Relationship Of The Anterior Humeral Line To The Capitellar Ossific Nucleus From X-rays Of Normal Elbows

ObjectiveThe anterior humeral line(AHL)is commonly used as a valuable radiographic tool in the assessment of pediatric elbow sagittal plane alignment following injury.It is said to pass through the middle third of the capitellum in the elbow of a normal child.However,few studies exist that examine the validity of the AHL,and the intra-rater and inter-rater reliability is not known.The purposes of this study were to discuss the position of the AHL in normal children,report the variability of the AHL,determine the reliability and the repeatability of this parameter.MethodsA total of 493 true lateral elbow radiographs of normal pediatric elbows were retrospectively identified and examined for the relationship of the AHL to the capitellum.Two observers(an orthopaedic resident,and a non-orthopaedic resident)recorded the location of the AHL on two occasions,and identical rulers were used to make the measurements.The percentage of AHLs falling outside the middle third of the capitellum was compared among different age,side and sex groups using Kappa,chi-square tests.ResultsAn average of the two observers of measurements was calculated.The anterior humeral line passed through the middle third of the capitellum in 88%of the elbows,but this is differentbetweenpatientsyoungerthan5yearsand patients older than 5 years in which the AHL fell outside of the middle third of the capitellum(P<0.001).In children younger than two years of age,the line was in the anterior third in 32%of the capitellum.Overall,intra-rater reliability and inter-rater reliability represented substantial agreement.ConclusionThe anterior humeral line passes through the middle third of the capitellum in the majority of normal children.With decreasing age variability increases,so the application of AHL for children’s elbow injury should be analyzed by age.In children less than two years of age,it tends to pass the anterior of the capitellum which means that the AHL is not a reliable tool to evaluate the injury of elbow.Among the children of 3～5 years,it passes more often through the anterior third of the capitellum,whereas in older children it more consistently passes through the middle third of the capitellum.This implies that the AHL as an auxiliary inspection indicator is not reliable or repeatable for these children.A child below 5 with the AHL falling outside the middle 1/3 of the capitellum should be considered to have a potential fracture until it can be proven otherwise.If the AHL does not touch the capitellum of the children over 5,it is appropriate to look for pathology.