Efficacy of Extracorporeal Shockwave Therapy on Pain and Function in Myofascial Pain Syndrome: A Systematic Review and Meta-analysis of Randomized Clinical Trials.

OBJECTIVE: The aim of the study is to examine the effectiveness of extracorporeal shockwave therapy in reducing pain, improving functionality, joint range of motion, quality of life, fatigue, and health status self-perception in people with myofascial pain syndrome. METHODS: PubMed, the Cochrane Library, CINAHL, the Physiotherapy Evidence Database, and SPORTDiscus were systematically searched for only randomized clinical trials published up to June 2, 2022. The main outcome variables were pain, as reported on the visual analog scale and pressure pain threshold, and functionality. A quantitative analysis was conducted using the inverse variance method and the random effects model. RESULTS: Twenty-seven studies were included ( N = 595 participants in the extracorporeal shockwave therapy group). The effectiveness of extracorporeal shockwave therapy for relieving pain was superior for the extracorporeal shockwave therapy group compared with the control group on the visual analog scale (MD = -1.7 cm; 95% confidence interval = -2.2 to -1.1) and pressure pain threshold (mean difference = 1.1 kg/cm 2 ; 95% confidence interval = 0.4 to 1.7) and functionality (standardized mean difference = -0.8; 95% confidence interval = -1.6 to -0.04) with high heterogeneity. However, no differences were found between extracorporeal shockwave therapy and other interventions as dry needling, exercises, infiltrations, and lasers interventions. CONCLUSIONS: Extracorporeal shockwave therapy is effective in relieving pain and improving functionality in patients with myofascial pain syndrome compared with control and ultrasound therapy. TO CLAIM CME CREDITS: Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME. TO CLAIM CME CREDITS: Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME. CME OBJECTIVES: Upon completion of this article, the reader should be able to: (1) Determine the effectiveness of radial and focal extracorporeal shockwaves on pain perception, the pressure pain threshold, and functionality in people with myofascial pain syndrome; (2) Describe the intervention protocol of extracorporeal shockwave therapy to improve pain perception in people with myofascial pain syndrome; and (3) Describe the advantages and disadvantages of extracorporeal shockwave therapy versus other intervention such as dry needling. LEVEL: Advanced. ACCREDITATION: The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s) ™. Physicians should only claim credit commensurate with the extent of their participation in the activity. LEVEL: Advanced. ACCREDITATION: The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s) ™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Effectiveness of Different Electrical Stimulation Modalities for Pain and Masticatory Function in Temporomandibular Disorders: A Systematic Review and Meta-Analysis.

Temporomandibular disorders comprise a set of conditions that include alterations of the temporomandibular joint and masticatory muscles. Although different modalities of electric currents are widely used for treating temporomandibular disorders, previous reviews have suggested these are ineffective. This systematic review and meta-analysis aimed to determine the effectiveness of different electrical stimulation modalities in patients with temporomandibular disorders for reducing musculoskeletal pain, increasing the range of movement, and improving muscle activity. An electronic search was conducted of randomized controlled trials published until March of 2022 that compared the application of an electrical stimulation therapy versus a sham or control group. The main outcome measure was pain intensity. Seven studies were included in the qualitative analysis and in the quantitative analysis (n = 184 subjects). The overall effect of electrical stimulation on pain reduction was statistically superior to sham/control (MD = -1.12 cm; CI 95%: -1.5 to -0.8), showing moderate heterogeneity of results (I2 = 57%, P = .04). The overall effect on range of movement of the joint (MD = 0.97 mm; CI 95%: -0.3 to 2.2) and muscle activity (SMD = -2.9; CI 95%: -8.1 to 2.3) were not significant. Transcutaneous electrical nerve stimulation (TENS) and high-voltage current stimulation reduces pain intensity clinically in people with temporomandibular disorders with a moderate quality of evidence. On the other hand, there is no evidence of the effect of different electrical stimulation modalities on range of movement and muscle activity in people with temporomandibular disorders with a moderate and low quality of evidence respectively. PERSPECTIVE: TENS and high voltage currents are valid options for the control of pain intensity in patients suffering from temporomandibular disorder. Data suggest clinically relevant changes compared to sham. Healthcare professionals should take this into account as it is inexpensive therapy, has no adverse effects and can be self-administered by patients.

