Low-Intensity Pulsed Ultrasound (LIPUS) is a therapeutic technology. This technique uses sound waves delivered at a specific, low-energy level to target tissue injury. It has become a recognized adjunctive treatment in orthopedic medicine, primarily to accelerate the natural healing timeline of bone fractures.
Understanding Low-Intensity Pulsed Ultrasound
LIPUS is defined by its specific physical parameters, which are distinct from diagnostic or high-intensity therapeutic ultrasound. The device emits a pressure wave with a spatial average and temporal average intensity of just 30 milliwatts per square centimeter (mW/cm²). This energy is delivered at a low frequency, typically 1.5 megahertz (MHz), in a pulsed pattern rather than a continuous stream.
The core scientific principle behind this therapy is called mechanotransduction, which is the process by which mechanical forces are converted into biochemical signals inside cells. The pulsed sound wave creates a gentle, physical force that causes nanosized movements at the fracture site. This micromechanical stress is transmitted through the cell membrane, activating specialized receptors. This physical stimulation initiates a signaling cascade within the bone-forming cells, known as osteoblasts and chondrocytes.
Specifically, LIPUS encourages the proliferation of undifferentiated mesenchymal stem cells and their eventual differentiation into bone-making cells. The treatment also stimulates the increased expression of various growth factors and enhances the formation of new blood vessels, a process called angiogenesis. These combined effects accelerate the formation and mineralization of the soft and hard callus required to bridge a fracture gap.
Accelerating Bone Fracture Healing
For fresh fractures, studies have indicated that the application of LIPUS can reduce the overall time to union by approximately 38 to 42 percent in specific long bone fractures, such as those of the tibia and radius. This acceleration allows patients to return to weight-bearing activities and normal function sooner than with standard care alone. The therapy is particularly beneficial for patients with underlying conditions, such as diabetes or advanced age, which naturally compromise the body’s ability to heal efficiently.
LIPUS has an established role in managing established non-union fractures, which are those that have failed to show progressive signs of healing after several months. In these challenging cases, the non-invasive nature of LIPUS offers a valuable alternative to surgical intervention, which would typically involve bone grafting. Clinical data suggests that this treatment can resolve established non-unions with success rates averaging around 85 to 87 percent, depending on the fracture location.
The application of LIPUS is also frequently recommended for delayed union fractures, where the healing process has started but is proceeding slower than expected. Starting the treatment soon after a diagnosis of delayed union can significantly boost the callus maturation process. By enhancing this natural bone remodeling, LIPUS can reduce the total recovery duration and potentially prevent the fracture from progressing to a complete non-union.
The Treatment Experience
For the patient, receiving LIPUS therapy is a straightforward and non-invasive process that is typically performed at home. The device itself is small and portable, designed for ease of use without requiring a clinic visit for every session. A physician prescribes the device, which consists of a transducer head connected to a control unit.
To apply the treatment, the patient first applies a small amount of coupling gel to the skin over the fracture site. The transducer head is then placed gently against the skin, ensuring direct contact with the area where the bone callus is forming. The device is worn for a specific duration each day, with the standard commitment being approximately 20 minutes per session. Because the waves are low-intensity and non-thermal, the treatment is generally painless, with the patient feeling little to no sensation during the application.
Consistency is necessary for the treatment to be effective, and patients are instructed to use the device daily throughout the prescribed course. The device maintains a record of usage, which helps the treating physician monitor patient adherence to the daily schedule.
Safety Profile and Contraindications
LIPUS is recognized for its favorable safety profile, largely due to its non-thermal and non-invasive nature. Unlike certain electrical stimulation methods, LIPUS does not interfere with metal internal fixation devices, such as plates, screws, or rods, which are often already in place to stabilize the fracture. The sound waves safely pass through these materials to stimulate the surrounding bone tissue.
The main contraindications include the presence of known or suspected malignancy (cancer) in the area to be treated, as ultrasound energy could potentially influence tumor growth. The treatment should also not be used over the abdomen or pelvis in pregnant women, as the effects on the developing fetus have not been fully established. Furthermore, application directly over unfused growth plates in pediatric patients is typically avoided to prevent any unintended stimulation or alteration of normal bone growth.