The acromion in supraspinatus outlet and Rockwood caudal tilt views from three-dimensional computed tomography scan of the shoulder

BACKGROUND: A hooked acromion on an outlet view and a keeled acromion on Rockwood tilt radiographs are associated with rotator cuff tears. The identification of the acromial morphology may be helpful for acromioplasty planning with regarding the acromial types. METHODS: Descriptive Laboratory Study. Three-dimensional computed tomography scans models of 108 shoulders in 91 patients with; (1) Normal shoulders, (2) Shoulders with osteoarthritis, and (3) Irreparable rotator cuff tears; were created and adjusted manually to provide the proper supraspinatus outlet and Rockwood views. The acromial morphology/spurs were analyzed, classified and tested for reliability. RESULTS: The intra-observer reliability of supraspinatus outlet view had a weak-to-strong agreement [0.828 (95%CI: 0.716–0.945, p-value<0.001), and 0.475 (95%CI: 0.288–0.672, p-value<0.001 from 2 evaluators]. The inter-rater of the supraspinatus outlet view has a minimal-to-moderate agreement [0.782 (95%CI: 0.662–0.907, p-value<0.001), and 0.344 (95%CI: 0.157–0.539, p-value<0.001) in the first and second readings]. The intra-observer reliability of the Rockwood view has a moderate-to-almost-perfect agreement [0.752 (95%CI: 0.652–0.860, p-value<0.001), and 0.903 (95%CI: 0.833–0.974, p-value<0.001) from 2 evaluators]. The inter-observer reliability of the Rockwood view has a moderate-to-strong agreement [0.854 (95%CI: 0.777–0.936, p-value<0.001), and 0.737 (95%CI: 0.634–0.847, p-value<0.001) in the first and second readings]. CONCLUSION: The classification of acromion morphology under Three-dimensional computed tomography in the supraspinatus outlet view has poor reliability. The Rockwood caudal tilt view model results in moderate-to-almost-perfect reliability that can be developed to the plain radiographic classification to determine the need for acromioplasty in rotator cuff surgery.