The science of ultrasound therapy for fracture healing

Comparison of Teriparatide and Combination of Cissus Quadrangularis and Dalbergia Sissoo on Bone Healing Against the Control Group in Maxillofacial Fractures: A Randomized Open-label Control Trial

Study Design

Randomized Control Trial.

Objective

A randomized control trial was planned to aim to assess whether subcutaneous Injection of Teriparatide and Tablet Reunion (combination of Cissus Quadrangularis and Dalbergia sissoo) improves maxillofacial fracture healing as compared to the control group.

Methods

24 patients of mandibular fracture with or without concomitant maxillofacial fractures were randomly divided into 3 equal groups (Group 1- Control, Group 2- Tablet Reunion, and Group 3- Injection Teriparatide) and the treatment duration was 4 weeks. Pain, fracture site mobility, bite force, serum markers, and radiographic healing were assessed preoperatively and postoperatively at regular intervals till 12 weeks.

Results

Group 2 showed early pain relief, although it was insignificant. Group 3 showed the highest anterior bite force at all the time points. Change in mean posterior bite force (PBF) showed a statistically significant increase at 8th week and 12th week in intergroup comparison; however, at 12th week, Group 3 was significantly better than Group 1 and reported the highest posterior bite force compared to other groups. Serum calcium and PTH level showed no significant difference, whereas Serum ALP showed a statistically significant increase in Group 3. The radiographic assessment showed no significant difference among the 3 groups.

Conclusions

Both the intervention group drugs showed a promising effect on accelerating the fracture healing and improving bite force restoration with the osteoanabolic action; however, early radiographic healing and increased serum osteogenic markers in Group 3 indicate its possible optimistic role in maxillofacial fracture healing.

The application of mechanobiotechnology for immuno-engineering and cancer immunotherapy

Immune-engineering is a rapidly emerging field in the past few years, as immunotherapy evolved from a paradigm-shifting therapeutic approach for cancer treatment to promising immuno-oncology models in clinical trials and commercial products. Linking the field of biomedical engineering with immunology, immuno-engineering applies engineering principles and utilizes synthetic biology tools to study and control the immune system for diseases treatments and interventions. Over the past decades, there has been a deeper understanding that mechanical forces play crucial roles in regulating immune cells at different stages from antigen recognition to actual killing, which suggests potential opportunities to design and tailor mechanobiology tools to novel immunotherapy. In this review, we first provide a brief introduction to recent technological and scientific advances in mechanobiology for immune cells. Different strategies for immuno-engineering are then discussed and evaluated. Furthermore, we describe the opportunities and challenges of applying mechanobiology and related technologies to study and engineer immune cells and ultimately modulate their function for immunotherapy. In summary, the synergetic integration of cutting-edge mechanical biology techniques into immune-engineering strategies can provide a powerful platform and allow new directions for the field of immunotherapy.

Electrical Stimulation Enabled via Electrospun Piezoelectric Polymeric Nanofibers for Tissue Regeneration

Electrical stimulation has demonstrated great effectiveness in the modulation of cell fate in vitro and regeneration therapy in vivo. Conventionally, the employment of electrical signal comes with the electrodes, battery, and connectors in an invasive fashion. This tedious procedure and possible infection hinder the translation of electrical stimulation technologies in regenerative therapy. Given electromechanical coupling and flexibility, piezoelectric polymers can overcome these limitations as they can serve as a self-powered stimulator via scavenging mechanical force from the organism and external stimuli wirelessly. Wireless electrical cue mediated by electrospun piezoelectric polymeric nanofibers constitutes a promising paradigm allowing the generation of localized electrical stimulation both in a noninvasive manner and at cell level. Recently, numerous studies based on electrospun piezoelectric nanofibers have been carried out in electrically regenerative therapy. In this review, brief introduction of piezoelectric polymer and electrospinning technology is elucidated first. Afterward, we highlight the activating strategies (e.g., cell traction, physiological activity, and ultrasound) of piezoelectric stimulation and the interaction of piezoelectric cue with nonelectrically/electrically excitable cells in regeneration medicine. Then, quantitative comparison of the electrical stimulation effects using various activating strategies on specific cell behavior and various cell types is outlined. Followingly, this review explores the present challenges in electrospun nanofiber-based piezoelectric stimulation for regeneration therapy and summarizes the methodologies which may be contributed to future efforts in this field for the reality of this technology in the clinical scene. In the end, a summary of this review and future perspectives toward electrospun nanofiber-based piezoelectric stimulation in tissue regeneration are elucidated.

