Remodeling of Sagittal Plane Malunion After Pediatric Supracondylar Humerus Fractures

Background: Pediatric supracondylar humeral fractures (SCHFs) can heal in hyperextension malunion after casting or surgical treatment. Here the authors present quantitative evidence concerning the ability of children to remodel sagittal plane malunion. Their null hypothesis was that like varus and valgus malunion, children have little capacity to remodel sagittal plane malunion after SCHFs. Methods: The authors performed a prospective longitudinal radiographic study of 41 children, aged 22 to 126 months, who were registered during the study interval. They calculated the percent displacement of the center of the capitellum behind the anterior humeral line (AHL) as the distance of the midpoint of the capitellum from the AHL, divided by the diameter of the capitellum, multiplied by 100. Longitudinal measurements were made using the embedded software on our institution's digital radiographic system. The primary outcome focus was the percent displacement of the center of the capitellum relative to AHL on the initial and on the latest radiograph. Results: The average initial displacement (hyperextension) of the capitellum behind the AHL for all patients was 61% (range, 23% to 134%). At an average follow-up of 21 months, 24 children (60%) had remodeled 100% the sagittal plane malunion, 12 children (30%) had remodeled such that the AHL passed through the central third of the capitellum, and 5 children (10%) had minimal or no remodeling. Conclusions: The authors rejected their null hypothesis. Children do have the capacity to remodel radiographically measurable sagittal plane malunion of SCHFs. Children younger than 5 years of age can remodel 100% displacement of the center of the capitellum, whereas those over 8 years of age have minimal remodeling capacity.