HealthManagement, Volume 16 - Issue 3, 2016

Imaging with EOS®

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The Radiologist’s View

The Hospital for Special Surgery (HSS) acquired the ‏EOS ® imaging system because the technology gives ‏us biplanar capability with a single exam, with no distortion ‏in the image and most importantly, it is low-dose. Our ‏orthopaedic surgeons wanted to reduce radiation dose for ‏their patients, particularly the pediatric patients who need ‏repeated x-rays for limb-length discrepancies or for scoliosis. ‏Previously, in order to get a long field of view of the patient, ‏such as the pelvis to the ankles or from the skull to the pelvis, ‏you would have to take two different exposures from the ‏anteroposterior (AP) or frontal view, and another two from ‏the lateral or side view. Both images of each view then had ‏to be digitally stitched together. Sometimes there was poor ‏stitching so you would not get an accurate image length. EOS ® ‏vertically scans the desired length and has the ability to image ‏from head to toe in one exam. Moreover, the system has two ‏detectors and two tubes so you can get both the frontal and ‏lateral views in one shot, greatly reducing the time required ‏for a full exam.


We have a lot of potential users wanting access to this technology
Theodore T. Miller

 

With EOS ®, in addition to getting a longer field of view and ‏simultaneous frontal and lateral acquisitions, we have the ‏ability to image patients in functional positions either standing ‏or sitting. With this, we can see how a patient’s lower limbs ‏(hips, knees) are positioned and aligned when standing and ‏how this changes when seated. We acquired this technology ‏originally for our pediatric patients. It quickly became very ‏popular with orthopaedic surgeons, because they realized how ‏important it was for all patient groups – adults with scoliosis, ‏limb length discrepancies, etc. We have a lot of potential users ‏wanting access to this technology.

 

3D Modelling

 

Once the biplanar images, frontal and lateral, are acquired ‏simultaneously, and since the system is pre-calibrated, the ‏sterEOS workstation can be used to build a personalized 3D ‏model of the patient’s lower limbs or spine. These models ‏are accompanied by automatically calculated 3D measurements ‏of the patient’s anatomy, all from a single pair of lowdose ‏radiographs.

 
Joint Replacement Research

 

We are using this technology for research with Dr. David ‏Mayman on total hip and knee replacements (Carroll et al. ‏2016; Esposito et al. 2016a; 2016b). For example, we want to ‏find out what the anatomy is beforehand, and discover why ‏some patients dislocate following hip surgery. That may be a ‏function of how the pelvis orientation changes between sitting ‏and standing, and EOS ® lets us see this. The relationship of ‏the patient’s spine to their pelvis is something people have ‏been looking at for years, but it’s been difficult to research, ‏especially in 3D, until now with EOS ®. This system gives us ‏that ability to look at the entire spine and the lower extremities ‏from front and side in a single exposure. It allows us to ‏see the relationship between the spine and pelvis changes ‏between standing and sitting, and that’s very important. We ‏were not able to do this very well with conventional x-rays. ‏EOS ® opens up a whole new area not just for patient care, ‏but research as well.

 

Conclusion

 

EOS ® is a tool that is especially adapted to long-axis imaging ‏in weight-bearing, functional positions (standing, sitting), for ‏children (scoliosis, leg lengths) as much as for adults (scoliosis, ‏leg lengths, joint replacement). Scans with EOS ® are ‏quicker and more accurate than doing the traditional radiograph ‏stitching, and the fact that you get a frontal and a ‏lateral view with a single exposure also gives a considerable ‏time advantage. It has improved our patient care and opened ‏up an important area of research.



The Orthopaedic Surgeon’s View


The EOS ® orthopaedic imaging device uses lowdose, ‏biplanar radiographs to capture full body, lower ‏extremity or spine images without stitching or vertical ‏distortion. Furthermore, it provides images in functional ‏positions.

 

EOS ® replaces standard preoperative radiographs, and at ‏the Hospital for Special Surgery (HSS), we have found EOS ® ‏to be extremely accurate in predicting component positioning ‏when compared to computed tomography (CT).

