Strontium Ranelate Treatment Enhances Hydroxyapatite-Coated Titanium Screws Fixation in Osteoporotic Rats

Increased bone turnover with excessive bone resorption and decreased bone formation is known to impair implant fixation. Strontium ranelate is well known as an effective antiosteoporotic agent by its dual effect of antiresorbing and bone-forming activity. This study was designed to evaluate the effect of systemic strontium ranelate (SR) treatment on fixation of hydroxyapatite (HA)-coated titanium screws in ovariectomized (OVX) rats. Twelve weeks after being OVX (n = 30) or sham (n = 10) operated, 40 female Sprague Dawley rats received unilateral implants in the proximal tibiae. The OVX rats were randomly divided into the following groups: OVX, OVX + SRL ("L" refers to low SR dose of 500 mg/kg/day), OVX + SRH ("H" refers to high SR dose of 1000 mg/kg/day).Twelve weeks after treatment, bone blocks with implants were evaluated with micro-CT and biomechanical push-out tests. Compared to OVX animals, SR treatment increased the bone volume ratio by 51.5% and 1.1-fold, the percentage osteointegration by 1.0-fold and 1.9-fold in micro-CT evaluation, and the maximal force by 1.9-fold and 3.3-fold in biomechanical push-out test, for the low and high dose of SR, respectively. Significant correlation between micro-CT and biomechanical properties demonstrated that trabecular parameters played an important role in predicting the biomechanical properties of implant fixation. Our findings suggest that SR treatment can dose-dependently improve HA-coated screw fixation in OVX rats and facilitate the stability of the implant in the osteoporotic bone. (C) 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:578-582, 2010