And our first presentation is
Chris Dunning will be speaking on

the relationship between skill to limb
position and optimal stability in

a stance controlled need put a focus of
determined by a computer simulation model.

Chris.

There's Gates said I'm Chris Dunning and
I'm going to talk to

you about the relationship between
skull the limb position and

optimal stability for a stance control
kneeing call for a poses as a term and

by computer simulation and I'm going to
go ahead and give the disclaimer that

there's some fairly complex step in the
sim this computer modeling that I'm not

going to have the opportunity to go into
fully just because of time constraints.

So start out with me I go for

the C's are traditionally been used
to treat me extensor pathologies or

felonies involving stabilities and
instabilities of the knee and

traditionally you either have the option
of a lock me joint or a free joint and

these lock me joints tended to
have to cause patients to elicit

different gait deviations to be able
to create a limb during stand space

including circumspection
hip hiking involving So

because of this stance control the ankle
for those years were invented and

these devices have been used to allow for
the flexion during the swing phase of gait

while still maintaining stability
in the stance phase and

this has the benefit of eliminating a lot
of these gait deviations that were seen

prior research has also shown
that these have these or

those have improved joint can
magically increase symmetry.

He creates energy expenditure a better
temporal spatial parameters particular

step one can speed as well as lower or
more normal muscle forces.

So how does stance control Nagel for
those whose work.

The knee joint will release when
the extension moment is president

towards late stance phase and

from here on this presentation I'm going
to refer to this is the trigger point.

I mean most models estimate this
by either estimating a whole or

a shank angle with
relationship to the ground and

determine at that point in time in the
knee joint you're at least a free flexion

but these current settings are either
just kind of recommended by manufacturers

Munt many of them arbitrarily or
just simply linear measurements and

it's a lot of this left up to us as
clinicians as clinical estimations as

a set piece to the correct point in time
and wish to release it in the flexion.

So I want to investigate this a little
bit more and kind of get some scientific

reasoning behind where we allow these or
those used to to release the name and

so my app offices are that a range of
stable trigger points can be found for

this population which would in
relationship to step link and

self selected walking speed and

then by utilizing the minimum force of
collection angle to trigger the flexion

we can maximize the benefits that
we are providing our patients.

So in order to do this as a computer
simulation I utilize the program open

sim and it's a free source
program available free online and

has an online library of all sorts of
kinematic data and information and

buying projects that are used between
members of the biomechanics modeling

community and I use this create
my model that was representative

of gate with a stance control cave.

And so my model seen here
consists of ten ridges segments

with twenty three degrees of freedom
representing the joints and ninety

two actuators representing the muscles
with realistic insertions and origins.

So in order to investigate the stability.

I took.
Input data for

our prior sources using healthy subjects
walking at different speeds and

I started to investigate what
happens at different speeds and

step links as far as doors function
angle goes to trigger the knee.

So each one of these data sets had
to be scaled to fit the model and

then inverse kinematics were
run to take these three D.

marker locations and
turn them into joining us from here.

I ran inverse dynamics which allow
me to find the joint moments and

forces applied within the model and
in order to term the stability I took

the point time that was the knee joint
moment went from being a flexion moment to

an extension moment internal stance and
I recorded the perspective Dorsett

flexion angle the model
a stance control specific gait.

I took inputs which for
this was slightly different.

I took the motion file and investigated
prior research on the subject and

basically made the the need
joint the hip joint angles and

the ankle joint angles all follow
a pattern if that were representative

of a person walking with
a stance control of those of us.

From here.

I was able to run a residual reduction
algorithm which essentially eliminates

we're minimizes the extraneous forces
that should really be present in

the system by slightly changing
the center of mass of the model.

And then I ran a computer muscle control
simulation which basically determines what

actuation is necessary
to drive this movement.

After this step.

I enter the force that Spore set
to take out the actuations for

the unique sensor much richer because our
this patient population typically has weak

it's new extensors and that's why they
need the support of the sort those of us.

And then I was able to run
a four dynamic simulation

to test if at a certain discipline angle.

He was still able to complete the motion.

So if you look here.

These are the words a bunch
of angles with that.

The speed on the left is that
wind on the right at which

this trigger point was appropriate and
in order to maintain

a a safe angle for trying to make
a recommendation I added a one and

a half times safety factor which a lot of
times isn't really done in our field but

it is very typical to medical devices.

I just use it slightly differently
than I Maybe originally planned.

And if you analyze a little
more upper left zones are where

you will be stable angles so that and
the bottom right zones will be unstable

and so what happens if we use a trigger
point that's not actually the most optimal

what's going to result from it and
what I really investigated in my study was

the hip joint moments that are excuse
me Forces of the musculature and

so if you see here that six degrees is
where I started out with angles below

that the simulation either didn't run or
had a completely extraneous

movement that wasn't wasn't what I
was describing the programming and

that represented that something else
was going on something was wrong and

that the system was unstable but
if we look from six degrees on the part or

we get away from six degrees which is the
optimal trigger point for this specific

model the muscle forces tend to go up and
this is representative that that

is the body's having to work hard to be
able to clear the wind during swing phase.

So the overall effect if it's
too small was going to happen.

Basically as represented in
our model failures either

the patients going to a risk of falling or

more commonly withstands control
devices that are out there today.

They have safety mechanisms to
prevent this from happening but

engaging that safety mechanism
on a regular basis has

a high potential of causing
premature wear on the earth osis

a miss to large then as shown here by
are increased muscle forces which.

Most likely will correlate to higher
energy expenditures which is one of

the benefits to be harped on
about states control of the Seas.

We might be maximizing those benefits and

I would like to investigate other
variables although I have not currently So

my conclusions is that I was able to
define a safe course of action range

to trigger these devices that with
regards to step length and speeds.

I was also able to somewhat
validate this by computer model but

there is further work is needed.

This is a simulation.

It's not on real patients.

That's always a big
disclaimer to these and so

I really like to take the next step and
test it on actual patients wearing stands

controlled in the universities and see
the effects it has on other variables for

Mike knowledge meds I think Gary Bedard
first clinical advice boards for lecky for

its current form in the right direction
with my clinical simulations.

I think Mark for offer me a job so I could
spend the last few months focusing on

research assess cramming around and I
think Gibson for his continued support for

basically surviving off trashing her for

the last two weeks at a time
like take any questions.

Yes can

pass neutral.

Yes well

essentially the knee would flex up
representing the collapse of a model of

a I guess the way the four dynamics of run
is that the center of mass is the stable

point and everything else is represented
as force is applied at the foot.

So the center mass stays in one
position while that leg flexes So

that would represent I can.

Laps of the center of mass or
stumble or fall right.

Absolutely.

I think it could be the end it probably
needs to be have there's a lot of

variables much like that that need to be
a counterforce as far as the footwear

that's being worn the heel height of that
how much compression is present in that

head and all these other justice
that are definitely possibilities.

Yes Leave your model.

If you like the girl you
just basically start

rebuilding degree course it's a very
crude estimation of a pathology but

yes there is a bit
recalculate like that all for

me for getting to know if it doesn't but
basically what I

was trying to investigate was if this
motion could still be completed.

If it was inherently stable.

So if the motion could still be completed.

Without these muscles saying and it proved
so for the angles that I predicted before.

OK thank you very much.