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Effects of capacitive and resistive electric transfer therapy in patients with knee osteoarthritis

a randomized controlled trial

Coccetta, Carlo A.a; Sale, Patriziob; Ferrara, Paola E.c; Specchia, Alessandroc; Maccauro, Giuliod; Ferriero, Giorgioa; Ronconi, Gianpaoloc

International Journal of Rehabilitation Research: June 2019 - Volume 42 - Issue 2 - p 106–111
doi: 10.1097/MRR.0000000000000324
Original Articles
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Capacitive and resistive electric transfer (CRET), an endogenous diathermy treatment, has been demonstrated to reduce pain and improve quality of life in numerous orthopedic degenerative and inflammatory problems but not in knee osteoarthritis (KOA). The aim of this prospective randomized controlled trial was to evaluate whether a 2-week program of CRET can reduce pain, stiffness and functional limitations in KOA compared with a sham treatment. Patients with KOA were randomly assigned to a study group (n = 31) or a control one (n = 22). The study group underwent six intermittent CRET applications, whereas the controls underwent a sham protocol without application of energy. The outcome measures were the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) (primary outcome) and the visual analogue scale (VAS) for pain and Medical Research Council Scale (secondary outcomes). All patients were evaluated before treatment (T0), at the end of treatment (T1), and at 1 (T2) and 3 months after treatment (T3). Results showed that CRET significantly improved strength, physical function and pain in patients with KOA. In the study group a reduction in WOMAC and VAS scores was observed at T1, T2, and T3 compared with T0. No significant changes of WOMAC and VAS scores were observed in the control group across all time points. Considering the small number of sessions, low cost and long-term benefits, CRET might be a useful therapeutic option for the conservative management of KOA to reduce pain, stiffness and functional limitation.

aIstituti Clinici Scientifici Maugeri, Pavia

bRehabilitation Unit, Department of Neuroscience, University of Padua, Padua, Italy

cUOC di Riabilitazione e Medicina Fisica, Fondazione Policlinico Universitario A. Gemelli

dIstituto di Ortopedia e Traumatologia, Università Cattolica del Sacro Cuore di Roma , Rome, Italy

Received 3 September 2018 Accepted 29 September 2018

Correspondence to Giorgio Ferriero, MD, PhD, Istituti Clinici Scientifici Maugeri, 27100 Pavia, Italy, Tel: +39 0394 6571; fax: +39 0394 657 279; e-mail: giorgio.ferriero@icsmaugeri.it

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Introduction

Knee osteoarthritis (KOA) is a chronic disease characterized by joint pain and functional impairment (Losina et al., 2011). It is highly prevalent in people aged more than 50 years (Dominick et al., 2004). In mild and moderate KOA, pharmacologic intervention is the most common treatment prescribed (Reid et al., 2012). Cases of unremitting pain and severe functional disability are referred for surgical joint replacement (Piscitelli et al., 2012). Most international guidelines recommend a regular rehabilitation program for the control of pain and disability in patients with KOA (Zhang et al., 2007; McAlindon et al., 2014). Another conservative approach to treat KOA is the use of physical therapy modalities such as diathermy (Wang et al., 2017). There are four main modes for producing diathermy - long-wave radio frequencies, short-wave radio frequencies, ultrasound, and microwaves – which differ in terms of wave frequency and consequent penetration capability. Some of these diathermy therapies have been demonstrated to be beneficial for relieving pain caused by KOA.

Capacitive and resistive electric transfer (CRET) is an endogenous diathermy treatment that operates within long-wave range using radiofrequency energy, generally about 0.5 MHz, to generate the warming up of the treated tissues (Tashiro et al., 2017). It consists of a generator of long-wave currents and electrodes with multifrequency sequential systems of emission that transfer energy to tissues in two modes: capacitive and resistive. Usually, an isolated electrode is used with a metal plate for capacitive CRET: the electrical charges produced by the radiofrequency generator are concentrated near the isolated electrode acting as a dielectric surface. This modality is used for treatment of superficial tissues near the isolated electrode. In the resistive mode, two metal electrodes diffuse electrical charges that tend to accumulate near bone, tendon and ligament tissue – with the highest electrical resistance (dielectric) located between the electrodes.