The effect on handgrip strength of low-frequency percutaneous electric stimulation applied to the median and cubital nerves: A randomized, double-blind controlled trial.

Percutaneous electrical nerve stimulation (PENS) consists of applying an electric current of <1,000 Hz to different neuromuscular structures through acupuncture needles. Currently, there is controversy surrounding the effect of PENS on muscle strength in the scientific literature. The main objective was to assess the effect of PENS applied to the median and cubital nerves on the maximum handgrip strength (MHS) compared to sham stimulation, as well as to determine the safety of the intervention. A parallel, randomized, double-blind controlled trial in a sample of 20 healthy subjects. Participants were randomly allocated in the experimental (n = 10) and control (n = 10) groups. A blinded researcher measured MHS. Measurements of MHS of the dominant hand were taken at four time points: preintervention, immediately postintervention, 24 hr after the intervention, and at a 10-day follow-up. A 10-Hz percutaneous electrical current stimulation was employed. The control group also received the same puncture method but with no electric stimulation. Compared to baseline, the MHS decreased 10.4% (SEM = 3.2, p = .02) in the PENS group at 24 hr postintervention, with no differences observed between baseline and at 10 days postintervention. No changes in grip strength were observed at any time point in the sham group. To sum up, PENS decreased MHS at 24 hr postintervention, which does not persist 10 days after the stimulation. PENS can be considered a safe technique. Trials with larger sample sizes are required to corroborate the findings of this study. Clinical Trials Registration: NCT, NCT04662229, filed on March 12th of 2020.

Percutaneous Versus Transcutaneous Electrical Nerve Stimulation for the Treatment of Musculoskeletal Pain. A Systematic Review and Meta-Analysis.

BACKGROUND: The justification for this review is the need for high-quality evidence to assist in the decision-making process when applying percutaneous electrical nerve stimulation (PENS) or transcutaneous electrical nerve stimulation (TENS) in a clinical setting. The main aim was to determine if the use of PENS is more effective and should be recommended when compared to TENS for the reduction of musculoskeletal pain intensity. METHODS: A search for randomized controlled trials (RCTs) was performed. Studies published until 31/12/2020, comparing the effectiveness of PENS and TENS, were considered. The main outcome was pain assessed with a visual analog scale or numerical pain rating scale. RESULTS: Nine RCTs were included in the qualitative analysis, with seven of them in the quantitative analysis (n = 527). The overall effect of PENS on pain was statistically but not clinically superior to TENS (mean difference [MD]=-1.0 cm; 95% confidence interval [CI]: -1.5 to -0.4) with a high level of heterogeneity (I2=76%, P > .01). When only studies with a lower risk of bias (n = 3) were analyzed, the heterogeneity decreased to I = 0% (P = .06) and no difference was observed between TENS and PENS (MD=-0.81 cm; 95% CI:-1.6 to 0.02) with a moderate recommendation level according to GRADE. There were no data concerning adverse effects. CONCLUSIONS: There is low-quality of evidence for more pain intensity reduction with PENS, but the difference was not clinically significant. However, when only studies with low risk of bias are meta-analyzed, there is a moderate quality of evidence that there is no difference when TENS or PENS is applied for pain intensity.

20-kHz alternating current stimulation: effects on motor and somatosensory thresholds.

