Design evolution enhances patient compliance for low-intensity pulsed ultrasound device usage.

Poor patient compliance or nonadherence with prescribed treatments can have a significant unfavorable impact on medical costs and clinical outcomes. In the current study, voice-of-the-customer research was conducted to aid in the development of a next-generation low-intensity pulsed ultrasound (LIPUS) bone healing product. An opportunity to improve patient compliance reporting was identified, resulting in the incorporation into the next-generation device of a visual calendar that provides direct feedback to the patient, indicating days for which they successfully completed treatment. Further investigation was done on whether inclusion of the visual calendar improved patient adherence to the prescribed therapy (20 minutes of daily treatment) over a 6-month period. Thus, 12,984 data files were analyzed from patients prescribed either the earlier- or the next-generation LIPUS device. Over the 6-month period, overall patient compliance was 83.8% with the next-generation LIPUS device, compared with 74.2% for the previous version (p<0.0001). Incorporation of the calendar feature resulted in compliance never decreasing below 76% over the analysis period, whereas compliance with the earlier-generation product fell to 51%. A literature review on the LIPUS device shows a correlation between clinical effectiveness and compliance rates more than 70%. Incorporation of stakeholder feedback throughout the design and innovation process of a next-generation LIPUS device resulted in a measurable improvement in patient adherence, which may help to optimize clinical outcomes.

Mode & mechanism of low intensity pulsed ultrasound (LIPUS) in fracture repair.

It has been 30years since the first level one clinical trial demonstrated low intensity pulsed ultrasound (LIPUS) could accelerate fracture repair. Since 1994 numerous investigations have been performed on the effect of LIPUS. The majority of these studies have used the same signal parameters comprised of an intensity of 30mW/cm(2) SATA, an ultrasound carrier frequency of 1.5MHz, pulsed at 1kHz with an exposure time of 20minutes per day. These studies show that a biological response is stimulated in the cell which produces bioactive molecules. The production of these molecules, linked with observations demonstrating the enhanced effects on mineralization by LIPUS, might be considered the general manner, or mode, of how LIPUS stimulates fractures to heal. We propose a mechanism for how the LIPUS signal can enhance fracture repair by combining the findings of numerous studies. The LIPUS signal is transmitted through tissue to the bone, where cells translate this mechanical signal to a biochemical response via integrin mechano-receptors. The cells enhance the production of cyclo-oxygenese 2 (COX-2) which in turn stimulates molecules to enhance fracture repair. The aim of this review is to present the state of the art data related to LIPUS effects and mechanism.

Osteocytes exposed to far field of therapeutic ultrasound promotes osteogenic cellular activities in pre-osteoblasts through soluble factors.

Low intensity pulsed ultrasound (LIPUS) was reported to accelerate the rate of fracture healing. When LIPUS is applied to fractures transcutaneously, bone tissues at different depths are exposed to different ultrasound fields. Measurement of LIPUS shows pressure variations in near field (nearby transducer); uniform profile was found beyond it (far field). Moreover, we have reported that the therapeutic effect of LIPUS is dependent on the axial distance of ultrasound beam in rat fracture model. However, the mechanisms of how different axial distances of LIPUS influence the mechanotransduction of bone cells are not understood. To understand the cellular mechanisms underlying far field LIPUS on enhanced fracture healing in rat model, the present study investigated the effect of ultrasound axial distances on (1) osteocyte, the mechanosensor, and (2) mechanotransduction between osteocyte and pre-osteoblast (bone-forming cell) through paracrine signaling. We hypothesized that far field LIPUS could enhance the osteogenic activities of osteoblasts via paracrine factors secreted from osteocytes. The objective of this study was to investigate the effect of axial distances of LIPUS on osteocytes and osteocyte-osteoblast mechanotransduction. In this study, LIPUS (plane; 2.2 cm in diameter, 1.5MHz sine wave, ISATA=30 mW/cm(2)) was applied to osteocytes (mechanosensor) at three axial distances: 0mm (near field), 60mm (mid-near field) and 130 mm (far field). The conditioned medium of osteocytes (OCM) collected from these three groups were used to culture pre-osteoblasts (effector cell). In this study, (1) the direct effect of ultrasound fields on the mechanosensitivity of osteocytes; and (2) the osteogenic effect of different OCM treatments on pre-osteoblasts were assessed. The immunostaining results indicated the ultrasound beam at far field resulted in more ß-catenin nuclear translocation in osteocytes than all other groups. This indicated that osteocytes could detect the acoustic differences of LIPUS at various axial distances. Furthermore, we found that the soluble factors secreted by far field LIPUS exposed osteocytes could further promote pre-osteoblasts cell migration, maturation (transition of cell proliferation into osteogenic differentiation), and matrix calcification. In summary, our results of this present study indicated that axial distance beyond near field could transmit ultrasound energy to osteocyte more efficiently. The LIPUS exposed osteocytes conveyed mechanical signals to pre-osteoblasts and regulated their osteogenic cellular activities via paracrine factors secretion. The soluble factors secreted by far field exposed osteocytes led to promotion in migration and maturation in pre-osteoblasts. This finding demonstrated the positive effects of far field LIPUS on stimulating osteocytes and promoting mechanotransduction between osteocytes and osteoblasts.

