Effect of low-intensity pulsed ultrasound on fracture callus mineral density and flexural strength in rabbit tibial fresh fracture

The effect of ultrasound on bone healing across a bone gap, an experimental study of a delayed union model

The aim of the study is to determine whether ultrasound accelerates bone repair across a bone gap. To replicate the clinical situation of bone repair in a severe tibial fracture, such as Gustilo grade three, we designed an experimental model to determine whether ultrasound can promote bone healing in the presence of a bone gap. The effect of ultrasound on bone healing of a tibial bone gap held in an external fixator was studied. 60 New Zealand White rabbits were divided into four groups. In one group of 6 animals, a tibial osteotomy was closed or compressed and studied at six weeks (Comparative Group). In 3 groups of 18 animals each, a tibial bone gap was maintained and was untreated, treated with ultrasound or mock ultrasound (Control Group). The repair of the bone gaps was studied in 3 animals each at 2,4,6,8,10 and 12 weeks. Investigation was by histology, angiography, radiography and densitometry. Three of the 18 untreated group progressed to delayed union, compared with 4 in the ultrasound and 3 in the mock ultrasound group (Control Group). Statistical analysis showed no difference between the three groups. 5 of the 6 closed/compressed osteotomies (Comparative Group) united faster at 6 weeks. The healing pattern of the bone gap groups were similar. We recommend this as a delayed union model. We found no evidence that ultrasound accelerated bone healing, reduced the rate of delayed union or increased callus formation in this model of delayed union. This study simulates delayed union following a compound tibial fracture and has clinical relevance concerning treatment of a delay in union with ultrasound.

Low-Intensity Pulsed Ultrasound Stimulation for Bone Fractures Healing: A Review

Low-intensity pulsed ultrasound (LIPUS) is a developing technology, which has been proven to improve fracture healing process with minimal thermal effects. This noninvasive treatment accelerates bone formation through various molecular, biological, and biomechanical interactions with tissues and cells. Although LIPUS treatment has shown beneficial effects on different bone fracture locations, only very few studies have examined its effects on deeper bones. This study provides an overview on therapeutic ultrasound for fractured bones, possible mechanisms of action, clinical evidences, current limitations, and its future prospects.

Is an anodizing coating associated to the photobiomodulation able to optimize bone healing in ovariectomized animal model?

This in vivo study investigated whether the bioactivity of anodizing coating, produced by plasma electrolytic oxidation (PEO), on mini-plate in femur fracture could be improved with the association of photobiomodulation (PBM) therapy. From the 20 ovariectomized Wistar female rats, 8 were used for model characterization, and the remaining 12 were divided into four groups according to the use of PBM therapy by diode laser (808 nm; power: 100 mW; energy: 6.0 J; energy density: 212 J/cm²; power density: 3.5 W/cm²) and the type of mini-plate surface (commercially pure titanium mini-plate -cpTi- and PEO-treated mini-plate) as follow: cpTi; PEO; cpTi/PBM; and PEO/PBM. After 60 days of surgery, fracture healing underwent microstructural, bone turnover, histometric, and histologic adjacent muscle analysis. Animals of groups with PEO and PBM showed greater fracture healing than cpTi control group under histometric and microstructural analysis (P < 0.05); however, bone turnover was just improved in PBM's groups (P < 0.05). there was no difference between cpTi and PEO without PBM (P > 0.05). Adjacent muscle analysis showed no metallic particles or muscle alterations in all groups. PEO and PBM are effective strategies for bone repair in fractures, however their association does not provide additional advantages.

Photobiomodulation guided healing in a sub-critical bone defect in calvarias of rats

Background

Photobiomodulation presents stimulatory effects on tissue metabolism, constituting a promising strategy to produce bone tissue healing.

Objective

the aim of the present study was to investigate the in vivo performance of PBM using an experimental model of cranial bone defect in rats.

