Sixty-seven closed or grade-I open fractures of the tibial shaft were examined in a prospective, randomized, double-blind evaluation of use of a new ultrasound stimulating device as an adjunct to conventional treatment with a cast. Thirty-three fractures were treated with the active device and thirty-four, with a placebo control device. At the end of the treatment, there was a statistically significant decrease in the time to clinical healing (86 +/- 5.8 days in the active-treatment group compared with 114 +/- 10.4 days in the control group) (p = 0.01) and also a significant decrease in the time to over-all (clinical and radiographic) healing (96 +/- 4.9 days in the active-treatment group compared with 154 +/- 13.7 days in the control group) (p = 0.0001). The patients' compliance with the use of the device was excellent, and there were no serious complications related to its use. This study confirms earlier animal and clinical studies that demonstrated the efficacy of low-intensity ultrasound stimulation in the acceleration of the normal fracture-repair process.

https://www.viktoraskubaitis.com/uploads/2/1/5/3/21539486/hecman_1994_article_ultrasound_jbjs_67_am.pdf

Acceleration of tibial fracture-healing by non-invasive, low-intensity pulsed ultrasound.

This selective review of the biological effects of ultrasound presents a synopsis of our current understanding of how cells insonated in vitro are affected by inertial cavitation from the standpoint of physical and chemical mechanisms. The focus of this review is on the physical and chemical mechanisms of action of inertial cavitation which appear to be effective in causing biological effects. There are several fundamental conditions which must be satisfied before cavitation-related bioeffects may arise. First, bubbles must be created and then brought into proximity to cells. Exposure methods are critical in this regard, and simple procedures such as rotation of a vessel containing the cells during exposure can drastically alter the results. Second, once association is achieved between bubbles and cells, the former must interact with the latter to produce a bioeffect. It is not certain that the inertial event is the prime mechanism by which cells are lysed; there is evidence that the turbulence associated with bubble translation may cause lysis. Additionally, there appear to be chemical and other physical mechanisms by which inertial cavitation may affect cells; these include the generation of biologically effective sonochemicals and the apparent emission of ultraviolet (UV) and soft X-rays. The evidence for inertial cavitation occurring within cells is critically reviewed.

A review of in vitro bioeffects of inertial ultrasonic cavitation from a mechanistic perspective

Possessing the ability to noninvasively elicit brain circuit activity yields immense experimental and therapeutic power. Most currently employed neurostimulation methods rely on the somewhat invasive use of stimulating electrodes or photon-emitting devices. Due to its ability to noninvasively propagate through bone and other tissues in a focused manner, the implementation of ultrasound (US) represents a compelling alternative approach to current neuromodulation strategies. Here, we investigated the influence of low-intensity, low-frequency ultrasound (LILFU) on neuronal activity. By transmitting US waveforms through hippocampal slice cultures and ex vivo mouse brains, we determined LILFU is capable of remotely and noninvasively exciting neurons and network activity. Our results illustrate that LILFU can stimulate electrical activity in neurons by activating voltage-gated sodium channels, as well as voltage-gated calcium channels. The LILFU-induced changes in neuronal activity were sufficient to trigger SNARE-mediated exocytosis and synaptic transmission in hippocampal circuits. Because LILFU can stimulate electrical activity and calcium signaling in neurons as well as central synaptic transmission we conclude US provides a powerful tool for remotely modulating brain circuit activity.

/pdf/remote-excitation-of-neuronal-circuits-using-low-intensity-2p0m70i79k.pdf

Remote excitation of neuronal circuits using low-intensity, low-frequency ultrasound.

Double-blind, prospective, placebo-controlled clinical trials demonstrate that healing times of fresh fractures of the radius and tibia are reduced by up to 40% with the use of low-intensity ultrasound.

Animal studies indicate that low-intensity ultrasound exposure results in stronger and stiffer callus formation and in acceleration of the endochondral ossification process.

Extensive clinical evidence demonstrates that ultrasound represents a safe, noninvasive method of accelerating the healing of fresh fractures of the tibia, the distal aspect of the radius, the scaphoid, and the metatarsals.