BACKGROUND: High frequency alternating current (HFAC) stimulation have been shown to produce a peripheral nerve conduction block. Currently, all the studies applying HFAC stimulation in clinical studies, have employed frequencies below 10 kHz. The main aim of this work was to investigate the neuromodulatory effect of transcutaneous 20 kHz stimulation on somatosensory and pain thresholds, and maximal handgrip strength. METHODS: A randomized, crossover, single-blinded, placebo-controlled trial was conducted following recruitment of fourteen healthy volunteers. Transcutaneous stimulation at 20 kHz and sham stimulation were applied over the ulnar and median nerves of fourteen healthy volunteers for 20 min. Maximal handgrip strength (MHS), mechanical detection threshold (MDT) and pressure pain threshold (PPT) were registered prior to, during (15 min), immediately after the end (20 min), and 10 min following stimulation. RESULTS: The 20 kHz stimulation showed a lower MHS during the stimulation at the 15 min (30.1 kgs SE 2.8) and at 20 min (31.8 kgs, SE 2.8) when compared to sham stimulation (35.1 kgs, SE 3.4; p < 0.001 and 34.2 kgs, SE 3.4; p = 0.03, respectively). The 20 kHz stimulation resulted in a slight increase in MDT at 15 min (0.25 mN; 0.25-2.00) when compared to the sham stimulation (0.25 mN; 0.25-0.25; p = 0.02), and no effects were showed for PPT. CONCLUSIONS: High-frequency stimulation at 20 kHz suggests a partial block of nerve activity. Studies in subjects with neurological disorders characterized by nerve hyperactivity are needed to confirm the clinical impact of this non-invasive electrical stimulation technique. TRIAL REGISTRATION: NCT, NCT02837458. Registered on 12 April 2017.

Soleus H-reflex modulation following transcutaneous high- and low-frequency spinal stimulation in healthy volunteers.

The main aim of this work was to investigate the difference in the excitability of the soleus H-reflex in healthy volunteers following spinal transcutaneous electrical nerve stimulation (TENS) and high-frequency alternating current (HFAC) at a frequency of 10 kHz applied at the lower thoracic spinal level (T10-T12). A double-blind, randomized, crossover, controlled clinical trial was designed. Participants received three randomized interventions (TENS, 10 kHz, and sham stimulation) during 40 min. The amplitude and latency of the soleus H-reflex were registered prior to, during, and 10 min following stimulation. Twenty-four participants completed the study. A significant inhibition of H-reflex amplitude was observed following transcutaneous spinal TENS (12.7%; 95% CI 1.5-22.2%) when compared with sham stimulation (5.5%; 95% CI 3.6-14.5%; p = 0.03). An increase in H-reflex latency was also observed following transcutaneous spinal stimulation at 10 kHz (2%; 95% CI 1.4-2.5%) as compared with sham stimulation (0.7%; 95% CI 0.07-1.3%; p < 0.01). No differences were found between TENS and 10 kHz for H-reflex modulation. Transcutaneous spinal TENS and HFAC at a frequency of 10 kHz had a modulatory effect on the soleus H-reflex when compared to sham stimulation; however, no differences were found between these two interventions.

Does Frequency Modulation of Transcutaneous Electrical Nerve Stimulation Affect Habituation and Mechanical Hypoalgesia? A Randomized, Double-Blind, Sham-Controlled Crossover Trial.