Material and Methods

rats were distributed in 2 different groups (control group and PBM group). After the surgical procedure to induce cranial bone defects, PBM treatment initiated using a 808 nm laser (100 mW, 30 J/cm², 3 times/week). After 2 and 6 weeks, animals were euthanized and the samples were retrieved for the histopathological, histomorphometric, picrosirius red staining and immunohistochemistry analysis.

Results

Histology analysis demonstrated that for PBM most of the bone defect was filled with newly formed bone (with a more mature aspect when compared to CG). Histomorphomeric analysis also demonstrated a higher amount of newly formed bone deposition in the irradiated animals, 2 weeks post-surgery. Furthermore, there was a more intense deposition of collagen for PBM, with ticker fibers. Results from Runx-2 immunohistochemistry demonstrated that a higher immunostaining for CG 2 week's post-surgery and no other difference was observed for Rank-L immunostaining.

Conclusion

This current study concluded that the use of PBM was effective in stimulating newly formed bone and collagen fiber deposition in the sub-critical bone defect, being a promising strategy for bone tissue engineering.

An innovative Mg/Ti hybrid fixation system developed for fracture fixation and healing enhancement at load-bearing skeletal site

Magnesium (Mg) is a potential biomaterial suitable for developing biodegradable orthopaedic implants, especially as internal fixators for fracture fixation at non-load bearing skeletal sites. However, Mg alone cannot provide sufficient mechanical support for stable fracture fixation at load bearing sites due to its rapid degradation in the early stage after implantation. In consideration of the strengths and weaknesses of Mg, we developed an innovative magnesium/titanium (Mg/Ti) hybrid fixation system for long bone fracture fixation and investigated the fixation efficacy. The finite element analysis (FEA) results indicated that the Mg/Ti hybrid fixation system provided sufficient mechanical support for fracture fixation at load-bearing skeletal site. As a proof-of-concept, we performed a "Z-shaped" open osteotomy at the mid-shaft of rabbit tibia. For comparison, the animals were divided into two groups: Mg/Ti group (fixated with Mg screws and Ti fixators) and Ti control group (fixated with Ti screws and Ti fixators). The radiographic, four-point bending mechanical test, histological and histomorphometric analysis were postoperatively performed in a temporal manner up to 12 weeks. Both X-ray and micro-CT images of the Mg/Ti group showed a larger callus (14.7% at 3rd week and 24.8% at 6th week, n = 5-7, p < 0.05) in the regions of interest (ROIs) over time, especially at the opposite cortex of the fixation plate. At the 12th week post-operation, the biomechanical test result indicated that the rabbit tibia in the Mg/Ti group healed better and the overall mechanical strength was approximately 3-fold higher (n = 8, p < 0.05) than that at 6th week. Furthermore, the FEA revealed that the Mg/Ti group had a higher mechanical strength (19.5% at week 6 and 31.5% at week 12) at the specified ROI and resulted in an earlier and faster endochondral ossification (68.0% at week 3 and 71.4% at week 6) with a higher expression of osteocalcin (54.0%) and collagen I (34.2%) than the Ti control group (n = 4, p < 0.05). Further evaluation suggested that a higher expression of calcitonin gene-related peptide (CGRP), a known osteogenic neuron peptide, in the fracture callus of the Mg/Ti group might be a major underlying mechanism of enhanced fracture healing attributed to the release of Mg ions during the degradation of Mg screws.

Integrative Approach to Facilitate Fracture Healing: Topical Chinese Herbal Paste with Oral Strontium Ranelate

Strontium ranelate (SrR) is one of the pharmaceutical agents reported to be effective on the promotion of fracture healing. This study aimed to evaluate the integrative effect of the oral SrR with a topical Chinese herbal paste, namely, CDR, on facilitation of bone healing. The in vivo efficacy was evaluated using rats with tibial fracture. They were treated with either CDR topically, or SrR orally, or their combined treatments. The in vivo results illustrated a significant additive effect of CDR on SrR in increasing the yield load of the fractured tibia. The in vitro results showed that neither SrR nor CDR exhibited a cytotoxic effect on UMR106 and bone-marrow stem cell (BMSC), but both of them increased the proliferation of BMSC at low concentrations. The combination of CDR at 200 μg/mL with SrR at 200 or 400 μg/ml also showed an additive effect on increasing the ALP activity of BMSC. Both SrR and CDR alone reduced osteoclast formation, and the effective concentration of SrR to inhibit osteoclastogenesis was reduced in the presence of CDR. This integrative approach by combining oral SrR and topical CDR is effective in promoting fracture healing properly due to their additive effects on proosteogenic and antiosteoclastogenic properties.

