[Narrator] Meet Erin and Abby.

They're craniopagus twins,

which means they're joined together by the head.

These surgeons successfully separated then.

So how do they do it?

One of the biggest challenges

with separating conjoined twins

when they're conjoined at the head

is making sure that each brain has sufficient

blood supply to it and sufficient drainage

away from the brain.

And that really becomes, in some ways,

the whole shooting match.

I'm Dr. Jesse Taylor and I'm the chief of plastic surgery

at the Children's Hospital of Philadelphia.

I'm Gregory Heuer.

I'm a pediatric neurosurgeon

at the Children's Hospital of Philadelphia.

We're gonna walk you through the tools we use

to separate conjoined twins.

Abby and Erin are connected like no other twins.

I think one of the hidden innovations

in the approach we took was rather than

just figure out how to separate them,

how do we change how they're connected?

How do we help ourselves before we do the actual separation?

One of the things we were trying to do

is use what we call the biological matrix

to gradually pull the twins apart using force,

instead of just chopping them apart,

which is a grotesque way of saying

what surgeons have done for over 50 years.

[Narrator] The biological matrix is how cells,

blood vessels and tissues work together

to heal the body after an injury.

Using this principle, along with these four tools,

allowed surgeons to separate Abby and Erin.

This is a model of the first CT scan

that we got of the girls as they were conjoined.

And what it showed us is that they were connected by bone

and then the covering of the brain,

and obviously they were missing twice as much skin

and subcutaneous tissue as would be on the top of your head.

The second thing about the models were we could turn them

and look at where those veins came into the head.

One of the major challenges of the surgery

was how we were going to handle a big vein in the head

called the superior sagittal sinus.

And that's a vein that runs down the center of your head.

And most of the blood that goes to your brain

runs through that sagittal sinus and into a part

called the transverse sinus, right?

Sort of where, if you were wearing a bald cap,

where that bald cap would rest in the back.

If you lose your vein in your arm, your arm might swell.

It'll likely have another way for the blood

to come back from your arm.

In the brain, because we're talking about

a closed structure,

if the blood isn't able to come back from the brain,

you'll have a stroke.

[Narrator] Before the twins were separated,

the team used distraction osteogenesis

to further push apart the twins at their connection.

Two unique things about distraction.

One is by slowly pulling bone apart,

the body lays down bone in between.

So it actually is a form of tissue engineering of bone.

Second interesting thing about distraction

is the side effect of boney distraction

is changing the shape of the soft tissues,

brain, blood vessels, dura, skin,

at the same time that you're changing the shape

or configuration of the bone.

We got together with the engineers from DePuy Synthes,

which is a subsidiary of Johnson & Johnson,

and designed these modified helmets

that fit on the tops of each of the two kids' heads.

And then in between the two modified helmets

were a series of three machine screws

that were about a half inch thick.

The device itself, the helmets plus the screws,

weighed maybe two pounds.

And there was a step before we placed

the halo devices on them.

So we created a soft channel all the way around them

to give those devices a bit of a mechanical advantage.

Although we're using things that we normally do in the OR

and sort of adapting and changing them,

this is a product that only fit these twins.

And so it went back and forth

until we could see what was working.

And ultimately the pressure that the screw was placing

on the skulls to pull the skulls apart

exceeded the perfusion pressure of the skin,

which led to skin ulcers.

We ultimately abandoned the distraction device.

After that, we went to a custom...

It really looks very similar to a hose clamp,

and what a hose clamp is is a band that's got notches

so that as you turn a screw on the band,

it decreases the circumference of the band itself.

And that was made out of a very in-elastic rubber

so that there was a bit of give but not much.

The distractors were on for about five weeks.

And then the contraction device was on for about four weeks.

[Narrator] The distractor pulled the twins apart

by 25 millimeters or about an inch.

And the band further constricted their shared space

by about 30 millimeters.

This realigned the twins and helped decrease

the complexity of the surgery.

Navigation system is something we use routinely

for brain tumors.

And for people who are doing brain surgeon,

which I guess is most people in the world,

what navigation is, an analogous to the GPS in your car.

That GPS isn't the exact locations your car is,

but it shows you on a map where your car...

It's a representation.

And what that allows is we then able to put a pointer

and I can see on the screen,

which will be right next to me,

where we are in the brain so that we get

some level of safety as to where we are.

So it never is a stop, see where we are.

It's a constant reassurance during the operation process.

So when we started the operation,

the twins were laying on their sides in one direction.

And we opened that side and we started to dissect

through the brain on that side.

When we got to the place where we thought

we were about halfway through,

we then flipped the twins onto the opposite side

and began operating from that opposite side.

So the surgical navigation, as we would point the wand,

would confirm to us that yes,

we're headed towards that cleavage point

that we had already opened on the other side.

So that was another way that it just allowed us

to kind of confirm that we were going

in the direction we wanted to go.

[Narrator] In 2017, the twins were successfully separated

after 11 hours in surgery.

Abby and Erin were the third set of conjoined twins

that Dr. Taylor and Dr. Heuer have separated.

So if I had a wish, it would be that we could

start our process of changing the connection

between the twins in utero,

where there's immensely more plasticity to the brain

and the soft tissues.

If you could sneak into the womb with some endoscopes

and put a rubber band in between the area of connection,

and that rubber band had just enough force

to not exceed the perfusion pressure of the tissues,

but at the same time, begin to constrict that connectivity.

To me, that's something like that is gonna be

the ultimate answer to this problem.

The morbidity from doing the surgery

the way it's currently done, it really is massive.

If I take one step back,

we're in front of the camera right now,

we're the ones talking about their separation.

There was an army of people.

So an anesthesia team, a great rehab team,

a great nursing team.

Ultimately what we're trying to do

isn't necessarily innovate in surgery.

It's to do better for our patients.

But not for innovation's sake.

We're doing innovation to make kids do better.

So it all comes back to a, a quote of our boss,

Dr. Adzick, If you save a child, you save a lifetime.

And so if you can't get geeked up over fixing newborn babies

and having them doing better after your surgery,

then you're in the wrong business.