Effect of Low-Intensity Pulsed Ultrasound on the Graft-Bone Healing of Artificial Ligaments: An In Vitro and In Vivo Study

BACKGROUND

As many researchers have focused on promoting the graft-bone healing of artificial ligaments, even with numerous chemical coatings, identifying a biosafe, effective, and immediately usable method is still important clinically.

PURPOSE

(1) To determine whether a low-intensity pulsed ultrasound system (LIPUS) promotes in vitro cell viability and osteogenic differentiation and (2) to assess the applicability and effectiveness of LIPUS in promoting the graft-bone healing of artificial ligaments in vivo.

STUDY DESIGN

Controlled laboratory study.

METHODS

Polyethylene terephthalate (PET) sheets and grafts were randomly assigned to control and LIPUS groups. MC3T3-E1 preosteoblasts were cultured on PET sheets. Cell viability and morphology were evaluated using a live/dead viability assay and scanning electron microscopy. Alkaline phosphatase activity, calcium nodule formation, and Western blot were evaluated for osteogenic differentiation. For in vivo experiments, the effect of LIPUS was evaluated via an extra-articular graft-bone healing model in 48 rabbits: the osteointegration and new bone formation were tested by micro-computed tomography and histological staining, and the graft-bone bonding was tested by biomechanical testing.

RESULTS

Cell viability was significantly higher in the LIPUS group as compared with control (living and dead compared between control and LIPUS groups, P = .0489 vs P = .0489). Better adherence of cells and greater development of extracellular matrix were observed in the LIPUS group. Furthermore, LIPUS promoted alkaline phosphatase activity, calcium nodule formation, and the protein expression of collagen 1 (P = .0002) and osteocalcin (P = .0006) in vitro. Micro-computed tomography revealed higher surrounding bone mass at 4 weeks and newly formed bone mass at 8 weeks in the LIPUS group (P = .0014 and P = .0018). Histological analysis showed a narrower interface and direct graft-bone contact in the LIPUS group; the surrounding bone area at 4 weeks and the mass of newly formed bone at 4 and 8 weeks in the LIPUS group were also significantly higher as compared with control (surrounding bone, P < .0001; newly formed bone, P = .0016 at 4 weeks and P = .005 at 8 weeks). The ultimate failure load in the LIPUS group was significantly higher than in the control group (P < .0001 at 4 weeks; P = .0008 at 8 weeks).

CONCLUSION

LIPUS promoted the viability and osteogenic differentiation of MC3T3-E1 preosteoblasts in vitro and enhanced the graft-bone healing of PET artificial ligament in vivo.

CLINICAL RELEVANCE

LIPUS is an effective physical stimulation to enhance graft-bone healing after artificial ligament implantation.

Comparison Between Clinically Available Low-Intensity Pulsed Ultrasound (LIPUS) and a Novel Bimodal Acoustic Signal System for Accelerating Fracture Healing

