Reliability and Validity of Radiographic Measurement of the Humerus-Elbow-Wrist Angle in Healthy Children

Background: We conducted a retrospective cohort study to evaluate the normal value, range, reliability, and validity of measurement of the humerus-elbow-wrist angle, an index of valgus-varus angulation of the elbow, in healthy children. This measurement has been used to assess postoperative radiographic results. Methods: Radiographs of the elbow in 62 healthy children ranging from 2 to 11 years of age were reviewed by 6 examiners at 2 sessions. The mean value and the reliability of measurement of the humerus-elbow-wrist angle, the carrying angle, and the Baumann angle were assessed. Intraobserver and interobserver reliability were calculated with use of intraclass correlation coefficients (ICCs). To determine concurrent validity, the association between the humerus-elbow-wrist angle and carrying angle measurements was examined with use of Pearson correlation coefficients. Results: The mean humerus-elbow-wrist angle value was 12.0° (range, 1° to 24°), and the mean carrying angle was 14.6° (range, 4° to 28°). The ICCs for intraobserver measurements of the humerus-elbow-wrist angle were almost perfect for 4 examiners and were substantial for 2 examiners, with a mean value of 0.85 (range, 0.73 to 0.94). The ICCs for interobserver reliability with regard to the first and second measurements of the humerus-elbow-wrist angle were both substantial (0.76 and 0.78). A significant association between the humerus-elbow-wrist angle and the carrying angle was observed, with the Pearson correlation coefficients ranging from 0.74 to 0.90 (p < 0.001). Conclusions: Measurement of the humerus-elbow-wrist angle demonstrated good reliability and validity. The humerus-elbow-wrist angle is a reliable radiographic measure of coronal alignment of the humerus and forearm.