Effect of bone sialoprotein coating on progression of bone formation in a femoral defect model in rats

Purpose In orthopedic and trauma surgery, calcium phosphate cement (CPC) scaffolds are widely used as substitute for autologous bone grafts. The purpose of this study was to evaluate bone formation in a femoral condyle defect model in rats after scaffold-coating with bioactive bone sialoprotein (BSP). Our hypothesis was that BSP-coating results in additional bone formation. Methods In 20 Wistar rats, defects of 3.0 mm diameter were drilled into the lateral femoral condyles of both legs. BSP-coated scaffolds or uncoated control scaffolds were implanted into the defects. After 4 and 8 weeks, five rats of each group were euthanized, respectively. µCT scans and histological analyses were performed. The ratio of bone volume–total volume (BV/TV) was analyzed and histological sections were evaluated. Results At week four, bone fraction reached 5.2 ± 1.7% in BSP-coated scaffolds and 4.5 ± 3.2% in the control ( p = 0.06). While bone fraction of the BSP-group did not change much between week four and eight [week eight: 5.4 ± 3.8% ( p = 0.53)], there was a tendency towards an increase in the control [week eight: 7.0 ± 2.2% ( p = 0.08)]. No significant difference in bone fraction were observable between BSP-coated and uncoated scaffolds at week eight ( p = 0.08). Conclusions A significant superiority of BSP-coated scaffolds over uncoated scaffolds could not be proven. However, BSP-coating showed a tendency towards improving bone ingrowth in the scaffolds 4 weeks after implantation. This effect was only short-lived: bone growth in the control scaffolds tended to outpace that of the BSP-group at week eight.