Validity of the distance between the anterior humeral line and capitellum as a quantitative measure of supracondylar humeral fracture in children

•The anterior humeral line and capitellum distance (AC distance) indicates correction losses in paediatric supracondylar humeral fractures.•Intra-observer and inter-observer variability values of 0.93 and 0.84, respectively, were calculated for the AC distance.•The AC distance is a more reliable radiographic measure than the Baumann angle and tilting angle.•The change in AC distance was significantly higher after lateral pinning than after crossed pinning. The anterior humeral line (AHL) is a radiographic marker used to quantify anterior-posterior displacement in supracondylar humeral fractures on lateral radiographs. As both the anterior border of the capitellum and the undeveloped ossific nucleus are clearly recognisable on lateral radiographs, we analysed the distance between the AHL and capitellum (AC distance). We hypothesised that the AC distance would provide a highly reproducible and useful index of correction losses in supracondylar humeral fractures. Forty-two patients (mean age: 6.5 years) who had suffered supracondylar humeral fractures were enrolled in this study. The fractures were corrected by cross pinning in 28 patients and by lateral or lateral and posterior pinning in 14 patients. The AC distance, Baumann angle, and tilting angle were measured in radiographs of the supracondylar humeral fractures obtained immediately after surgery and after bone union. Correction losses were calculated and defined as changes in the AC distance, tilting angle, and Baumann angle. We investigated inter-observer and intra-observer variability in all three radiological parameters and also compared these parameters between children who underwent lateral pin fixation and those who underwent crossed pin fixation. An analysis of intra-observer variability yielded values of 0.93, 0.73, and 0.92 for the AC distance, tilting angle, and Baumann angle, respectively. An analysis of inter-observer variability yielded corresponding values of 0.84, 0.46, and 0.79, respectively. Notably, the change in AC distance was significantly smaller in the cross pinning group than in the lateral pinning group. Compared with the Baumann angle and tilting angle, the AC distance was identified as the most reliable method for measuring radiographs. Moreover, smaller correction losses were observed with cross pinning than with lateral pinning. Therefore, the AC distance is a useful and accurate quantitative parameter when analysing supracondylar fractures in children using sagittal plane