Low-intensity pulsed ultrasound does not enhance distraction callus in a rabbit model

Effect of low-intensity pulsed ultrasound on distraction osteogenesis: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Low-intensity pulsed ultrasound (LIPUS) is a common adjunct used to promote bone healing for fresh fractures and non-unions, but its efficacy for bone distraction osteogenesis remains uncertain. This study aims to determine whether LIPUS can effectively and safely reduce the associated treatment time for patients undergoing distraction osteogenesis.

METHODS

MEDLINE, EMBASE, and the Cochrane Library were searched until May 1, 2018, without language restriction. Studies should be randomized controlled trials (RCTs) or quasi-RCTs of LIPUS compared with sham devices or no devices in patients who undergo distraction osteogenesis. The primary outcome was the treatment time. The secondary outcome was the risk of complications. Treatment effects were assessed using mean differences, standardized mean differences, or risk ratios using a random-effects model. The Cochrane risk-of-bias tool was used to assess the risk of bias. The I² statistic was used to assess the heterogeneity. The GRADE system was used to evaluate the evidence quality.

RESULTS

A total of 7 trials with 172 patients were included. The pooled results suggested that during the process of distraction osteogenesis, LIPUS therapy did not show a statistically significant reduction in the treatment time (mean difference, - 8.75 days/cm; 95% CI, - 20.68 to 3.18 days/cm; P = 0.15; I² = 72%) or in the risk of complications (risk ratio, 0.90 in favor of LIPUS; 95% CI, 0.65 to 1.24; I² = 0%). Also, LIPUS therapy did not show a significant effect on the radiological gap fill area (standardized mean difference, 0.48 in favor of control; 95%CI, - 1.49 to 0.52; I² = 0%), the histological gap fill length (standardized mean difference, 0.76 in favor of control; 95%CI, - 1.78 to 0.27; I² = 0%), or the bone density increase (standardized mean difference, 0.43 in favor of LIPUS; 95%CI, - 0.02 to 0.88; I² = 0%).

CONCLUSIONS

Among patients undergoing distraction osteogenesis, neither the treatment time nor the risk of complications could be reduced by LIPUS therapy. The currently available evidence is insufficient to support the routine use of this intervention in clinical practice.

TRIAL REGISTRATION

CRD 42017073596.

Low-frequency, low-magnitude vibrations (LFLM) enhances chondrogenic differentiation potential of human adipose derived mesenchymal stromal stem cells (hASCs)

The aim of this study was to evaluate if low-frequency, low-magnitude vibrations (LFLM) could enhance chondrogenic differentiation potential of human adipose derived mesenchymal stem cells (hASCs) with simultaneous inhibition of their adipogenic properties for biomedical purposes. We developed a prototype device that induces low-magnitude (0.3 g) low-frequency vibrations with the following frequencies: 25, 35 and 45 Hz. Afterwards, we used human adipose derived mesenchymal stem cell (hASCS), to investigate their cellular response to the mechanical signals. We have also evaluated hASCs morphological and proliferative activity changes in response to each frequency. Induction of chondrogenesis in hASCs, under the influence of a 35 Hz signal leads to most effective and stable cartilaginous tissue formation through highest secretion of Bone Morphogenetic Protein 2 (BMP-2), and Collagen type II, with low concentration of Collagen type I. These results correlated well with appropriate gene expression level. Simultaneously, we observed significant up-regulation of α3, α4, β1 and β3 integrins in chondroblast progenitor cells treated with 35 Hz vibrations, as well as Sox-9. Interestingly, we noticed that application of 35 Hz frequencies significantly inhibited adipogenesis of hASCs. The obtained results suggest that application of LFLM vibrations together with stem cell therapy might be a promising tool in cartilage regeneration.

Effect of Low-Intensity Pulsed Ultrasound on Distraction Osteogenesis Treatment Time: A Meta-analysis of Randomized Clinical Trials

OBJECTIVES

The objectives of this systematic review with a meta-analysis were to critically analyze the available scientific literature regarding the effects of low-intensity pulsed ultrasound (US) on stimulating bone regeneration and bone maturation during distraction osteogenesis in humans and to determine whether the stimulatory effect of low-intensity pulsed US can effectively reduce the associated treatment time.

METHODS

Studies were considered for inclusion if they were randomized clinical trials that examined the effect of low-intensity pulsed US on distraction osteogenesis compared to conventional distraction osteogenesis. The primary outcome was reduced treatment time. Study selection, risk of bias assessment, and data extraction were performed in duplicate. A random-effects meta-analysis model was used when more than 3 trials were eligible for a quantitative analysis and considering the expected differences in interventions and measurement tools.

RESULTS

Five randomized clinical trials, with a moderate to high risk of bias, met the eligibility criteria. Four trials examining tibial distraction osteogenesis in 118 patients were combined in a meta-analysis. A statistically significant difference for reduced treatment time between distraction osteogenesis with low-intensity pulsed US and standard distraction osteogenesis was evident (mean difference, -15.236 d/cm; random-effects 95% confidence interval, -19.902 to -10.569 d/cm; P < .0001). As for the mandible, only 1 clinical trial was available, which showed no significant effect of low-intensity pulsed US therapy on distraction osteogenesis.

