172 Musculoskeletal Ultrasound to Diagnosis Dislocated Shoulders Study

Abstract

Shoulder dislocations are common, and most practitioners order pre- and post-reduction plain films. There is evidence that point-of-care shoulder ultrasound (SUS) accurately diagnoses shoulder dislocations and humeral fractures. We determined the accuracy and timeliness of a point-of-care SUS from a posterior approach to detect shoulder dislocations and fractures compared with plain radiography. We performed a multi-center, prospective, observational study at 2 academic EDs with fellowship-trained ED ultrasonographers. We included all adult patients presenting to the ED for suspected shoulder dislocation or humerus fracture. The SUS was performed from a posterior approach by an ultrasound-trained physician with a curvilinear or high-frequency linear transducer in the transverse plane. Probe choice was at the discretion of the sonographer. Presence or absence of dislocation was determined by measuring the displacement of the humeral head either anteriorly or posteriorly relative to the glenoid rim. Plain radiographs served as the criterion standard and were interpreted by board-certified radiologists blinded to SUS results. We compared continuous variables between radiographs and SUS using paired t-tests. ROC analysis with Youden’s Index was used to identify displacement cutoffs for diagnosing dislocations. Of 37 subjects enrolled, 21 (57%) were male, 11 (30%) had a history of shoulder dislocation, and 18 (49%) sustained injuries from ground level falls. We excluded 2 subjects who declined radiography. Of 35 included patients, 23 (66%) had shoulder dislocations on radiography and of these, 21 (91%) were correctly diagnosed by SUS. Compared to the criterion standard, SUS had 91% sensitivity (95% CI 70-98%), 100% specificity (70-100%), 100% positive predictive value (PPV) (81-100%), and 86% negative predictive value (NPV) (56-97%). All 12 of 35 patients (34%) without dislocations were correctly identified by SUS. Thirteen of 35 subjects (37%) had fractures, of which 7 (54%) were detected by SUS, and all 22 (63%) without fractures were correctly ruled-out. Five of 6 missed fractures were Hill-Sachs deformities. For detecting fractures as compared to radiography, SUS had a 54% sensitivity (26-80%), 100% specificity (82-100%), 100% PPV (56-100%), and 79% NPV (59-91%). The optimal cut point for displacement distance was 0.875, resulting in 89% sensitivity (64-98%), 100% specificity (68-100%), 100% PPV (76-100%), and 85% NPV (54-97%). The mean time from triage to SUS was 62 minutes versus 100 minutes for radiography (p < 0.001). Sonographers’ confidence in their SUS diagnosis was high. SUS from the posterior approach is a highly accurate method to diagnose shoulder dislocations and humeral fractures. It can be performed faster than radiographs, and sonographers have high confidence levels in their diagnoses. All missed fractures were clinically insignificant, and all patients without dislocations and fractures were correctly identified. SUS should be considered as a routine diagnostic tool for the detection of shoulder dislocation in the ED.