Mechanical means to improve bone strength: ultrasound and vibration

Low-Intensity Continuous Ultrasound Therapies—A Systematic Review of Current State-of-the-Art and Future Perspectives

Therapeutic ultrasound has been studied for over seven decades for different medical applications. The versatility of ultrasound applications are highly dependent on the frequency, intensity, duration, duty cycle, power, wavelength, and form. In this review article, we will focus on low-intensity continuous ultrasound (LICUS). LICUS has been well-studied for numerous clinical disorders, including tissue regeneration, pain management, neuromodulation, thrombosis, and cancer treatment. PubMed and Google Scholar databases were used to conduct a comprehensive review of all research studying the application of LICUS in pre-clinical and clinical studies. The review includes articles that specify intensity and duty cycle (continuous). Any studies that did not identify these parameters or used high-intensity and pulsed ultrasound were not included in the review. The literature review shows the vast implication of LICUS in many medical fields at the pre-clinical and clinical levels. Its applications depend on variables such as frequency, intensity, duration, and type of medical disorder. Overall, these studies show that LICUS has significant promise, but conflicting data remain regarding the parameters used, and further studies are required to fully realize the potential benefits of LICUS.

Osteogenic effect of low-intensity pulsed ultrasound and whole-body vibration on peri-implant bone. An experimental in vivo study

OBJECTIVES

The aims of this study were (i) to compare the osteogenic impact of low-intensity pulsed ultrasound (LIPUS) and low-magnitude high-frequency (LMHF) loading achieved with whole-body vibration (WBV) on peri-implant bone healing and implant osseointegration in rat tibiae, and (ii) to examine their combined effect on these processes.

MATERIAL AND METHODS

Titanium implants were inserted in the bilateral tibiae of 28 Wistar rats. Rats were randomly divided into four groups: LIPUS + WBV, LIPUS, WBV, and control. LIPUS was applied to the implant placement site for 20 min/day on 5 days/week (1.5 MHz and 30 mW/cm² ). WBV was applied for 15 min/day on 5 days/week (50 Hz and 0.5 g). In the LIPUS + WBV group, both stimuli were applied under the same stimulation conditions as in the LIPUS and WBV groups. After 4 weeks of treatment, peri-implant bone healing and implant osseointegration were assessed using removal torque (RT) tests, micro-CT analyses of relative gray (RG) value, and histomorphometrical analyses of bone-to-implant contact (BIC) and peri-implant bone formation (BV/TV).

RESULTS

The LIPUS + WBV group had significantly greater BIC than the WBV and control groups. Although there were no significant intergroup differences in RT, RG value, and BV/TV, these variables tended to be greater in the LIPUS + WBV group than the other groups.

CONCLUSIONS

The combination of LIPUS and LMHF loading may promote osteogenic activity around the implant. However, further study of the stimulation conditions of LIPUS and LMHF loading is necessary to better understand the osteogenic effects and the relationship between the two stimuli.

An experimental evaluation of fracture movement in two alternative tibial fracture fixation models using a vibrating platform

Several studies have investigated the effect of low-magnitude-high-frequency vibration on the outcome of fracture healing in animal models. The aim of this study was to quantify and compare the micromovement at the fracture gap in a tibial fracture fixed with an external fixator in both a surrogate model of a tibial fracture and a cadaver human leg under static loading, both subjected to vibration. The constructs were loaded under static axial loads of 50, 100, 150 and 200 N and then subjected to vibration at each load using a commercial vibration platform, using a DVRT sensor to quantify static and dynamic fracture movement. The overall stiffness of the cadaver leg was significantly higher than the surrogate model under static loading. This resulted in a significantly higher fracture movement in the surrogate model. Under vibration, the fracture movements induced at the fracture gap in the surrogate model and the cadaver leg were 0.024 ± 0.009 mm and 0.016 ± 0.002 mm, respectively, at 200 N loading. Soft tissues can alter the overall stiffness and fracture movement recorded in biomechanical studies investigating the effect of various devices or therapies. While the relative comparison between the devices or therapies may remain valid, absolute magnitude of recordings measured externally must be interpreted with caution.

