Repair of rabbit femoral head necrosis by release of alendronate and growth differentiation factor-5 from injectable alginate/calcium phosphate carriers

Osteonecrosis of the femoral head (ONFH) is a common disease with limited options of treatment. In this study, we prepared self-setting nano-sized hydroxyapatite carriers incorporating microspheres for controlled release of growth differentiation factor-5 (GDF-5) and/or alendronate (ALN). GDF-5 release enhanced the proliferation of rabbit bone mesenchymal stem cells (BMSCs), and ALN release inhibited the proliferation of macrophages. A rabbit ONFH model was created by liquid nitrogen infusion, and the carriers were implanted into the channelshaped defects and harvested at 12 weeks. Imaging examination and histological analyses found that all carriers increased new bone formation in the defects, with the group simultaneously incorporating GDF-5 and ALN yielding the greatest improvement. The synergistic release of ALN and GDF-5 from the carrier may offer a promising option for the treatment of ONFH after surgical decompression.