Use of physical forces in bone healing

The science of electrical stimulation therapy for fracture healing

This article is a brief review of the basic science research conducted in the field of electrical stimulation for fracture healing. Direct electrical current, capacitive coupling, and inductive coupling have been studied as potential techniques to enhance fracture healing through the proliferation and differentiation of osteogenic cells. These techniques are particularly appealing as they offer a potential minimally invasive solution to the difficult clinical problem of delayed fracture healing and nonunion. Basic science studies have shown conclusively that electrical stimulation techniques lead to bone cell proliferation and have attempted to elucidate the intracellular processes by which this bone cell proliferation occurs. Further basic science and clinical research is required to enhance the effectiveness of this therapy for the treatment of fracture nonunions.

Does exposure to extremely low frequency magnetic fields produce functional changes in human brain?

Behavioral and neurophysiological changes have been reported after exposure to extremely low frequency magnetic fields (ELF-MF) both in animals and in humans. The physiological bases of these effects are still poorly understood. In vitro studies analyzed the effect of ELF-MF applied in pulsed mode (PEMFs) on neuronal cultures showing an increase in excitatory neurotransmission. Using transcranial brain stimulation, we studied noninvasively the effect of PEMFs on several measures of cortical excitability in 22 healthy volunteers, in 14 of the subjects we also evaluated the effects of sham field exposure. After 45 min of PEMF exposure, intracortical facilitation produced by paired pulse brain stimulation was significantly enhanced with an increase of about 20%, while other parameters of cortical excitability remained unchanged. Sham field exposure produced no effects. The increase in paired-pulse facilitation, a physiological parameter related to cortical glutamatergic activity, suggests that PEMFs exposure may produce an enhancement in cortical excitatory neurotransmission. This study suggests that PEMFs may produce functional changes in human brain.

Therapeutic ultrasound induces periosteal ossification without apparent changes in cartilage

Low intensity pulsed ultrasound (LIPUS) is an extremely useful noninvasive treatment which halves the duration of fracture healing when the bone is exposed once a day for 20 min. To elucidate the direct reactions of bone and cartilage, dissected rat femora were immobilized in culture dish wells, exposed to LIPUS from a certain angle every day, and the local pattern of ossification was analyzed in relation to the ultrasound. Daily 20-min exposures were started 24 hr after isolation of the femora, and at days 5, 10, and 15, samples were harvested for measurements, morphological, and histochemical analyses. While the gross features of the samples were identical to the untreated controls, extended mineralization of the periosteum was observed with alizarin red staining, antiosteocalcin immunohistochemical staining, and micro-three dimensional computed tomography. Interestingly, the newly deposited mineral was found perpendicular to the ultrasound path, strongly suggesting that LIPUS accelerates periosteal bone formation. Zones of epiphyseal cartilage and hypertrophic and calcified cartilage did not exhibit any differences with and without this exposure. LIPUS also did not influence the secreted proteoglycan components or amounts in the culture medium. The absence of any additional longitudinal growth of the femur demonstrated that LIPUS did not accelerate endochondral bone formation. We conclude that cartilage alone does not directly respond to therapeutic ultrasound, whereas the periosteum does.

Mild electrical stimulation with heat shock ameliorates insulin resistance via enhanced insulin signaling

Low-intensity electrical current (or mild electrical stimulation; MES) influences signal transduction and activates phosphatidylinositol-3 kinase (PI3K)/Akt pathway. Because insulin resistance is characterized by a marked reduction in insulin-stimulated PI3K-mediated activation of Akt, we asked whether MES could increase Akt phosphorylation and ameliorate insulin resistance. In addition, it was also previously reported that heat shock protein 72 (Hsp72) alleviates hyperglycemia. Thus, we applied MES in combination with heat shock (HS) to in vitro and in vivo models of insulin resistance. Here we show that 10-min treatment with MES at 5 V (0.1 ms pulse duration) together with HS at 42°C increased the phosphorylation of insulin signaling molecules such as insulin receptor substrate (IRS) and Akt in HepG2 cells maintained in high-glucose medium. MES (12 V)+mild HS treatment of high fat-fed mice also increased the phosphorylation of insulin receptor β subunit (IRβ) and Akt in mice liver. In high fat-fed mice and db/db mice, MES+HS treatment for 10 min applied twice a week for 12–15 weeks significantly decreased fasting blood glucose and insulin levels and improved insulin sensitivity. The treated mice showed significantly lower weight of visceral and subcutaneous fat, a markedly improved fatty liver and decreased size of adipocytes. Our findings indicated that the combination of MES and HS alleviated insulin resistance and improved fat metabolism in diabetes mouse models, in part, by enhancing the insulin signaling pathway.