CONCLUSIONS

Current available evidence suggests that low-intensity pulsed US therapy may provide a reduction in the overall treatment time for tibial distraction osteogenesis. However, this conclusion should be considered with caution, given the moderate to high risk of bias in the included randomized clinical trials.

Effects of ultrasound on osteotomy healing in a rabbit fracture model

This study investigated the effects of ultrasound (US) at different frequencies on fracture healing over a three-week period in a rabbit fibular fracture model. Forty-five adult New Zealand White rabbits were divided into five groups: a control group and four groups treated with US frequencies of 0.5, 1.0, 1.5 and 2.0 MHz (0.5 W/cm(2), 200-μs burst, pulsed 1:4). After anesthesia, transverse osteotomy was performed on the fibula bone. This was followed by intravital staining and fluorescence microscopic examination of new bone formation and biomechanical tests of torsional stiffness at the osteotomy site. Results showed that total new bone formation and torsional stiffness of the fibula were greater in all US-treated groups than in the control group. No significant difference was found between any of the four US-treated groups. The US treatment also enhanced bone growth of the sham-treated contralateral fracture site. These results suggest that US treatment at 0.5, 1.0, 1.5 or 2.0 MHz can enhance fracture healing in a rabbit model. Furthermore, the effects of US on fracture healing at present parameters might not be confined locally.

Ultrasound for fracture healing: current evidence

Low-intensity pulsed ultrasound (LIPUS) is a relatively new technique for the acceleration of fracture healing in fresh fractures and nonunions. It has a frequency of 1.5 MHz, a signal burst width of 200 micros, a signal repetition frequency of 1 kHz, and an intensity of 30 mW/cm2. In 1994 and 1997, two milestone double-blind randomized controlled trials revealed the benefits of LIPUS for the acceleration of fracture healing in the tibia and radius. They showed that LIPUS accelerated the fracture healing rate from 24% to 42% for fresh fractures. Some literature, however, has shown no positive effects. The beneficial effect of acceleration of fracture healing by LIPUS is considered to be larger in the group of patients or fractures with potentially negative factors for fracture healing. The incidence of delayed union and nonunion is 5% to 10% of all fractures. For delayed union and nonunion, the overall success rate of LIPUS therapy is approximately 67% (humerus), 90% (radius/radius-ulna), 82% (femur), and 87% (tibia/tibia-fibula). LIPUS likely has the ability to enhance maturation of the callus in distraction osteogenesis and reduce the healing index. The critical role of LIPUS for fracture healing is still unknown because of the heterogeneity of results in clinical trials for fresh fractures and the lack of controlled trials for delayed unions and nonunions.

Extremely small-magnitude accelerations enhance bone regeneration: a preliminary study

High-frequency, low-magnitude accelerations can be anabolic and anticatabolic to bone. We tested the hypothesis that application of these mechanical signals can accelerate bone regeneration in scaffolded and nonscaffolded calvarial defects. The cranium of experimental rats (n = 8) in which the 5-mm bilateral defects either contained a collagen scaffold or were left empty received oscillatory accelerations (45 Hz, 0.4 g) for 20 minutes per day for 3 weeks. Compared with scaffolded defects in the untreated control group (n = 6), defects with a scaffold and subject to oscillatory accelerations had a 265% greater fractional bone defect area 4 weeks after the surgery. After 8 weeks of healing (1-week recovery, 3 weeks of stimulation, 4 weeks without stimulation), the area (181%), volume (137%), and thickness (53%) of the regenerating tissue in the scaffolded defect were greater in experimental than in control animals. In unscaffolded defects, mechanical stimulation induced an 84% greater bone volume and a 33% greater thickness in the defect. These data provide preliminary evidence that extremely low-level, high-frequency accelerations can enhance osseous regenerative processes, particularly in the presence of a supporting scaffold.

Effects of Ultrasound Modes on Mandibular Osteodistraction

Previous studies have shown that therapeutic pulsed ultrasound (pulsed) has superior stimulatory effect on bone fracture healing compared with continuous ultrasound (continuous). Our predictive hypothesis was that pulsed ultrasound can produce better bone formation during mandibular osteodistraction than continuous ultrasound. Thirty-six New Zealand rabbits were divided into 3 groups of 12. Osteodistraction was performed at 3 mm/day for 5 days. Group 1 received pulsed, group 2 received continuous ultrasound, and group 3 was the control group (distraction only). Bone formation was assessed by quantitative bone density (QBD), mechanical testing, and histological examination. In the first 2 wks post-distraction, group 2 showed enhanced bone formation more than group 1 ( p < 0.05); however, in the 3rd and 4th wks, group 1 showed more bone formation than group 2 ( p < 0.05). Earlier stages of bone healing were enhanced more by continuous, whereas late stages were enhanced more by pulsed, ultrasound. Abbreviations: PULSED, low-intensity pulsed ultrasound; CONTINUOUS, low-intensity continuous ultrasound.