Twins are born with their heads joined together and after surgery they look like this!

Meet Aaron and Abby. They’re craniopagus twins, which means they’re joined together by the head. These surgeons successfully separated them, 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,” said Dr. Jesse Taylor, 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 going to walk you through the tools we use to separate conjoined twins,” he added.

Abby and Aaron 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?” Dr. Taylor explained. “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.”

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 Aaron.

“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. Obviously, they were missing twice as much skin and subcutaneous tissue as would be on the top of your head,” Dr. Taylor noted.

“The second thing about the models where 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 ball cap, where that ball 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,” Dr. Heuer explained.

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 bony 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,” Dr. Taylor said.

“We got together with the engineers from DePuy Synthes, which is a subsidiary of Johnson & Johnson, in designing 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,” Dr. Heuer described. “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.”

“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,” Dr. Taylor admitted. “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 inelastic 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. 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 aren’t doing brain surgery—which I guess is most people in the world. What navigation is, is analogous to the GPS in your car. That GPS isn’t the exact location of your car, but it shows you on a map where your car is, it’s a representation. And what that allows is we’re 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,” Dr. Heuer explained.

“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 in,” Dr. Taylor added.

In 2017, the twins were successfully separated after 11 hours in surgery. Abby and Aaron 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, something like that is going to be the ultimate answer to this problem. The morbidity from doing the surgery the way it’s currently done, it really is massive,” Dr. Taylor shared.

“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: 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 quote of our boss, Dr. Adzic: 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,” Dr. Heuer concluded.