Microbubble-Mediated Ultrasound Outweighs Low-Intensity Pulsed Ultrasound on Osteogenesis and Neovascularization in a Rabbit Model of Steroid-Associated Osteonecrosis

Microbubbles magnify the acoustic pressure of low-intensity pulsed ultrasound (LIPUS) and may enhance its bioeffect for diagnostic and therapeutic purposes. This study compared the effect of this novel microbubble-mediated ultrasound (MUS) with that of the traditional LIPUS on osteogenesis and neovascularization in a rabbit model of steroid-associated osteonecrosis. We hypothesized that MUS might outweigh LIPUS on promoting osteogenesis and neovascularization in steroid-associated osteonecrosis. The bilateral femoral head necrosis was induced by lipopolysaccharide and methylprednisolone in the rabbits. The indices of bone mineral density (BMD), trabecular number, maximal loading strength, and mineral apposition rate were analyzed, demonstrating that the animal model of steroid-associated osteonecrosis was successfully established. Both the MUS group (G_M) and the LIPUS group (G_L) were insonated 20 min daily for six weeks. G_M received an extra intracapsular injection of microbubbles before insonation every other day. Fluorescence bone labeling, Micro-CT Analysis, biomechanical test, quantitative real-time PCR, Western blot analysis, and histological evaluation were performed for comparing G_M with G_L. The results demonstrated a 39% higher mineral apposition rate in G_M compared with G_L. The BMD and the maximal loading strength of femoral head of G_M increased by 4.3% and 27.8% compared to those of G_L, respectively. The mRNA and protein expression of BMP-2 and VEGF were also significantly higher in G_M. The number of blood vessels of G_M was 65% greater than that of G_L. MUS is more potent than LIPUS in enhancing osteogenesis, neovascularization, and biomechanical strength of femoral head in the animal model of steroid-associated osteonecrosis. Without increasing the intensity of insonation or the risk of tissue damage, MUS is better for inhibiting the process of steroid-associated osteonecrosis.

Low-intensity pulsed ultrasound induces osteogenic differentiation of human periodontal ligament cells through activation of bone morphogenetic protein-smad signaling

OBJECTIVES

Low-intensity pulsed ultrasound (US) can accelerate fracture healing and osteogenic differentiation. The aim of this study was to investigate the osteogenic effect of low-intensity pulsed US on human periodontal ligament cells and to determine whether bone morphogenetic protein (BMP)-Smad signaling was involved.

METHODS

Human periodontal ligament cells were exposed to low-intensity pulsed US at a frequency of 1.5 MHz and intensity of 90 mW/cm(2) for 20 min/d. Osteogenic differentiation was determined by assaying alkaline phosphatase (ALP) and calcium deposition. Expression of BMP-2, BMP-6, and BMP-9 was detected by real-time polymerase chain reaction analysis. Phosphorylated Smad was detected by western blotting; Smad in the cells was labeled by an immunofluorescent antibody and observed by laser-scanning confocal microscopy.

RESULTS

The optical density of ALP stimulated by US at 1.5 MHz and 90 mW/cm(2) for 20 min/d was significantly higher than in other groups (P < .01); therefore, this dosage was considered optimal for promoting osteogenic differentiation. After 13 days of US exposure, ALP increased gradually after 5 days, peaked at 11 days, and decreased at 13 days, with a significant difference compared with the control group (P < .05). Osteocalcin production increased from 9 to 13 days and peaked at 15 days, with a significant difference compared with the control group (P < .05). BMP-2 and BMP-6 increased dynamically after exposure for 13 days. BMP-2 increased 6.07-fold at 3 days, 6.39-fold at 11 days, and 5.97-fold at 13 days. BMP-6 expression increased 6.82-fold at 1 day and 51.5-fold at 3 days and decreased thereafter. BMP-9 was not expressed. Phospho-Smad1/5/8 expression was significantly increased after exposure (P< .05) and transferred from the cytoplasm into the nuclei.

