Systemic treatment with pulsed electromagnetic fields do not affect bone microarchitecture in osteoporotic rats

Purpose

Pulsed electromagnetic fields (PEMF) are currently used in the treatment of spinal fusions and non-unions. There are indications that PEMF might also be effective in the treatment of osteoporosis. In this study we examined whether whole-body PEMF treatment affects the bone microarchitecture in an osteoporotic rat model.

Methods

Twenty-week-old female rats were ovariectomised (n = 20). Four different PEMF treatment protocols based on previous experimental studies and based on clinically used PEMF signals were examined (2 h/day, 5 days/week). A control group did not receive PEMF. At zero, three and six weeks cancellous and cortical bone architectural changes at the proximal tibia were evaluated using in vivo microCT scanning.

Results

PEMF treatment did not induce any changes in cancellous or cortical bone compared to untreated controls.

Conclusions

Although previous studies have shown strong effects of PEMF in osteoporosis we were unable to demonstrate this in any of the treatment protocols. Using in vivo microCT scanning we were able to identify small bone changes in time. Subtle differences in the experimental set-up might explain the differences in study outcomes in the literature. Since PEMF treatment is safe, future experimental studies on the effect of PEMF on bone can better be performed directly on humans, eliminating the potential translation issues between animals and humans. In this study we found no support for the use of PEMF in the treatment of osteoporosis.     

Pulsed electromagnetic fields enhance BMP‐2 dependent osteoblastic differentiation of human mesenchymal stem cells

Mesenchymal stem cells (MSCs) express an osteoblastic phenotype when treated with BMP‐2, and BMP‐2 is used clinically to induce bone formation although high doses are required. Pulsed electromagnetic fields (PEMF) also promote osteogenesis in vivo, in part through direct action on osteoblasts. We tested the hypothesis that PEMF enhances osteogenesis of MSCs in the presence of an inductive stimulus like BMP‐2. Confluent cultures of human MSCs were grown on calcium phosphate disks and were treated with osteogenic media (OM), OM containing 40 ng/mL rhBMP‐2, OM + PEMF (8 h/day), or OM + BMP‐2 + PEMF. MSCs demonstrated minor increases in alkaline phosphatase (ALP) during 24 days in culture and no change in osteocalcin. OM increased ALP and osteocalcin by day 6, but PEMF had no additional effect at any time. BMP‐2 was stimulatory over OM, and PEMF + BMP‐2 synergistically increased ALP and osteocalcin. PEMF also enhanced the effects of BMP‐2 on PGE2, latent and active TGF‐β1, and osteoprotegerin. Effects of PEMF on BMP‐2–treated cells were greatest at days 12 to 20. These results demonstrate that PEMF enhances osteogenic effects of BMP‐2 on MSCs cultured on calcium phosphate substrates, suggesting that PEMF will improve MSC response to BMP‐2 in vivo in a bone environment. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1250–1255, 2008     

Evidence that pulsed electromagnetic fields inhibit coupling of adenylate cyclase by parathyroid hormone in bone cells

To investigate the biochemical effects of pulsed electromagnetic fields (PEMF) on bone in particular and on cell membrane-associated activity in general, we have studied the modification by PEMF of cAMP metabolism in primary calvarial bone cells. We report that PEMF inhibited cAMP accumulation stimulated by bovine PTH(1-34) peptide. After a 1-hr PEMF exposure, the cAMP response to PTH (2-7 min) was decreased in exposed cells to 48-70% (p less than 0.05) of the response of unexposed cells; furthermore, this inhibition disappeared after 10-20 min with PTH. This inhibition occurred at submaximal PTH doses (2.4-7.3 nM) and no effect was observed at maximal PTH doses (24 nM). Thus with PEMF, the dose response curve for PTH became 0.5 log unit less sensitive. PEMF did not affect the cAMP response to cholera toxin and forskolin. However, when submaximal doses of both forskolin (0.5-1.0 microM) and PTH (0.24-2.4 nM) were used, forskolin prevented inhibition of cAMP production by PEMF in the range of fields and stimulus epochs which normally inhibit cAMP production. It is proposed that PEMF inhibits PTH-stimulated coupling of the adenylate cyclase system and that this inhibition does not affect the intrinsic activity of the G-protein and the catalytic subunit.     

