Background: Angular deformity is the most common complication of supracondylar humerus fracture. Baumann's angle (BA) is an established radiographic measure of coronal plane deformity after this injury. Numerous radiographic methods have been used to assess sagittal plane deformity, however, the mean, variability, and reliability of these measures has not been established. The purpose of this study was to determine the mean, SD, and intraobserver/interobserver reliability of the lateral capitellohumeral angle (LCHA) in children without evidence of fracture and compare them with those of BA.
Methods: Seventy-one sets of anteroposterior and lateral elbow radiographs were selected and stratified into 6-year age categories with equal number of males and females in each category. Five physicians performed 3 separate measurements of LCHA and BA on each film set. Statistical calculations were performed to determine mean, SD, measurement reliability, and differences between patients groups.
Results: The mean LCHA ±1 SD and BA ± 1 SD measurements were 50.8 ± 6 degrees and 71.5 ± 6.2 degrees, respectively, and did not vary significantly by age, side, or sex (P>0.05). The LCHA showed good intraobserver (correlation coefficient 0.67) and fair interobserver (0.37) reliability, whereas BA showed excellent intraobserver (0.86) and interobserver (0.80) reliability. The expected SD for repeated measurement of a radiograph by a single observer was 2.6 degrees for BA and 5.2 degrees for LCHA.
Conclusions: The LCHA is a simple measurement to perform using digital tools. In normal elbows, the mean angle is 51 ± 6 degrees and does not vary by age, side, or sex. LCHA variability in normal elbow radiographs is similar to BA. Its reliability is inferior to BA, but improves with age. Sagittal angulation abnormality of at least 12 degrees (<39 or >63 degrees) is necessary to be confident that the change is not because of measurement error alone. Further research is needed to better define the relationship of sagittal plane angular deformity to clinical outcome.
Level of evidence: Diagnostic study with poor reference standard, Level IV.