CONCLUSIONS

Low-intensity pulsed US effectively induced osteogenic differentiation of human periodontal ligament cells, and the BMP-Smad signaling pathway was involved in the mechanism.

Effect of whole-body vibration therapy on health-related physical fitness in children and adolescents with disabilities: a systematic review

PURPOSE

To summarize the current literature regarding the effects of whole-body vibration (WBV) therapy on the health-related physical fitness of children and adolescents with disabilities.

METHODS

A literature search using MEDLINE-PubMed, SPORT DISCUS, and EMBASE databases was conducted up to August 2013. A total of 22 articles were included in this review (eight randomized controlled trials, four non-randomized controlled trials, three case reports, and seven reviews).

RESULTS

Most of the studies showed positive effects of WBV on health-related physical fitness in children and adolescents with disabilities. Overall, 10-20 minutes at least three times per week, for a minimum of 26 weeks, with high frequency (between 15 and 35 Hz) and low amplitude (no more than 4 mm of peak-to-peak displacement) might be an appropriate protocol to achieve improvement in body composition and muscular strength.

CONCLUSIONS

Because no serious adverse events have been observed, WBV might be defined as a safe treatment to be applied in children and adolescents with disabling conditions. Further research is recommended to explore the minimum dose of exposure to WBV required to elicit an optimal response in children and adolescents for improving health-related physical fitness. These may be translated into a more specific WBV protocol.

Tibia shaft fractures: costly burden of nonunions

BACKGROUND

Tibia shaft fractures (TSF) are common for men and women and cause substantial morbidity, healthcare use, and costs. The impact of nonunions on healthcare use and costs is poorly described. Our goal was to investigate patient characteristics and healthcare use and costs associated with TSF in patients with and without nonunion.

METHODS

We retrospectively analyzed medical claims in large U.S. managed care claims databases (Thomson Reuters MarketScan®, 16 million lives). We studied patients ≥ 18 years old with a TSF diagnosis (ICD-9 codes: 823.20, 823.22, 823.30, 823.32) in 2006 with continuous pharmaceutical and medical benefit enrollment 1 year prior and 2 years post-fracture. Nonunion was defined by ICD-9 code 733.82 (after the TSF date).

RESULTS

Among the 853 patients with TSF, 99 (12%) had nonunion. Patients with nonunion had more comorbidities (30 vs. 21, pre-fracture) and were more likely to have their TSF open (87% vs. 70%) than those without nonunion. Patients with nonunion were more likely to have additional fractures during the 2-year follow-up (of lower limb [88.9% vs. 69.5%, P < 0.001], spine or trunk [16.2% vs. 7.2%, P = 0.002], and skull [5.1% vs. 1.3%, P = 0.008]) than those without nonunion. Nonunion patients were more likely to use various types of surgical care, inpatient care (tibia and non-tibia related: 65% vs. 40%, P < 0.001) and outpatient physical therapy (tibia-related: 60% vs. 42%, P < 0.001) than those without nonunion. All categories of care (except emergency room costs) were more expensive in nonunion patients than in those without nonunion: median total care cost $25,556 vs. $11,686, P < 0.001. Nonunion patients were much more likely to be prescribed pain medications (99% vs. 92%, P = 0.009), especially strong opioids (90% vs. 76.4%, P = 0.002) and had longer length of opioid therapy (5.4 months vs. 2.8 months, P < 0.001) than patients without nonunion. Tibia fracture patterns in men differed from those in women.

CONCLUSIONS

Nonunions in TSF's are associated with substantial healthcare resource use, common use of strong opioids, and high per-patient costs. Open fractures are associated with higher likelihood of nonunion than closed ones. Effective screening of nonunion risk may decrease this morbidity and subsequent healthcare resource use and costs.

