Levels of free thyroxine are higher in displaced pediatric supracondylar humerus fractures compared with non‑displaced fractures.

Relationships between bone metabolic biomarkers and fracture displacement have been reported in the elderly. However, factors related to bone metabolism that predict fracture displacement remain unclear in children. The present study investigated bone metabolic biomarkers associated with the displacement of pediatric supracondylar humerus fractures. A total of 19 patients (7 male and 12 female patients; mean age, 6.3 years) with pediatric supracondylar humerus fractures who underwent surgical treatment at Juntendo University Hospital (Tokyo, Japan) between December 2020 and September 2022 were included. They were divided into two groups according to the Gartland classification: 14 type II patients (6 male and 8 female patients; mean age, 6.3±3.0 years) and 5 type III patients (1 male and 4 female patients; mean age, 6.4±4.0 years). The following bone metabolic biomarkers were examined: 25-hydroxyvitamin D [25(OH)D], intact parathyroid hormone (iPTH), calcium, phosphate, thyroid-stimulating hormone, free triiodothyronine and free thyroxine (FT4). These markers were also compared between the two groups. A total of 16 out of 19 patients (84%) had insufficient serum 25(OH)D levels. Although iPTH levels were elevated, other bone metabolic biomarkers were within normal ranges. When the serum levels of bone metabolic biomarkers were compared, FT4 levels were significantly higher in type III patients than in type II patients (P=0.009). No significant differences were observed in other bone metabolic biomarkers between the two groups. The present results suggest that high FT4 levels are associated with the displacement of pediatric supracondylar humerus fractures.