Effects of surface modification and nanometer material on bone-prosthesis osseointegration in osteoporosis models

Abstract

BACKGROUND: Hydroxyapatite (HA) coating can improve the initial and mid-term fixation of prosthesis. However, its long-term stabilization is unsatisfactory. A large number of studies report that nano-HA coating and surface modification of prosthesis can improve the osteointegration at prosthesis-bone interface. Yet, comparative study on osteointegration of nano-materials and surface modification has not been reported. OBJECTIVE: To compare effects of nano-materials and surface modification on osteointegration in osteoporosis (OP) model. DESIGN, TIME AND SETTING: A randomized control experiment was performed in the Animal Experimental Centre of Sun Yat-sun University from September to December 2007 and Histomorphometry Laboratory of the Hong Kong University from March to May 2008, respectively. MATERIALS: Porous HA-coating and surface modified nanometer prostheses sized 3 mm x 3 mm were provided by Department of Materials, South China University of Technology. METHODS: Thirty-two female SD rats, five-month old, were randomly divided into four groups: group A in which rats received sham surgery and was implanted with porous HA, group B in which rats received sham surgery and was implanted with smooth surface nano-HA, group C in which ovariectomized (OVX) rats was implanted with porous HA, and group D in which OVX rats was implanted with smooth surface nano-HA, with eight rats in each group. Rats in group C and D underwent ovariectomy to establish osteoporosis models. Porous and smooth surface HA prostheses were implanted into superior segments of tibia in each group. MAIN OUTCOME MEASURES: At 12 weeks after sacrifice, the bone quantity and osteointegration around the HA implant were observed and the osteointegration at the surface between bone and implant was calculated. RESULTS: Circled digit one; Osteointegration rate (OIS) in group C was 23.7%, which was significantly higher than group D 16.9% (P < 0.05). Circled digit two The OIS in the OVX groups was significantly less than sham surgery groups, reducing 30.8% and 13.0%, respectively. CONCLUSION: Surface modification can notably promote osteointegration at implant-bone interface in osteoporosis condition. The smooth surface of nano-HA prothesis fails to take advantage of the benefit of nano-HA. Referring to HA coating, surface modification of coating plays a more important role in promoting osteointegration, compared to coating material.