HARP

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. Even so, there is a more pressing reason for this choice. The knee angle graphs is generally seen as what the knee is doing. ?? What THE KNEE is DOING? Knee is doing he doing? Brace yourself, here it comes… The knee is NOT DOING nearly EVERYTHING it “is doing”. At nearly every segment along that graph we see what momentum, inertia, energy from toes, feet, ankles braces, and hips are doing TO the knee which is accommodating all of it! It isn’t a graph of a knee DOING but rather a knee accepting what is being done through it from all directions near and far. It is a window to the complex interactions that ALLOW eccentric control to exist. If eccentric accomodation is cut off, then concentric (brute force) takes over. [Read the Range vs Resist book]. In it we see when and from where things go astray in timing and degree. We see hip and ankle FUNCTIONAL contributions better than in their own scientificy looking graphs with cute ‘normal’ envelopes.

This book is for the geeks but is not opaque.

The awful 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. Also some technical documenting of the evolution of our methodology might help fend off some of the mud slung this way. Yes, these books are content redundant. Redundancy & simplicity are at the core of reliability & how we learn languages, in this case the language of walking.

Muybridge In MUD , we took a broad look at the knee angle graph (minus its erroneous standard deviation envelopes) and developed 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. Braune & Fischer

Soon after, 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 laborously hand calculated data as well as advanced maps (eg hysteresis curves) and calculations also measurements taken 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] Dr. Sutherland worked with our trying to

catch up (to Sputnik) rocketeers using the Vanguard (above) film exam device which had 2 wheels like an Etch-a-Sketch that displayed, mechanically, X & Y of the Vanguard built in cross hairs (2 wires). Those were pencil copied and unknowingly the engineers redid what Braun & Fischer had done so long before – math wise but without the big worn flashing contraption (making clinical use impossible). Dr Sutherland, in California, worked with these measurements on films taken of kids with cerebral palsy (and other stuff as well, of course). Now we had ball park numerics of expectation for commonly seen pathologies. Now begins scientific speculation and proposing with numeric tags that can support or refute hypotheses (hypotheses without numerics is called WAG). Sometimes WAG works, but you don’t know it for sure.

But, again, broad useage clinically was not usefully feasible with calculations from tediously etch-a-sketched-like 2 knobs twisting taking weeks to get a data set. It WAS a start. RERC, in Boston,

(MIT/Harvard) rebuilt the Vanguard setting the hand cranked knobs aside, and applying two sound sensors (like long skinny microphones) along th sides of the viewing area.

The mouse-like device let off a squeek (ultrasonic) and the time lag to each microphone was numerically a screen X & Y which was sent in ‘octal’ base form which was easy to feed directly to the computer. In a sense the computer could squeek and know where this mouse looking probe was (had cross hairs in it). No more pencils. Film still needed processing but that could be done quite fast as x ray processors could already easily do it .. a sightly modified dedicated film processor had squeeking x,y octal data quick to follow feeding the computer. 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 .

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). Whoever contributed a solution to a lingering problem got a fresh baked apple pie (or two or three…)! The computer, itself had a fatal flaw… in gobbeling and computing all that possible data.. [later] Still this was film.

Then came video... and video engineers… We built a control stick crosshair that wandered in the LIVE video as well as in freeze frames.

Things are moving fast now …..

ooooooo… replace real time mainframe super computer with a … .. a ..

DESKTOP COMPUTER ... and shortly after we got ''home' [desktop] computers designed to work with video ... live video or playback...

which grew & grew making it fast and easy[er] and part of the clinical exam. An office tool that allowed VISUAL sequences ( as with Muybridge) and what if idea testing in office visits.

It kept going like that... but … THOSE MUDDY FOOTPRINTS! All this didn't shed the mud! Approved terminology was an anchor. 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. But a grimace could be an event.

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 taking 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 Line vs knee angle (measure same thing?)

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.

Adding 10 degrees of knee flexion may or may not clear the foot over an pbstacle. That depends on the orientation of the entire leg to the ground. In one orientation most of the angular change is in the vertical direction. However, in a different orientation the same knee angular chane may contribute close to nothing in the vertical direction. So a seething dog bites your sorry a__, or not, depending on the height of that fence, your speed, and whether the knee angle attained was in a best orientation to help clear the fence.

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.....