Hydroxyapatite as a bone graft substitute: Use in cortical and cancellous bone

Background : Autogenous bone is regarded as the best bone graft material. Various grafting materials have been advocated to fill bony defects. Our purpose was to study the utility of amorphous hydroxyapatite as an autogenous bone graft substitute in cancellous and cortical bone. Methods : A prospective study was undertaken over a period of five years. Patients included were those which would otherwise require bone grafting in cancellous and cortical bone fractures (15 in each group). Hydroxyapatite (HA) ceramic blocks of standard size (5mm x10m) were either used alone or mixed with autogenous cancellous graft in metaphyseal locations, along with bone marrow (derived from reaming or drilling) in intertrochanteric regions and mixed with cancellous graft in cortical areas. The results were assessed on standard radiographs. Biopsy of hydroxyapatite regenerated bone was taken at implant removal. Results: In cancellous areas as graft incorporation ensues over months the intrinsic structure of the hydroxyapatite blocks blurred with blunting of the sharp edges (on radiographs). Biopsy confirmed bone in-growth. In cortical areas the blocks did not show evidence of bone in-growth. Conclusion: Hydroxyapatite alone or when mixed with cancellous bone marrow is an effective adjuvant for autogenous bone grafts, especially in cancellous areas of bone. Mixing it with host marrow provides osteoinductive stimulus. It is biocompatible, osteoconductive but not osteogenic.