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ndcga66
06-29-2007, 01:50 AM
I have received a wonderful response from the Biomch-L audience. I have asked each of the contributors who had e-mailed directly to me for permission to summarize their responses here. I thank them all for their insights, reference material and ideas and hope this may continue some discussion.



Nancy Denniston

Center for Gait and Movement Analysis

Denver, Colorado



----- Original Message -----

From: "Denniston, Nancy"

To:

Sent: Wednesday, June 27, 2007 12:43 PM

Subject: [BIOMCH-L] Marker sets and gait models





We are exploring other marker sets for walking models that we could use in lieu of our present use of the Helen Hays set-curious to see what some of the other places are using in terms of lower body sets with or without multi-segment foot model, and full body sets. Models that have 6 degrees of freedom as well as those that do not .



Any information on this would be appreciated.

Nancy Denniston









Dr. Harald Böhm writes:

We are using motion analysis for evaluation and optimization of sport equipment. To my experience different movements as well as different motion tracking systems require different marker sets. We are often forced to use our own marker set depending on the systems requirements (Vicon, SIMI, ...) and the motion to be tracked (golf, gait, skiing, ...) . For the typical example of Gait analysis using a Vicon automatic tracking system we would use the following steps to define our own marker set:



1. It is essential to define the anatomical landmarks based on markers (at least during a standing trial) to obtain the joint angles defined by the ISB standardisation e.g. (Grood, E.W., Suntay, W.J., 1983. A joint coordinate system for the clinical description of three-dimensional motions: Applications to the knee. Journal of Biomedical Engineering 105, 97-106). After a standing trial some anatomical landmarks on the medial side must be removed since they will fall off during gait anyways.



2. Vicon requires minimally 3 markers for a rigid segment (foot, shank thigh ...) to track the segment automatically during the motion. The tracking is improved when the markers of one segment are not moving relative to another This is best when the markers are attached to a bony surface e.g. the tibia. More markers are helpful for the tracking and might improve the calculations (Soederkvist, I, Wedin, P.A., 1993. Determining the movements of the skeleton using well-configured markers. Journal of Biomechanics 26, 1473-1477) or (Journal of Biomechanics 34 (2001) 355±361 Correcting for deformation in skin-based marker systems Eugene J. Alexander, Thomas P. Andriacchi). The markers of the left and right side body side must be slightly different otherwise the tracking of the actual left and right side is not reliable. With this approach 6 DOF for all segments are defined.



3. The markers must be visible during gait which depends often on the number of the cameras you are using. This can be done usually only by testing and it is very time consuming. Using a standard marker set from a company usually works well for their product and their specified movement.



Regarding tests of calculations based on marker sets a good collection of methods can be found at: (Journal of Biomechanics 39 (2006) 1778-1786 Determining rigid body transformation parameters from ill-conditioned spatial marker co-ordinates A.B. Carman, P.D. Milburn)



Dr. Harald Böhm

Technical University Munich

Faculty of Sport Science

Department Sport Equipment and Materials



Dr. Patria Hume writes:

I have recently conducted a sabbatical with Benno Nigg and Gweneth DeVries at Uni of Calgary on a LisFranc fracture project. We developed a new multi-segment foot model as part of that project. We are currently finalising papers on the project and the foot model, soon to be submitted for publication and has yet to be reviewed.



Associate Professor Patria Hume

Director, Institute of Sport and Recreation Research NZ
Division of Sport and Recreation, Faculty of Health & Environmental Sciences
AUT University
Auckland, New Zealand



David Carmines writes:

We use the regular Helen Hayes marker set. For the upper body, we only use the C7, T10, CLAV, STRN, SHO, ELB, LWA, LWB, and Fin and not the mid-upper arm or mid-lower arm, except where research requires them. Our skeletons appear with the above minimal set (plus the 4 head markers for the skull - very important in a skeleton!). That saves us time and provides fewer things to go wrong. However, we only use the skeleton for the upper body, and I can't confirm that the rotations and center of mass is correct without all the arm markers.



Dave Carmines

Clinical Engineer

Kluge Children's Rehab. Ctr. - UVA



Alec Black writes

I think the gist of what we are doing is testing other marker sets for clinical evaluation using Visual 3D. Those marker sets include a modified Helen Hayes, the NIH model and the Oxford foot model.



Alec Black

Director, Shriners Gait Lab

Sunny Hill Health Centre for Children

Vancouver, B.C.



Note from Nancy: another site reports using a Cleveland Clinic marker set (full or lower body only) with an AI duPont multisegment foot.








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