脉冲电磁场治疗骨质疏松症的临床研究进展

脉冲电磁场（pulsed electromagnetic field，PEMF）作为一种无创、安全、有效的物理治疗手段，早期在临床上用于治疗骨折延迟愈合和不愈合的患者，目前已用于骨质疏松症的临床辅助治疗。体外及动物模型研究已经证实PEMF能够刺激成骨细胞的骨形成而抑制破骨细胞的骨吸收，最终实现骨结构的完整及骨量和骨强度的维持。大量临床研究也表明PEMF在增加骨质疏松症患者骨密度、缓解疼痛及改善患者生活质量方面具有很好的治疗效果，但是PEMF对骨质疏松症积极作用的确定性仍需进一步研究。本文对国内外有关PEMF治疗骨质疏松症的相关临床文献进行了总结，并对可能机制进行了探讨，旨在为日后的临床研究提供一定的参考。     

Role of pulsed electromagnetic fields (PEMF) on tenocytes and myoblasts—potential application for treating rotator cuff tears

The post‐surgery integrity of the tendons and muscle quality are the two major factors in success of rotator cuff (RC) repair. Though surgical techniques for rotator cuff repair have significantly improved in the past two decades, there are no effective treatments to improve tendon‐to‐bone healing and muscle quality after repair at this point in time. Pulsed electromagnetic fields (PEMF) have previously been used for promoting fracture healing. Previous studies have shown that PEMF has a positive role in promoting osteoblast precursors proliferation and differentiation. However, PEMFs effect on tenocytes and muscle cells has not been determined fully yet. The purpose of this study is to define the role of a commercially available PEMF on tenocytes and myoblasts growth and differentiation in vitro. Human rotator cuff tenocytes and C2C12 murine myoblasts were cultured and treated with PEMF for 2 weeks under regular and inflammatory conditions. Our results showed that 2 weeks treatment of PEMF enhanced gene expressions of growth factors in human rotator cuff tenocytes under inflammatory conditions. PEMF significantly enhanced C2C12 myotube formation under normal and inflammatory conditions. Results from this study suggest that PEMF has a positive role in promoting tenocyte gene expression and myoblast differentiation. Therefore, PEMF may potentially serve as a non‐operative treatment to improve clinical incomes rotator cuff tendon repairs. Results © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:956–964, 2017.

     

Electrical stimulation of human femoral intertrochanteric osteotomies. Double-blind study

Low-frequency pulsing electromagnetic fields (PEMF) are being used in nonunion healing at several centers around the world. Much debate exists about quantification of PEMF effects, especially in humans where no randomized studies have been performed. The results of a double-blind treatment of 32 consecutive patients treated with femoral intertrochanteric osteotomy for hip degenerative arthritis are reported. Roentgenographic evaluation and callus density measurements performed with an image analyzer showed a statistically significant difference between controls and stimulated patients (p less than 0.01). In this extremely homogeneous patient population, PEMF stimulation favored osteotomy healing.     

Pulsed Electromagnetic Fields Partially Preserve Bone Mass,Microarchitecture, and Strength by Promoting Bone Formation in Hindlimb‐Suspended Rats

