Musculoskeletal Ultrasonography to Diagnose Dislocated Shoulders: A Prospective Cohort

Abstract

Study objective: Shoulder dislocations are a common injury leading to emergency department presentations. Point-of-care ultrasonography has the potential to reduce radiation and time to diagnosis. We determine the accuracy of a novel point-of-care ultrasonographic technique to diagnose dislocated shoulders. We also investigate its accuracy to detect fractures, time to image acquisition, the optimal cutoff for the glenohumeral distance, and compare the time to diagnose dislocations from triage between point-of-care ultrasonography and radiography.

Methods: This was a multicenter prospective observational study. Ultrasonography fellows and fellowship-trained physicians enrolled a convenience sample of patients with suspected shoulder dislocation. Point-of-care ultrasonography was performed with a novel posterior approach with either a curvilinear or a linear transducer. Shoulder dislocation was confirmed with a 3-view radiograph interpreted by an independent radiologist. Sensitivity, specificity, positive predictive values, and negative predictive values were determined for point-of-care ultrasonography, with radiography as the criterion standard. Time to image acquisition, presence or absence of fracture, glenohumeral distance, sonographer confidence, and difference in time to diagnosis from triage for point-of-care ultrasonography and radiograph were also determined. A second investigator independently reviewed all images and interobserver agreement was calculated.

Results: Sixty-five patients were enrolled in the study. The sensitivity and specificity of point-of-care ultrasonography for identifying dislocations were 100% (95% confidence interval [CI] 87% to 100%) and 100% (95% CI 87% to 100%), respectively. Point-of-care ultrasonography was 92% sensitive (95% CI 60% to 99.6%) and 100% specific (95% CI 92% to 100%) for non-Hill-Sachs/Bankart's fractures of the humerus. Point-of-care ultrasonography was faster from triage than standard radiology in diagnosing dislocations (median difference 43 minutes; interquartile range [IQR] 23 to 60 minutes). The median total time required for diagnosis by point-of-care ultrasonography was 19 seconds (IQR 10 to 36 seconds). The median glenohumeral distance was -1.83 cm (IQR -1.98 to -1.41 cm) in anterior dislocations, 0.22 cm (IQR 0.10 to 0.35 cm) on nondislocated shoulders, and 3.30 cm (IQR 2.59 to 4.00 cm) in posterior dislocations.

Conclusion: A posterior approach point-of-care ultrasonographic study is a quick and accurate tool to diagnose dislocated shoulders. Ultrasonography was also able to accurately identify humeral fractures and significantly reduce the time to diagnosis from triage compared with standard radiography.