 

I have been using EOS ® for the past two and a half years. ‏I use it for all preoperative templating for total hip and total ‏knee arthroplasty to predict intraoperative implant sizes and ‏component positions. The corrected image magnification ‏results in more accurate templating than traditional radiographs. ‏In the case of total hip arthroplasty, EOS ® is very userfriendly ‏and accurate with excellent inter-observer agreement. ‏


EOS® should become the preoperative imaging standard of care for arthroplasty patients
David J. Mayman

The ability to use hipEOS, the 3D pre-operative surgical planning ‏software, for patients with increased native version has ‏been very helpful. In certain cases, after preoperative planning ‏with hipEOS , I have changed my plan and used different ‏components. The 3D models allow us to gain more knowledge ‏preoperatively to save intraoperative time. This has enabled ‏me to be more efficient in the operating room and decrease ‏the time spent requesting different implant sizes.

 

The technology has changed my practice. I have been able ‏to decrease radiation exposure to my patients and decrease ‏the number of radiographs that are required for surgery.

 

Value of 3D

 

Especially when combined with hipEOS ,3D models can be ‏used to create a patient-specific plan where the surgeon is ‏able to visualize and manipulate various implants. This is not ‏possible with standard radiographs or even 2D EOS images. ‏The 3D models allow us to see rotation of the femur and to ‏identify patients with varying offset and neck anteversion ‏that may change our preoperative planning. Most commonly, ‏patients with arthritic hips stand with their femur externally ‏rotated, which makes it very difficult to template. However, the ‏3D capabilities of hipEOS takes this into account.

 

We can now accurately measure component position in ‏two planes such that we can consider flexion contractures ‏at the knee or pelvic tilt at the hip. Additionally, this allows us ‏to measure implant position in functional positions such as ‏standing and sitting. The ability to evaluate standing/sitting ‏and spine radiographs with one low-dose 2D-3D system ‏provides additional information that will help us determine ‏which patients may be at high risk for dislocation. Absence ‏of variation in pelvic tilt between standing and sitting positions ‏reduces posterior acetabular coverage, which may put ‏patients at higher risk of dislocation in the sitting position. ‏The ability to identify these patients and plan accordingly will ‏provide better patient outcomes.

 

Benefits for Pediatric, Arthroplasty, and Spine Patients

 

The HSS acquired the EOS ® system originally for pediatrics. ‏However, we found it to be extremely useful in arthroplasty, ‏and we acquired two additional units for adult and ‏spine patients.

 

EOS ® has been a valuable tool for our surgical cases and ‏for the patient, it provides an alternative to standard imaging ‏with less radiation exposure. In difficult cases, the 3D model ‏EOS provides us to plan specifics such as leg-length and ‏version that radiographs are unable to do.

 

EOS ® should become the preoperative imaging standard ‏of care for arthroplasty patients to decrease radiation exposure ‏and provide a patient-specific, 3D model of each patient ‏so that their surgery is planned based on their individual ‏anatomy.


References:

Carroll K, Esposito C, ‏Miller T, Lipman J, Padgett ‏DE, Jerabek SA, Mayman ‏DJ (2016) Accuracy of ‏measuring combined anteversion ‏in total hip arthroplasty ‏using EOS(r) Imaging. ‏Orthopaedic Proceedings, ‏98-B (Suppl 7): 129.

 

Esposito CI, Miller TT, Kim ‏HJ, Barlow BT, Wright TM, ‏Padgett DE, Jerabek SA, ‏Mayman DJ (2016a) Does ‏degenerative lumbar spine ‏disease influence femoroacetabular ‏flexion in patients ‏undergoing total hip arthroplasty? ‏Clin Orthop Relat ‏Res, 474(8): 1788-97. doi: ‏10.1007/s11999-016-4787-2.

 

Epub 2016 Mar 28. ‏Esposito C, Miller T, Kim ‏HJ, Mayman DJ, Jerabek ‏SA (2016b) Functional acetabular ‏component position ‏in total hip replacement ‏patients during standing and ‏sitting using EOS Imaging. ‏Orthopaedic Proceedings, ‏98-B (Suppl 1): 126..



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