Low-Magnitude High-Frequency Vibration (LMHFV) Enhances Bone Remodeling in Osteoporotic Rat Femoral Fracture Healing

Low-magnitude high-frequency vibration (LMHFV) (35 Hz, 0.3 g) accelerates fracture healing by enhancing callus formation and mineralization for both normal and osteoporotic rats in our previous studies.(1,2) We hypothesized that LMHFV enhances fracture healing through bone remodeling. Ibandronate was used to suppress LMHFV-stimulated bone remodeling and changes in remodeling were investigated to verify our hypothesis. Closed femoral fractures were created in 80 osteoporotic female Sprague-Dawley rats. The rats were randomly assigned into control (CG), LMHFV (VG) (20 min/day, 5 days/week), ibandronate (BG) (7 mu g/kg/week), or LMHFV + ibandronate (VBG) for a treatment duration of 2, 4, 6, or 8 weeks. Blood was taken and the femora were harvested for histological and radiological analyses. VG had the fastest drop in callus area (CA) and width (CW), and bone volume to tissue volume ratio (BV/TV); whereas, a plateaued trend in BG and VBG was observed. The fastest callus reduction, highest mineral apposition rate at week 6, and increased serum concentration of osteocalcin and TRAP5b in VG suggested enhanced remodeling. LMHFV partially reversed the inhibition of bone remodeling by ibandronate suggested LMHFV had an opposite effect on bone remodeling to ibandronate. In conclusion, LMHFV accelerated fracture healing by enhancing bone remodeling and the administration of ibandronate can impair this enhancement. LMHFV has great potential in improving fracture outcome clinically. (C) 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:746-752, 2011