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 × 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:
① Osteointegration rate (OIS) in group C was 23.7%, which was significantly higher than group D 16.9% (P < 0.05). ② 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.