Low-intensity pulsed ultrasound (LIPUS) accelerates fracture healing by stimulating the production of bone callus and the mineralization process. This study compared a novel bimodal acoustic signal (BMAS) device for bone fracture healing to a clinical LIPUS system (EXOGEN; Bioventus, Durham, NC, USA). Thirty rabbits underwent a bilateral fibular osteotomy. Each rabbits' legs were randomized to receive 20-min treatment daily for 18 days with BMAS or LIPUS. The latter utilizes a longitudinal ultrasonic mode only, while the former employs ultrasound-induced shear stress to promote bone formation. Power Doppler imaging (PDI) was acquired days 0, 2, 4, 7, 11, 14, and 18 post-surgery to monitor treatment response and quantified off-line. X-rays were acquired to evaluate fractures on days 0, 14, 18, and 21. Seventeen rabbits completed the study and were euthanized day 21 post-surgery. The fibulae were analyzed to determine maximum torque, initial torsional stiffness, and angular displacement at failure. ANOVAs and paired t-tests were used to compare pair-wise outcome variables for the two treatment modes on a per rabbit basis. The BMAS system induced better fracture healing with greater stiffness (BMAS 0.21 ± 0.19 versus LIPUS 0.16 ± 0.19 [Formula: see text]cm/°, p = 0.050 ) and maximum torque (BMAS 7.84 ± 5.55 versus LIPUS 6.26 ± 3.46 [Formula: see text]cm, p = 0.022 ) than the LIPUS system. Quantitative PDI assessments showed a higher amount of vascularity with LIPUS than BMAS on days 4 and 18 ( ). In conclusion, the novel BMAS technique achieved better bone fracture healing response than the current Food and Drug Administration (FDA)-approved LIPUS system.

Enhancement of Bone Regeneration Through the Converse Piezoelectric Effect, A Novel Approach for Applying Mechanical Stimulation

Serious bone injuries have devastating effects on the lives of patients including limiting working ability and high cost. Orthopedic implants can aid in healing injuries to an extent that exceeds the natural regenerative capabilities of bone to repair fractures or large bone defects. Autografts and allografts are the standard implants used, but disadvantages such as donor site complications, a limited quantity of transplantable bone, and high costs have led to an increased demand for synthetic bone graft substitutes. However, replicating the complex physiological properties of biological bone, much less recapitulating its complex tissue functions, is challenging. Extensive efforts to design biocompatible implants that mimic the natural healing processes in bone have led to the investigation of piezoelectric smart materials because the bone has natural piezoelectric properties. Piezoelectric materials facilitate bone regeneration either by accumulating electric charge in response to mechanical stress, which mimics bioelectric signals through the direct piezoelectric effect or by providing mechanical stimulation in response to electrical stimulation through the converse piezoelectric effect. Although both effects are beneficial, the converse piezoelectric effect can address bone atrophy from stress shielding and immobility by improving the mechanical response of a healing defect. Mechanical stimulation has a positive impact on bone regeneration by activating cellular pathways that increase bone formation and decrease bone resorption. This review will highlight the potential of the converse piezoelectric effect to enhance bone regeneration by discussing the activation of beneficial cellular pathways, the properties of piezoelectric biomaterials, and the potential for the more effective administration of the converse piezoelectric effect using wireless control.

Biodegradable Nanofiber Bone-Tissue Scaffold as Remotely-Controlled and Self-Powering Electrical Stimulator

Electrical stimulation (ES) has been shown to induce and enhance bone regeneration. By combining this treatment with tissue-engineering approaches (which rely on biomaterial scaffolds to construct artificial tissues), a replacement bone-graft with strong regenerative properties can be achieved while avoiding the use of potentially toxic levels of growth factors. Unfortunately, there is currently a lack of safe and effective methods to induce electrical cues directly on cells/tissues grown on the biomaterial scaffolds. Here, we present a novel bone regeneration method which hybridizes ES and tissue-engineering approaches by employing a biodegradable piezoelectric PLLA (Poly(L-lactic acid)) nanofiber scaffold which, together with externally-controlled ultrasound (US), can generate surface-charges to drive bone regeneration. We demonstrate that the approach of using the piezoelectric scaffold and US can enhance osteogenic differentiation of different stem cells in vitro, and induce bone growth in a critical-sized calvarial defect in vivo. The biodegradable piezoelectric scaffold with applied US could significantly impact the field of tissue engineering by offering a novel biodegradable, battery-free and remotely-controlled electrical stimulator.

