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  • Symmetry index - summary of replies

    At 05:20 PM 2/16/99 , I wrote:
    >We are collecting temporal and spatial measures of gait from elderly
    >people, some of whom are hemiparetic.
    >I am searching for an index of symmetry to apply to these parameters.
    >
    >I recall seeing an argument recently that such an index should be based
    >upon differences between right and left side values, rather than upon a
    >ratio of the two. This made sense, but unfortunately I cannot now find the
    >paper in which I read this.
    >
    >There are a few references in the archives, which I am following up, but I
    >would appreciate any further thoughts on this matter.


    I received a variety of replies, some giving a formula for side-to-side
    symmetry, while others suggested references, a summary of which I have put
    below.

    Many thanks to all who replied - I'm still trying to get hold of some of
    these papers - special thanks to those who emailed copies
    Jane

    First: A summary of the references given:

    Allard, P, Capopozzo A, Lundberg, A, & Vaughan C. (eds) Three-dimensional
    Analysis of Human Locomotion" 1997, John Wiley & Sons pp. 307-334

    Dingwell, J.B., Davis, B.L., and Frazier, D.M., (1996) "Use Of An
    Instrumented Treadmill For Real-Time Gait Symmetry Evaluation And Feedback
    In Normal And Below-Knee Amputee Subjects," Prosthetics And Orthotics
    International, 20: 101-110.

    Giakas G and V Baltzopoulos, (1997). Variability and inter-trial symmetry
    of ground reaction forces during walking using time and frequency domain
    parameters. Gait & Posture 5, 189-197.

    Giakas G, V Baltzopoulos, PH Dangerfield, JC Dorgan and S Dalmira. (1996).
    Comparison of gait patterns between healthy and scoliotic patients using
    time and frequency domain analysis of ground reaction forces. Spine 21(19),
    2235-2242.

    Herzog, W., Nigg, B.M., Read, L.J., and Olsson, E. (1989). Asymmetries in
    Ground Reaction Force Patterns in Normal Human Gait. Medicine and Science
    in Sports and Exercise, 21 (1): 110 - 114.

    Jeng, Holt, Fetters and Certo, (1996). Self-optimization of walking in
    nondisabled children and children with spastic hemiplegic cerebral palsy.
    Journal of Motor Behavior, 28(1), 15-27.

    Kaufman & al. (1996). Gait asymmetry in patients with limb length
    inequality. Journal of Pediatric Orthopaedics 16: 144-150.

    Kulkarni J., Curran B., Ebdon-Parry M., Harrison D., (1995) 'Total contact
    silicone partial foot prostheses for partial foot amputations'. The Foot
    vol.5, pp.32-35.

    Liu & al. (1998). Kinematic and kinetic asymmetry in patients with
    leg-length discrepancy. Journal of Pediatric Orthopaedics 18: 187-189.

    Peham C, Scheidl M, Licka T. A method of signal processing in motion
    analysis of the trotting horse
    J. Biomechanics, Vol. 29, No. 8, pp. 1111-1114, 1996

    Peham C, Licka T, Scheidl M, Girtler D. Supporting forelimb lameness:
    clinical judgement versus computerised symmetry measurement. Equine
    Veterinary Journal, in print


    Here are the replies I received:

    I did some work on gait symmetry in BK amputee patients for my maters
    thesis a few years ago. After looking at the various ways several other
    people had used to quantify asymmetries, we decided on the following
    formula:
    Symmetry Index ("SI") = (Xl - Xr) / (Xl + Xr) * 100%
    where "Xl" and "Xr" are the values of any variable X for the left and right
    sides. This equation resulted in SI values with a continuous linear range
    from -100% to +100%, where 0% denoted perfect symmetry between left and
    right. We modified this from a paper by Herzog et al. (1989) where they
    had used the difference divided by the average, which resulted in a similar
    distribution, with a range of -200% to +200%.
    I have a *.pdf file of the manuscript we published in Prosth. & Orth Intl.
    which I can send you if you would like.
    References:
    Dingwell, J.B., Davis, B.L., and Frazier, D.M., (1996) "Use Of An
    Instrumented Treadmill For Real-Time Gait Symmetry Evaluation And Feedback
    In Normal And Below-Knee Amputee Subjects," Prosthetics And Orthotics
    International, 20:
    101-110.
    Herzog, W., Nigg, B.M., Read, L.J., and Olsson, E. (1989). Asymmetries in
    Ground Reaction Force Patterns in Normal Human Gait. Medicine and Science
    in Sports and Exercise, 21 (1): 110 - 114.
    >--------------------------------------------------------
    ----------------------------------------------------------
    Jonathan Dingwell, Ph.D.
    Postdoctoral Research Associate
    Rehabilitation Institute of Chicago
    345 East Superior, room 1406
    Chicago, Illinois, 60611
    Phone: (312) 908-8738
    FAX: (312) 908-2208
    E-Mail: j-dingwell@nwu.edu
    Web: http://www.smpp.nwu.edu/
    ----------------------------------------------------------
    You might consider calculating the residual difference between the right
    and left data sets as an index of asymmetry. This is the Root Mean Squared
    RMS difference and the RMS value will be directly proportional to the
    degree of asymmetry between right and left sides. I have attached an excel
    file to illustrate the process. I used this method for determining a
    Right-Left asymmetry in the following paper on partial foot prostheses:
    Kulkarni J., Curran B., Ebdon-Parry M., Harrison D., (1995) 'Total contact
    silicone partial foot prostheses for partial foot amputations'. The Foot
    vol.5, pp.32-35.
    Drew Harrison
    Have a hunt for work by Pat Goldie (probably in Archives), she has done
    some work on gait symmetry after stroke but I can't recall if this has been
    published.
    I would suggest that you contact her directly but at present she is away
    from La Trobe University (Australia) on sick leave. She will be back in
    April sometime [P.Goldie@latrobe.edu.au]
    Good luck
    Julie
    Julie Bernhardt, PhD
    Physiotherapy Research Coordinator
    North West Sector
    North Western Health Care
    Melbourne, VIC, Australia

    Malcolm Granat - working at theUniv of Strathclyde carried out work on
    assessing gait in a hemiparertic stroke population. Their work has been
    published and a search should provide you with a possible reference. David
    Dr. Anand.D.Pandyan
    Centre for Rehab. Eng. Studies
    M25-Stephenson Bldg
    University of Newcastle
    Newcastle Upon Tyne
    UK - NE1 7RU

    Tel ++ 44 (0)191 - 222 5434
    Fax ++ 44 (0)191 - 222 8600
    e-mail A.D.Pandyan@ncl.ac.uk
    http://www.ncl.ac.uk/crest/

    We use a symmetry index to evaluate the lameness of horses. I think this
    method is also useful in human motion analysis. We place a marker in the
    symmetry-axis (e. g. head) and than we calculate the Fourier-coefficients
    of the vertical motion. The Fourier-coefficients separate the motion in
    symmetrical and asymmetrical parts. We described this method in:
    "A method of signal processing in motion analysis of the trotting horse"
    C. Peham, M. Scheidl and Theresia Licka J. Biomechanics, Vol. 29, No. 8,
    pp. 1111-1114, 1996

    "Supporting forelimb lameness: clinical judgement versus computerised
    symmetry measurement"
    C. Peham, Theresia Licka, M. Scheidl and D. Girtler Equine Veterinary
    Journal, in print

    This method can be extended to use all three motion direction, but you have
    to take care, because in vertical and horizontal (running direction) the
    fundamental wave and the odd harmonical parts are the asymmetrical part and
    the even harmonical waves are the symmetrical parts of the motion. In the
    transversal motion the fundamental wave represents a symmetrical motion.
    Christian Peham [christian.peham@vu-wien.ac.at]

    I'm using a transformation of right and left kinetic parameters (obtained
    from force plates) into a common differential mode, in clear analogy with
    electronics.
    If p1 were a parameter obtained with the left plate and p2 were the same
    parameter measured with the right plate, the derived parameters would be
    defined as follows:
    p(COM)=(p1+p2)/2
    p(DIF)
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