Retrospective Study
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. May 18, 2021; 12(5): 301-309
Published online May 18, 2021. doi: 10.5312/wjo.v12.i5.301
Usefulness of computed tomography based three-dimensional reconstructions to assess the critical shoulder angle
Dominic Mah, Uphar Chamoli, Geoffrey CS Smith
Dominic Mah, Faculty of Medicine, University of New South Wales, Sydney 2052, New South Wales, Australia
Uphar Chamoli, Spine Service Research Group, St. George and Sutherland Clinical School, University of New South Wales, Sydney 2052, New South Wales, Australia
Uphar Chamoli, School of Biomedical Engineering, University of Technology Sydney, Sydney 2007, New South Wales, Australia
Geoffrey CS Smith, St. George and Sutherland Clinical School, Faculty of Medicine, University of New South Wales, Sydney 2217, New South Wales, Australia
Geoffrey CS Smith, Department of Orthopaedics, St. George Hospital, Sydney 2217, New South Wales, Australia
Author contributions: Mah D designed and performed the research, and wrote the paper; Chamoli U designed the research, and contributed to the analysis; Smith GCS designed and performed the research, and supervised the report.
Institutional review board statement: This study was reviewed and approved by the Ethics Committee of the University of New South Wales.
Informed consent statement: The private patients of Dr Geoffrey Smith sign a consent form for their deidentified radiographic imaging data and intra-operative images to be used for teaching, medical education and research purposes (including computer modelling).
Conflict-of-interest statement: We have no financial relationships to disclose.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Geoffrey CS Smith, FRCS, MBChB, Surgeon, St. George and Sutherland Clinical School, Faculty of Medicine, University of New South Wales, Sydney 2217, New South Wales, Australia. gcssmith@icloud.com
Received: January 9, 2021
Peer-review started: January 9, 2021
First decision: January 18, 2021
Revised: January 28, 2021
Accepted: March 8, 2021
Article in press: March 8, 2021
Published online: May 18, 2021
Abstract
BACKGROUND

The critical shoulder angle (CSA) is a radiographic measurement that provides an assessment of both glenoid inclination and acromial length. Higher values may correlate with the presence of rotator cuff tears. However, it is difficult to obtain a high-quality true anteroposterior (AP) radiograph of the shoulder, with any excess scapular version or flexion/extension resulting in deviation from the true CSA value. Three-dimensional (3D) bony reconstructions of computed tomography (CT) shoulder scans may be able to be rotated to obtain a similar view to that of true AP radiographs.

AIM

To compare CSA measurements performed on 3D bony CT reconstructions, with those on corresponding true AP radiographs.

METHODS

CT shoulder scans were matched with true AP radiographs that were classified as either Suter-Henninger type A or C quality. 3D bony reconstructions were segmented from the CT scans, and rotated to replicate an ideal true AP view. Two observers performed CSA measurements using both CT and radiographic images. Measurements were repeated after a one week interval. Reliability was assessed using intraclass correlation coefficients (ICCs) and Bland-Altman plots [bias, limits of agreement (LOA)].

RESULTS

Twenty CT shoulder scans were matched. The mean CSA values were 32.55° (± 4.26°) with radiographs and 29.82° (± 3.49°) with the CT-based method [mean difference 2.73° (± 2.86°); P < 0.001; bias +2.73°; LOA -2.17° to +7.63°]. There was a strong correlation between the two methods (r = 0.748; P < 0.001). Intra-observer reliability was similar, but the best intra-observer values were achieved by the most experienced observer using the CT-based method [ICC: 0.983 (0.958-0.993); bias +0.03°, LOA -1.28° to +1.34°]. Inter-observer reliability was better with the CT-based method [ICC: 0.897 (0.758-0.958), bias +0.24°, LOA -2.93° to +3.41°].

CONCLUSION

The described CT-based method may be a suitable alternative for critical shoulder angle measurement, as it overcomes the difficulty in obtaining a true AP radiographic view.

Keywords: Critical shoulder angle, Computed tomography, Osteoarthritis, Rotator cuff tear, Acromioplasty, Arthroscopic lateral acromial resection

Core Tip: The critical shoulder angle (CSA) is a radiographic measure which correlates with the presence of rotator cuff tears. However, it is difficult to obtain high-quality true anteroposterior radiographs that are suitable for CSA measurements. Three-dimensional bony reconstructions may be produced from computed tomography shoulder scans and be rotated to replicate a more ideal true anteroposterior view, and hence obtain a more accurate CSA measurement. This retrospective study demonstrated its improved intra-observer and inter-observer reliability, compared to the standard radiographic method.