A reliable radiographic measurement technique for extra-articular scapular fractures
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BACKGROUND: Currently, neither well-defined nor standardized measurement techniques exist for assessing deformity of extra-articular scapular fractures. To properly evaluate these injuries, compare observations across studies, and make clinical decisions, a validated measurement protocol for evaluating scapular fractures is needed. QUESTIONS/PURPOSES: We describe techniques to quantitatively characterize extra-articular scapular fracture deformity; evaluate the reliability of these characterizations in plain film radiographs and CT scans; and determine potential differences in the characterization of the deformity between the two imaging modalities. PATIENTS AND METHODS: We evaluated injury radiographs and three-dimensional CT images of 45 patients with extra-articular scapular fracture. Techniques for measuring medial/lateral displacement, angulation, translation, glenopolar angle, and glenoid version were established and utilized in two trials, performed 6 weeks apart, by three observers. We determined descriptive statistics for each measurement parameter. RESULTS: Interobserver reliability based upon interclass correlation coefficients ranged from 0.36 to 0.76 for radiographs and from 0.48 to 0.87 for three-dimensional CT. Intraobserver reliability using Pearson r coefficient ranged from 0.60 to 0.75 for radiographs and 0.64 to 0.89 for three-dimensional CT. Both individual and pooled measurements for angulation and glenopolar angle were higher on three-dimensional CT versus radiographs. CONCLUSIONS: Our data suggest three-dimensional CT is more reliable than plain radiography in the assessment of scapula fracture displacement. Therefore, we believe this modality should be utilized if fracture deformity warrants surgical consideration and to adequately compare data across studies. LEVEL OF EVIDENCE: Level IV, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.
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