Reliability of Upright Chest Radiography as a Diagnostic Screening Tool for Acromioclavicular Joint Dislocations

Background: The standard radiographic view for diagnosing acromioclavicular joint (ACJ) dislocations is the Zanca view of both shoulders to assess superior displacement of the distal clavicle by measuring the coracoclavicular distance (CCD) and comparing it with the uninjured shoulder; however, there is no consensus on a gold standard for diagnostic measures to classify acute ACJ injuries. Purpose: To compare the CCD from an upright chest radiograph with a standard Zanca view of both shoulders in patients with an ACJ dislocation. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: We reviewed the records of 70 patients with an ACJ dislocation between 2010 and 2021 who had both an upright chest radiograph and a Zanca view. An ACJ dislocation was classified as low grade (Rockwood types 1-3) or high grade (Rockwood type 5). The CCD was measured on the upright chest radiograph and the Zanca view by 2 independent reviewers, and the percentage of the CCD difference compared with the unaffected side (ΔCCD) was calculated and compared between the upright chest radiograph and the Zanca view. Interrater and intrarater reliability were determined using the intraclass correlation coefficient. Results: Included were 70 patients (55 male and 15 female; mean age, 46 years). There were 29 patients (41.43%) with a low-grade injury and 41 patients (58.57%) with a high-grade injury. In the overall analysis, the ΔCCD on the upright chest radiograph and Zanca view was significantly different (130.25% ± 88.42% vs 152.69% ± 106.56%, respectively; mean difference, 22.44% [95% CI, 2.40% to 42.48%]; P = .029). The subgroup analysis revealed that the ΔCCD on the upright chest radiograph and Zanca view was significantly different for patients with a low-grade injury (60.71% ± 25.79% vs 91.46% ± 68.54%, respectively; mean difference, 30.76% [95% CI, 7.18% to 54.33%]; P = .012) but not different for patients with a high-grade injury (179.45% ± 83.87% vs 196.00% ± 107.97%, respectively; mean difference, 16.56% [95% CI, –14.06% to 47.18%]; P = .281). The intraclass correlation coefficients for the ΔCCD measurements indicated good to excellent interrater and intrarater reliability. Conclusion: The study findings indicated that upright chest radiography can be used as a diagnostic screening tool for high-grade ACJ dislocations, but not for low-grade ACJ injuries, compared with the Zanca view.