In a message dated 2/23/2004 7:25:04 PM Eastern Standard Time, [log in to unmask] writes:

> If you are not measuring an average over several steps you
> are still working at a subjective level.

Eric and others,

I have been following this discussion from afar as I have been traveling in China on a business trip.  I have avoided joining the discussion as my time has been very limited.  I could not, however, let the above comment pass without a reply.

After reviewing thousands of in-shoe pressure tests over many years (EDG initially and then F-scan), I have come to see that steps are like snow flakes, and none are identical.  Patterns can be discerned, but total reproduceablity simply does not occur.

There is no doubt in my mind that averaging a series of steps would be a major error for intrepreting the information produced by these systems.  Eric, as a strong proponent of pain avoidance, I am quite sure you recognize that if one step is the "pain producer", and the subsequent step the "avoidance response" what would averaging show?  Observing a series of steps (usually 4-6/side)over scan can show STRONG TRENDS in a subjects motion pattern, and be an indicator of the biomechanical response to the particular device prescribed. These systems, however, do not function within a vacuum, and require careful biomechanical assessment to understand any particular patient's problem.

The real advantage is being able to determine the intended effect of both the prescribed intervention as well as any unintended responses.  I have often been surprised by a result that in 9 of 10 subjects causes shortening of heel contact duration, but in the 10th, elongates it.  Having not had this information at the time of treatment initiation would clearly lead to failure.  Knowing (via the test orthotic process)what the real vs. intended outcome is goes a very long way to treatment success.

That said, in an earlier post you commented that 2 eyes are equivalent to multidirectional video analysis.  If that were true, why bother to take more than one x-ray view?  I am often SHOCKED at what I see on video analysis vs. what I saw during a hallway visual exam.  In addition, having recorded the subject's pre-treatment gait, a far more objective review of the post treatment gait becomes possible.  And, if you think you can remember precisely how they walked, you are kidding yourself.  I will regularly go back and forth with pre and post video to review the changes that have occurred to understand how these motions have been altered.  Trying to really remember what happened is very influenced by what you believe you are seeing.

Regards,
Howard

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