A dynamical model of oncotripsy by mechanical cell fatigue: selective cancer cell ablation by low-intensity pulsed ultrasound

The method of oncotripsy, first proposed in Heyden & Ortiz (Heyden & Ortiz 2016 J. Mech. Phys. Solids 92, 164-175 (doi:10.1016/j.jmps.2016.04.016)), exploits aberrations in the material properties and morphology of cancerous cells in order to ablate them selectively by means of tuned low-intensity pulsed ultrasound. We propose the dynamical model of oncotripsy that follows as an application of cell dynamics, statistical mechanical theory of network elasticity and 'birth-death' kinetics to describe the processes of damage and repair of the cytoskeleton. We also develop a reduced dynamical model that approximates the three-dimensional dynamics of the cell and facilitates parametric studies, including sensitivity analysis and process optimization. We show that the dynamical model predicts-and provides a conceptual basis for understanding-the oncotripsy effect and other trends in the data of Mittelstein et al. (Mittelstein et al. 2019 Appl. Phys. Lett. 116, 013701 (doi:10.1063/1.5128627)), for cells in suspension, including the dependence of cell-death curves on cell and process parameters.

Nanofilm generated non-pharmacological anabolic bone stimulus

Stimulus-responsive nanomaterials have mainly been employed to ablate or destroy tissues or to facilitate controlled release of drugs or biologics. Herein, we demonstrate the potential of stimulus-responsive nanomaterials to promote tissue regeneration via a non-pharmacological and noninvasive strategy. Thin nanofilms of an optically-absorbing organic dye or nanoparticle (single-walled graphene nanoribbons [SWOGNR]) were placed over (without touching the skin) a rodent femoral fracture site. A nanosecond pulsed near-infrared laser diode was employed to generate photoacoustic (PA) signals from the nanofilms. X-ray micro-computed tomography (microCT), histology, and mechanical testing results showed that daily PA stimulations of upto 45 min for 6 weeks (complete fracture healing) do not adversely affect bone regeneration and quality. Further, microCT and histological analysis showed 10 min daily stimulation for 2 weeks significantly increases bone quantity at the fracture sites of rats exposed to the nanoparticle-generated PA signals. In these rats, up to threefold increase in bone volume to callus volume ratio and twofold increase in bone mineral density within the callus were noted, compared to rats that were not exposed to the photoacoustic signals. The results taken together indicate that nanofilm-generated photoacoustic signals serve as an anabolic stimulus for bone regeneration. The results, in conjugation with the ability of these nanofilms to serve as PA contrast agents, present opportunities toward the development of integrated noninvasive imaging and noninvasive or invasive treatment strategies for bone loss due to disease or trauma.

Osseous outgrowth on the buccal maxilla associated with piezosurgery-assisted en-masse retraction: A case series

Piezoelectric surgery is a novel surgical approach used in orthodontic treatment for rapid tooth movement. This paper presents a case series wherein osseous outgrowths were observed in response to piezosurgery-assisted en-masse retraction. Sixteen patients requiring upper premolar extractions were treated with miniscrew-supported en-masse retraction and received minimally invasive decortication via piezosurgery. Computed tomography (CT) of the maxillary anterior region was performed to investigate the nature of the outgrowths. In 8 of the 16 patients, hemispheric or disc-shaped osseous outgrowths were observed on the sites where piezosurgery was performed during retraction. CT images revealed that these outgrowths were alveolar bone. This case series presents a previously unreported osseous response to piezosurgery-assisted tooth movement during orthodontic treatment. The response is mostly transient and is observed in 50% of the treated patients, suggesting a bone turnover that can be assessed clinically and radiographically.

Effect of low-intensity pulsed ultrasound on the biological behavior of osteoblasts on porous titanium alloy scaffolds: An in vitro and in vivo study