Electrical stimulation for long-bone fracture-healing: a meta-analysis of randomized controlled trials

BACKGROUND

Bone stimulation represents a $500 million market in the United States. The use of electromagnetic stimulation in the treatment of fractures is common; however, the efficacy of this modality remains uncertain. We conducted a systematic review and meta-analysis of randomized controlled trials to evaluate the effect of electromagnetic stimulation on long-bone fracture-healing.

METHODS

We searched four electronic databases (MEDLINE, EMBASE, CINAHL, and all Evidence-Based Medicine Reviews) for trials of electromagnetic stimulation and bone repair, in any language, published from the inception of the database to April 2008. In addition, we searched by hand seven relevant journals published between 1980 and April 2008 and the bibliographies of eligible trials. Eligible trials enrolled patients with long-bone lesions, randomly assigned them to electromagnetic stimulation or a control group, and reported on bone-healing. Information on the methodological quality, stimulation device, duration of treatment, patient demographics, and all clinical outcomes were independently extracted by two reviewers.

RESULTS

Of 2546 citations obtained in the literature search, eleven articles met the inclusion criteria. Evidence from four trials reporting on 106 delayed or ununited fractures demonstrated an overall nonsignificant pooled relative risk of 1.76 (95% confidence interval, 0.8 to 3.8; p = 0.15; I(2) = 60.4%) in favor of electromagnetic stimulation. Single studies found a positive benefit of electromagnetic stimulation on callus formation in femoral intertrochanteric osteotomies, a limited benefit for conservatively managed Colles fracture or for lower limb-lengthening, and no benefit on limb-length imbalance and need for reoperation in surgically managed pseudarthroses or on time to clinical healing in tibial stress fractures. Pain was reduced in one of the four trials assessing this outcome.

CONCLUSIONS

While our pooled analysis does not show a significant impact of electromagnetic stimulation on delayed unions or ununited long-bone fractures, methodological limitations and high between-study heterogeneity leave the impact of electromagnetic stimulation on fracture-healing uncertain.

Ultrasound: a potential technique to improve osseointegration of dental implants

Dental implants have been widely used in clinic for the restoration of lost teeth in recent decades, but there still remains a great challenge for even a higher success rate and a shorter rehabilitation time. The osseointegration between dental implant and alveolar bone tissue is crucial for a successful implantation. Ultrasound has been proved to be an effective treatment for bone fracture healing. The underlying mechanism of the mechanotransduction pathway involved in cellular responses to ultrasound is still not clear, however, numerous studies have confirmed its ability to enhance osteogenesis and therefore facilitate bone regeneration. In this paper, we hypothesize that this kind of wave might have an ability to strengthen and accelerate osseointegration of dental implants, and thus a potential usage in dental therapy.

Low-intensity pulsed ultrasound accelerates osteogenesis at bone-tendon healing junction

This study was designed to evaluate low-intensity pulsed ultrasound (LIPUS) in acceleration of mineralization and remodeling of the new bone formed at the healing interface of bone-tendon junction. Thirty-two mature New Zealand white rabbits underwent partial patellectomy and direct repair of the patellar tendon and proximal patella. Animals were then divided into LIPUS treatment group (20 min/d, 5 times/wk) and placebo control group and were euthanized at week 8 and 16 postoperatively (n = 8, for each group and time point). The main outcome measures included new bone size and its bone mineral density (BMD). Results showed that the size of new bone was found to be 2.6 and 3.0 times significantly greater in the LIPUS group compared with that of the control group at weeks 8 and 16, respectively. In addition, the LIPUS group showed significantly higher BMD at week 8 than controls, but not at week 16. In conclusion, this was the first experimental study to show that LIPUS was able to enhance osteogenesis at the healing bone-tendon junction, especially before the postoperative week 8. Findings of this study formed a scientific basis for future clinical trials and establishment of indication of LIPUS for enhancing bone-tendon junction repair.

Fracture healing in the elderly patient

Clinical experience gives rise to the impression that there are differences in fracture healing in different age groups. It is evident that fractures heal more efficiently in children than in adults. However, minimal objective knowledge exists to evaluate this assumption. Temporal, spatial, and cellular quantitative and qualitative interrelationships, as well as signaling molecules and extracellular matrix have not been comprehensively and adequately elucidated for fracture healing in the geriatric skeleton. The biological basis of fracture healing will provide a context for revealing the pathophysiology of delayed or even impaired bone regeneration in the elderly. We will summarize experimental studies on age-related changes at the cellular and molecular level that will add to the pathophysiological understanding of the compromised bone regeneration capacity believed to exist in the elderly patient. We will suggest why this understanding would be useful for therapeutics focused on bone regeneration, in particular fracture healing at an advanced age.

