The Effect of Bolus Vitamin D3 Supplementation on Distal Radius Fracture Healing: A Randomized Controlled Trial using HR-pQCT

Vitamin D is an important factor in bone metabolism. Animal studies have shown a positive effect of vitamin D3 supplementation on fracture healing, but evidence from clinical trials is inconclusive. A randomized controlled trial was performed to assess the effect of vitamin D3 supplementation on fracture healing using high-resolution peripheral quantitative computed tomography (HR-pQCT) based outcome parameters. Thirty-two postmenopausal women with a conservatively treated distal radius fracture were included within two weeks post-fracture and randomized to a low-dose (N = 10) and a high-dose (N = 11) vitamin D intervention group receiving a 6-week bolus dose, equivalent to 700 and 1,800 IU vitamin D3 supplementation per day respectively, in addition to a control group (N = 11) receiving no supplementation. After the baseline visit 1-2 weeks post-fracture, follow-up visits were scheduled at 3-4, 6-8 and 12 weeks post-fracture. At each visit, HR-pQCT scans of the fractured radius were performed. Cortical and trabecular bone density and microarchitectural parameters and μFEA derived torsion, compression and bending stiffness were assessed. Additionally, serum markers of bone resorption (C-terminal telopeptide of type I collagen; CTX) and bone formation (N-terminal propeptide of type I procollagen; PINP) were measured. Baseline serum levels of 25(OH)D3 were < 50 nmol/L in 33% of all participants and < 75 nmol/L in 70%. Compared to the control group, high-dose vitamin D3 supplementation resulted in a decreased trabecular number (regression coefficient B: -0.22; p < 0.01) and lower compression stiffness (B: -3.63; p < 0.05, together with an increase in the bone resorption marker CTX (B: 0.062; p < 0.05). No statistically significant differences were observed between the control and low-dose intervention group. In conclusion, the bolus equivalent of 700 U/day vitamin D3 supplementation in a Western postmenopausal population does not improve distal radius