[Effect of low-intensity pulsed ultrasound stimulation on maturation of regenerate bone]

To explore the effect of low intensity pulsed ultrasound stimulation (LIPUS) on the maturation of regenerate bone in a rabbit limb lengthening model.

Sixty skeletal mature female New Zealand white rabbits were randomly divided into an LIPUS treatment group and a control group. All rabbits were underwent mid-diaphyseal tibial osteotomy and immobilized in an Orthofix M103 Mini lengther. Gradual distraction at 0.5 mm every 12 h for 10 d was performed at day 7 postoperatively. A 4-week course of LIPUS treatment group was applied over the distraction site for 20 min daily starting immediately after the completion of the distraction only for the treatment group. Rabbits were euthanized and the mid-diaphyseal tibia was harvested for evaluation at 4, 8, and 12 wk after the completion of the bone lengthening protocol. Radiographic analysis was performed to study the formation of bone callus using the ImageJ software at 12 wk after the completion of the bone lengthening protocol. Bone mineral density (BMD) of regenerate bone was measured by Dual energy X-ray absorptiometry (DEXA). Torsional testing to failure was performed on the tibia specimens at 8 and 12 wk after the completion of the bone lengthening protocol.

Radiographic measurement showed higher relative gray scale of bone callus in the LIPUS group than that in the control group at 12 wk (P<0.05). BMD in the LIPUS group was significantly higher than that in control group at 8 and 12 wk (P<0.05). Biomechanical testing showed that the ultimate torque, ultimate torsional stiffness, and energy absorption at failure of regenerated bone at 8 and 12 wk in the LIPUS treatment group were better than those in the control group (P<0.05).

LIPUS as a biophysical stimulation may accelerate the formation and maturation of regenerate bone in rabbit tibia lengthening model.