A large body of evidence indicates that pulsed electromagnetic fields (PEMF), as a safe and noninvasive method, could promote in vivo and in vitro osteogenesis. Thus far, the effects and underlying mechanisms of PEMF on disuse osteopenia and/or osteoporosis remain poorly understood. Herein, the efficiency of PEMF on osteoporotic bone microarchitecture, bone strength, and bone metabolism, together with its associated signaling pathway mechanism, was systematically investigated in hindlimb‐unloaded (HU) rats. Thirty young mature (3‐month‐old), male Sprague‐Dawley rats were equally assigned to control, HU, and HU + PEMF groups. The HU + PEMF group was subjected to daily 2‐hour PEMF exposure at 15 Hz, 2.4 mT. After 4 weeks, micro–computed tomography (µCT) results showed that PEMF ameliorated the deterioration of trabecular and cortical bone microarchitecture. Three‐point bending test showed that PEMF mitigated HU‐induced reduction in femoral mechanical properties, including maximum load, stiffness, and elastic modulus. Moreover, PEMF increased serum bone formation markers, including osteocalcin (OC) and N‐terminal propeptide of type 1 procollagen (P1NP); nevertheless, PEMF exerted minor inhibitory effects on bone resorption markers, including C‐terminal crosslinked telopeptides of type I collagen (CTX‐I) and tartrate‐resistant acid phosphatase 5b (TRAcP5b). Bone histomorphometric analysis demonstrated that PEMF increased mineral apposition rate, bone formation rate, and osteoblast numbers in cancellous bone, but PEMF caused no obvious changes on osteoclast numbers. Real‐time PCR showed that PEMF promoted tibial gene expressions of Wnt1, LRP5, β‐catenin, OPG, and OC, but did not alter RANKL, RANK, or Sost mRNA levels. Moreover, the inhibitory effects of PEMF on disuse‐induced osteopenia were further confirmed in 8‐month‐old mature adult HU rats. Together, these results demonstrate that PEMF alleviated disuse‐induced bone loss by promoting skeletal anabolic activities, and imply that PEMF might become a potential biophysical treatment modality for disuse osteoporosis. © 2014 American Society for Bone and Mineral Research.     

The effects of low-intensity pulsed ultrasound and pulsed electromagnetic fields bone growth stimulation in acute fractures: a systematic review and meta-analysis of randomized controlled trials

Introduction

The aim of this systematic review and meta-analysis was to evaluate the best currently available evidence from randomized controlled trials comparing pulsed electromagnetic fields (PEMF) or low-intensity pulsed ultrasound (LIPUS) bone growth stimulation with placebo for acute fractures.

Materials and methods

We performed a systematic literature search of the medical literature from 1980 to 2013 for randomized clinical trials concerning acute fractures in adults treated with PEMF or LIPUS. Two reviewers independently determined the strength of the included studies by assessing the risk of bias according to the criteria in the Cochrane Handbook for Systematic Reviews of Interventions.

Results

Seven hundred and thirty-seven patients from 13 trials were included. Pooled results from 13 trials reporting proportion of nonunion showed no significant difference between PEMF or LIPUS and control. With regard to time to radiological union, we found heterogeneous results that significantly favoured PEMF or LIPUS bone growth stimulation only in non-operatively treated fractures or fractures of the upper limb. Furthermore, we found significant results that suggest that the use of PEMF or LIPUS in acute diaphyseal fractures may accelerate the time to clinical union.

Conclusions

Current evidence from randomized trials is insufficient to conclude a benefit of PEMF or LIPUS bone growth stimulation in reducing the incidence of nonunions when used for treatment in acute fractures. However, our systematic review and meta-analysis suggest that PEMF or LIPUS can be beneficial in the treatment of acute fractures regarding time to radiological and clinical union. PEMF and LIPUS significantly shorten time to radiological union for acute fractures undergoing non-operative treatment and acute fractures of the upper limb. Furthermore, PEMF or LIPUS bone growth stimulation accelerates the time to clinical union for acute diaphyseal fractures.     

Microcirculatory effects of pulsed electromagnetic fields

Purpose: Pulsed electromagnetic fields (PEMF) are used clinically to expedite healing of fracture non‐unions, however, the mechanism of action by which PEMF stimulation is effective is unknown. The current study examined the acute effects of PEMF stimulation on arteriolar microvessel diameters in the rat cremaster muscle. The study hypothesis was that PEMF would increase arteriolar diameters, a potential mechanism involved in the healing process. Methods: Local PEMF stimulation/sham stimulation of 2 or 60 min duration was delivered to the cremaster muscle of anesthetized rats. Arteriolar diameters were measured before and after stimulation/sham stimulation using intravital microscopy. Systemic hemodynamics also were monitored during PEMF stimulation. Results: Local PEMF stimulation produced significant (p < 0.001) vasodilation, compared to pre‐stimulation values, in cremasteric arterioles in anesthetized rats (n = 24). This dilation occurred after 2 min of stimulation (9% diameter increase) and after 1 h of stimulation (8.7% diameter increase). Rats receiving “sham” stimulation (n = 15) demonstrated no statistically significant change in arteriolar diameter following either “sham” stimulation period. PEMF stimulation of the cremaster (n = 4 rats) did not affect systemic arterial pressure or heart rate, nor was it associated with a change in tissue environmental temperature. Conclusions: These results support the hypothesis that local application of a specific PEMF waveform can elicit significant arteriolar vasodilation. Systemic hemodynamics and environmental temperature could not account for the observed microvascular responses. © 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.     