BACKGROUND: Devices for applying transcutaneous electrical nerve stimulation (TENS) use numerous frequency modulation patterns for decreasing habituation to currents. However, there is no evidence supporting the use of an optimal pattern instead of the others, or even modulated frequencies instead of a fixed frequency. OBJECTIVE: The objectives of this study were to determine the effects of 3 TENS patterns (fixed frequency, random modulation, and 6-second-6-second [6s-6s] modulation) on habituation, to examine the subjective perception of habituation and comfort, and to determine their effects on the mechanical pain threshold (MPT). DESIGN: This study was a randomized, double-blind, sham-controlled crossover trial. SETTING: The study took place in a university research laboratory under attenuated noise conditions at a regulated temperature of 22°C to 26°C. PARTICIPANTS: Thirty-nine volunteers who were healthy participated in this trial. INTERVENTION: The participants received 4 different TENS interventions (fixed frequency, random modulation, 6s-6s modulation, and sham) in random order, with a 24-hour washout period, on the radial nerve. MEASUREMENTS: The main outcome-habituation-was quantified by the increase in current density and the number of times the intensity had to be increased during the session. Secondary outcome variables were subjective perception of habituation and comfort and MPT. RESULTS: Random modulation reduced the number of times the intensity had to be increased because of habituation compared with no modulation (1.6 times; 95% confidence interval [CI] = 0.7-2.6) and 6s-6s modulation (0.8 times; 95% CI = 0.01-1.6). No differences were observed between interventions in terms of an increase in current density, self-perceived habituation, or self-perceived comfort. MPT increased during the intervention in the random-modulation group (4.4 N; 95% CI = 1.8-7.0) and the no-modulation group (5.9 N; 95% CI = 1.9-10.0); there were no significant changes in the other 2 groups. LIMITATIONS: The success of masking or blinding procedures of the participants was not assessed. CONCLUSIONS: Randomly modulated frequencies caused less habituation than nonmodulated frequencies or 6s-6s modulation. Further research on more prolonged (hours-long) interventions in participants with pain is required.

[Analgesic effects of transcutaneous electrical nerve stimulation (TENS) in patients with fibromyalgia: A systematic review]. / Efectos analgésicos de la estimulación eléctrica nerviosa transcutánea en pacientes con fibromialgia: una revisión sistemática.

OBJECTIVE: To determine whether transcutaneous electrical nerve stimulation (TENS) has an analgesic effect greater than placebo or other treatments in patients with fibromyalgia. Furthermore, it was intended to analyze the optimal application parameters to achieve a greater reduction of pain. DESIGN: A systematic review. DATA SOURCE: Randomized clinical trials on the effect of TENS on fibromyalgia in the databases Pubmed, Cochrane and PEDro until November 2016. SELECTION OF STUDIES: 8 studies out of a total of 62 were selected. Controlled clinical trials in which TENS was applied in patients with fibromyalgia were included. DATA EXTRACTION: Pain was analyzed as the main variable, although other variables such as fatigue, quality of life and impact, range of motion and depression were also included. RESULTS: 6 out of 8 studies obtained a significant decrease of pain. In 2 studies, TENS was applied as complementary treatment to therapeutic exercise with results evidencing a decrease in pain. The rest of the variables studied presented a great variability and conclusive results could not be established. CONCLUSIONS: Treatment with TENS is effective for reducing pain in people with fibromyalgia. In addition, the inclusion of TENS in therapeutic exercise programs seems to have a greater effect than practicing therapeutic exercise in isolation. However, no efficacy has been demonstrated in other variables different to pain. Further studies are needed to investigate the optimization of the parameters of the TENS and a greater consensus among the variables used.

Effect of high-frequency alternating current transcutaneous stimulation over muscle strength: a controlled pilot study.

BACKGROUND: High-frequency alternating currents of greater than 1 kHz applied on peripheral nerves has been used in animal studies to produce a motor nerve block. It has been evidenced that frequencies higher than 5 kHz are necessary to produce a complete peripheral nerve block in primates, whose nerve thickness is more similar to humans. The aim of the study was to determine the effect on muscle strength after the application of a high-frequency stimulation at 5 and 10 kHz compared to sham stimulation in healthy volunteers. FINDINGS: Transcutaneous stimulation at 5 kHz, 10 kHz and sham stimulation were applied to eleven healthy volunteers over the ulnar and median nerves for 20 min. Maximal handgrip strength was measured before, during, immediately after the intervention, and 10 min after the end of intervention. The 10 kHz stimulation showed a lower handgrip strength during the intervention (28.1 N, SEM 3.9) when compared to 5 kHz (31.1 N, SEM 3.6; p < 0.001) and to sham stimulation (33.7 N, SEM 3.9; p < 0.001). Furthermore, only stimulation at 10 kHz decreased handgrip strength when compared to baseline. CONCLUSIONS: These findings suggest high-frequency stimulation has an inhibitory effect over muscle strength. Future studies are required in patients that are characterized by motor hyperactive such as spasticity or tremors. CLINICAL TRIAL REGISTRATION: NCT, NCT03169049 . Registered on 30 May 2017.

