Abstract

• PURPOSE: The effects of ultrasound on mechanical properties of the callus in distraction osteogenesis was assessed in this study. MATERIAL AND METHOD: Forty mature New Zealand white rabbits were divided into two groups (ultrasound group and control group). A midshaft femoral osteotomy was made and fixed with a small external fixator. After a latent period of a week, lengthening was performed at the rate of 1mm a day for 2 weeks. Low intensity ultrasound (EXOGEN inc, Piscataway, NJ U.S.A) was applied to the operated limb for 20 minutes a day in the ultrasound group, while the control group waited for natural maturation of the callus. The bone mineral density and mechanical properties such as ultimate load, ultimate stress, deflection at ultimate load, ultimate stiffness and energy absorption at ultimate load were measured and analyzed. RESULT: The bone mineral density, the area of the callus, ultimate load, ultimate stress and energy absorption at ultimate load were not significantly different between the two groups (p>0.05). The ultimate stiffness in the ultrasound group was significantly higher than those of the control group (p<0.01). The deflection at ultimate load in the ultrasound group was significantly lower than those of the control group (p<0.01). CONCLUSION: The low density ultrasound has a positive effect on the mechanical properties of the distracted callus in the rabbit femoral model in terms of the ultimate stiffness and the deflection at ultimate load.
• Key words: Rabbit femur, Distraction Osteogenesis, Ultrasound, Mechanical test

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