The epic faceplant GIF is the Mom’s apple pie of online culture. Representative of all that the Internet stands for, it is reliable and true blue. Many things will change. You will age. Life will be irrevocably altered. But there will always be some poor soul--or idiot--falling flat on their face, over and over and over.
The Journal of Craniofacial Surgery recently published a clinical study analyzing the forces at work on the face of one such young man. Titled “Video Analysis of the Biomechanics of a Bicycle Accident Resulting in Significant Facial Fractures”, the paper claims to be the first analysis of an actual recorded faceplant trauma. That may be true for bicycle accidents, but it’s not the only time scientists have used video of an impact to understand what happens to the faces involved in that collision. In fact, the most interesting takeaway here isn’t from this paper, itself, but from the window it provides into a scientific field — injury biomechanics, the study of how we hurt ourselves.
First, some background. Thomas Jenkyn is a mechanical engineer at The University of Western Ontario, who works with plastic surgeons from the medical school. Through that connection, he got a hold of a video, showing a young man attempting to ride a bicycle off the shoreline, onto a dock, and off a ramp into a lake. To cross the gap between the shoreline and dock, the young man was supposed to ride along a board “bridge”. But he missed it. Instead, the front wheel of the bike hit the dock’s edge, flipping the bike forward, and plowing the young man’s face into the dock. FAIL, as the kids say.
The good news is that this kid turned out alright. Eventually. He did have a massive facial fracture and had to go to the ER, but he’s okay now, Jenkyn says. His reputation, on the other hand, may never be the same. Although he’s been anonymized here for science, the young man’s faceplant was on YouTube before he’d even made it to the hospital.
When Jenkyn watched the video, though, he saw more than just an example of youthful stupidity. He saw an opportunity to document the biomechanical forces of an accident, as it happens in the real world.
“The body is a structure like any other, it just happens to be alive,” Jenkyn told me. “Forces and pressures get loaded onto it in different ways and if they get too big the body breaks.” Injury biomechanics is the science of how and when those forces break the body. Scientists use cadavers and crash test dummies to test the results of different impacts at different forces. What they learn becomes the basis of designing better safety equipment for the automotive industry, sports teams, and the military. In fact, the father of injury biomechanics was an Air Force flight surgeon named John Stapp.
Shortly after World War II, Stapp began a series of tests aimed at designing ejection seats that wouldn’t hurt the pilots they were meant to save. To understand how the seats were injuring people, Stapp ran experiments on living humans — frequently himself — subjecting them to high speeds followed by sudden stops. Just sitting at the computer, reading this story, you’re experiencing a g-force of 1. On December 10, 1954, Stapp strapped himself into a rocket sled, set a land-speed record, and then set a record for the greatest g-force ever experienced by a human when the brakes kicked in. He broke almost all the capillaries in his eyes, but by surviving 46.2 g’s of force, Stapp proved that pilots could eject from a supersonic aircraft — experiencing the massive deceleration that happens when a not-very-aerodynamic human body hits the relatively slow air after leaving a superfast jet. All they needed was the right safety equipment.
Thomas Jenkyn hoped his video analysis would help injury biomechanics researchers better understand a kind of facial fracture called a Le Fort 2, where the face cracks in a triangle shape from one side of the upper jaw, over the top of the nose, and back down to the other side. While there are very few people who go around riding bikes into docks, that’s not the only way you can end up with a Le Fort 2. It’s the sort of injury that people can get when they go over the handlebars of a bike, Jenkyn said. It’s also an injury that can happen when a face impacts an air bag — better than what might have happened if the face had hit a steering wheel, but still unpleasant. The more scientists understand the force it takes to produce this fracture and what happens to the bone when the fracture happens, the better a job they can do designing bicycle safety equipment and air bags, and advising surgeons on how to fix Le Fort 2 fractures.