Early Effects of Extracorporeal Shock Wave Treatment on Osteoblast-like Cells: A Comparative Study Between Electromagnetic and Electrohydraulic Devices

BACKGROUND

Extracorporeal shockwave therapy (ESWT) has been increasingly applied to treat orthopedic and musculoskeletal pathologies. ESWT involves mechanical perturbations that, as with other physical therapies, can result in mechanical stimuli to a large number of cells, including bone cells. The aim of this study was to evaluate the effects of shock waves on osteoblast-like cells (MG63) when using two different generators of shock waves (electrohydraulic and electromagnetic devices), in terms of cell damage, cell viability, osteogenic phenotype expression, and cytokine production.

METHODS

MG63 cells were suspended in 1.5 mL screw-cap cryotubes (1 x 10 cells/mL), containing phosphate buffer solution (PBS), which were maintained at 37 degrees C during all the experimental times. Two levels of energy flux density (EFD) were evaluated for each device: 0.15 to 0.18 mJ/mm2 and 0.40 mJ/mm2. Cells were then cultivated for 72 hours starting from a concentration of 1 x 10 cells/mL, and biological activity and viability were evaluated 24 and 72 hours after treatment.

RESULTS

The results obtained demonstrate that the factors most affecting osteoblast activity involve both the device and the level of EFD selected, and they must be considered all together.

CONCLUSIONS

The use of the electromagnetic device and a level of EFD lower than 0.40 mJ/mm2 would appear to induce fewer immediate cytodestructive effects and better stimulate subsequent proliferation and the synthetic activity of MG63.

Low intensity pulsed ultrasound increases the matrix hardness of the healing tissues at bone-tendon insertion-a partial patellectomy model in rabbits

BACKGROUND

This study evaluated the low intensity pulsed ultrasound enhancement on matrix hardness of the healing tissues at the bone-tendon junction.

METHODS

Sixteen 18 week-old mature female rabbits were used. An established transverse partial patellectomy was performed at the distal one-third of the patella. Animals were then divided according to their body weight into ultrasound group (n = 8) with daily treatment of low intensity pulsed ultrasound and control group (n = 8) without ultrasound treatment. Animals were euthanized at week 8 and 16 postoperatively to evaluate the radiographic new bone formation and the Vickers hardness of the matrix of the healing tissues at the bone-tendon junction.

FINDINGS

(1) Comparing with the control group, the anterior-posterior area of the new bone in the ultrasound treated group was found on average to be 3.0 and 3.1 times greater at week 8 and 16, respectively (P < 0.01). (2) The Vickers hardness of the new bone in ultrasound group was 11.3% (P < 0.05) significantly lower at week 8 but 20.0% (P < 0.05) significantly higher at week 16 as compared with that of the control group. (3) The Vickers hardness of the newly regenerated fibrocartilage zone, healing tendon, and cartilaginous metaplasia in ultrasound group was found higher than the control group at both week 8 and 16, but the difference was significant at week 16 only, being 44.1% (P < 0.05), 20.1% (P < 0.01), and 46.4% (P < 0.01) higher, respectively.

INTERPRETATION

The preliminary findings suggested for the first time that low intensity pulsed ultrasound treatment resulted in the enhancement of the matrix hardness in new bone, fibrocartilage, cartilaginous metaplasia, and healing tendon at the healing bone-tendon junction. These findings can be extrapolated into clinical practice, i.e. the more rapid healing induced by low intensity pulsed ultrasound, the earlier mobilization of the affected joint. The beneficial effects on prevention of the musculoskeletal deterioration resulting from the prolonged immobilization would be therefore expected.

Electric stimulation and hyperbaric oxygen therapy in the treatment of nonunions

Up to 10% of the fractures occurring annually in the U.S. end up in non-union or delayed union. Classical treatment with osteosynthesis and bone grafting is not always successful. Alternatives in treatment have long ago been considered. This article presents current concepts in treatment with electrical stimulation and hyperbaric oxygen, the mechanisms of action, experimental and clinical evidence of their application.

Electrical bone stimulation: an overview and its use in high risk and Charcot foot and ankle reconstructions

Since early work done in the 1950s on the "piezoelectricity of bone," a growing body of basic science and clinical evidence suggests the use of electrical bone stimulation as an adjunct in the treatment of foot and ankle nonunions, fusions, and Charcot arthropathy. Both implantable designs (that allow for direct constant stimulation of bone) and nonimplantable (such as pulsed and combined electromagnetic fields) devices have been studied. Ongoing research continues to support the potential usefulness of these modalities.

