Novel nano‐hydroxyapatite coating of additively manufactured three‐dimensional porous implants improves bone ingrowth and initial fixation

Electron beam melting (EBM) has been used to fabricate three‐dimensional (3D) porous Ti‐6Al‐4V surfaces for acetabular cups in total hip arthroplasty. However, there are radiographic concerns regarding poor implant fixation and bone ingrowth around electron beam melted (EBMed) 3D porous cups. We hypothesize that nano‐hydroxyapatite (nHA) coating can promote bone ingrowth and thus decrease the occurrence of radiolucent lines around EBMed 3D porous cups. This study aimed to investigate the effect of a novel nHA coating on the biological performance of EBMed 3D porous implants in a beagle transcortical model. Low‐porosity (control) and high‐porosity 3D porous Ti‐6Al‐4V implants were manufactured using EBM. Half of the high‐porosity implants were coated with nHA without clogging the 3D pores. Implants were inserted into the femoral diaphysis of the beagles. The beagles were euthanized at 4, 8, and 12 weeks postoperatively, and push‐out testing was performed. Bone ingrowth was evaluated by histological analysis. Although the increase in porosity alone had no effect on biological behavior, the addition of nHA to high‐porosity 3D implants significantly improved early bone fixation and bone ingrowth into the deep region of porous structures compared to low‐porosity implants. This is the first report of a novel nHA coating that improved bone ingrowth into the deeper regions of 3D porous implants, which can prevent the occurrence of radiolucent lines around EBMed 3D porous cups.