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Technical Briefs

The Knee Loading Apparatus: Axial, Anterior, and Compressive Loading With Magnetic Resonance Imaging

[+] Author and Article Information
Jessica C. Küpper

e-mail: johnsojc@ucalgary.ca

Ion Robu

e-mail: ion.robu@albertahealthservices.caDepartment of Mechanical and Manufacturing Engineering,
University of Calgary,
2500 University Drive N.W., Calgary,
Alberta, T2N 1N4,
Canada

Richard Frayne

Department of Radiology and Clinical Neurosciences,
University of Calgary,
2500 University Drive N.W., Calgary,
Alberta, T2N 1N4, Canada;
Seaman Family MR Centre,
Foothills Medical Centre,
Alberta Health Services,
1403 29th Street N.W., Calgary,
Alberta, T2N 2T9, Canada
e-mail: rfrayne@ucalgary.ca

Departments of Mechanical and Manufacturing Engineering,
Schulich School of Engineering and
Faculties of Kinesiology and Medicine,
University of Calgary,
2500 University Drive N.W., Calgary,
Alberta, T2N 1N4, Canada
e-mail: jlronsky@ucalgary.ca

1Corresponding author.

Contributed by the Design Automation Committee of ASME for publication in the Journal of Mechanical Design. Manuscript received March 22, 2011; final manuscript received November 2, 2012; published online January 7, 2013. Assoc. Editor: Matthew B. Parkinson.

J. Mech. Des 135(2), 024501 (Jan 07, 2013) (8 pages) Paper No: MD-11-1168; doi: 10.1115/1.4023152 History: Received March 22, 2011; Revised November 02, 2012

When magnetic resonance (MR) images are collected while applying a load to the knee joint, additional information about the joint response to loading can be acquired such as cartilage deformation, whole joint and ligament stiffness, or physiological estimates of weight-bearing joint positions. To allow load application and controlled lower limb movement in supine MR imaging, the knee loading apparatus (KLA) was designed to apply safe and physiologically relevant controlled loads to the knee joint, position the knee through a range of flexion angles, and operate successfully in a magnetic environment. The KLA is composed of three main components: a remotely operated custom hydraulic loading system, a logic system that interfaces with the user, and modular non ferromagnetic positioning frames. Three positioning frames are presented for application to anterior tibial loading, tibiofemoral compression, and patellofemoral compression at multiple knee flexion angles. This system design makes improvements over current devices. Safe remotely applied loads (hydraulic loading system) can be applied by either subject or tester and in multiple locations simultaneously. Additionally, loads can be altered at any time in a continuous manner without electrical interference. Transportability was improved due to a smaller footprint. The KLA has the flexibility to attach any positioning frame with many possible loading scenarios without changing the loading mechanism or logic systems, and allows force values over time to be output rather than estimated. An evaluation of the load repeatability (within 7% of applied load) and accuracy (0.5–14.9%) demonstrates the feasibility of this design for investigations into in vivo knee joint responses to loading.

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References

Figures

Grahic Jump Location
Fig. 3

Free body diagram of the shank support indeterminate force system for the anterior positioning frame during testing. Forces include the applied force from the hydraulic loading system (Fa), the reaction forces and moments at the knee (Fry, Frx, Mr), the under-mounted weight force (Fw), the lower-limb (shank) weight (Fl), the shank support weight (Fs), and the reaction forces at the hinge (Fhx, Fhy).

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Fig. 1

KLA schematic diagram for the (i) control room setup with hydraulic loading and logic systems, (ii) axial, (iii) anterior, and (iv) compressive positioning frames. The control room setup (i) is the same for all positioning frames.

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Fig. 2

KLA positioning frame adjustable components indicating direction of adjustability, and movement during testing.

Grahic Jump Location
Fig. 4

Free body diagram of the shank support determinate force system for the anterior positioning frame calibration. Forces include the applied force from the hydraulic loading system (Fa), calibration weight force (Fcw), the under-mounted weight force (Fw), the shank support weight (Fs), and the reaction forces at the hinge (Fhx, Fhy).

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