Afferent stimulation inhibits abnormal cutaneous reflex activity in patients with spinal cord injury spasticity syndrome.

BACKGROUND: Tibialis Anterior (TA) cutaneous reflex (CR) activity evoked following cutaneous stimulation of the plantar (Pl) surface (Pl-TA CR) has demonstrated hyperreflexia and damage of inhibitory mechanisms in subjects with spinal cord injury (SCI) and spasticity. OBJECTIVES: To modulate Pl-TA CR and Soleus H-reflex activity with transcutaneous electrical nerve stimulation (TENS) and vibratory stimulation of the plantar pad during rest and controlled isometric plantarflexion. METHODS: Non-injured subjects (n = 11) and individuals with incomplete SCI with (n = 14) and without spasticity (n = 14) were recruited. The effect of TENS and vibratory stimuli on Pl-TA CR and soleus H-reflex activity were assessed during rest and controlled ramp-and-hold plantarflexion. RESULTS: Vibration failed to inhibit H-reflex activity during rest or plantarflexoin following SCI compared to healthy subjects. In contrast, vibration-induced inhibition of Pl-TA CR was specifically detected in SCI spastic subjects during both rest and the hold phase of plantarflexion. TENS inhibited Pl-TA CR activity in the SCI spasticity group only during hold plantarflexion. CONCLUSIONS: Plantar vibratory stimuli inhibited the pl-TA CR, but not the H reflex, during rest and controlled movement in SCI spastic subjects. Assessment of Pl-TA CR modulation should contribute to the development of modality-specific sensory stimuli programmes for the neurorehabilitation of SCI spasticity.

Intensity matters: Therapist-dependent dose of spinal transcutaneous electrical nerve stimulation.

The intensity used during transcutaneous electrical nerve stimulation (TENS) in both, clinical practice and research studies, is often based on subjective commands such as "strong but comfortable sensation". There is no consensus regarding the effectiveness dose of TENS. The objective was to determine the difference in the effect of spinal TENS on soleus H-reflex modulation when applied by two therapists instructed to apply the stimulation at a "strong but comfortable" intensity. Twenty healthy volunteers divided into two groups: Therapist 1 (n = 10) and Therapist 2 (n = 10). Both therapist applied spinal TENS and sham stimulation at the T10-12 spinal level for 40min in random order to each subject, at an intensity designed to produce a "strong but comfortable" sensation. To avoid habituation, the intensity was adjusted every 2min. Soleus H-reflex was recorded before, during, and 10min after TENS by an observer blinded to the stimulus applied. Despite the instruction to apply TENS at a "strong comfortable" level, a significant difference in current density was identified: Therapist 1 (0.67mA/cm2, SD 0.54) applied more than Therapist 2 (0.53mA/cm2, SD 0.57; p<0.001) at the onset of the intervention. Maximal peak-to-peak H-reflex amplitude was inhibited significantly more 10min following TENS applied by Therapist 1 (-0.15mV, SD 0.16) compared with Therapist 2 (0.04mV, SD 0.16; p = 0.03). Furthermore, current density significantly correlated with the inhibitory effect on peak-to-peak Soleus H-reflex amplitude 10 min after stimulation (Rho = -0.38; p = 0.04). TENS intensity dosage by the therapist based on the subjective perception of the participants alone is unreliable and requires objective standardization. In addition, higher current density TENS produced greater inhibition of the Soleus H-reflex.