Treatment of ununited tibial fractures: a comparison of surgery and pulsed electromagnetic fields (PEMF).

The use of pulsed electromagnetic fields (PEMF) is gaining acceptance for the treatment of ununited fractures. The results of 44 articles published in the English language literature have been compiled to assess the effectiveness of PEMF vs surgical therapy. For ununited tibial fractures, 81% of reported cases healed with PEMF vs 82% with surgery. After multiple failed surgeries, the success rate of PEMF is reported to be greater than with surgery; this discrepancy increases with additional numbers of prior surgeries. In infected nonunions, the results of surgical treatment decreased by 21% and were less than the results utilizing PEMF (69% vs 81%). In open fractures, surgical healing exceeded PEMF (89% vs 78%), whereas in closed injuries PEMF cases healed more frequently (85% vs 79%). In general, PEMF treatment of ununited fractures has proved to be more successful than noninvasive traditional management and at least as effective as surgical therapies. Given the costs and potential dangers of surgery, PEMF should be considered an effective alternative. Experience supports its role as a successful method of treatment for ununited fractures of the tibia.     

Effects of low‐frequency pulsed electromagnetic fields on plateau frostbite healing in rats

Plateau frostbite (PF) treatments have remained a clinical challenge because this condition injures tissues in deep layers and affected tissues exhibit unique pathological characteristics. For instance, low‐frequency pulsed electromagnetic field (PEMF) can affect tissue restoration and penetrate tissues. Therefore, the effect of PEMF on PF healing should be investigated. This study aimed to evaluate the effects of low‐frequency PEMF on PF healing systematically. Ninety‐six Sprague‐Dawley rats were randomly and equally divided into three groups: normal control, partial thickness plateau frostbite (PTPF), and PTPF with low‐frequency PEMF exposure (PTPF + PEMF). PTPF wounds were induced in the dorsum of the rats. The PTPF + PEMF group was exposed to low‐frequency PEMF daily. During PF healing, wound microcirculation in each group was monitored through contrast ultrasonography. Wound appearance, histological observation, and wound tensile strength were also evaluated. Results showed that the rate of the microcirculation restoration of the PTPF + PEMF group was nearly 25% faster than that of the PTPF group, and wound appearance suggested that the healing of the PTPF group was slower than that of the PTPF + PEMF group. Histological observation revealed that PEMF accelerated the growth of different deep tissues, as confirmed by tensile strength examination. Low‐frequency PEMF could penetrate PF tissues, promote their restoration, and provide a beneficial effect on PF healing. Therefore, this technique may be a potential alternative to treat PF.     

Low-level laser therapy vs. pulsed electromagnetic field on neonatal rat calvarial osteoblast-like cells

To compare the effects of pulsed electromagnetic field (PEMF) and low-level laser therapy (LLLT) on osteoblast cells in a cell culture model. Fifty thousand neonatal rat calvarial osteoblast-like cells per milliliter were seeded and 0.06 mT PEMF, 0.2 mT PEMF, and LLLT at 808 nm were applied for 24 and 96 h on the cells. To evaluate cellular proliferation and differentiation, specimens were examined for DNA synthesis, alkaline phosphatase (ALP) activity, cell numbers, and viability of the cells. Morphological appearances of the cells were observed using scanning electron microcopy after 24 and 96 h of incubation. At 24 and 96 h, the control group had a higher cell proliferation than 0.06 and 0.2 mT PEMF groups (p?=?0.001). At 96 h, 0.2 mT PEMF group had higher cell proliferation rate than 0.06 mT PEMF and LLLT groups (p?=?0.001). The cell count and cell viability in 0.2 mT PEMF group were higher than the 0.06-mT PEMF and LLLT groups, although these differences were not statistically significant at 96 h (p?>?0.05). At 24 and 96 h, cell viability in the control group was higher than the test groups. Alkaline phosphatase levels of the groups were comparable in both time intervals (p?>?0.05). 0.2 mT PEMF application on osteoblast-like cells led to cell proliferation and differentiation better than 0.06 mT PEMF and LLLT at 808 nm, although a remarkable effect of both PEMF and LLLT could not be detected. The ALP activity of 0.2 and 0.06 mT PEMF and LLLT were comparable.     