Low-intensity pulsed ultrasound (LIPUS) may prevent polyethylene induced periprosthetic osteolysis in vivo

We investigated the effect of local low-intensity pulsed ultrasound (LIPUS) on polyethylene debris induced periprosthetic osteolysis. The periprosthetic osteolysis model was made by injecting endotoxin-free pure polyethylene particles into the distal part of the femur canal and inserting a stainless steel plug into this femur. The effects of polyethylene and LIPUS were assessed histologically and by the shear strength test and periprosthetic bone mineral density (BMD) test. Sixteen rabbits received a stainless steel plug on one side and both polyethylene and a stainless steel plug on the other side. Three months later, the side that received polyethylene showed periprosthetic osteolysis. Subsequently, another 16 rabbits received polyethylene plus local LIPUS (200 mW/cm(2) for 20 min daily) on one side and polyethylene alone on the other side. Three months later, LIPUS effectively prevented the periprosthetic osteolysis caused by polyethylene in this rabbit model.

Low-intensity pulsed ultrasound regulates proliferation and differentiation of osteoblasts through osteocytes

Low-intensity pulsed ultrasound (LIPUS) has been used as a safe and effective modality to enhance fracture healing. As the most abundant cells in bone, osteocytes orchestrate biological activities of effector cells via direct cell-to-cell contacts and by soluble factors. In this study, we have used the osteocytic MLO-Y4 cells to study the effects of conditioned medium from LIPUS-stimulated MLO-Y4 cells on proliferation and differentiation of osteoblastic MC3T3-E1 cells. Conditioned media from LIPUS-stimulated MLO-Y4 cells (LIPUS-Osteocyte-CM) were collected and added on MC3T3-E1 cell cultures. MC3T3-E1 cells cultured in LIPUS-Osteocyte-CM demonstrated a significant inhibition of proliferation and an increased alkaline phosphatase activity. The results of PGE(2) and NO assay showed that LIPUS could enhance PGE(2) and NO secretion from MLO-Y4 cells at all time points within 24h after LIPUS stimulation. We conclude that LIPUS regulates proliferation and differentiation of osteoblasts through osteocytes in vitro. Increased secretion of PGE(2) from osteocytes may play a role in this effect.

Análise da influência do ultrassom de baixa intensidade na região de reparo ósseo em ratos sob ausência de carga

Há evidências de que o ultrassom (US) de baixa intensidade pode acelerar a regeneração óssea. Este trabalho objetivou verificar a ação do US no defeito ósseo, criado experimentalmente em tíbias de ratos sob ausência de carga. Vinte Rattus novergicus albinus, Wistar adultos, divididos em: G1 (n=10), grupo experimental de 15 dias sem suspensão, e G2 (n=10), grupo experimental de 15 dias suspenso pela cauda, foram submetidos à osteotomia em ambas as tíbias e à aplicação do US, frequência de 1,5 MHz, ciclo de trabalho 1:4, 30 mW/cm², nas tíbias direitas por 12 sessões de 20 minutos. Após o sacrifício, as tíbias foram submetidas à análise da Densidade Mineral Óssea (DMO). Os resultados demonstraram DMO de 0,139±0,018 g/cm² para tíbia tratada; 0,131±0,009 g/cm² para tíbia controle no G1; e no G2 registrou-se 0,120±0,009 g/cm² para tíbia tratada e 0,106±0,017 g/cm² para tíbia controle. Houve diferença significante entre os grupos nos quais o G2 apresentou menor DMO, o que demonstra que a suspensão prejudica a manutenção das propriedades ósseas, e entre as tíbias tratadas e controles do G2, demonstrando que o US acelerou o processo de reparo, concluindo que a impossibilidade do estímulo mecânico causada pela não deambulação em um processo de reparo ósseo pode ser minimizada pela ação do US. No G1, a aplicação do US não teve influência significante no aumento da DMO, talvez pelo fato dos animais já terem estímulo mecânico suficiente à formação óssea.