Background: Low-intensity transcutaneous ultrasound can accelerate
and augment the fracture-healing process. The aim of this study was to
investigate the effect of transosseous application of low-intensity ultrasound
on fracture-healing in an animal model.
Methods: A midshaft osteotomy of the left tibia was performed in
forty sheep. An external fixator was used to stabilize the osteotomy site. A
thin stainless-steel pin was inserted into the bone, 1.0 cm proximal to the
osteotomy site. Ultrasound was transmitted through the free end of this pin,
with a PZT-4D transducer. In twenty animals, the treated limb received a
200-µsec burst of 1-MHz sine waves repeated at 1 kHz with an average
intensity of 30 mW/cm2 for twenty minutes daily. Twenty other
animals underwent the same surgery but did not receive the ultrasound
(controls). Animals were killed at seventy-five and 120 days postoperatively.
Radiographic evaluation was performed every fifteen days. Mechanical testing
and quantitative computed tomography were performed after death.
Results: Fractures treated with ultrasound healed significantly more
rapidly, as assessed radiographically, than did the controls (seventy-nine
compared with 103 days, p = 0.027). On day 75, the mean cortical bone mineral
density (and standard deviation) was 781 ± 52 mg/mL in the treated
limbs compared with 543 ± 44 mg/mL in the control group (p = 0.014),
and the average ultimate strength (as assessed with a lateral bending test)
was 1928 ± 167 N in the treated limbs compared with 1493 ± 112 N
in the control group (p = 0.012). No significant differences were noted on day
Conclusions: This study demonstrated that low-intensity transosseous
ultrasound can significantly accelerate the fracture-healing process, increase
the cortical bone mineral density, and improve lateral bending strength of the
healing fracture in a sheep osteotomy model.
Clinical Relevance: Transosseous application of low-intensity
ultrasound at close proximity to the fracture site may enhance the mechanical
properties of the fracture callus and reduce the time to fracture-healing.
However, further investigation is needed to establish the safety and efficacy
of the technique.