Effects of Transfer Energy Capacitive and Resistive On Musculoskeletal Pain: A Systematic Review and Meta-Analysis

The use of transfer energy capacitive and resistive (TECAR) therapy to treat musculoskeletal pain has not been clearly established. Hence, this study was conducted to combine the available results. We searched the main databases, including PubMed (January 1950), Web of Knowledge (January 1945), Scopus (January 1980)


Introduction
M usculoskeletal disorders, also known as cumulative trauma disorders, occur when the pressure applied to the musculoskeletal tissues exceeds their strain tolerance. These injuries are caused over time by the physical activity of muscles, tendons, bones, and joints [1].
These structures may present complications in a range of mild to severe symptoms. Musculoskeletal pain can be confined to one or more widespread origins [2]. Although various treatment options are available, some are disfavoured due to the high cost and/or their side effects [3]. One option is transfer energy capacitive and resistive (TECAR) therapy to reduce muscu-GMJ.2022;11:e2407 www.gmj.ir loskeletal pain [4]. TECAR therapy employs high-frequency electromagnetic waves (0.3 to 1.2 MHz) [5] and reduces activity-induced spasms and contractions, improves blood flow, and helps muscle oxygenation via hemoglobin activation. Hence, TECAR therapy enhances the body's natural ability to repair tissues and reduce pain [6].
The efficiency of TECAR therapy has been established in reducing pain induced by musculoskeletal disorders [7][8][9][10]. The results obtained from a review of this modality demonstrated that TECAR therapy is an effective treatment for knee, shoulder, hip, ankle, spine, and hand pain. Furthermore, it competently improves painful inflammation caused by bone and joint disorders [11]. Another systematic review showed that TECAR therapy is more effective in the treatment of musculoskeletal pain than other modalities [12]. To date, no meta-analysis has been conducted to provide a conclusive result combined with previous findings. Therefore, we performed a meta-analysis to review the combined results of high-quality studies in the literature.

Inclusion and Exclusion Criteria
We included randomized controlled trial (RCT), case-control, and cross-sectional studies that assessed the pain in participants who received TECAR therapy regardless of subjects' race, age, gender, publication year, and language. The primary variable investigated in this study was the pain experienced in the leg, shoulder, low back, and femur by patients with musculoskeletal disorders. Also, the pain was assessed by a visual analogue scale (VAS), which measures pain intensity on a scale of 0 to 10. All patients who underwent TECAR therapy received a high-frequency electromagnetic wave (0.3 to 1.2 MHz).

Search Strategy and Sources
The primary databases used to search the studies were PubMed (January 1950), Web of Knowledge (January 1945), Scopus (January 1980), and ProQuest (January 1983) until December 2021. Also, we checked the references list of all relative articles.
The following search keywords (

Study Selection and Data Extraction
After removing the duplicates, all references are imported to EndNote X9 (Clarivate Analytics, Toronto, Canada). Two researchers independently assessed the title and abstract of all these references to select the related papers. Then, we reviewed the full text of selected articles to ensure that they meet the inclusion criteria. The degree of agreement between the two reviewers was measured, which showed a 79.8% inter-rater reliability in Cohen's kappa coefficient.
We summarized the studies' data related to author name, publication date, country, type of study, age, gender, pathology understudy, evaluation period, sample size, and pain scores before and after therapy in intervention and control groups. The data collected were then entered into an electronic data form. The process of data extraction was performed by two authors independently, and disagreements were solved by taking a consensus-building approach.

Quality Assessment
The quality of included studies was explored using the 5-point score of the Jadad scale [13].
Briefly, the Jadad scale evaluated the quality of the study based on the following items: 1) description of randomization, 2) methods used to generate the sequence of randomization, 3) blinding, 4) method of blinding, and 5) description of withdrawals and dropouts [14]. We categorized the studies into two groups low-(score<4) and high-quality (score≥4). Two authors independently performed the quality assessment, and a consensus was made in the case of disagreement.

Heterogeneity and Reporting Bias
Measuring inconsistency in our metaanalysis, the I 2 statistics test was used to assess heterogeneity quantitatively according to the following equation: I 2 =[(Q 2 df)/Q]×100 [15]. A level of I 2 higher than 75% was considered high heterogeneity [16]. Also, we explored heterogeneity using Q-test at a 95% of confidence interval (CI) [17].

