Emerging Concepts In Podiatric Biomechanics

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A pressure mat, such as the MatScan system illustrated at left, contains several thousand sensing elements that allows one to detect multiple discrete plantar pressures and force loading parameters every few milliseconds. (Photo courtesy of Tekscan, Inc.)
In-shoe pressure analysis systems, such as the F-Scan system illustrated above, allow one to compare plantar pressures both with and without foot orthoses.  Comparing a patient with posterior tibial dysfunction without an orthosis (left) to the same patie
Here one can see an experimental setup utilizing a uniaxial strain gauge to measure tibial strain within a cadaver limb during simulated running. In the experimental setup, researchers also utilized accelerometers to determine if a relationship exists bet
These illustrations depict finite element analysis, a computer modeling process that allows one to study simulated loading conditions to determine the internal mechanical responses of the tissues of the foot to various loading conditions, and different ty
In the subtalar joint (STJ) axis location theory, feet are divided into three types: medially deviated STJ axis (left), normal STJ axis (center) and laterally deviated STJ axis (right). The spatial location of the STJ axis relative to the plantar weightbe
In a child with severe pes valgus deformity, there will always be a medially deviated STJ axis. The STJ axis location/rotational equilibrium theory of foot function predicts that this medial STJ axis location will cause excessive STJ pronation moments fro
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Author(s): 
By Kevin A. Kirby, DPM, MS

    The world of podiatric biomechanics is very different now than when Merton Root, DPM, created the first Department of Podiatric Biomechanics at the California College of Chiropody in San Francisco in 1966.1 During those exciting early years of development within the new subspecialty of “podiatric biomechanics,” Dr. Root and his podiatric colleagues created a classification system, based on the subtalar joint (STJ) neutral position, that remains to this day the most complete method by which to classify the structure of the foot and lower extremity.1,2

    During that same period of seminal intellectual growth, Dr. Root also developed a new type of thermoplastic foot orthosis, popularly called the Root functional orthosis, which has served as the basis for the modern custom foot orthosis that is currently in wide use in multiple medical specialties.3,4

    Largely due to the intellectual seeds that Dr. Root and coworkers planted on the West Coast nearly 40 years ago with Dr. Root’s pioneering work in foot biomechanics and custom foot orthoses, there has been a significant increase in the use of custom foot orthoses by foot health professionals for the treatment of foot and lower extremity pathologies.1 In addition, over the past 40 years, there has been a literal explosion in the amount, sophistication and quality of foot and lower extremity biomechanics research within the worldwide podiatric, medical and biomechanics literature.

    Due to this ever increasing body of fascinating scientific research by multiple clinical scientific disciplines, it is understandably very difficult for the busy podiatrist to remain abreast of new theories, technologies and therapeutic techniques that are being considered by experts within the scientific discipline of biomechanics. Accordingly, let us take a closer look at the latest available technologies, theories and therapeutic advances within the international biomechanics community in order to facilitate a better understanding of emerging concepts in podiatric biomechanics.

How Modern Technological Advances Have Reinvented Gait Analysis

    Today’s modern foot and lower extremity biomechanics research laboratories have technologies and equipment that researchers from Dr. Root’s early years of investigation could only dream of. These computer-based technologies enable one to precisely determine the forces and moments (i.e. kinetics), and the movement patterns (i.e. kinematics) of the foot and lower extremity during nearly any type of weightbearing activity.

    This knowledge allows clinicians more accurate measurement and more rapid analysis of both the external and internal loading forces that act upon on the structural components of the human locomotor system.5-8

    The time savings for today’s researcher, when compared to the early biomechanics researchers, is probably the most remarkable aspect of this research revolution. For example, when researchers attempted to apply mechanical analysis to gait at the turn of the 20th century, they were limited by the fact that it took over 1,000 hours to process the data generated from a single step.9 Today, we can perform this same analysis, using the technology and computing power available in most modern biomechanics labs, with far more accuracy and it often takes less than a minute to perform.

    The force plate, pressure mat and pressure insole are the main technologies that allow one to determine the kinetics of the foot and lower extremity during weightbearing activities in the modern biomechanics lab and in the clinical setting. The force plate is a rigid plate- type device that can be mounted in the floor of the biomechanics lab. It facilitates the precise determination of the magnitude and three-dimensional location of the ground reaction force vector while the patient stands, walks, runs or performs other activities over the plate.

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