Pulsed electromagnetic field therapy improves tendon‐to‐bone healing in a rat rotator cuff repair model

Rotator cuff tears are common musculoskeletal injuries often requiring surgical intervention with high failure rates. Currently, pulsed electromagnetic fields (PEMFs) are used for treatment of long‐bone fracture and lumbar and cervical spine fusion surgery. Clinical studies examining the effects of PEMF on soft tissue healing show promising results. Therefore, we investigated the role of PEMF on rotator cuff healing using a rat rotator cuff repair model. We hypothesized that PEMF exposure following rotator cuff repair would improve tendon mechanical properties, tissue morphology, and alter in vivo joint function. Seventy adult male Sprague–Dawley rats were assigned to three groups: bilateral repair with PEMF (n = 30), bilateral repair followed by cage activity (n = 30), and uninjured control with cage activity (n = 10). Rats in the surgical groups were sacrificed at 4, 8, and 16 weeks. Control group was sacrificed at 8 weeks. Passive joint mechanics and gait analysis were assessed over time. Biomechanical analysis and μCT was performed on left shoulders; histological analysis on right shoulders. Results indicate no differences in passive joint mechanics and ambulation. At 4 weeks the PEMF group had decreased cross‐sectional area and increased modulus and maximum stress. At 8 weeks the PEMF group had increased modulus and more rounded cells in the midsubstance. At 16 weeks the PEMF group had improved bone quality. Therefore, results indicate that PEMF improves early tendon healing and does not alter joint function in a rat rotator cuff repair model. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:902–909, 2017.

     

Pulsed electromagnetic stimulation of regenerate bone in lengthening procedures

Distraction osteogenesis for limb lengthening represents the treatment of choice in patients with small stature or limb length discrepancies. Bone lengthening and callus formation requires a long therapy. Pulsed electromagnetic fields (PEMF) are normally used to enhance osteogenesis in patients with non-unions. In this study we investigated whether pulsed electromagnetic fields could be used effectively to encourage callus formation and maturation during limb lengthening procedures. Thirty patients underwent bilateral bone lengthening of the humerus, femur or tibia. At day 10 after surgery, PEMF stimulation was started on one side, for 8 hours/day. Stimulated distraction sites exhibited earlier callus formation and progression, and a higher callus density compared to non-stimulated sites. External fixation could be removed on average one month earlier in PEMF stimulated bones. Our results show that the use of pulsed electromagnetic fields stimulation during limb lengthening allows shortening the time of use of the external fixation.     

Randomized, prospective, and controlled clinical trial of pulsed electromagnetic field stimulation for cervical fusion.