Investigation of rat bone fracture healing using pulsed 1.5 MHz, 30 mW/cm(2) burst ultrasound--axial distance dependency.

This study investigated the effect of LIPUS on fracture healing when fractures were exposed to ultrasound at three axial distances: z=0 mm, 60 mm, and 130 mm. We applied LIPUS to rat fracture at these three axial distances mimicking the exposure condition of human fractures at different depths under the soft tissue. Measurement of LIPUS shows pressure variations in near field (nearby transducer); uniform profile was found beyond it (far field). We asked whether different positions of the fracture within the ultrasound field cause inconsistent biological effect during the healing process. Closed femoral fractured Sprague-Dawley rats were randomized into control, near-field (0mm), mid-near field (60 mm) or far-field (130 mm) groups. Daily LIPUS treatment (plane, but apodized source, see details in the text; 2.2 cm in diameter; 1.5 MHz sine waves repeating at 1 kHz PRF; spatial average temporal average intensity, ISATA=30 mW/cm(2)) was given to fracture site at the three axial distances. Weekly radiographs and endpoint microCT, histomorphometry, and mechanical tests were performed. The results showed that the 130 mm group had the highest tissue mineral density; and significantly higher mechanical properties than control at week 4. The 60 mm and 0 mm groups had significantly higher (i.e. p<0.05) woven bone percentage than control group in radiological, microCT and histomorphometry measurements. In general, LIPUS at far field augmented callus mineralization and mechanical properties; while near field and mid-near field enhanced woven bone formation. Our results indicated the therapeutic effect of LIPUS is dependent on the axial distance of the ultrasound beam. Therefore, the depth of fracture under the soft tissue affects the biological effect of LIPUS. Clinicians have to be aware of the fracture depth when LIPUS is applied transcutaneously.

Effects of different therapeutic ultrasound intensities on fracture healing in rats.

Low-intensity pulsed ultrasound (LIPUS) with I(SATA)= 30 mW/cm(2) has been proven in facilitating fracture healing, which the spatial average intensity over the on period (I(SATP)) equals 150 mW/cm(2). As active ultrasound wave is only delivered during the on period, we postulate 150 mW/cm(2) is responsible for the beneficial effect of LIPUS. In this study, we compare the biologic effects of 30 mW/cm(2) and 150 mW/cm(2). We propose I(SATA) = 150 mW/cm(2) could further enhance fracture healing process. Closed femoral fractured Sprague-Dawley rats were randomized into control, LIPUS-30 (30 mW/cm(2)) and LIPUS-150 (150 mW/cm(2)) groups. Weekly radiographs and endpoint microCT, histomorphometry, and biomechanical tests were performed. The results show that LIPUS-30 had significantly higher low-density bone volume fraction and woven bone percentage than that of control and LIPUS-150 in microCT and histologic measurements, respectively. Mechanically, failure torque of LIPUS-30 was significantly higher than control and LIPUS-150 at week 6. In conclusion, LIPUS at I(SATA)= 150 mW/cm(2) did not further enhance fracture healing.

Fracture healing enhancement with low intensity pulsed ultrasound at a critical application angle.

Low-intensity pulsed ultrasound (LIPUS) was shown to have dose-dependent enhancement effect on the osteogenic activity of human periosteal cells that played an important role in fracture healing. It was hypothesized that the stimulatory effects of LIPUS on the periosteal cells could be optimized by adjusting the ultrasound delivered at its critical angle to the surface of bone. This increased the transmission of ultrasound waves on periosteum. By using a rat femoral fracture model, the stimulatory effects of LIPUS transmitted at 0°, 22°, 35° and 48°, and the sham-treatment control were investigated. Treatment efficacy was assessed using radiography, micro-computed tomography (micro-CT), histomorphometry and torsional test. The results showed that callus mineralization and bridging, biomechanical properties were significantly enhanced in the 35° group over the control and 0° groups after week 8. LIPUS transmitted at 35°, which could be the critical application angle, showed the best enhancement effects among all the other groups. LIPUS transmitted at a critical application angle may have greater enhancement effects in fracture healing.