Effect of Unmodulated 5-kHz Alternating Currents Versus Transcutaneous Electrical Nerve Stimulation on Mechanical and Thermal Pain, Tactile Threshold, and Peripheral Nerve Conduction: A Double-Blind, Placebo-Controlled Crossover Trial.

OBJECTIVE: To investigate the effect of unmodulated 5-kHz alternating current on mechanical pain threshold (MPT), heat pain threshold (HPT), tactile threshold (TT), and peripheral nerve conduction (PNC) compared with transcutaneous electrical nerve stimulation (TENS) and sham stimulation. SETTING: National referral center. DESIGN: Randomized, double-blind, placebo-controlled crossover trial. PARTICIPANTS: Healthy volunteers (N=38). No dropouts or adverse events were reported. INTERVENTION: TENS, unmodulated 5-kHz currents, and sham stimulation were applied on the radial nerve for 20 minutes with a 24-hour washout period between them and concealed intervention allocation. MAIN OUTCOME MEASURES: Four measures were taken: before, during, and 2 after the interventions. Algometry was used to assess MPT, a Peltier thermode for HPT using the method of limits, Von Frey filaments for TT, and radial nerve compound action potential. RESULTS: No differences were observed on MPT, HPT, and PNC when 5-kHz current and TENS were compared. However, TT increased 56.2mN (95% confidence interval [CI], 28.8-83.6) in the TENS group compared with the 5-kHz current group during intervention. Compared with sham stimulation during intervention, MPT increased 4.7N (95% CI, 0.3-9.2) using 5-kHz current and 10.4N (95% CI, 3.5-17.3) with TENS. TT increased 17.2mN (95% CI, 4.7-29.7) with 5-kHz current and 73.4mN (95% CI, 47.5-99.2) with TENS. However, HPT increased 1.0°C (95% CI, 0.2-2.0) only with TENS. For the PNC, no differences were found among the 3 groups. CONCLUSIONS: Unmodulated 5-kHz current produced an increase in somatosensory thresholds that was greater than placebo but not when compared with TENS; however, participants perceived 5-kHz currents to be more comfortable and showed more habituation to them.

Botulinum toxin type A and myofascial pain syndrome: a retrospective study of 301 patients.

BACKGROUND: Botulinum toxin type A (BTX-A) intramuscular injections have been used for the treatment of myofascial pain syndrome (MPS), although its efficacy remains still unknown and its safety is controversial. OBJECTIVE: To analyze the effectiveness and safety of the injection protocol for BTX-A in the shoulder-scapular and lumbar-pelvic girdles combined with physiotherapy in patients with primary and secondary MPS. METHODS: Retrospective descriptive study including 301 medical files of patients with persistent MPS. Positive responses to treatment were considered to be a satisfactory level of effectiveness with 50% pain relief or a fully satisfactory level of effectiveness at 80%. RESULTS: Overall, 58.1% of patients obtained a positive result at 6 months. Differences in effectiveness were found between primary MPS (82.9% of patients) and secondary MPS (54.9%; p=0.002). In patients with secondary MPS, differences in effectiveness arose based on pathologies associated with MPS (p=0.03). In 23.9% of cases, mild and temporary adverse effects were observed post-infiltration. CONCLUSIONS: BTX-A injections and physiotherapy is an alternative to conventional treatment which should be considered when treating refractory MPS. Nonetheless, the differences in effectiveness based on diagnosis suggest the need to clarify the criteria used to select patients with MPS in future clinical trials and applications.

Habitualmente cuando hablamos de electroterapia no hacemos referencia únicamente a la aplicación de corrientes eléctricas, sino que citamos otras «terapias afines» en las que se aplican vibraciones mecánicas (ultrasonidos), radiaciones fototerápicas o campos magnéticos...[editorial] / No disponible

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