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BioMed Research International
Volume 2017, Article ID 3681458, 11 pages
Research Article

Are CT Scans a Satisfactory Substitute for the Follow-Up of RSA Migration Studies of Uncemented Cups? A Comparison of RSA Double Examinations and CT Datasets of 46 Total Hip Arthroplasties

1Department of Surgical and Perioperative Sciences, Umeå University, Umeå, Sweden
2School of Information and Communication Technology, KTH Royal Institute of Technology, Kista, Sweden
3Department of Radiology, New York University School of Medicine, New York, NY, USA
4School of Computing, College of Engineering, University of Utah, Salt Lake City, UT, USA
5Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden

Correspondence should be addressed to Volker Otten; es.umu@netto.reklov

Received 6 August 2016; Revised 18 November 2016; Accepted 12 December 2016; Published 24 January 2017

Academic Editor: Cristiana Corsi

Copyright © 2017 Volker Otten et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


As part of the 14-year follow-up of a prospectively randomized radiostereometry (RSA) study on uncemented cup fixation, two pairs of stereo radiographs and a CT scan of 46 hips were compared. Tantalum beads, inserted during the primary operation, were detected in the CT volume and the stereo radiographs and used to produce datasets of 3D coordinates. The limit of agreement between the combined CT and RSA datasets was calculated in the same way as the precision of the double RSA examination. The precision of RSA corresponding to the 99% confidence interval was 1.36°, 1.36°, and 0.60° for -, -, and -rotation and 0.40, 0.17, and 0.37 mm for -, -, and -translation. The limit of agreement between CT and RSA was 1.51°, 2.17°, and 1.05° for rotation and 0.59, 0.56, and 0.74 mm for translation. The differences between CT and RSA are close to the described normal 99% confidence interval for precision in RSA: 0.3° to 2° for rotation and 0.15 to 0.6 mm for translation. We conclude that measurements using CT and RSA are comparable and that CT can be used for migration studies for longitudinal evaluations of patients with RSA markers.