Comparison of effects of LLLT and LIPUS on fracture healing in animal models and patients: A systematic review

The aim of this paper is to study the in vivo potency of low-level laser therapy (LLLT) and low intensity pulsed ultrasound (LIPUS) alone, accompanied by bone grafts, or accompanied by other factors on fracture healing in animal models and patients. In this paper, we aim to systematically review the published scientific literature regarding the use of LLLT and LIPUS to accelerate fracture healing in animal models and patients. We searched the PubMed database for the terms LLLT or LIPUS and/or bone, and fracture. Our analysis also suggests that both LIPUS and LLLT may be beneficial to fracture healing in patients, and that LIPUS is more effective. These finding are of considerable importance in those treatments with a LIPUS, as a laser device may reduce healing time. The most clinically relevant impact of the LIPUS treatment could be a significant reduction in the proportion of patients who go on to develop a nonunion. If it is confirmed that the therapeutic influence is true and reliable, patients will obtain benefits from LIPUS and LLLT. Further clinical trials of high methodological quality are needed in order to determine the optimal role of LIPUS and LLLT in fracture healing in patients.

Inhibitory Effect of Low-Intensity Pulsed Ultrasound on the Expression of Lipopolysaccharide-Induced Inflammatory Factors in U937 Cells

OBJECTIVES

Low-intensity pulsed ultrasound (US) has been reported to promote periodontal tissue regeneration and reduce inflammation in soft tissues and in bone infectious diseases. Here we investigated the effect of low-intensity pulsed US on the expression of lipopolysaccharide (LPS)-induced inflammatory factors in U937 macrophage cells.

METHODS

U937 cells were stimulated with different concentrations of LPS and exposed to different intensities of low-intensity pulsed US. Cell viability and apoptosis of U937 cells were determined by cell-counting kit assays and flow cytometry. A real-time polymerase chain reaction and an enzyme-linked immunosorbent assay were used to test the expression of inflammatory factors. The expression levels of toll-like receptor 4, p65, p-IκBα, and IκBα were assessed by western blots.

RESULTS

Tumor necrosis factor α began to increase in U937 cells on induction with 1-μg/mL LPS. Low-intensity pulsed US at the intensity of 60 mW/cm² was more effective in reducing interleukin 8 (IL-8) expression. Furthermore, LPS inhibited the viability and increased apoptosis of U937 cells, whereas low-intensity pulsed US significantly reversed these effects (P < .05). Low-intensity pulsed US reduced the protein expression of IL-6 and IL-8 at both gene and protein levels in U937 cells. The western blot and immunofluorescence showed that low-intensity pulsed US primarily suppressed the degradation and phosphorylation of IκBα and the translocation of p65 into the nuclei.

CONCLUSIONS

Low-intensity pulsed US alleviated the expression of inflammatory factors induced by LPS in U937 cells. This process was modulated by suppressing the toll-like receptor 4-nuclear factor κB signaling pathway. Therefore, low-intensity pulsed US might be a potential immunomodulatory therapy for the treatment of periodontitis.

Low-intensity pulsed ultrasound enhances bone formation around miniscrew implants

Miniscrew implants (MSIs) are currently used to provide absolute anchorage in orthodontics; however, their initial stability is an issue of concern. Application of low-intensity pulsed ultrasound (LIPUS) can promote bone healing. Therefore, LIPUS application may stimulate bone formation around MSIs and enhance their initial stability.

