Low-intensity pulsed ultrasound increases bone ingrowth into porous hydroxyapatite ceramic

Synthetic porous ceramic made of hydroxyapatite (HA) has been used as a bone graft substitute. In the present study we investigated whether low-intensity pulsed ultrasound (LIPUS) accelerates bone ingrowth into the pores of HA ceramic. Application of LIPUS did not mechanically weaken porous ceramic that was immersed in water in vitro. In vivo experiments using rabbits showed that LIPUS application for 2 weeks significantly increased osteoblast number and bone area in the central part of the porous HA ceramic implanted in the femoral condyle in comparison with similarly implanted HA ceramic that was not exposed to LIPUS. LIPUS application for 3 weeks significantly increased mineralized tissue volume and mineral content in the porous HA ceramic. Wound healing assays revealed increased migration of MC3T3-E1 cells as a result of LIPUS treatment, partly accounting for the increased osteoblast number. Use of porous HA ceramic combined with LIPUS may be a promising treatment for filling large bone defects in a clinical setting.