Vitamin D Status and Fracture Healing: A Systematic Review of 63 Studies

CATEGORY: Other INTRODUCTION/PURPOSE: There is little consensus on the effects of vitamin D on fracture healing. This review aims to clarify that effect in addition to determining trends in the classification of deficiency and supplementation. METHODS: This systematic review searched Pubmed, Embase, and Web of Science for manuscripts related to vitamin D status/deficiency and fracture healing. Two independent reviewers screened articles, graded evidence quality, and extracted data. A total of 38 human studies, 11 in vivo studies and 14 systematic reviews were analyzed. RESULTS: The median vitamin D deficiency prevalence reported amongst the human studies was 41.2% which is comparable to subset of patients with deficiency defined as <20 ng/mL, 43.3%. Amongst the 9 human studies reporting vitamin D supplementation, the exact dosage varied greatly. No RCTs reported any radiographic evidence of increased fracture union with any form of supplementation. Several RCTs reported reduction in pain with smaller daily supplementation compared to placebo or single large boluses. Animal studies reported mixed results, with some showing no significant effects of vitamin D status on the biomechanical properties of bone, while others demonstrated a correlation between supplementation improved biomechanical stiffness. Furthermore, the metabolite 24,25D may be a mediator in Vitamin D's probable osteoprotective effects. CONCLUSION: While the role of vitamin D in fracture healing appears to be osteoprotective in animal models, the degree and significance of its effects on human fracture healing and prevention remains inconclusive. We recommend standardizing the definitions for vitamin D deficiency to be <20 ng/mL for deficiency and >30 ng/mL for sufficiency. Although there is no radiographic evidence, daily smaller doses of vitamin D supplementation seem to have a stronger impact on clinical fracture healing than large boluses.