EFFECTS OF SINGLE HIGH-DOSE VITAMIN-D3 ON FRACTURE-HEALING - AN ULTRASTRUCTURAL-STUDY IN HEALTHY GUINEA-PIGS

The benefits of vitamin D3 on fracture healing have been commonly demo nstrated in vitamin-D3-depleted animal models. The aim of this study w as to examine the effects of a single high dose of vitamin D3 on fract ure healing in a healthy animal model, which has not been previously r eported. Twenty healthy young adult guinea pigs were randomly divided into two groups as 'control' and 'vitamin D', and their right tibias w ere fractured with digital manipulation. Guinea pigs in vitamin D grou p were injected intramuscularly with 50000 IU/kg of vitamin D3. The an imals were killed at 7, 14, 21 and 28 days following fracture. Ultrast ructural analysis of the harvested tibias revealed that a single high dose of vitamin D3 stimulated fracture healing. The observed effects a t the fracture zone in a healthy animal model included advancement of blood supply, acceleration of synthesis and organization of collagen f ibres, acceleration of the proliferation and differentiation of osteop rogenitor cells, and activation of the mineralization of the matrix.