Hip Int 2014; 24 ( 6): 664-665

DOI: 10.5301/hipint.5000176

LETTER TO the EDITOR

How to measure wear following total hip arthroplasty – EBRA not mentioned! To the Editors, Grillini L. and Affatato S. have published a review article with the title “How to measure wear following total hip arthroplasty” in Hip International (1). The article claims to discuss the most common in vivo and in vitro methods for evaluating the wear of hip prosthesis components. Unfortunately, the authors did not mention neither the work of Ilchmann (2, 3) on this topic nor the EBRA method (4). Ilchmann has compared three different methods to measure acetabular wear with exact results gained by RSA in 1995. EBRA has been shown to be the best of the three methods. Wear can be detected with a threshold of 0.5 mm in plain x-rays. The EBRA method to measure wear has been used in different publications in different regions. The citations below show only a sample of those published (5-9).

Financial Support: None.

Conflict of Interest: Both authors have been involved in the development of EBRA and published papers on it.

Martin Krismer, Rainer Biedermann Department of Orthopaedics, Innsbruk Medical School, Innsbruck - Austria

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Address for correspondence: Martin Krismer niv. Klinik für Orthopädie Anichstrasse 35 6020 Innsbruck, Austria [email protected]

REFERENCES 1.

Grillini L, Affatato S. How to measure wear following total hip arthroplasty. Hip Int. 2013;23(3):233-242. 2. Ilchmann T, Mjöberg B, Wingstrand H. Measurement accuracy in acetabular cup wear. Three retrospective methods compared with Roentgen stereophotogrammetry. J Arthroplasty. 1995;10(5):636-642. 3. Ilchmann T. Radiographic assessment of cup migration and wear after hip replacement. Acta Orthop Scand Suppl. 1997;276:1-26. 4. Krismer M, Bauer R, Tschupik J, Mayrhofer P. EBRA: a method to measure migration of acetabular components. J Biomech. 1995;28(10):1225-1236. 5. Ilchmann T, Gelzer JP, Winter E, Weise K. Acetabular reconstruction with the Burch-Schneider ring: an EBRA analysis of 40 cup revisions. Acta Orthop. 2006;77(1):79-86. 6. Thirion T, Georis P, Gillet P. Migration and wear of the Duraloc “1200 series” cup associated with Enduron UHWMPE using the EBRA method and the Imagika software. Hip Int. 2010;20(2):198-203. 7. Wilkinson JM, Hamer AJ, Stockley I, Eastell R. Polyethylene wear rate and osteolysis: critical threshold versus continuous dose-response relationship. J Orthop Res. 2005;23(3):520-525. 8. Wilkinson JM, Gordon A, Stockley I. Experiences with the Plasmacup—early stability, wear, remodelling, and outcome. Int Orthop. 2003;27(Suppl 1):S16-S19. 9. Wyss T, Kägi P, Mayrhofer P, Nötzli H, Pfluger D, Knahr K. Five-year results of the uncemented RM pressfit cup clinical evaluation and migration measurements by EBRA. J Arthroplasty 2013;28(8):1291-1296.

© 2014 Wichtig Publishing - ISSN 1120-7000

Authors’ response Dear Sir, First of all thank you for your interest in our work. Our work [How to measure wear following total hip arthroplasty] was not a review of all methods used to measure wear, but a discussion of the most common methods used in the last year. I have no doubts that the EBRA method is a validated and a succesfully used procedure in different regions. This method was used in the 1990s and there is no evidence today of an improved accuracy with respect to the other methods used to measure wear in vivo. Wear measurement and characterisation are essential for determining failure mechanisms, prediction of wear and longevity of implants. Measuring wear in the laboratory on retrieved specimens can be done with great accuracy. Radiographic, gravimetric, volumetric and optical techniques are current methods for measuring wear in retrieved implants. Measuring wear in vivo, however, is more challenging.

In our study we wanted to describe the commonly used or basilar techniques, that are the “gold standard” in this field because of their reliability, from which the others were derived. The strict comparison of the techniques was not the focus of the present work. Future work could consider a critical comparison between the techniques, comparing the EBRA method to the so-called “gold standard”. Financial Support: None. Conflict of Interest: None.

Laura Grillini, Saverio Affatato Laboratory of Medical Technology, Rizzoli Orthopaedic Institute, Bologna - Italy Address for correspondence: Saverio Affatato Laboratorio di Tecnologia Medica - Istituto Ortopedico Rizzoli Via di Barbiano, 1/10 40136 Bologna, Italy [email protected]

© 2014 Wichtig Publishing - ISSN 1120-7000

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How to measure wear following total hip arthroplasty - EBRA not mentioned! Letter to the Editor and Authors' response.

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