Low-intensity pulsed ultrasound to promote healing of delayed-union and non-union fractures

2.1 Fractures are a common result of trauma, and are usually described as either closed (skin over the fracture site is intact) or open (involves an open wound). They may vary in complexity from a single break (transverse or oblique) to comminuted, in which the bone has broken into several pieces.

2.2 Fractures usually heal within a few weeks after treatment by closed or open reduction, and immobilisation using a cast or internal fixation. Sometimes healing may be delayed or not happen at all (non-union). There is no agreed precise definition of a fracture non-union but, typically, it is considered to be when there is failure of bony union 6 to 9 months after the fracture. Risk factors for non-union of fractures include: systemic medical conditions (for example, diabetes, malnutrition, osteoporosis); smoking; use of non-steroidal anti-inflammatory drugs; local factors such as infection; vascular problems; magnitude of injury (for example, fracture location and gap, traumatic fractures); advanced age; and other iatrogenic factors. Treatment of non-union may need complex and prolonged management with implications for the patient's quality of life and functional capacity.

2.3 The aim of low-intensity pulsed ultrasound is to promote healing by delivering micro-mechanical stress to the bone to stimulate bone healing. This procedure is used to treat fractures that are slower to heal than expected (delayed healing) and fractures that have failed to unite (non-union).

2.4 An ultrasound probe is positioned on the skin over the fracture and patients self-administer low-intensity pulsed ultrasound daily, usually for 20 minutes. If a patient's limb is immobilised in a cast, a hole is cut into the cast for the ultrasound probe. The probe delivers acoustic radiation and coupling gel is used on the skin to aid conduction of the ultrasound signal. An operating frequency of 1.5 MHz, pulse width of 200 microseconds, repetition rate of 1 kHz, and a temporal average power of 30 milliwatts per cm² is typically used. The exact treatment protocol and duration of treatment may vary.

2.5 Progress towards fracture healing is usually assessed radiographically. The duration of treatment ranges from a few weeks to several months.