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EOS Low-Dose Radiography: A Reliable and Accurate Upright Assessment of Lower-Limb Lengths
Benjamin G. Escott, MBBS1; Bheeshma Ravi, BSc, MD1; Adam C. Weathermon, MASc, MD2; Jay Acharya, MD3; Christopher L. Gordon, PhD4; Paul S. Babyn, MD5; Simon P. Kelley, MBChB, FRCS6; Unni G. Narayanan, MBBS, MSc, FRCS(C)6
1 Division of Orthopaedic Surgery, University of Toronto, 100 College Street, Room 302, Toronto, ON M5G 1L5, Canada
2 Department of Radiology, Faculty of Medicine, University of British Columbia, 3350-950 W 10th Avenue, Vancouver, BC V5Z 4E3, Canada
3 Department of Radiology, Westchester Medical Center, 100 Woods Road, Valhalla, NY 10595
4 Department of Diagnostic Imaging, The Hospital for Sick Children, 555 University Avenue, 2175A, Toronto, ON M5G 1X8, Canada
5 Department of Medical Imaging, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK S7N 0W8, Canada
6 Division of Orthopaedic Surgery, The Hospital for Sick Children, 555 University Avenue, S-107, Toronto, Ontario M5G 1X8, Canada. E-mail address for U.G. Narayanan: unni.narayanan@sickkids.ca
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Investigation performed at The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada

Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. None of the authors, or their institution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

Copyright © 2013 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2013 Dec 04;95(23):e183 1-7. doi: 10.2106/JBJS.L.00989
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Children with lower-limb-length discrepancy require repeated radiographic assessment for monitoring and as a guide for management. The need for accurate assessment of length and alignment is balanced by the need to minimize radiation exposure. We compared the accuracy, reliability, and radiation dose of EOS, a novel low-dose upright biplanar radiographic imaging system, at two different settings, with that of conventional radiographs (teleoroentgenograms) and computed tomography (CT) scanograms, for the assessment of limb length.


A phantom limb in a standardized position was assessed ten times with each of four different imaging modalities (conventional radiographs, CT scanograms, EOS-Slow, EOS-Fast). A radiation dosimeter was placed on the phantom limb, on a portion closest to the radiation source for each modality, in order to measure skin-entrance radiation dose. Standardized measurements of bone lengths were made on each image by consultant orthopaedic surgeons and residents and then were assessed for accuracy and reliability.


The mean absolute difference from the true length of the femur was significantly lower (most accurate) for the EOS-Slow (2.6 mm; 0.5%) and EOS-Fast (3.6 mm; 0.8%) protocols as compared with CT scanograms (6.3 mm; 1.3%) (p < 0.0001), and conventional radiographs (42.2 mm; 8.8%) (p < 0.0001). There was no significant difference in accuracy between the EOS-Slow and EOS-Fast protocols (p = 0.48). The mean radiation dose was significantly lower for the EOS-Fast protocol (0.68 mrad; 95% confidence interval [CI], 0.60 to 0.75 mrad) compared with the EOS-Slow protocol (13.52 mrad; 95% CI, 13.45 to 13.60 mrad) (p < 0.0001), CT scanograms (3.74 mrad; 95% CI, 3.67 to 3.82 mrad) (p < 0.0001), and conventional radiographs (29.01 mrad; 95% CI, 28.94 to 29.09 mrad) (p < 0.0001). Intraclass correlation coefficients showed excellent (>0.90) agreement for conventional radiographs, the EOS-Slow protocol, and the EOS-Fast protocol.


Upright EOS protocols that utilize a faster speed and lower current are more accurate than CT scanograms and conventional radiographs for the assessment of length and also are associated with a significantly lower radiation exposure. In addition, the ability of this technology to obtain images while subjects are standing upright makes this the ideal modality with which to assess limb alignment in the weight-bearing position. This method has the potential to become the new standard for repeated assessment of lower-limb lengths and alignment in growing children.

Clinical Relevance: 

This study assesses the reliability and accuracy of a diagnostic test used for clinical decision-making.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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