Statistical Analysis
Using a standardized mean difference (SMD) method, the intergroup comparisons were made at a 95% CI level. All statistical analyses were carried out by Stata software v.11 (StataCorp, College Station, TX, USA) using a random effect model [18].

Results
A total of 919 articles were found in the initial comprehensive search in databases and selected articles reference list. Out of these, 417 were duplicates. After the title and abstract screening of 502 articles, 13 articles were considered for full-text review ( Figure-1). Accordingly, five studies were excluded for the following reasons: one study [6] assessed pain by other scales, such as the Ely test and pelvic tilt instead of VAS; two studies [19,20] evaluated tissue temperature changes post-TECAR therapy; and two studies were not randomized clinical trial (one case-control study [21] and one cross-sectional study [22]). Finally, eight studies were included in the final analysis [7][8][9][10][23][24][25][26].

Studies Characteristics
Totally, 678 participants with a mean age of 49.9±15.24 years were evaluated. As shown in Table-2, five studies [8-10, 23, 25] were conducted in Italy, two in Iran [7,24], and one in South Korea [26]. The smallest sample size was related to the survey of Kim et al. [26] with 22 patients, and the largest was related to the study carried out by Ganzit et al. [25] with 327 participants. Subjects in one study [9] suffered from femoral pain. Low back pain (LBP) was the chief complaint in three studies [8,10,25], of which two studies [10,25] investigated athletes suffering from musculoskeletal pain. Participants in another study [8] also had disc herniation. Pain in the knee [23], shoulder [26], and ankle joints [24] were observed in other study populations. One study [7] examined patients with diabetic neuropathy. Pain as the significant variable was measured using VAS in all studies.

Different Therapeutic Approaches for Relief Musculoskeletal Pain
The studies included employed different methods of TECAR therapy for the intervention group (Table-2). The course GMJ.2022;11:e2407 www.gmj.ir of treatment duration varied between two [10,25], four [7,23,24,26], and eight weeks [8,9]. Five studies had a control group that underwent other therapies, including laser treatment [8], SonoStim [26], and physiotherapy [24], and the same intervention technique but without energy [7,23]. In general, all studies were performed to evaluate the effect of TECAR therapy in reducing the symptoms of patients with chronic pain. In addition to pain measurement, motor function post-treatment was assessed in one study [10]. Also, some studies [23,24,26] investigated the performance limitation adjunct to the pain variable. Further, the improvement of the symptoms in patients with diabetic neuropathy [7] was examined.
Overall, studies showed a reduction in pain intensity experienced by patients with chronic pain. Regarding Table-2, Tranquilli et al. [10] revealed that the patients who underwent TECAR therapy had shorter recovery times and regained normal limb function sooner. In another study [25], TECAR therapy was an effective method for improving bone, muscle, and joint injuries in athletes. Also, TECAR therapy is a better alternative for neuromuscular injuries than other modalities, which are more likely to fail in treatment [25]. Some studies reported the superiority of TECAR therapy over laser therapy [8] and physiotherapy [24]. The comparison between the effects of a deep heating device (HIPER®) and SonoStim showed that both modalities had an almost equal barbaric impact on pain relief and recovered physical activity [26].  However, HIPER therapy seemed slightly more effective than the other methods [26].

Subgroup Analysis
Whether the intervention effects vary across subpopulations, we performed subgroup analysis based on the pathology from which the participants suffered. Comparing the pain before and after the intervention, the patients experienced significantly lower pain intensity in the leg after two weeks (SMD=-6.98, 95% CI: -13.74 to -0.22, I 2 =98.2%) and in the low back after four weeks (SMD=-3.68, 95% CI: -5.08 to -2.16, I 2 =97.4%) of TECAR therapy (P<0.01).

Quality Assessment, Publication Bias, and Heterogeneity of Studies
According to the Jadad scale (Table-3) only one study [23] had a high-quality score. The rest of included studies did not demonstrate the quality measures of randomization,  Table-4 shows the results of Begg and Egger tests for assessing the publication bias. There was no significant publication bias in the inter-group comparison. Based on Q-test analysis, the heterogeneity between the two groups at the intervention intervals of two and four weeks as well as before and after in the intervention group was significant (P<0.05).

