Enhanced bone ingrowth into hydroxyapatite with interconnected pores by Electrical Polarization

Hydroxyapatite (HA) ceramics are used as implants to repair damaged/removed bone, and negative or positive electrical polarization enhances osteoblast and decreases osteoclast activity, respectively, in vivo. We compared the ability of electrically polarized and non-polarized HA with interconnected pores (IPHA) implants to promote bone growth. Polarized or non-treated IPHAs were implanted into the right or left femoral condyle of rabbits (N=10 in each group), and we performed histological examination, including enzymatic staining for osteoblasts and osteoclasts, 3 and 6 weeks after implantation. We observed improved bone ingrowth and increased osteoblast activity in polarized implants with complete bone penetration into polarized implants occurring as early as 3 weeks after surgery. In contrast, non-polarized implants were not fully ossified at 6 weeks after surgery. Furthermore, positively charged implant regions had decreased osteoclast activity compared to negatively charged or uncharged regions. We propose two different models to explain these observations.