IntroductionEOS imaging system is intended for general radiology exams that typically require either standard radiological fi lms or a digital sys-tem (DR, CR). EOS allows acquisition, in a single scan, of the whole body or a specifi c anatomical area of interest. Two orthogonal, ultra low dose X-ray images are acquired simultaneously (AP or PA and lateral). A 3D modeling of the bone envelope can be obtained from these two images using the sterEOS workstation. EOS is a bi-plane radiographic system having the following innovative characteristics:

• Large reduction in radiation dose and a high image quality com-pared to conventional radiology (fi lm, DR, CR) and other tomograph-ic X-ray modalities in an upright position.• A semi-automatic 3D weight-bearing modeling and visualization of the skeletal structures from the two bi-plane images can be readily performed on the sterEOS workstation.

Consequently, the combination of high quality images and the 3D modeling, as well as the ultra low dose, makes it possible for more frequent and complete follow up of the patient. The 3D modeling al-lows for the automatic calculation of new clinical parameters, which are potentially more relevant than the parameters currently being calculated from standard radiographs. The weight-bearing position image makes it possible to obtain all calculations and measure-ments from a functional position.

Clinical Study1.1 Patient HistoryAn 83-year old male presented with gait impairment and standing defi cit, and was examined at Saint Vincent de Paul Hospital in Paris, France. He underwent a full body x-ray with the EOS system and

a 3D modeling of the spine was obtained with the sterEOS work-station. The clinical examination revealed that his symptoms were directly related to progressive spinal deformity.Although his fi rst examination in 2003 showed good balance, knee fl exion in both limbs was an indication of compensation for failing spinal and pelvic balance. At this time, additional investigations were also performed in order to detect possible stenosis in the spi-nal canal. However, no signs of stenosis were identifi ed.Additional caution was necessary with this patient because he was wearing a pacemaker and had also previously undergone GI surgery for digestive disease. As his standing and walking defi cits progressed, a therapeutic option was eventually needed that was compatible with his age and general health status.

1.2 Therapy Planning and OutcomeThe patient underwent another full body exam three years later, us-ing the EOS system that revealed the progression of his deformity. When looking only at the X-ray exams, although a slight change can be detected, it is rather diffi cult to quantify the changes in the pel-vis. It appears as if the pelvis and spinal column moved between 2003 and 2006, but this movement remains diffi cult to assess. When viewing the sterEOS three-dimensional (3D) modeling, how-ever, the changes appear much more obvious. For example, when comparing the 2003 and 2006 3D images (without the brace) a ver-tebral rotation in the thoraco-lumbar area is seen.In order to address the deformity progression problem while mini-mizing additional risks with regard to the patient’s general condi-tion, a brace was recommended. The brace was intended to prevent the further collapse of the spine and retroversion of the pelvis. After being fi tted for his brace, the patient underwent an additional x-ray exam to evaluate the correction provided by the brace.

Clinical Case: Degenerative Scoliosis in the elderlyPr. Jean Dubousset, St. Vincent de Paul Hospital, Paris*

EOS - ultra low dose 2D|3D imaging system

DON’T GUESS. SEE. w w w . e o s - i m a g i n g . c o m

Figure 1.1:2003 X-ray Without Brace

Figure 1.2: 2006 X-ray Without Brace

Figure 1.3: 2006 X-ray With Brace

Figure 1.4: 2007 X-ray With Brace

1.2 Therapy Planning and Outcome (Continued)We can see on the 3D modeling with the brace that the rotation was corrected. Also, changes in the pelvic orientation are visible when observing that the obturator foramen appears “flatter” in the 3D modeling of the patient in the 2006 pre-bracing. This feature change ultimately illustrates a projection angle change, indicating pelvic anteversion which was fixed with the brace as seen in Figure 2.1. Although, this change in pelvic orientation is first noticeable in the frontal view of the 3D modeling, it is more noticeable in the top-down axial view (see figure 2.2).

Looking at the sagittal view of the sterEOS 3D modeling, a clear progression between 2003 and 2006 can be seen in both the pelvic orientation and the degree of spinal kyphosis (see figure 2.3). Also, an anterior shift of the pelvis is seen, which is asso-ciated with a slight pelvic rotation. However, when the patient wears the brace, the pelvis regains its initial orientation.

Below, the sterEOS 3D modeling provided the physician with a rather unique view – the top-down view. This view allows for a better estimation of the deformity and the degree of correc-tion provided by the brace in the axial plane, in upright weight-bearing position. When the top-down view is considered, all

c) d)observations made previously on the sagittal view of the 3D modeling above are further highlighted and confirmed: the 3D location of the obturator foramen demonstrates the pelvic anteversion between 2003 and 2006, which was ultimately corrected by the brace. However, the lateral shift of the spine remained unchanged, despite wearing of the brace. The brace continued to offer further improvement, as seen in the 2007 image series.

1.3 ConclusionIn conclusion, this particular patient benefited greatly by hav-ing his exams performed using EOS. Not only was his physi-cian able to obtain long length, weight-bearing X-ray images, important in observing overall balance and posture, but the various 3D views offered by the sterEOS 3D modeling al-lowed better visualization of the disease. The 3D modeling helped quantify the spinal degeneration of the patient, while also helping the physician confirm the results of his therapy decision. In addition, the top-down view allowed for a better quantification of the benefit obtained in pelvic shift correc-tion attributable to the brace. This view also provided addi-tional information regarding the incomplete correction of the lateral shift of the spine.

EOS imaging SA.10 rue Mercoeur | 75011 Paris France | +33 (0) 155 25 60 60

EOS imaging Inc.185 Alewife Brook Parkway #410 | Cambridge, MA 02138 USA | 678.564.5400

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2003 Without Brace

Lateral CurvatureSmall Vetebral Rotation

2006 Without Brace

Increased Lateral CurvatureVetebral Rotation, L2-L4

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Correction of rotationCorrection of lateral and

anterior imbalance

2007 Without Brace

Increase in rotation, L2-L4Intense Muscular Fatigue and

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Correction of Vetebral rotation, lateral, and

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*Pr. Jean Dubousset is a Professor of pediatric orthopedics and the former head of surgery at Saint Vincent de Paul Hospital in Paris. Pr. Dubousset is best known for co-inventing the “CD”

(Cotrel-Dubousset) instrumentation, that could be applied to several areas of spinal pathology requiring correction and/or stabilization. Pr. Dubousset also identified the unmet clinical

needs of the orthopedic imaging community leading to the eventual physical design of the EOS ultra low dose 2D|3D acquisition system.