Unfortunately, this study doesn’t really do much to help that, according to injury biomechanics engineers Stefan Duma and Joseph Cormier. Duma is the head of the Virginia Tech - Wake Forest University School of Biomedical Engineering and Sciences. Cormier is a researcher with the Biodynamic Research Corporation. Both of them told me that the Jenkyn paper didn’t bring anything new to the table. In fact, they both found some pretty serious flaws. Chief among those problems is the fact that the video Jenkyn and his team use to analyze the accident is really low quality. It’s just a video somebody took on a camera phone, which captured images at 30 frames a second. An impact like the one in the video can be done in as little as 10-20 milliseconds, Cormier told me. The camera’s frame rate was way too slow for the accident it was trying to capture. “In the time it takes to strike platform and be over, you may not record any frames at all. You may totally miss it. And if you do, you're missing important data that you'd need for analysis,” Cormier said.
That flaw means the calculations made from the video can’t be terribly accurate and, contrary to Jenkyn’s goals, they’re unlikely to be more accurate than or to add to the calculations that scientists come up with from laboratory experiments — experiments that are done with the aid of high-speed video and built-in measurement systems that record the forces directly, rather than calculating them indirectly from measurements in a video. What’s more, Duma pointed out, Jenkyn’s analysis relies on a lot of assumptions about variables (how quickly the kid’s face would decelerate when it hit the dock, for instance) that add unknowns to the equation, rather than subtracting them. If you wanted to get accurate measurements based on the video, Duma said, you’d need to go out to the site and reconstruct the accident on the actual dock, using a dummy body. “They're just estimating this stuff from the literature so the model is very crude and not state of the art,” he said. While Jenkyn’s team comes up with an estimate of the impact force being 1910 Newtons and 47.8 Newtons of force necessary to cause the actual fracture, this isn’t any different from what we already knew about these kind of accidents, in general. “If it were written 20 years ago, it would have been interesting,” Duma said.
That’s not to say that there’s no value in video analysis. In fact, both Duma and Cormier pointed me towards the work of Elliot Pellman and David Viano, who use video footage of professional football tackles to better understand the forces that affect players. Those studies use high quality video that captures the actual impact from multiple angles. They also then recreate the impacts with crash test dummies rigged up in elaborate harness systems. One of these studies, published in the journal Neurosurgery in October 2003, was the first to discover that players who suffered head impacts, but didn’t end up with a concussion, were being hit in very different places compared to players who did get concussions.* Their data suggested that there should be more emphasis on enforcing rules that protect players from unexpected tackles from the side or the back — hits that were disproportionately involved in concussions, compared to hits on the front crown of the helmet.
Ultimately, this all boils down to a simple equation: Force = mass x acceleration. How heavy an object is, times how fast that object changes speed becomes the force acting on the object. It’s the job of injury biomechanics researchers to figure out what masses and what kinds of impacts lead to the kind of forces that cause serious injuries. It’s also their job to figure out what force causes what kinds of injuries. Then, they put it all together and figure out how to reduce the force of impact to the point that it doesn’t cause a certain injury. That’s what an airbag is all about — if you lengthen the amount of time it takes a human body to come to a stop in a car accident, then you reduce the force acting on them, and you reduce and change the injuries they suffer. A better football helmet can do that same job. One of the big successes of the last decade in injury biomechanics is a helmet rating system, based on research that showed us the level of acceleration necessary to cause a concussion, Duma said. The better the rating on the helmet, the more it does to reduce that level of acceleration down to something safer.
Video can certainly help scientists as they try to learn this stuff. Good quality video can show us exactly the kind of impacts people experience in the real world. It can answer questions like where concussed football players are actually being hit. But the video, itself, shouldn’t be the end of the story. It’s only useful if it leads to a recreation of the accident, to a more realistic laboratory experiment. Estimated accelerations and estimated mass don’t lead to important changes in safety. It’s the exact measurements that come from lab tests that tell us something really valuable.
(*This particular paper has been widely praised by other researchers in the field. That said, Elliot Pellman lost a lot of his credibility in more recent years because of his support for official NFL positions downplaying concerns about concussions, especially the neurological effects of repeat concussions. It’s best to think of this as some good research produced by a guy who has a bad reputation for interpreting his own research in really problematic ways.)
Photo: Felxitsao CC
Published 7:00 am Thu, May 29, 2014
faceplant, injuries, memes, Science