Published online May 18, 2021. doi: 10.5312/wjo.v12.i5.301
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
Processing time: 123 Days and 3.7 Hours
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.
To compare CSA measurements performed on 3D bony CT reconstructions, with those on corresponding true AP radiographs.
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)].
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°].
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.
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.