Low-Intensity Pulsed Ultrasound (LIPUS) is a non-invasive medical technology that accelerates the body’s natural process of healing broken bones. This treatment applies low-level sound wave energy directly to the fracture site to stimulate biological activity. The goal is to accelerate the formation of new bone tissue, reducing the time required for a fracture to fully mend. LIPUS is commonly used as an adjunctive therapy alongside traditional orthopedic care.
Understanding Low-Intensity Pulsed Ultrasound
LIPUS differs fundamentally from the high-intensity ultrasound used in physical therapy or the ultrasound used for diagnostic imaging. The technology uses specific parameters designed to create a mechanical, rather than thermal, effect within the tissue. The sound waves are delivered in a pulsed manner, emitted in short bursts instead of a continuous stream.
The acoustic energy intensity is extremely low, typically 30 milliwatts per square centimeter (mW/cm²). This is well below the threshold that would produce heat or tissue damage. The waves usually have a frequency of 1.5 megahertz (MHz), repeated at 1 kilohertz (kHz). The device is small, portable, and often handheld, consisting of a transducer placed directly on the skin over the fracture site.
This precise, low-intensity, pulsed delivery allows the mechanical energy to safely penetrate soft tissues and reach the bone. These specific parameters create subtle mechanical stresses within the bone without causing any noticeable sensation. This gentle mechanical stimulation converts physical energy into a biological signal, forming the foundation of the healing mechanism.
How Sound Waves Stimulate Cellular Repair
LIPUS accelerates bone repair through mechanotransduction, the process of converting mechanical energy into biochemical signals within cells. The sound waves create extremely tiny mechanical displacements, on the nanometer scale, at the fracture site. This mechanical stress is detected by specialized proteins on the cell surface called integrins, which act as mechanoreceptors.
Once activated, these integrins initiate intracellular signaling pathways that promote new bone formation. The mechanical signal prompts the stimulation and differentiation of cells essential for bone formation, particularly osteoblasts and chondrocytes. LIPUS enhances the proliferation and activity of osteoblasts, the cells responsible for laying down the new bone matrix. This accelerates the transition from a soft to a hard bony callus.
The treatment also increases the local expression of growth factors necessary for healing, such as Bone Morphogenetic Proteins (BMPs) and Vascular Endothelial Growth Factor (VEGF). BMPs are crucial for bone regeneration, while VEGF promotes angiogenesis, the formation of new blood vessels. Improved blood flow delivers the oxygen and nutrients needed to support rapid tissue repair. LIPUS also shortens the period of endochondral ossification, where cartilage is replaced by bone, reducing the overall healing time.
What to Expect During LIPUS Treatment
LIPUS treatment is designed to be convenient and self-administered, allowing the patient to use the device at home. The treatment protocol is standardized: patients are instructed to apply the transducer directly to the skin overlying the fracture site once per day.
Each session commonly lasts 20 minutes. The entire treatment period ranges from several weeks to several months, continuing until X-ray imaging confirms the fracture is fully healed. Due to the extremely low power output, the treatment is non-invasive and painless; patients do not feel any heat or sensation during the daily session.
The device requires a prescription from a physician, who provides instructions on application. A coupling gel is applied between the transducer and the skin to ensure effective sound wave transmission. The device’s ease of use and portability maximize patient adherence to the daily treatment schedule, which is a significant factor in achieving the desired healing outcome.
Specific Bone Conditions Treated by LIPUS
LIPUS has an established role in orthopedic medicine, particularly in managing fractures that are slow to heal. Its most common application is treating nonunion fractures, defined as those that fail to show signs of healing after nine months or more. For these challenging cases, LIPUS provides a mechanical stimulus intended to kickstart the stalled biological process.
The technology also treats delayed union fractures, which show slower-than-expected healing progression between three and nine months post-fracture. LIPUS may also be prescribed as an adjunct therapy for fresh acute fractures, aiming to accelerate consolidation from the outset. Starting the treatment as early as possible after the injury can maximize its effectiveness in speeding up recovery.
LIPUS is frequently applied to long bones, such as the tibia and radius. It has also shown benefit in high-risk fractures, including those in patients with comorbidities like diabetes or who smoke, factors that typically impair natural bone healing. The therapy is sometimes used following surgical procedures, such as open-reduction internal fixation, to encourage the bone to fuse around the hardware.