Pulsed low-intensity ultrasound for fracture healing

A large body of evidence confirms the stimulatory effect of pulsed low-intensity ultrasound on fresh fractures, nonunions, and other osseous defects such as osteotomies. This article presents the findings of some of these studies and briefly discusses our current understanding of its molecular mechanisms.

How does pulsed low-intensity ultrasound enhance fracture healing?

Pulsed low-energy ultrasound, a non-invasive therapeutic treatment modality, may improve callus formation and enhance fracture healing by initiating enhanced angioneogenesis.

Effects of ultra-wideband electromagnetic pulses on pre-neoplastic mammary epithelial cell proliferation

Electromagnetic ultra-wideband pulses (UWB) or nanopulses, are generated by a wide range of electronic devices used in communications and radar technology. However, the specific effects of nanopulse exposure on cell growth and function have not been extensively investigated. Here, studies have been conducted to determine the effects of prolonged exposure to non-ionizing, low to moderate intensity nanopulses on the growth of pre-neoplastic CL-S1 mammary epithelial cells in vitro. Cells were grown in culture and maintained in serum-free defined medium containing 10 ng/ml EGF and 10 microg/ml insulin as comitogens. Studies showed that 0.25-3.0 h exposure to nanopulses of 18 kV/m field intensity, 1 kHz repetition rate and 10 ns pulse width had no effect on CL-S1 cell growth or viability during the subsequent 72-h culture period. However, exposure to similar nanopulses for prolonged periods of time (4-6 h) resulted in a significant increase in cell proliferation, as compared to untreated controls. Additional studies showed that nanopulse exposure enhanced CL-S1 cell growth when cells were maintained in media containing only EGF, but had no effect on cells maintained in defined media that were mitogen-free or containing only insulin. Studies also showed that the growth-promoting effects of nanopulse exposure were associated with a relatively large increase in intracellular levels of phospho-MEK1 (active) and phospho-ERK1/2 (active) in these cells. These findings demonstrate that prolonged exposure to moderate levels of UWB enhanced EGF-dependent mitogenesis, and that this growth-promoting effect appears to be mediated by enhanced activation of the mitogen-activated protein kinase (MAPK) signalling pathway in pre-neoplastic CL-S1 mammary epithelial cells.

Engineering approaches for the detection and control of orthopaedic biofilm infections

Artificial joints are subject to chronic infections associated with bacterial biofilms, which only can be eradicated by the traumatic removal of the implant followed by sustained intravenous antibiotic therapy. We have adopted an engineering approach to develop electrical-current-based approaches to bacterial eradication and microelectromechanical systems that could be embedded within the implanted joint to detect the presence of bacteria and to provide in situ treatment of the infection before a biofilm can form. In the former case we will examine the combined bactericidal effects of direct and indirect electrical fields in combination with antibiotic therapy. In the latter case, bacterial detection will occur by developing a microelectromechanical-systems-based biosensor that can "eavesdrop" on bacterial quorum-sensing-based communication systems. Treatment will be effected by the release of a cocktail of pharmaceutical reagents contained within integral reservoirs associated with the implant, including a molecular jamming signal that competitively binds to the bacteria's quorum sensing receptors (which will "blind" the bacteria, preventing the production of toxins) and multiple high dose antibiotics to eradicate the planktonic bacteria. This approach is designed to take advantage of the relatively high susceptibility to antibiotics that planktonic bacteria display compared with biofilm envirovars. Here we report the development of a generic microelectromechanical systems biosensor that measures changes in internal viscosity in a base fluid triggered by a change in the external environment.

Biological effects of low intensity ultrasound: the mechanism involved, and its implications on therapy and on biosafety of ultrasound

The biological effects of low intensity ultrasound (US) in vitro; the mechanisms involved; and the factors that can enhance or inhibit these effects are reviewed. The lowest possible US intensities required to induce cell killing or to produce free radicals were determined. Following sonication in the region of these intensities, the effects of US in combination with either hyperthermia, hypotonia, echo-contrast agents (ECA), CO2, incubation time, high cell density or various agents were examined. The results showed that hyperthermia, hypotonia and microbubbles are good enhancers of the bioeffects, while CO2, incubation time and high cell density are good inhibitors. Cellular membrane damage is pivotal in the events leading to cell death, with the cellular damage-and-repair mechanism as an important determinant of the fate of the damaged cells. The optimal level of apoptosis (with minimal lysis) and optimal gene transfection efficiency were attained using a pulsed low intensity US. In summary, the findings suggest that low intensity US is potentially useful in therapy, while on the other hand, they also call for further investigation of such clinical scenarios as high-grade fever, edema or use of ECA which may lead to the lowering of the threshold for bioeffects with diagnostic US.