EOS Imaging at the University of Minnesota Provides Pathway for Increased Precision and Reduced Radiation in Orthopaedic Surgery
Musculoskeletal deformities have historically been assessed using 2-D imaging, despite the 3-D nature of the conditions. The University of Minnesota Clinics and Surgery Center, as well as Gillette Children’s Specialty Healthcare, have employed an innovative new tool used to create highly precise, low radiation 3-D models of the musculoskeletal system called EOS imaging.
“Using EOS imaging, physicians are able to obtain highly accurate 3-D skeletal models, while also administering very low doses of radiation, making this an ideal technique for individuals who would typically receive multiple x-rays,” said David Polly Jr., MD, professor and spine surgeon at the University of Minnesota.
One study conducted by Spine Deformity found that EOS imaging reduced radiation exposure by roughly 50 percent in comparison to standard spine radiographs.
“The biggest reason to use EOS imaging, of course, would be the lower radiation exposure, which is great for our patients,” said Jonathan Sembrano, MD, an associate professor and spine surgeon at the University of Minnesota.
In addition to the decreased radiation exposure, several studies have found measurements taken from these 3-D models are also more accurate than traditional 2-D images.
“Because EOS utilizes parallel radiation beams, it significantly decreases the parallax error, so you see everything in parallel, and that’s very important when you are measuring alignment,” Sembrano added.
He also noted that EOS imaging takes a much larger field of view and crops it. For billing purposes, this is still considered a lumbar x-ray, although it takes a larger image comparable to a full spinal x-ray. This saves money and resources, and reduces the need for additional x-rays if the originals do not capture all that was intended.
“The field of view is not limited by the size of your plate. Traditionally we’ve had those long or short cassette films, and that’s pretty much the size of the image you get. So, if you have a very tall person, whatever body part you are trying to get an image of may not fit on the plate,” Sembrano explained.
EOS imaging has meaningful applications in subspecialties other than spine, and has been used in limb lengthening and deformity correction, as well as total hip arthroplasty.
“In my specialties of Limb Lengthening and Deformity Correction Surgery and Joint Replacement Surgery, the EOS 3-D reconstruction model has been shown to be just as accurate as a CT scan with 20 times less radiation,” said Mark Dahl, MD, an assistant professor and orthopaedic surgeon at the University of Minnesota and Gillette Children’s Specialty Healthcare.
It has recently been used in preoperative digital templating for total hip replacements, boosting precision in selecting implant size.
“In particularly complex deformities, 3-D models can be made preoperatively, allowing us to simulate and even test the surgical correction,” Dahl explained.
He added that EOS x-rays can also be taken while the patient is standing, rather than supine, increasing the accuracy of findings by showing weight-bearing results.
“A lot of the spinal deformities, like scoliosis for example, are best appreciated on a weight-bearing film. The thing is, if you take an x-ray with a patient laying down, supine, without gravity, the deformity could relax and the spine might straighten out,” Sembrano said.
He added that comparative studies between standing and supine film can give physicians a better understanding of how flexible the spine is when weight is applied. Furthermore, in conditions like spondylolisthesis, which is a form of spinal instability, a diagnosis may be missed when x-rays are taken in the supine position. When an x-ray is taken of the patient standing, the slippage becomes more evident and the diagnosis is clear.
“It is a big injustice to the patient to miss the diagnosis just because you did not take the proper x-ray study,” Sembrano noted.
Although Dr. Sembrano uses EOS imaging for roughly 75 percent of his patients, he says it does have limitations.
“The disadvantage of EOS is that it’s a low radiation, low-resolution image,” Sembrano said.
“So, if you want crisp, very clear images, EOS is not the best for that. For example, a fractured or broken rod that is undisplaced may be picked up more easily by a conventional x-ray than by EOS.”
EOS also requires patients to stand in a small space.
“The biggest requirement for EOS is that you have to get into that small closet space, and you have to be able to stand,” Sembrano explained.
“It’s a standing alignment picture, so people who are non-ambulatory or are too big and can’t get in there, can’t use EOS. So, it does not completely replace everything that we have been able to do with regular x-ray machines, it’s a good adjunct, but it’s not meant as a substitute.”
EOS imaging is the technological result of breakthroughs in radiation detection that resulted in a Nobel Peace Prize in Physics in 1992. Currently, only four healthcare centers in the state of Minnesota use EOS Imaging. Sembrano noticed that overall patients are pleased with the new technology.
“The feedback we have gotten from patients, and this is after they have taken the pictures, they are really impressed. They compare it to a Star Trek holodeck, it’s kind of a futuristic time machine that they went into. So they like it, they obviously cannot compare the images taken with EOS versus non-EOS, but the experience is good for them,” Sembrano said.