Low-intensity pulsed ultrasound (LIPUS) has been used in patients with fresh fractures, delayed union and non-union to enhance bone healing and improve functional outcome. However, there were few studies concerning the effects of LIPUS on the biological behavior of osteoblasts on porous scaffolds. This study aimed to evaluate the effects of LIPUS on the biological behavior of osteoblasts on porous titanium-6aluminum-4vanadium (Ti6Al4V) alloy scaffolds in vitro and in vivo. Scaffolds were randomly divided into an ultrasound group and a control group. Mouse pre-osteoblast cells were cultured with porous Ti6Al4V scaffolds in vitro. The effects of LIPUS on the biological behavior of osteoblasts were evaluated by observing the adhesion, proliferation, differentiation and ingrowth depth on porous Ti6Al4V scaffolds. In addition, scaffolds were implanted into rabbit mandibular defects in vivo. The effects of LIPUS on bone regeneration were evaluated via micro-CT, fluorescent staining and toluidine blue staining. The results revealed that osteoblast adhered well to the scaffolds, and there was no significant difference in the methyl thiazolyl tetrazolium value between the ultrasound group and the control group (p>0.05). Compared with the control group, ultrasound promoted the alkaline phosphatase activity, osteocalcin levels and ingrowth depth of the cells on the scaffolds (p<0.05). In addition, micro-CT and histomorphological analysis showed that the volume and amount of new bone formation were increased and that bone maturity was improved in the ultrasound group compared to the control group. These results indicate that LIPUS promotes osteoblast differentiation as well as enhances bone ingrowth in porous Ti6Al4V scaffolds, and promotes bone formation and maturity in porous Ti6Al4V scaffolds.

Improved Human Bone Marrow Mesenchymal Stem Cell Osteogenesis in 3D Bioprinted Tissue Scaffolds with Low Intensity Pulsed Ultrasound Stimulation

3D printing and ultrasound techniques are showing great promise in the evolution of human musculoskeletal tissue repair and regeneration medicine. The uniqueness of the present study was to combine low intensity pulsed ultrasound (LIPUS) and advanced 3D printing techniques to synergistically improve growth and osteogenic differentiation of human mesenchymal stem cells (MSC). Specifically, polyethylene glycol diacrylate bioinks containing cell adhesive Arginine-Glycine-Aspartic acid-Serene (RGDS) peptide and/or nanocrystalline hydroxyapatite (nHA) were used to fabricate 3D scaffolds with different geometric patterns via novel table-top stereolithography 3D printer. The resultant scaffolds provide a highly porous and interconnected 3D environment to support cell proliferation. Scaffolds with small square pores were determined to be the optimal geometric pattern for MSC attachment and growth. The optimal LIPUS working parameters were determined to be 1.5 MHz, 20% duty cycle with 150 mW/cm(2) intensity. Results demonstrated that RGDS peptide and nHA containing 3D printed scaffolds under LIPUS treatment can greatly promote MSC proliferation, alkaline phosphatase activity, calcium deposition and total protein content. These results illustrate the effectiveness of the combination of LIPUS and biomimetic 3D printing scaffolds as a valuable combinatorial tool for improved MSC function, thus make them promising for future clinical and various regenerative medicine application.

Low-intensity pulsed ultrasound in lower limb bone stress injuries: a randomized controlled trial

OBJECTIVE

To evaluate the effectiveness of low-intensity pulsed ultrasound (LIPUS) for the improvement of lower limb bone stress injuries in a civilian population.

DESIGN

A prospective, randomized, double-blinded, placebo-controlled trial to compare LIPUS with placebo.

SETTING

Civilian private practice population in Sydney, Australia.

PARTICIPANTS

Subjects were recruited if a grade II-IV bone stress injury was diagnosed on magnetic resonance imaging (MRI) of either the postero-medial tibia, fibula or second, third, or fourth metatarsal. Subjects of all levels of sporting activity were included. Thirty subjects were initially recruited, and 23 subjects were included in the final analysis.

INTERVENTIONS

Subjects were randomized into either the treatment or placebo arm and matched to the site of injury (tibia, fibula, or metatarsal). Subjects in both arms used either treatment or placebo devices for 20 minutes daily for 4 weeks.

MAIN OUTCOME MEASURES

Six clinical parameters (night pain, pain at rest, pain on walking, pain with running, tenderness, and pain with single leg hop) were compared before and after intervention. The changes in MRI grade and bone marrow edema size were also compared.

RESULTS

There were no significant differences between the treatment and placebo conditions for changes in MRI grading (2.2 vs 2.4, P = 0.776) or bone marrow edema size (3 vs 4.1, P = 0.271). There were no significant differences between the treatment and placebo conditions for the 6 clinical parameters.

