The diagnostic value of an upright chest radiograph in diagnosing acromioclavicular joint dislocation.

Introduction: A chest radiograph (CXR), whether supine or upright, is the primary tool for assessing blunt thoracic and abdominal trauma. Thoracic injuries often come with shoulder girdle injuries such as scapular or clavicular fractures, and acromioclavicular joint (ACJ) dislocations. The Zanca view is standard for diagnosing ACJ dislocation. While upright CXR can screen for high-grade ACJ dislocation, its diagnostic value in these cases remains unreported.

Objective: This study aimed to determine the diagnostic value of upright CXR, compared to the standard Zanca view in diagnosing ACJ dislocation.

Methods: Upright CXRs from 70 patients with ACJ dislocation were matched 1:1 by age and gender with 70 control CXRs from individuals with no shoulder disorders. A total of 140 CXRs were randomized and blinded to clinical information, then assessed for coracoclavicular distance (CCD) differences by two independent evaluators. The study compared the diagnostic accuracy of the upright CXR against the Zanca view, the gold standard. Interobserver and intraobserver agreements on ACJ dislocation categorization using upright CXRs were also measured.

Results: There were 55 male and 15 female patients, with an average age of 46 in both cases and controls. In the disease group, the percentage of CCD difference compared to the unaffected side (DCCD) was not statistically significantly different (p value ​= ​0.052) between the upright CXR and Zanca view. The median of DCCD was 121.64 (interquartile range ​= ​69.45, 159.76) and 135.57 (interquartile range ​= ​88.64, 200.18) in upright CXR and Zanca view, respectively. Totally, 140 CXRs, Zanca as the gold standard, the upright CXRs with the definition of an abnormal CCD difference of ≥25%, revealed 95.71% sensitivity, 85.71% specificity, 6.7 of the positive likelihood ratio, and 0.05 of the negative likelihood ratio. The accuracy was 90.71%. The intraobserver reliability was 94.29% agreement and 0.94 of weighted kappa coefficient (95% confidence interval [CI] ​= ​0.89-0.98). The interobserver reliability was 95.7% agreement and 0.95 with a weighted kappa coefficient (95% CI ​= ​0.92-0.99).

Conclusion: Upright CXR is a reliable diagnostic screening tool for ACJ dislocation, particularly for displacements of ≥25%. It provides high sensitivity and specificity compared to the Zanca view, with nearly perfect interobserver and intraobserver reliabilities.

Level Of Evidence: 3: This was a retrospective matched case-control study.