AIM

To investigate the effect of LIPUS exposure on bone formation after implantation of titanium (Ti) and stainless steel (SS) MSIs.

METHODS

MSIs made of Ti-6Al-4V and 316L SS were placed on rat tibiae and treated with LIPUS. The bone morphology around MSIs was evaluated by scanning electron microscopy and three-dimensional micro-computed tomography. MC3T3-E1 cells cultured on Ti and SS discs were treated with LIPUS, and the temporary expression of alkaline phosphatase (ALP) was examined.

RESULTS

Bone-implant contact increased gradually from day 3 to day 14 after MSI insertion. LIPUS application increased the cortical bone density, cortical bone thickness, and cortical bone rate after implantation of Ti and SS MSIs (P<0.05). LIPUS exposure induced ALP upregulation in MC3T3-E1 cells at day 3 (P<0.05).

CONCLUSION

LIPUS enhanced bone formation around Ti and SS MSIs, enhancing the initial stability of MSIs.

Evaluation of a topical herbal agent for the promotion of bone healing

A topically used Chinese herbal paste, namely, CDNR, was designed to facilitate fracture healing which is usually not addressed in general hospital care. From our in vitro studies, CDNR significantly inhibited the release of nitric oxide from RAW264.7 cells by 51 to 77%. This indicated its anti-inflammatory effect. CDNR also promoted the growth of bone cells by stimulating the proliferation of UMR106 cells up to 18%. It also increased the biomechanical strength of the healing bone in a drill-hole defect rat model by 16.5% significantly. This result revealed its in vivo efficacy on facilitation of bone healing. Furthermore, the detection of the chemical markers of CDNR in the skin and muscle of the treatment area demonstrated its transdermal properties. However, CDNR did not affect the bone turnover markers in serum of the rats. With its anti-inflammatory and bone formation properties, CDNR is found effective in promoting bone healing.

Genes responsive to low-intensity pulsed ultrasound in MC3T3-E1 preosteoblast cells

Although low-intensity pulsed ultrasound (LIPUS) has been shown to enhance bone fracture healing, the underlying mechanism of LIPUS remains to be fully elucidated. Here, to better understand the molecular mechanism underlying cellular responses to LIPUS, we investigated gene expression profiles in mouse MC3T3-E1 preosteoblast cells exposed to LIPUS using high-density oligonucleotide microarrays and computational gene expression analysis tools. Although treatment of the cells with a single 20-min LIPUS (1.5 MHz, 30 mW/cm(2)) did not affect the cell growth or alkaline phosphatase activity, the treatment significantly increased the mRNA level of Bglap. Microarray analysis demonstrated that 38 genes were upregulated and 37 genes were downregulated by 1.5-fold or more in the cells at 24-h post-treatment. Ingenuity pathway analysis demonstrated that the gene network U (up) contained many upregulated genes that were mainly associated with bone morphology in the category of biological functions of skeletal and muscular system development and function. Moreover, the biological function of the gene network D (down), which contained downregulated genes, was associated with gene expression, the cell cycle and connective tissue development and function. These results should help to further clarify the molecular basis of the mechanisms of the LIPUS response in osteoblast cells.

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.

Ultrasound therapy modulates osteocalcin expression during bone repair in rats

The aim of this study was to measure the temporal pattern of the protein expression of RUNX2, RANKL, OPG, and osteocalcin after ultrasound therapy during the process of bone healing by immunohistochemistry. The animals were randomly distributed into two groups: control or ultrasound-treated group. A non-critical size bone defects were surgically created at the upper third of the tibia. The treatments started 24h post-surgery, and they are performed for 3, 6, and 12 sessions, with an interval of 48h. A low-intensity pulsed ultrasound (1.5MHz, 1:4 duty cycle, intensity SATA 30mW/cm(2), 20min/session, stationary mode application) was used. On days 7, 13, and 25 post-injury, rats were killed individually by carbon dioxide asphyxia. The tibias were removed for analysis. The histopathological analysis pointed out no remarkable differences between groups for all periods evaluated. However, immunohistochemical data revealed that ultrasound therapy produced an up-regulation of osteocalcin at day 7th and 13th post-surgery. Taken together, our results indicate that ultrasound therapy modulates osteocalcin expression during bone repair in rats as depicted by differential immunopression at the initial and intermediate stages of recovery.