CONCLUSIONS

Low-intensity pulsed ultrasound was found not to be an effective treatment for the healing of lower limb bone stress injuries in this study. However, this was measured over a relatively short duration of 4 weeks in a small, mostly female population.

CLINICAL RELEVANCE

This double-blinded, randomized, placebo-controlled trial has shown that LIPUS is not an effective treatment for lower limb bone stress injuries.

Pulsed focused ultrasound treatment of muscle mitigates paralysis-induced bone loss in the adjacent bone: a study in a mouse model

Bone loss can result from bed rest, space flight, spinal cord injury or age-related hormonal changes. Current bone loss mitigation techniques include pharmaceutical interventions, exercise, pulsed ultrasound targeted to bone and whole body vibration. In this study, we attempted to mitigate paralysis-induced bone loss by applying focused ultrasound to the midbelly of a paralyzed muscle. We employed a mouse model of disuse that uses onabotulinumtoxinA-induced paralysis, which causes rapid bone loss in 5 d. A focused 2 MHz transducer applied pulsed exposures with pulse repetition frequency mimicking that of motor neuron firing during walking (80 Hz), standing (20 Hz), or the standard pulsed ultrasound frequency used in fracture healing (1 kHz). Exposures were applied daily to calf muscle for 4 consecutive d. Trabecular bone changes were characterized using micro-computed tomography. Our results indicated that application of certain focused pulsed ultrasound parameters was able to mitigate some of the paralysis-induced bone loss.

Does the Implant Surgical Technique Affect the Primary and/or Secondary Stability of Dental Implants? A Systematic Review

Background. A number of surgical techniques for implant site preparation have been advocated to enhance the implant of primary and secondary stability. However, there is insufficient scientific evidence to support the association between the surgical technique and implant stability. Purpose. This review aimed to investigate the influence of different surgical techniques including the undersized drilling, the osteotome, the piezosurgery, the flapless procedure, and the bone stimulation by low-level laser therapy on the primary and/or secondary stability of dental implants. Materials and methods. A search of PubMed, Cochrane Library, and grey literature was performed. The inclusion criteria comprised observational clinical studies and randomized controlled trials (RCTs) conducted in patients who received dental implants for rehabilitation, studies that evaluated the association between the surgical technique and the implant primary and/or secondary stability. The articles selected were carefully read and classified as low, moderate, and high methodological quality and data of interest were tabulated. Results. Eight clinical studies were included then they were classified as moderate or high methodological quality and control of bias. Conclusions. There is a weak evidence suggesting that any of previously mentioned surgical techniques could influence the primary and/or secondary implant stability.

Pilot Clinical Studies of Long Duration, Low Intensity Therapeutic Ultrasound for Osteoarthritis

Osteoarthritis is one of the leading causes of disability in the aging population. Long duration, low intensity therapeutic ultrasound has had promising impact in animal models to slow the progression of the disease and provide joint relief. Two pilot studies were conducted using a novel, wearable platform for delivering ultrasound to evaluate the potential clinical benefits of ultrasound therapy on knee osteoarthritis. There was a pain reduction effect from using ultrasound, as high as fifty two percent in one study. As well, initial data demonstrates that mobility may be increased for patients experiencing mild to moderate arthritis of the knee.

The effects of mechanical loading on mesenchymal stem cell differentiation and matrix production

Mesenchymal stem cells or stromal cells (MSCs) have the potential to be used therapeutically in tissue engineering and regenerative medicine to replace or restore the function of damaged tissues. Therefore, considerable effort has been ongoing in the research community to optimize culture conditions for predifferentiation of MSCs. All mesenchymal tissues are subjected to mechanical forces in vivo and all fully differentiated mesenchymal lineage cells respond to mechanical stimulation in vivo and in vitro. Therefore, it is not surprising that MSCs are highly mechanosensitive. We present a summary of current methods of mechanical stimulation of MSCs and an overview of the outcomes of the different mechanical culture techniques tested. Tissue engineers and stem cell researchers should be able to harness this mechanosensitivity to modulate MSC differentiation and matrix production; however, more research needs to be undertaken to understand the complex interactions between the mechanosensitive and biochemically stimulated differentiation pathways.