Clinical studies indicate that ultrasound reduces the confounding effect of smoking and patient age on the fracture-healing process.

Ultrasound requires a brief, twenty-minute, daily at-home treatment regimen and has no known contraindications.

The effectiveness of low-intensity ultrasound has also been demonstrated in the clinical treatment of delayed unions and nonunions.

Fracture-healing is a complex biological process that involves the spatial and temporal orchestration of numerous cell types, hundreds if not thousands of genes, and the intricate organization of an extracellular matrix, all working toward restoring the bone's mechanical strength and rapid return to full function. It has often been argued that nature has optimized this process and thus it would be difficult to interventionally accelerate or augment fracture-healing. How can science conceivably improve upon 600 million years of vertebrate evolution? Nevertheless, it is just this goal that has inspired an intense effort among basic-science and clinical investigators from a vast array of biotechnology and bioengineering disciplines at academic as well as industrial laboratories, to seek a means of accelerating the healing of fractured bones. In this article, the basic-science and clinical evaluation of the use of low-intensity ultrasound is reviewed and the case is made that nature's process of fracture-healing, while elegant, can be accelerated with respect to achieving the ability to support clinically relevant loads.

The …

The use of low-intensity ultrasound to accelerate the healing of fractures.

Millions of fractures occur every year worldwide, with nearly 6.2 million fractures reported annually in the United States alone. Even though treatment methods have improved over the last few decades, 5-10% of fractures still show delayed healing. A significant subpopulation of these delayed healings do not heal by nine months and are thus termed non-unions. Experimental studies have shown some evidence that low intensity pulsed ultrasound stimulation (LIPUS) results in enhanced bone regeneration during fracture healing and callus distraction. LIPUS treatment has led to increased callus area and accelerated return of bone strength following fracture. Histological studies suggest that LIPUS influences all major cell types involved in bone healing, including osteoblasts, osteoclasts, chondrocytes and mesenchymal stem cells. The affect of LIPUS seems to be limited to cells in soft tissue, whereas cells in calcified bone seem not to be effected. In vitro cell culture studies as well as tissue culture studies have shown some effects on cell differentiation and protein synthesis. Even though the energy used by LIPUS treatment is extremely low, the effects are evident. The most probable source of the therapeutic benefits observed with LIPUS treatment involves nonthermal mechanisms that influence cell membrane permeability and increase cellular activity. Despite clinical and experimental studies demonstrating the enhancing effect of LIPUS on bone regeneration, the biophysical mechanisms involved in the complex fracture healing process remain unclear and requires further research.

The enhancement of bone regeneration by ultrasound

It is demonstrated that the potassium content of rat thymocytes in vitro is decreased following exposure to 2W/cm 2 , 3MHz ultrasound for 40 min at 37°C, without inducing cell lysis or gross membrane damage. The abnormal values for potassium are maintained after completion of insonation. The changes are shown to arise from ultrasound-induced decreases in ion influx together with increases in potassium efflux. Recorded temperature changes in the media are shown to be insufficient to account for the observed decreases in cell potassium. The magnitude of cell potassium decrease at 3 MHz is shown to be similar in aerated and degassed water. Acoustic microstreaming either at the cell membrane of within the cell is suggested as the damage mechanism leading to ion flux changes.

Ultrasound-induced changes in rates of influx and efflux of potassium ions in rat thymocytes in vitro.

The experiments discussed here involve investigations of variations in radiation force values for ultrasound incident on an inverted cone of a sensitive radiation pressure balance. The variations were observed to coincide with changes in the oxygen content of a constant volume of water between the transducer and the inverted cone balance pan (Fig. 1; Materials and Methods). The relationship between intensity per unit area of ultrasound entering unit volume of water (I0 and the intensity at the exit face (/2) is expressed by the equation 12 = l ~ e x p ( 1 0 -3~) where /~ represents the intensity absorption coefficient for water. The absorption of water increases when water is progressively aerated, compared to degassed water and can be accounted for by considering gas bubbles as inhomogeneities in

I.V. Chapman

Papers

Ultrasound-induced changes in rates of influx and efflux of potassium ions in rat thymocytes in vitro.

Variation of radiation force values with differing gas content of propagating media.