Mechanical means to improve bone strength: ultrasound and vibration

Not all fractures heal well. One method that has been used to improve fracture healing is low-intensity pulsed ultrasound (LIPUS). LIPUS has been US Food and Drug Administration approved for several years, and some preclinical and clinical evidence indicates that fracture healing can be improved by this technique, which appears to be generally safe. There are several suggested mechanisms of action of LIPUS. Clinical studies generally support its usefulness in accelerating fracture healing. A less-established modality is whole body vibration (WBV), which appears to stimulate bone and muscle growth while suppressing adipogenesis in animal studies. Early studies in humans, including some in children with disabilities, suggest that WBV holds promise as a technique for reducing fracture risk. The exact place of WBV in preventing fracture remains to be established.

The evidence of low-intensity pulsed ultrasound for in vitro, animal and human fracture healing

BACKGROUND

Physical stimulation therapies are currently available to enhance fracture healing.

SOURCES OF DATA

A search of PubMed, Medline, CINAHL, DH data and Embase databases was performed using the keywords 'ultrasound' and 'fracture healing'.

AREAS OF AGREEMENT

The evidence in vitro and animal studies suggests that low-intensity pulsed ultrasound (LIPUS) produces significant osteoinductive effects, accelerating the healing process and improving the bone-bending strength.

AREAS OF CONTROVERSY

The evidence in human trials is controversial in fresh, stress fractures and in limb lengthening. LIPUS is effective in delayed unions, in smokers and in diabetic population.

GROWING POINTS

LIPUS is an alternative, less invasive form of treatment for complicated fractures, in patients with poor bone healing and may play a role in the management of large-scale bone defects producing substantial cost savings and decreasing associated disability.

AREAS TIMELY FOR DEVELOPING RESEARCH

There is heterogeneity among in vitro, animal studies and their application to human studies. Further randomized controlled trials of high methodological quality are needed.

Low-intensity pulsed ultrasound (LIPUS) therapy may enhance the negative effects of oxygen radicals in the acute phase of fracture

Though it is well accepted that low-intensity pulsed ultrasound (LIPUS) can accelerate the healing process of a fracture with very good results, we should still pay attention to its side effects and further improve its application in detail, such as the appropriate time and point for the application. In the early phase of a bone fracture, there are millions of oxygen radicals released by neutrophils in the injured area. This article focuses on whether the increased permeability of normal cell membranes by LIPUS makes the concentration of oxygen radicals increase to such a high degree that damage occurs to healthy tissue cells. It is proposed that it may be better not to use LIPUS in the acute phase of a fracture (i.e. within 1week after injury) but instead delay its application until after any inflammatory reaction has weakened to yield better results.

Low-intensity ultrasound application in distal radius metaphyseal bone defects of dogs

We assessed the repair of transverse, 3-mm wide bone gaps created at the distal radius in 28 dogs that were randomly divided into two 14-animal groups; one was the control group and the other received a daily, 20-min application of low-intensity pulsed ultrasound for 100 days. Sequential radiographs, histomorphometrics, bone fluorescent histology and bone vascularity assessments found that all animals from both groups obtained a stage of hypertrophic-type nonunion with fibrocartilage tissue formation throughout the region of osteotomy. However, treated animals exhibited areas of endochondral ossification within the fibrocartilage region. There was no difference in type of vascularity or the newly formed bone process obtained by tetracycline labeling. Application of low-intensity ultrasound was not capable of significantly changing the reparative process and it may not be sufficiently powerful to overcome a combination of local deleterious effects on bone healing, created by gapping, excessive motion and periosteal resection.