Background: Plain radiographs still play a role in management of extraarticular scapular neck fractures. Glenopolar angle (GPA) is one of the radiograph measurements that is used to determine the necessity for surgery. Our aim was to establish reliability of GPA on plain radiograph in patients with extraarticular scapular neck fractures.
Methods: We performed a multicentre retrospective study including all patients with extraarticular scapular neck fractures with available imaging between 2006 and 2012. We excluded intra-articular glenoid fractures, scapular blade fractures, acromion fractures, and scapular spine fractures. We compared GPA on plain radiograph with three dimensional computed tomography (3D CT) measurement, as well as contribution of radiograph rotational error, glenoid inclination, and medial shortening of glenoid fragment towards GPA measurement.
Results: One hundred patients met the inclusion criteria. The mean difference between the GPA measurements on radiographs and 3D CT was 6.1±0.85° (95% confidence interval) as an absolute value. In terms of contribution to GPA values, GPA changed by one degree with ten degrees of radiograph rotational error, three degrees of glenoid inclination, and three millimetres of glenoid fragment medial shortening.
Conclusion: Plain radiograph can provide a clinician with a reasonable estimation of the GPA. Glenoid inclination has a greater influence on GPA compared to medial shortening.
Keywords: 3D CT; GPA; Glenopolar angle; Scapula; Scapular neck; Scapular neck fracture; Shoulder fracture.
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