Inter- and intra-observer reliability of the Baumann angle of the humerus in children with supracondylar humeral fractures

The Baumann angle of the humerus has been commonly used as an outcome measure for supracondylar fractures in children. However, there is limited or no information about the reliability of this measurement. The purpose of this study was to determine the inter-observer reliability (IEOR) and intra-observer reliability (IAOR) of the Baumann angle of the humerus. The Baumann angle of the humerus was measured by five observers on the anteroposterior radiographs of 35 children’s elbows, all of which had sustained a nondisplaced supracondylar humeral fracture. The values of IEOR and IAOR were calculated using a Pearson coefficient of correlation. Ranges of differences in the measurement of the Baumann angle of the humerus were established, and the percentage of agreement between observers was then calculated using those ranges. The Baumann angle of the humerus is a simple, repeatable and reliable measurement that can be used for the determination of the outcome of supracondylar humeral fractures in the paediatric population. An excellent IEOR was found for the measurement of the Baumann angle (r = 0.78, p = 0.0001). When the difference between observers in the reported measurement of the Baumann’s angle was calculated to be within seven degrees of each other, at least four of the five observers agreed 100% of the time. Similarly, excellent values of IAOR were found for the measurement of the Baumann’s angle (r = 0.80, p = 0.0001). Level of evidence for this study was III.