BACKGROUND CONTEXT: Multilevel fusions, the use of allograft bone, and smoking have been associated with an increased risk of nonunion after anterior cervical discectomy and fusion (ACDF) procedures. Pulsed electromagnetic field (PEMF) stimulation has been shown to increase arthrodesis rates after lumbar spine fusion surgery, but there are minimal data concerning the effect of PEMF stimulation on cervical spine fusion. PURPOSE: To determine the efficacy and safety of PEMF stimulation as an adjunct to arthrodesis after ACDF in patients with potential risk factors for nonunion. STUDY DESIGN: A randomized, controlled, prospective multicenter clinical trial. PATIENT SAMPLE: Three hundred and twenty-three patients with radiographic evidence (computed tomography-myelogram [CT-myelo] or magnetic resonance imaging [MRI]) of a compressed cervical nerve root and symptomatic radiculopathy appropriate to the compressed root that had failed to respond to nonoperative management were enrolled in the study. The patients were either smokers (more than one pack per day) and/or were undergoing multilevel fusions. All patients underwent ACDF using the Smith-Robinson technique. Allograft bone and an anterior cervical plate were used in all cases. OUTCOME MEASURES: Measurements were obtained preoperatively and at each postoperative interval and included neurologic assessment, visual analog scale (VAS) scores for shoulder/arm pain at rest and with activity, SF-12 scores, the neck disability index (NDI), and radiographs (anteroposterior, lateral, and flexion-extension views). Two orthopedic surgeons not otherwise affiliated with the study and blinded to treatment group evaluated the radiographs, as did a blinded radiologist. Adverse events were reported by all patients throughout the study to determine device safety. METHODS: Patients were randomly assigned to one of two groups: those receiving PEMF stimulation after surgery (PEMF group, 163 patients) and those not receiving PEMF stimulation (control group, 160 patients). Postoperative care was otherwise identical. Follow-up was carried out at 1, 2, 3, 6, and 12 months postoperatively. RESULTS: The PEMF and control groups were comparable with regard to age, gender, race, past medical history, smoking status, and litigation status. Both groups were also comparable in terms of baseline diagnosis (herniated disc, spondylosis, or both) and number of levels operated (one, two, three, or four). At 6 months postoperatively, the PEMF group had a significantly higher fusion rate than the control group (83.6% vs. 68.6%, p=.0065). At 12 months after surgery, the stimulated group had a fusion rate of 92.8% compared with 86.7% for the control group (p=.1129). There were no significant differences between the PEMF and control groups with regard to VAS pain scores, NDI, or SF-12 scores at 6 or 12 months. No significant differences were found in the incidence of adverse events in the groups. CONCLUSIONS: This is the first randomized, controlled trial that analyzes the effects of PEMF stimulation on cervical spine fusion. PEMF stimulation significantly improved the fusion rate at 6 months postoperatively in patients undergoing ACDF with an allograft and an anterior cervical plate, the eligibility criteria being patients who were smokers or had undergone multilevel cervical fusion. At 12 months postoperatively, however, the fusion rate for PEMF patients was not significantly different from that of the control group. There were no differences in the incidence of adverse events in the two groups, indicating that the use of PEMF stimulation is safe in this clinical setting.     

In vitro chondrogenic differentiation of human articular cartilage derived chondroprogenitors using pulsed electromagnetic field

BackgroundThe ability to grow new cartilage remains the standard goal of any treatment strategy directed at cartilage repair. Chondroprogenitors have garnered interest due to their applicability in cell therapy. Pulsed electromagnetic field (PEMF) favors chondrogenesis by possible upregulation of genes belonging to TGFβ superfamily. Since TGFβ is implicated in chondrogenic signalling, the aim of the study was to evaluate the ability of PEMF to induce chondrogenesis via endogenous TGFβ production in chondroprogenitors vs differentiation using chondrogenic medium inclusive of TGFβ.MethodsChondroprogenitors were harvested from three non-diseased human knee joints via fibronectin assay. Passage 3 pellets were subjected to four different culture conditions: a) negative control contained chondrogenic medium without TGFβ2, b) positive control contained medium with TGFβ2, c) PEMF 1 contained medium of negative control plus single exposure to PEMF and d) PEMF 2 contained medium of negative control plus multiple exposures to PEMF. Following differentiation (day 21), pellets were assessed for gene expression of ACAN, SOX9, COL2A1, TGFβ1, TGFβ2, and TGFβ3. Alcian blue staining to detect glycosaminoglycan deposition was also performed. Medium supernatant was used to detect endogenous latent TGF-β1 levels using ELISA.ResultsAll study arms exhibited comparable gene expression without any significant difference. Although positive control and PEMF study arms demonstrated notably better staining than negative control, the level of latent TGF-β1 was seen to be significantly high in supernatant from positive control (P < 0.05) when compared to other groups.ConclusionOur results indicate that PEMF induced chondrogenesis might involve other signalling molecules, which require further evaluation.     

