View Full Version : Marker-set independent gait analysis

07-05-2007, 09:37 PM
I don't usually get entangled in these debates; however, the recent post by
Thomas Greiner really hit the mark and motivated me to chime in.

What I wanted to add is that there is no need to rely on the HH marker set,
or *any* marker set for that matter. It is entirely possible and practical
to obtain functional joint parameters (Hip Center, Knee Center, and
Effective Knee Axis) in a manner that doesn't depend on marker placement
(within reason; markers need to be visible and reasonably well spaced,

We have been doing this at Gillette Children's Specialty Healthcare Center
for Gait and Motion Analysis since Jan 1 2004 on EVERY patient that we see.
That covers over 2000 patient visits and a wide range of ages, diagnoses,
levels of involvement. We use a method developed in our lab (Schwartz &
Rozumalski, J Biomech, 38:107-116, wherein the marker independence is
demonstrated among other things), but there are lots of good functional
methods available (a quick survey of the literature will reveal many
options) and most/all work well if properly implemented.

One thing worth noting is that because the functional methods don't rely on
a specific marker set, they can be run *simultaneously* with any of the
commercial models. This is what we do at our center - we run functional and
PIG models simultaneously. In addition to providing a "second opinion" (the
two models are largely independent) this approach also allows us to acquire
concurrent validity data on the functional method.

Finally, I think it's worth pointing out that the functional approach is
compatible with the kinematic fitting method (championed in this thread by
my esteemed colleague, a great scientist, great humanitarian, and my
dearest, dearest friend for nearly a decade...Richard Baker). Rather than
starting out the kinematic fitter with regression/alignment-jig based
parameters, you can start out with subject-specific functional joint
parameters. You can also use the ROM trials (collected in order to define
the functional parameters) as input for the kinematic fitter.

Michael H. Schwartz, Ph.D.

Director of Bioengineering Research
Gillette Children's Specialty Healthcare

Associate Professor - Orthopaedic Surgery
University of Minnesota

Graduate Faculty - Biomedical Engineering
University of Minnesota