Supracondylar humerus fractures continue to receive a large amount of attention in the pediatric literature. There remains controversy regarding the pin construct, although most authors prefer lateral entry divergent pinning. There have been numerous biomechanical and clinical studies, but none have assessed pin size on outcome. There authors introduce the concept of “pin size ratio” to control for patient size. The ratio of the diameter of the pin was compared to the humeral mid-shaft cortical thickness. A “large pin” was defined as the ratio less than 1 with the diameter of the pin similar to the thickness of the mid-shaft cortex. A small pin is determined by the reversed ratio.
The authors retrospectively applied this concept to their patients that underwent operative fixation of supracondylar humerus fractures. One hundred and fifty nine patients were included and they carefully looked at coronal and sagittal alignment. The coronal alignment was defined by Baumann’s angle and the sagittal alignment was defined by the anterior humeral line.
Results revealed no statistical difference between the postoperative and final follow-up of Baumann’s angles indicative of maintenance of coronal alignment. In contrast, the maintenance of sagittal alignment was related to the pin size ratio. The anterior humeral line bisected the middle third of the capitellum in 42% of the large pin size ratio group, compared to only 23% of the small pin size ratio group. Therefore, loss of sagittal alignment was more common with smaller pins.
Within the discussion section, the authors compare and contrast their results to previous studies. Despite its retrospective limitations, this study infers larger pins are more likely to control sagittal alignment. This article emphasizes the saying “large pins are for large people, and large pins are for small people.” We prefer to utilize 1.6mm (.062 inch) K-wires in all pediatric elbow fractures.