Weighted or internal rotation radiographs are not useful in the classification of acromioclavicular joint dislocations

Background: Weighted radiographs are performed to classify acromioclavicular joint dislocations; however, the evidence regarding their usefulness is conflicting. Laboratory studies suggest that internal rotation views can replace weighted radiographs, but this has not been clinically evaluated. Purpose: To evaluate whether weighted or internal rotation radiographs uncovers more high-grade acromioclavicular joint dislocations than non-weighted radiographs. Material and Methods: A total of 162 patients with acromioclavicular joint dislocations were prospectively included. After applying exclusion criteria, 140 remained. Three panorama radiographs, including both coracoclavicular intervals, were completed of each participant: first, a weighted radiograph with 5-kg weights suspended from the wrists; second, a non-weighted radiograph; and third, an internal rotation radiograph. The coracoclavicular intervals were measured by two radiologists independently, and measurements were translated into Rockwood classifications. The classifications and measurements derived from the different radiographic views were compared. Results: Weighted radiographs caused no significant changes in classification. For the internal rotation views, there was a significant change in classification for radiologist 2; however, the reason was that more injuries were downgraded compared to the non-weighted views. Relative to the non-weighted radiographs, the mean increase of the coracoclavicular interval on the injured side in the weighted view was 0.5 mm (95% confidence interval [CI] 0.37–0.65) and in the internal rotation view 0.2 mm (95% CI 0.04–0.33). While these changes were statistically significant, they were small and not clinically important. Conclusion: This study does not support the use of weighted and internal rotation radiographs in the classification of acromioclavicular joint dislocations