Discussion
The present study combined the results of different studies to ascertain the effectiveness of TECAR therapy in reducing pain. For this purpose, all studies that evaluated the pain intensity in patients who received TECAR therapy or did not (control group) before and after the intervention were included. Although the pain intensity was numerically a bit lower before the intervention compared to the control group subjects, this difference was not statistically significant. Therefore, the baseline level of pain was relatively equal in both groups. At different follow-up intervals, the pain intensity was compared before and after intervention in the control group. The control participants showed significantly lower pain intensity in the second, fourth, and eighth weeks' post-intervention compared to baseline pain levels before the intervention. However, the measure of SMD after two weeks was higher than at four and eight weeks, and the intra-group difference of controls was reduced with time. Also, the SMD between before and two, four, and eight weeks after the intervention was significant among patients who underwent TECAR therapy. Interestingly, SMD in the TECAR therapy group was higher than in the control group, which shows that TECAR therapy has more effectiveness in musculoskeletal pain. In contrast to the control group, the SMD increased after four and eight weeks in the TECAR therapy group. One of the main findings in the current study was an GMJ.2022;11:e2407 www.gmj.ir evaluation of the SMD between the control and TECAR therapy groups. This comparison showed that patients who received TECAR therapy experienced significantly lower pain levels than the control group after four and eight weeks' post-intervention. Based on these results, it seems that TECAR therapy is the more effective treatment choice for musculoskeletal pain. TECAR therapy is a complementary method for joint pain treatment and is a valuable tool for physiotherapists, and it does not interfere with other therapies [27]. In addition to physiotherapy, TECAR is used in several other fields, such as orthopedic, rheumatic, and aesthetic vascular areas [25], and the fact that recovery time noticeably decreases is its main advantage. Owe to three important physiological effects of TECAR therapy; its major therapeutic applications are as follows: antispastic, analgesic, and metabolic stimulants. Also, the adjunction of TECAR therapy causes a rapid improvement of the acute inflammatory process and return of muscle strength in comparison with other combination therapies.
In addition, three studies were conducted on LBP [8,10,25] and two on leg pain [7,24]. Other studies [9,23,26] were performed on the shoulder, femur, and knee. The similarity of methodology in the studies reviewed allowed us to combine the results. Further, subgroup analysis was carried out in two or more studies concerning patients' underlying pathology. This analysis compared the subgroups of LBP (two weeks after TECAR therapy) and leg pain (four weeks after TECAR therapy). The results showed that the pain was significantly lower two weeks after the intervention than at baseline. Patients with leg pain demonstrated the highest SMD [7] after four weeks of treatment compared to baseline leg pain. In consistence, TECAR therapy was also influential on LBP. Notarnicola et al. [8] reported that TECAR and laser therapies significantly GMJ.2022;11:e2407 www.gmj.ir 9 Figure 5. Comparison of pain score before and after intervention in the TECAR therapy group affect LBP. However, TECAR therapy was more effective than laser in pain relief over time [8]. Improvement progress over time can be explained by the biological effects of treatment, including anti-edema and antiinflammatory effects, muscle relaxant effect in paravertebral, endorphin secretion, and increasing cellular metabolism [8]. In another study [28], considerable improvement in pain of patients who underwent a combination of TECAR and massage therapies was observed, while the massage therapy was not effective alone. Hence, it suggested that TECAR therapy is helpful in LBP management [28]. Therefore, TECAR therapy simultaneously reduces these disorders' complications from the initial moments of rehabilitation by reducing the severity of LBP in the acute stage with different techniques [28]. Also, Terranova et al. showed that pain and edema decreased considerably after TECAR therapy [9]. Also, TECAR therapy has a more noticeable and immediate analgesic effect compared with the transcutaneous electrical nerve stimulation method [29]. TECAR therapy was also compared with cryoultrasound therapy. Costantino et al. reported that cryoultrasound therapy had a better impact than TECAR therapy, but the difference showed no statistical significance [27]. Ultimately, it may be inferred that TECAR therapy is an effective method for musculoskeletal pain. It seems that TECAR therapy is an excellent complementary treatment along with other manual physiotherapy techniques. Therefore, the rehabilitation protocol improves with the synergistic effect between TECAR treatment and physiotherapy. Thus, it results in higher satisfaction for both patients and physiotherapists. Our study had some limitations. Indeed, only a limited number of studies met our inclusion criteria; hence, we could not assess the subgroup analysis based on pathology. Also, the majority of included studies have low quality; thus, information GMJ.2022;11:e2407 www.gmj.ir bias was not avoidable.

Conclusion
Our findings provide appropriate evidence for the efficacy of TECAR therapy on musculoskeletal pain. Therefore, TECAR therapy can serve as a complementary treatment along with physiotherapy.