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In Vivo Tests of Improved Method for Functional Location of STJ Axis

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Kevin Kirby, Dec 2, 2008.


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    Our research paper on a new method for locating the three-dimensional location of the subtalar joint axis has just been listed in the "Articles in Press" section of the Journal of Biomechanics website. It is titled In Vivo Tests of an Improved Method for Functional Location of the Subtalar Joint Axis.

    This paper represents the collaborative efforts between researchers with The Department of Mechanical and Nuclear Engineering, Department of Orthopaedics and Rehabilitation, and the Department of Kinesiology at Penn State University, the National Institutes of Health in Bethesda, Maryland, the Department of Biomedical Engineering at Marquette University and the Department of Applied Biomechanics at the California School of Podiatric Medicine. This multidisciplinary research represents a significant step forward in our ability to non-invasively track the three-dimensional location of the subtalar joint axis during weightbearing activities.

    The paper should be published within the Journal of Biomechanics within the next six months. Those that are interested in obtaining a pdf copy of the paper may e-mail me privately.
     
    Last edited: Dec 2, 2008
  2. Thanks to all of those who have expressed an interest in our upcoming paper in the Journal of Biomechanics on "In vivo tests of an Improved method for functional location of the subtalar joint axis". I have just posted a video to YouTube from research done at the Penn State Biomechanics Laboratory from four years ago which marks the beginning of the intellectual-research journey that has culminated in this paper.

    Here is the experimental setup:

    1. A fresh-frozen male cadaver limb is shown that has been recently thawed to room temperature
    2. The tibia is fixed in a horizontal position with a steel rod on the testing platform.
    3. The Achilles tendon is tethered with a cable so that ankle joint dorsiflexion will be restricted by Achilles tendon tensile force.
    4. Steel pins are drilled into the tibia, talus and calcaneus with retro-reflective marker clusters then attached to the tibial, talar and calcaneal pins.

    Notice that while I am moving the subtalar joint of the cadaver foot with the forefoot loaded into dorsiflexion, the talar marker moves very little relative to the tibial marker, indicating little ankle joint motion during subtalar joint (STJ) motion by loading the forefoot with a dorsiflexion force. The increase in ankle joint dorsiflexion moment by my manual forefoot dorsiflexion loading force is counterbalanced by an equal magnitude of ankle joint plantarflexion moment by the Achilles tendon tensile force. The ankle joint compression loading force will be approximately three times the compression load that I am placing manually on the plantar forefoot, which helps prevent ankle joint motion during this STJ range of motion procedure.

    These same concepts were used to create the testing apparatus which we have now used in two papers in our quest to more accurately determine the three-dimensional STJ axis location in live subjects during gait.

    Lewis GS, Kirby KA, Piazza SJ: Determination of subtalar joint axis location by restriction of talocrural joint motion. Gait and Posture. 25:63-69, 2007.

    Lewis GS, Cohen TL, Seisler AR, Kirby KA, Sheehan FT, Piazza SJ: In vivo tests of an Improved method for functional location of the subtalar joint axis. Submitted to J Biomechanics, November 2007.

     
    Last edited by a moderator: Sep 22, 2016
  3. Our paper on "In vivo tests of an improved method for functional location of the subtalar joint axis" has just been published in the January 2009 issue of the Journal of Biomechanics. Here is the full reference:

    Lewis GS, Cohen TL, Seisler AR, Kirby KA, Sheehan FT, Piazza SJ: In vivo tests of an improved method for functional location of the subtalar joint axis. J Biomechanics, 42:146-151, 2009.

    Those who would like a pdf copy of the paper may contact me privately via e-mail.
     
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