The effects of low-intensity pulsed ultrasound upon diabetic fracture healing.

In the United States, over 17 million people are diagnosed with type 1 diabetes mellitus (DM) with its inherent morbidity of delayed bone healing and nonunion. Recent studies demonstrate the utility of pulsed low-intensity ultrasound (LIPUS) to facilitate fracture healing. The current study evaluated the effects of daily application of LIPUS on mid-diaphyseal femoral fracture growth factor expression, cartilage formation, and neovascularization in DM and non-DM BB Wistar rats. Polymerase chain reaction (PCR) and ELISA assays were used to measure and quantify growth factor expression. Histomorphometry assessed cartilage formation while immunohistochemical staining for PECAM evaluated neovascularization at the fracture site. In accordance with previous studies, LIPUS was shown to increase growth factor expression and cartilage formation. Our study also demonstrated an increase in fracture callus neovascularization with the addition of LIPUS. The DM group showed impaired growth factor expression, cartilage formation, and neovascularization. However, the addition of LIPUS significantly increased all parameters so that the DM group resembled that of the non-DM group. These findings suggest a potential role of LIPUS as an adjunct for DM fracture treatment.

Low intensity pulsed ultrasound for fracture healing: a review of the clinical evidence and the associated biological mechanism of action.

Low intensity pulsed ultrasound is used in the clinical treatment of fractures and other osseous defects. Level I clinical studies demonstrate the ability of a specific ultrasound signal (1.5 MHz ultrasound pulsed at 1 kHz, 20% duty cycle, 30 mW/cm(2) intensity (SATA)) to accelerate the healing time in fresh tibia, radius and scaphoid fractures by up to 40%. Additionally, the same ultrasound signal has been shown to be effective at resolving all types of nonunions of all ages, following a wide range of fracture types and primary fracture management techniques. Recently, significant efforts have resulted in a more comprehensive understanding of the biological mechanism of action that produces the documented clinical outcomes. Low intensity pulsed ultrasound has been demonstrated to accelerate in vivo all stages of the fracture repair process (inflammation, soft callus formation, hard callus formation). In particular, accelerated mineralisation has been demonstrated in vitro with increases in osteocalcin, alkaline phosphatase, VEGF and MMP-13 expression. Integrins, a family of mechanoreceptors present on a wide range of cells involved in the fracture healing process, have been shown to be activated by the ultrasound signal. Downstream of the integrin activation, focal adhesions occur on the surface of cells with the activation of multiple signalling pathways, including the ERK, NF-kappabeta, and PI3 kinase pathways. These pathways have been directly linked to the production of COX-2 and prostaglandin, which are key to the processes of mineralisation and endochondral ossification in fracture healing.

Effect of low intensity pulsed ultrasound on healing of an ulna defect filled with a bone graft substitute.

A 1.5 cm unilateral rabbit ulna defect model was performed in 18 adult NZ white rabbits. The defects were filled with a beta-tricalcium phosphate bone graft substitute (JAX TCP). The surgical site in half the animals was treated daily with 20 min of low intensity pulsed ultrasound (LIPUS). Animals were sacrificed at 4 weeks (n = 3 per group) or 12 weeks (n = 6 per group) following surgery for radiographic and histologic endpoints. Radiography revealed some resorption of the JAX TCP by 12 weeks in the control and LIPUS treated groups. LIPUS treatment did not accelerate this resorption. Some new bone formation was noted in the control groups at the defect margins while little bone formed in the center of the defect at 4 and 12 weeks. In contrast, radiographs revealed more new bone at 4 and 12 weeks in the LIPUS treated animals throughout the section. Bone mineral density (DEXA) revealed a statistically significant difference at 4 weeks with LIPUS while no differences were found at 12 weeks. Histology of the LIPUS treated sections demonstrated new woven bone formation on and between the JAX TCP bone graft substitute particles across the defect. VEGF expression was increased with LIPUS treatment at 4 weeks and remained elevated at 12 weeks compared with controls. CBFA-1 expression levels were elevated with LIPUS treatment at both time points. LIPUS treatment increased bone formation in ulna defect healing with a beta-tricalcium phosphate bone graft substitute.