Enhanced fracture repair and mitigation of fracture-healing risk factors using low-intensity pulsed ultrasound

Low-intensity pulsed ultrasound (LIPUS) is used clinically to enhance fracture healing. Level-I clinical studies demonstrate that a specific signal (1.5 MHz ultrasound pulsed at 1 kHz, 20% duty cycle, 30 mW/cm2 SATA) can accelerate the healing of acute fractures. This result remains a unique benefit of LIPUS, and to date, no other drug or device has been approved by the FDA for accelerated fracture repair. The same signal has been shown in many studies to heal a high proportion of non-union fractures. LIPUS appears to be effective for all three types of non-unions—atrophic, oligotrophic and hypertrophic—even in the absence of revision surgery. The findings are broadly applicable to orthopedics, with similar results regardless of fracture type, fracture location and fracture-management technique. Given the varied causes of non-union, the ability of LIPUS to overcome a high proportion of obstacles to healing indicates that the signal is likely to have pleiotropic effects on multiple cell types within the healing process. Smoking, age, and diabetes are known risk factors for delayed union and nonunion. Clinical data, including randomized controlled trials and a registry of 1546 nonunion patients, suggest that LIPUS mitigates these risks and restores the course of normal bone healing.