engineering,
Indianapolis, IN 46202
e-mail: trdodge@iupui.edu

Stanley Chien

Department of Electrical Engineering,
Indianapolis, IN 46202
e-mail: schien@iupui.edu

Hiroki Yokota

Department of Biomedical Engineering,
Indianapolis, IN 46202
e-mail: hyokota@iupui.edu

Sohel Anwar

Department of Mechanical Engineering,
Indianapolis, IN 46202
e-mail: soanwar@iupui.edu

Manuscript received August 9, 2012; final manuscript received May 2, 2013; published online September 24, 2013. Assoc. Editor: Jahangir Rastegar.

J. Med. Devices 7(4), 041007 (Sep 24, 2013) (10 pages) Paper No: MED-12-1101; doi: 10.1115/1.4024830 History: Received August 09, 2012; Revised May 02, 2013

Joint loading is a recently developed mechanical modality, which potentially provides a therapeutic regimen to activate bone formation and prevent degradation of joint tissues. To our knowledge, however, few joint loading devices are available for clinical or point-of-care applications. Using a voice-coil actuator, we developed an electromechanical loading system appropriate for human studies and preclinical trials that should prove both safe and effective. Two specific tasks for this loading system were development of loading conditions (magnitude and frequency) suitable for humans, and provision of a convenient and portable joint loading apparatus. Desktop devices have been previously designed to evaluate the effects of various loading conditions using small and large animals. However, a portable knee loading device is more desirable from a usability point of view. In this paper, we present such a device that is designed to be portable, providing a compact, user-friendly loader. The portable device was employed to evaluate its capabilities using a human knee model. The portable device was characterized for force-pulse width modulation duty cycle and loading frequency properties. The results demonstrate that the device is capable of producing the necessary magnitude of forces at appropriate frequencies to promote the stimulation of bone growth and which can be used in clinical studies for further evaluations.

Copyright © 2013 by ASME
Topics: Stress , Bone , Design , Knee , Engines , Cycles , Circuits
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Fig. 1

(a) Depiction of fluid flow, pressure, and deformation within a bone, and (b) mechanical loading of a knee joint

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Fig. 2

Table setup version of a knee-loading device used for testing the knee of a rat

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Fig. 3

Diagram of proposed mechanism

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Fig. 4

Adjustable side using contact resistance

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Fig. 5

Pro/Engineer solid model of device

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Fig. 6

Simplified representation of the slider crank mechanism used for the force transmission in the device

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Fig. 7

(a) The top curve shows the motion of the end point of the connecting rod through the x–y plane; the long solid lines (vertically aligned and diagonally aligned) show three positions of the connecting and crank links, respectively. (b) Motion of the end point of the connection rod showing its linear approximation.

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Fig. 8

Circuit design for the device control module

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Fig. 9

(a) Device controller box and (b) as-built knee loading device

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Fig. 10

(a) Circuit model for PSpice analysis with 200 Hz step input and (b) resulting voltage response across the motor

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Fig. 11

(a) Loading and constraints of ANSYS analysis (b) Von-Mises stress analysis

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Fig. 12

Device setup for displacement and force measurements using an artificial knee

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Fig. 13

Microcontroller output at 1 Hz loading frequency and 50% PWM duty cycle

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Fig. 14

(a) Average peak force measured over 1 min of operation at 1 and 5 Hz. (b) Maximum peak force occurrence measured over 1 min of operation at 1 and 5 Hz.

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Fig. 15

Force and displacement data for an artificial knee loaded at 1 Hz and (a) 50% duty cycle and (b) 100% duty cycle



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