Acetabular Version Measurement in Total Hip Arthroplasty: the Impact of Inclination and the Value of Multi-Planar CT Reformation

HSS Journal Volume 11, Number 1 February, 2015

Michael Loftus, MD, MBA

Department of Radiology, NewYork-Presbyterian Hospital

Bernard Ghelman, MD
Bernard Ghelman, MD

Attending Radiologist, Hospital for Special Surgery
Associate Attending Radiologist, New York Presbyterian Hospital
Associate Professor of Radiology, Weill Cornell Medical College

Yan Ma, PhD
Yan Ma, PhD

Assistant Scientist, Hospital for Special Surgery

Assistant Professor of Biostatistics, Department of Public Health, Weill Medical College of Cornell University



The orientation of the acetabular cup component of a total hip arthroplasty can be evaluated in a number of ways, utilizing a myriad of imaging techniques and measurement parameters, including intraoperative surgical estimates, postoperative radiographs, and cross-sectional imaging such as computed tomography (CT) and magnetic resonance imaging (MRI).


How do traditional versus corrected measurements of acetabular version vary from one another based on the inclination of the cup? What is the reliability of the corrected acetabular version measurements based on interobserver and intraobserver consistency?

Patients and Methods

Two fellowship-trained musculoskeletal radiologists reviewed CT scans on 60 total hip arthroplasties. Acetabular inclination, traditional CT acetabular version, and CT acetabular version corrected for inclination (by utilizing multi-planar reformations to measure in the plane of the cup face) were each measured. The difference was then calculated between the “traditional” axial CT and “corrected” acetabular version measurements, and the association between this difference and the acetabular inclination was assessed.


The “traditional” axial CT and “corrected” acetabular version measurements differed from one another in every case, with the traditional method yielding a version measurement that was on average 9.5° higher than the corrected technique. However, as the acetabular cup inclination angle decreased, the “traditional” measurement became more variable and increasingly discordant with the “corrected” version measurement.


There is inherent variability between the many methods utilized for defining and measuring acetabular version, with axial CT measurements often used as an accepted proxy for true cup anteversion. However, the variability between different measurement techniques is correlated with acetabular inclination, and this variability is most pronounced when acetabular inclination is low, ultimately leading to potential confusion in measurement terminology. The increasingly widespread availability of multi-planar CT reformations provides an opportunity to standardize methodology, eliminate the impact of inclination on acetabular version measurements, and potentially provide a more reliable comparison of the impact of cup orientation on surgical outcomes.

Level of Evidence: Diagnostic Study, level III.

This article appears in the HSS Journal: Volume 11, Issue 1.
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About the HSS Journal

HSS Journal, an academic peer-reviewed journal published three times a year, February, July and October. The Journal accepts and publishes peer reviewed articles from around the world that contribute to the advancement of the knowledge of musculoskeletal diseases and disorders.


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