In Vivo and In Vitro Effects of a Pulsed Electromagnetic Field on Net Calcium Flux in Rat Calvarial Bone

Although PEMF's have been found to promote fracture healing and to modulate the activity of bone cells in vitro, effects on bone metabolism are largely unexplored. A bioassay using neonatal rat calvarial bone was used to determine the early effects of a pulsing electromagnetic field (PEMF) exposure in vivo and in vitro on bone metabolic calcium exchange. Bone discs taken from whole body exposed animals (0-4 hours) show a log exposure time-dependent average increase in net Ca uptake in the 0-50% range (r2 = 0.83). This increase could be detected immediately after exposure and also after 24 hours, but not 48 hours later. Animals given whole body PEMF exposure also showed a decrease in serum calcium and did not elevate serum Ca after administration of exogenous parathyroid hormone (PTH). Bone discs from untreated rats, exposed to PEMF for 15 minutes in vitro and then assayed, showed net Ca uptake increases of a similar magnitude and also were refractory to the Ca-releasing effect of PTH. Unexposed discs responded normally to PTH by decreasing net Ca uptake. Treatment of calvarial discs with calcitonin or acetazolamide, both of which inactivate osteoclasts, made the bone refractory to further increases in Ca uptake by PEMF. These results suggest that PEMF exposure produces PTH-refractory osteoclastics and has a relatively rapid effect on increasing net bone Ca uptake, putatively due to a decrease in PTH/paracrine-mediated bone resorption.     

Bone ingrowth into porous calcium phosphate ceramics: influence of pulsing electromagnetic field

The effect of a pulsing electromagnetic field (PEMF) on bone ingrowth into porous hydroxyapatite (HA) and porous tricalcium phosphate (TCP) implanted in rabbit tibiae was studied. To quantitate the biological response, a recently developed method of surface measurement using a scanning electron microscope was used. The morphometrical findings in the HA pores demonstrated a significantly greater amount of bone and thicker bone trabeculae in the PEMF group as compared with the nonpulsed control group at 3 to 4 weeks postimplantation. No significant differences for these parameters were found in the TCP pores. Histologically, more bone and wider bone trabeculae were observed in the HA implants for the PEMF-treated animals at the early time periods when compared with those of the control animals. Alternatively, the histological findings of the TCP implants were similar between these two groups. These histological results tended to correlate with the morphometrical data. Together, these results suggest that accelerated bone formation and bone maturation occurred in response to PEMF in the HA pores but was without effect in the TCP pores. This stimulatory effect is most significant after 3-4 weeks of PEMF stimulation.     

Noninvasive up-regulation of angiopoietin-2 and fibroblast growth factor-2 in bone marrow by pulsed electromagnetic field therapy

Background  

Pulsed electromagnetic field (PEMF) therapy has been widely used in clinical practice for bone fracture healing. However, the mechanism of its action remains to be elucidated. Our object was to investigate the mechanism by which PEMF accelerates bone fracture healing.     

Effects of Pulsed Electromagnetic Field Therapy on Rat Achilles Tendon Healing

The Achilles tendon is frequently injured. Data to support specific treatment strategies for complete and partial tears is inconclusive. Regardless of treatment, patients risk re-rupture and typically have long-term functional deficits. We previously showed that pulsed electromagnetic field (PEMF) therapy improved tendon-to-bone healing in a rat rotator cuff model. This study investigated the effects of PEMF on rat ankle function and Achilles tendon properties after (i) complete Achilles tendon tear and repair with immobilization, (ii) partial Achilles tendon tear without repair and with immobilization, and (iii) partial Achilles tendon tear without repair and without immobilization. We hypothesized that PEMF would improve tendon properties, increase collagen organization, and improve joint function, regardless of injury type. After surgical injury, animals were assigned to a treatment group: (i) no treatment control, (ii) 1 h of PEMF per day, or (iii) 3 h of PEMF per day. Animals were euthanized at 1, 3, and 6 weeks post-injury. Joint mechanics and gait analysis were assessed over time, and fatigue testing and histology were performed at each time point. Results indicate no clear differences in Achilles healing with PEMF treatment. Some decreases in tendon mechanical properties and ankle function suggest PEMF may be detrimental after complete tear. Some early improvements were seen with PEMF after partial tear with immobilization; however, immobilization was found to be a confounding factor. This body of work emphasizes the distinct effects of PEMF on tendon-to-bone healing and supports trialing potential treatment strategies pre-clinically across tendons before applying them clinically. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:70–81, 2020