The Distal Humerus Axial View: Assessment of Displacement in Medial Epicondyle Fractures

Background: The assessment and treatment of childhood medial epicondyle humerus fractures continues to be associated with significant debate. Several studies demonstrate that standard radiographic views are unable to accurately portray the true displacement. Without reliable ways to assess the amount of displacement, how can we debate treatment and outcomes? This study introduces a novel imaging technique for the evaluation of medial epicondyle fractures. Methods: An osteotomy of a cadaveric humerus was performed to simulate a medial epicondyle fracture. Plain radiographs were obtained with the fracture fragment displaced anteriorly in 2-mm increments between 0 and 18 mm. Anteroposterior (AP), internal oblique (IR), lateral (LAT), and distal humerus axial (AXIAL) views were performed. Axial images were obtained by positioning the central ray above the shoulder at 15 to 20 degrees from the long axis of the humerus, centered on the distal humerus. Displacement (mm) was measured by 7 orthopaedic surgeons on digital radiographs. Results: At 10mm displacement, AP views underestimated displacement by 5.5+/-0.6mm and IR views underestimated by 3.8+/-2.1 mm. On LAT views, readers were not able to visualize fragments with < 10mm displacement. Displacement >= 10mm from LAT views was overestimated by 1 reader by up to 4.6mm and underestimated by others by up to 18.0 mm. AXIAL images more closely estimated the true amount of displacement, with a mean 1.5+/-1.1mm error in measurement for < 10mm displacement and a mean 0.8+/-0.7mm error for displacements of Z10 mm. AXIAL measurements correlated strongly with the actual displacement (r=0.998, P< 0.05); AP measurements did not (r= 0.655, P= 0.55). Intraclass correlation coefficient (ICC) was 0.257 for AP and IR measurements; ICC was 0.974 for AXIAL measurements. Conclusions: Standard imaging, consisting of AP, IR, and LAT radiographs, consistently underestimates the actual displacement of medial epicondyle humerus fractures. The newly described AXIAL projection more accurately and reliably demonstrated the true displacement while reducing the need for advanced imaging such as computed tomography. Clinical Relevance: This simple view can be easily obtained at a clinic visit, enhancing the surgeon's ability to determine the true displacement.