Pulsed sine wave ultrasound accelerates fracture healing in the rabbit fibula

Ultrasound (US) has been shown to have a significant impact on the rate of fibula osteotomy healing in 130 mature 3.5-5 kg female New Zealand white rabbits. Bilateral midshaft 1-mm fibular osteotomy-fractures were made using a gigli saw. US was applied to one limb for 20 min daily starting on postoperative day one using a 2.5-cm PZT transducer excited with a 200- mu m burst of 1.5 MHz sine waves repeating at 1 kHz and delivering 10-20 mW/cm/sup 2/. Animals were sacrificed at 6, 10, 14, 16, 17, 18, 21 and 28 days. All specimens were examined radiographically and from day 14 using destructive torsional testing. All radiographs were analyzed using contrast enhancement and when evaluated in a blind manner correlated highly with mechanical strength data. Ultimate strength increases compared to controls were most notable on postoperative days 16-21, when the treated limbs were 50% to 80% (p<0.01) stronger. Examination of the healing curve shows that intact strength is reached for the treated limb approximately twice as fast as for contralateral controls.<>