Lower Extremity Above Ankle Fractures Are Associated With Significantly Lower Serum 25-Hydroxyvitamin D Levels and...

Studies on the effect of low serum 25-hydroxyvitamin D level (25OH vit D) on the fracture risk in pediatric patients have had inconsistent results when comparing patients with fractures to healthy controls and patients with upper to lower extremity fractures. Some studies reported that low 25OH vit D was associated with operative treatment of fractures. We decided to compare 25OH vit D between different fracture sites and between fractures treated operatively and nonoperatively. Our primary null hypothesis was that there would not be any differences in 25OH vit D between different sites of fracture. Secondary null hypothesis was that there would be no difference in 25OH vit D between operative and non-operative treatment subgroups.

After IRB approval, we prospectively enrolled pediatric patients with fractures and ordered the lab test for 25OH vit D between October 2021 and April 2025. Inclusion criteria were ages 3 to 18 and upper or lower extremity fractures; exclusion criteria were pathologic fracture, vertebral or pelvic fracture, or patients with metabolic and neuromuscular disorders. Eligible patients were divided into upper extremity (UE), lower extremity above ankle (LEAA), and ankle/foot (AF) fracture groups.

The 25OH vit D in the LEAA group (18.9 ng/mL, n=52) was significantly lower than that in the UE group (25.7 ng/mL, n=64, P <.0001) and that in the AF group (23.7 ng/mL, n=40, P =.0033). Defining vitamin D deficiency as 25OH vit D <20 ng/mL and sufficiency as ≥ 30 ng/mL, the percentage of patients with vitamin D deficiency in LEAA group (58%) was significantly greater than that in the UE (30%) and in the AF (30%) groups. The percentage of patients with 25OH vit D sufficiency in the LEAA group (8%) was significantly less than that in the UE (31%) and in the AF (23%) groups. The overall operative treatment subgroup 25OH vit D (21.4 ng/mL, n=87) was lower than that of the non-operative treatment subgroup (24.7 ng/mL, n=69, P =.02). However, within each group, LEAA, UE, and AF, 25OH vit D in the operative and nonoperative treatment subgroups were not significantly different.

In our study, lower extremity above ankle fractures had significantly lower 25OH vit D, higher incidence of vitamin D deficiency, and lower incidence of vitamin D sufficiency compared with upper extremity or ankle/foot fractures. Comparing operative and non-operative treatment subgroups, 25OH vit D was lower in the overall operative treatment subgroup but within each group, UE, LEAA, and AF, no significant differences were found between the subgroups. One possible explanation for the discrepancy was that a greater percentage of upper extremity fractures with the higher 25OH vit D was treated nonoperatively (58% = 37/64) and a greater percentage of LEAA fractures with the lower 25OH vit D was treated operatively (81%=42/52). Further studies to confirm these findings and to study associations of vitamin D levels with sites of fracture and treatment methods are needed. Our finding that vitamin D deficiency is in ≥30% of pediatric patients with upper and lower extremity fractures would support the recommendation made by other authors to test 25OH vit D in all pediatric fracture patients.

Diagnostic level II-development of diagnostic criteria on basis of consecutive patients.