Zoledronic Acid Improves Femoral Head Shape in a Rat Model of Perthes Disease

INTRODUCTION: No effective non-operative treatments are available for Perthes disease. We have previously reported significant improvement in outcome in traumatic osteonecrosis in growing rats by intervention with zoledronic acid (ZA), a potent third generation bisphosphonate. In this study we examine the effect of ZA on a model of spontaneous osteonecrosis in growing rats. We hypothesized that administration of ZA could favorably alter femoral head shape by preserving architecture while allowing bone repair to proceed. METHODS: A model of spontaneous osteonecrosis was utilized in 120 male spontaneously hypertensive rats (SHR). Animal ethics approval was received (WAEC-103.06-02). Approximately 50% of SHR rats develop osteonecrosis in the first 15 weeks of life, resulting in femoral head deformity similar to Perthes disease. 120 4-week old rats were divided into three dosing groups of 40, each group received either saline monthly, 0.05 mg/kg ZA monthly for 3 doses, or 0.015 mg/kg ZA weekly for 10 doses. The same total dose was given to active groups.