Influence of Tilt and Rotation on Coracoclavicular Distance Measurements and Rockwood Classification in Panorama View Radiographs in the Diagnosis of Acromioclavicular Dislocations.

Background: The severity of acromioclavicular (AC) joint dislocation is evaluated through bilateral anterior-posterior radiographs of the AC joint. AC joint dislocations are graded based on the classification system of Rockwood, which is the foundation for further decision-making regarding therapy regimen. Purpose/Hypothesis: The purpose of this study was to simulate technical irregularities in obtaining panoramic views and the effect they might have on the measured coracoclavicular (CC) distance. It was hypothesized that vertical tilt and horizontal rotation of the radiographic panoramic view of the AC joints affect the measured CC distance and, therefore, the Rockwood classification and reliability of the measurement method. Study Design: Level IV, Diagnosis Study, Case Series. Methods: A retrospective analysis including 14 patients with AC joint dislocations and available computed tomography scans of the upper body was conducted. Three-dimensional models of a simulated bilateral panoramic view were tilted and rotated from -15° to 15° in 5° increments around the vertical and horizontal axes. Three raters with different experience levels independently measured the CC distance and repeated this process with a minimum 6-week interval. The intra- and interclass correlation coefficients for intra- and interrater reliability were calculated. Changes in CC distance and Rockwood classification due to rotation or tilt were reported. Results: The measurements of intra- and interclass correlation coefficients in the neutral (0° position) showed a high intra- and interrater reliability (0.878 and 0.952 for intrarater reliability; 0.851 and 0.952 for interrater reliability). By adding vertical tilt and horizontal rotation to simulated panoramic views, the intra- and interreliability of the 3 raters decreased. Vertical tilt showed a higher impact on the measurement reliability than horizontal rotation. In 10 of 14 cases, the initially determined Rockwood classification changed through adding tilt (9/14) or rotation (5/14). In 5 cases, the injury was graded more severe. In 3 cases, the classification was changed to a milder grade according to Rockwood. In 2 cases, the injury was changed to a higher or a lower type in the Rockwood classification, respectively, depending on the amount of tilt or rotation. Of the 10 cases that were reclassified by tilt and rotation, 5 were Rockwood type 3 injuries. Conclusion: Vertical tilt and horizontal rotation in simulated panoramic views of the AC joints were demonstrated to have a significant influence on CC distances and Rockwood classification as well as intra- and interrater reliability. This effect was more pronounced with a higher degree of tilt/rotation. This may affect clinical decision-making, whether to treat this injury nonoperatively or operatively. Clinical Relevance: The panoramic view is widely used as the gold standard for diagnosing and classifying AC joint dislocations according to Rockwood. Thus, it is a decisive criterion to choose the best treatment. This study investigates the reliability of the radiographic diagnosis of AC joint dislocations when adding tilt and rotation, which may occur in clinical practice while obtaining the panoramic view.