Comprehensive Analysis of Pediatric Elbow Radiographic Lines and Angles.

OBJECTIVES: The study aimed to determine relevant radiographic lines and angles of children's elbow.

DESIGN: A retrospective cross-sectional study.

SETTING: Tertiary pediatric trauma center.

PATIENT SELECTION CRITERIA: X-rays of healthy children's elbows 0-18 years of age in whom the radiographic image of the elbow in 2 projections was read without signs of fracture and possible indirect signs of fracture, whereas the exclusion criterion was a clearly visible poor image projection.

OUTCOME MEASURES AND COMPARISONS: Gender, age [patients were divided into 6 groups-group 1 (0-3 years), group 2 (4-6 years), group 3 (7-9 years), group 4 (10-12 years), group 5 (13-15 years), group 6 (16-18 years)], side, intersection of the radiocapitellar line in the anteroposterior (AP) projection, intersection of the radiocapitellar line in the lateral projection, intersection of the anterior humeral line, Baumann angle, carrying angle, lateral capitellohumeral angle, shaft condylar angle, intersection of the coronoid line and radioulnar overlap.

RESULTS: Two hundred elbows were evaluated. The radiocapitellar line in AP and lateral projections passed through the middle third of the capitellum in 74.5% and 93%, respectively. The anterior humeral line passed through the middle third of the capitellum in 88.5% of cases. When observing the proportion of radiocapitellar lines passing through the middle third of the capitellum in the AP, with increasing age an increasing proportion of lines pass through the middle third of the capitellum [from 8.3% in group 1 (0-3 years) to 94.1% in group 6 (16-18 years), P = 0.001] and lateral projection (from 50% in group 1%-100% in group 6, P = 0.023) and anterior humeral line (from 25% in group 1%-100% in group 6, P = 0.0001). The mean Baumman angle, carrying angle, lateral capitellohumeral angle, shaft condylar angle were 71.59 degrees, 10.97 degrees, 50.84 degrees, and 55.31 degrees, respectively. With age, the shaft condylar angle records the greatest increase (from 41.6 degrees in group 1-68.2 degrees in group 6, P = 0.000). A correlation was observed between Baumann angle and carrying angle (r = -0.674) and between Baumann angle and radioulnar overlap (r = 0.542).

CONCLUSIONS: Considering the anatomical variability of children's elbow, radiologic measurements and their interpretation, in the context of timely diagnostics, must be approached with great caution, especially in younger age groups, because it is with them that the largest proportion of lines and angles do not follow established principles.

LEVEL OF EVIDENCE: Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.