HARP line tool

HARP

You will notice in this library that knee angle graphs get disproportionate attention. The reason is that just about every detail of walking that can be functionally benefited is also present in the knee graphs. One ring to rule them all my precious? Not obvious. But, it is all in there. This book is for the geeks but is not opaque. The academic approach is to get a p value of everything - starting with hair, then eyelids which we suppose have poor p values for associated effects on walking – unless they affect vision? Eventually they get to the p-values of toe nails affecting walking. What does that sci-ency method do to help us know what at a minimum a patient needs and what choices have the least scope and risk to satisfy? Not much. Couple that with dated terminology which is, today, really badly misleading. This is why you are here. You might want to read the

footprints in the MUD book first in order to cleanse yourself of the misinformation that current terminology throws at you.

Yes, these books are content redundant. Redundancy & simplicity are at the core of reliability & how we learn languages.

In MUD , we took a broad look at the knee angle graph (minus its erroneous standard deviation envelopes) and acquired a new language of walking. Academics began with footprints in fossilized mud and kind of got stuck in it as well. Strobe methods eventually followed with Muybridge using a battery of sequentially triggered still photo cameras.

to Braune & Fischer (using worn strobe lights) whose flashes were collected on large photoplates in two planes (3D).

Actual stick figures (wooden sticks) were built by B&F from their data as well as advanced maps (eg hysteresis curves) and calculations from cadavers of centers of mass of each body part. Later, widely used was strobe

lighting which made the capture of sequence easier but required other calculation gymnastics to get at reportable data.

Well, not exactly rocket science?

But it was! ==>

[Using high speed film] Also Dr. Dudley of the Smithsonian

Astrophysical Observatory, over the phone, gave us the math to track an object that can't be seen if you know other objects that circle it (hip circled by knee and mid-neck). An advertising firm on the Boston perimeter that did Channel 5 commercials (the 5 image tumbled into view) also helped us to efficiently embed

coordinates (each body part having its own spatial existence). Then there was the Harvard Math vs the MIT engineering dormitories vying for fresh made apple pies to answer new obscure problems . Then came video... and video engineers...

... and shortly after we got ''home' [desktop] computers designed to work with computers... which grew & grew making it fast and easy[er] and part of the clinical exam.

It kept going like that... but … THOSE MUDDY FOOTPRINTS! All this didn't shed the mud! A huge question was “What is midstance?” By time? By progression distance? But what was STANCE and what was SWING (again muddy footprints). How do we relate the x,y,z graphs to the actual thing seen? [ maybe stop here & read the MUD book first]

Y axis is whatever thing is being plotted vs X = time. Mark the time axis with “events” [things seen]. Right heel strike (RHS) etc.. Things seen in the MUD? Mostly.

Yes. MUDDY FOOTPRINTS to make sense of the graph. Here distance of center of mass vs time... The blue line is a computed least distance pathway vs the actual patient data showing an excess of movement. A similar graph of both using side plane 2D is plenty good. In it we see steps as forward travel is in packets of go & stop. These graphs are called STEPPING as is the gait. NICE. But it took hours of work to get that detail which was obvious simply looking at the video. There are no numbers to publish by just looking at video. Without a good 'p' you can't wear a red ribbon at meetings. Mmmmmm.

Looking at our anatomic wheels in the lab, the spokes (long bones) are whatever they are. That leaves pendulum and velocity properties. We can shorten the overall leg length by hyper-flexing the knee and pointing the foot as speed runners do for faster thigh forward flexion. Our main variable is speed which costs energy equally to go faster or slower than the pendulum properties. Speed in a chosen direction gives us velocity – a vector with magnitude and a relationship to the ground as well as to the person. If we consider the whole leg, then the big contribution is knee motion (flexion/extension) as pivoted on the hip center. Leg = H-K-A which typically is tracked as an angle.

However, the distance from hip center to ankle 1. measures what the knee angle is, flexion/extension 2. measures hip flexion/extension 3. measures the effective spatial orientation to the floor 4. scales everything to patient stature 5. measures (in cms, inches, or statures) forward progression 6. measures (in cms, inches, or statures) clearance contribution All this from the same data as knee angle. So we have the hip to ankle line relative to the room... Hip Ankle Relative Positioning. HARP

We will call the longest string of this HARP the Harp Line .

We can imagine smaller harps with one long string or just smaller strings as representing smaller (younger?) statures. The string is always = 1 stature, but stature has a sub value (cms etc.). In many ways this is akin to radian measure except that the harp line is straight and not the wheel's perimeter arc curvature length.

You quickly find yourself looking at an event and asking just what did THAT take to get there? Or, what did that accomplish? Center the video on the key event frame then

the harp function looks forward and backward in time . You can adjust how far and what intervals.

Example: Here's a left midstance. What did the knee do on coming into midstance and then on going out? Did it help or hurt?

Or... here is a left midswing. What did the knee do to help (or hurt)? Pick midswing frame and before & after frames to bracket the span concerned.

All the angles are there, but the harp lines tell us what that did.

Hip, knee and ankle trajectories are likewise tracked and we get to

know what knee flexion did to contribute... or... where it failed. Pick two other start stop frames (green & orange)...We get to see what that portion contributed to win or woe.

Select a vector (orange here) and check it vs the environment. Horizontal progression of both ends and vertical orientation and clearance ( below) and vertical rise above...

HARP can be followed from neck pubis heel in frontal view to dissect if sway is pathologic (against energy) or functional (source of clearance of stiff swing leg.

Harp shoulder, bat grip & bat end? Hand to mouth? Reach to object? It is time for your imagination to take over here.....