CRET has a documented capacity to reduce pain and improve the quality of life in patients with numerous orthopedic degenerative and inflammatory problems (Takahashi et al., 2000; Costantino et al., 2005; Raffaetà et al., 2007; Stagi et al., 2008; Terranova et al., 2008; Sanguedolce et al., 2009; Notarnicola et al., 2017). Among the various methods used for diathermy, CRET is considered the most convenient and safe as it has no limits concerning treatment area – unlike ultrasound – and does not cause excessive heat generation between the skin and the electrode (Yokota et al., 2016). To date, to the best of our knowledge, there are no published studies investigating the effects of CRET in KOA. Therefore, the aim of this study was to evaluate whether CRET can reduce pain, stiffness and functional limitations in patients with KOA, compared with a sham treatment.

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Participants and methods

Participants

The study was designed as a prospective randomized controlled trial (RCT). A convenience sample of 70 patients with knee pain who were referred from August to December 2012 to the outpatient clinic of the Department of Physical Medicine and Rehabilitation of the University Hospital ‘Agostino Gemelli’ (Catholic University of the Sacred Heart, Rome, Italy) was consecutively recruited. Inclusion criteria were as follows: (a) patients of both sexes aged 18 years or older, (b) radiographic diagnosis of KOA (Kellgren–Lawrence grade I, II or III) (Altman et al., 1986), and (3) presence of knee pain for at least 3 weeks. Exclusion criteria were as follows: (a) history of surgery or intra-articular injection therapy of the affected knee, (b) inflammatory or neurological disease involving the lower limbs, (c) presence of knee ligament lesions, (d) history of physical therapy for at least 6 months, (e) chronic pharmacological treatment with corticosteroids or NSAIDs, (f) diagnosis of psychiatric disorders or cognitive impairment; (g) pregnancy or breast feeding, and (h) presence of any contraindications to CRET (neoplasia, local vascular disease, local sensory impairment, local or systemic acute infections, bone tuberculosis, severe osteoporosis, and presence of pace-maker implants).

The University’s Ethical Committee approved the study protocol, and all participants were asked to carefully read and sign their informed consent. This study is registered on the ClinicalTrials.gov registry (identified: NCT01800955).

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Intervention

We utilized for CRET treatment a Tecar Unibell HCR 902 device (Unibell, Calco, Lecco, Italy) with different electrodes capable of generating capacitive or resistive CRET modalities. The settings used in this study are shown in Table 1.

Table 1

Table 1

Eligible patients were randomly assigned to two groups: study group (31 patients) and control (sham) group (22 patients). The study group underwent a protocol of six intermittent (three times a week) CRET applications on the quadriceps and peripatellar region of 20-min duration (5 min of capacitive mode CRET followed by 10 min of resistive mode CRET and then 5 min of capacitive mode CRET). The control group was treated with a simulated protocol without application of energy. No kinesiotherapy was administered in any group or any self-administered therapeutic exercise.

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Outcomes

The primary outcome measure was the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) (Salaffi et al., 2003) for the assessment of pain, stiffness and functional limitation. Secondary outcome measures were the visual analogue scale (VAS) (Huskisson, 1974) for pain evaluation and the Medical Research Council Scale (MRC) (Medical Research Council, 1976) for the evaluation of quadriceps muscle strength, as quadriceps weakness has been associated with KOA (Benedetti et al., 2017). All patients were evaluated before treatment (baseline, T0), at the end of treatment (T1), and at 1 month (T2) and 3 months after treatment (T3) with all outcome measures. The a priori hypothesis was that only the study group would show a significant improvement in both primary and secondary outcomes.

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Randomization

Randomization was performed using an open access software program (http://www.random.org). The randomization list was kept by an independent researcher (not involved in the study), and the assignment code of each patient was disclosed only to the physiotherapist who performed the treatment at the beginning of the therapeutic protocol.

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Blinding

Both patients and the researcher responsible for the outcome assessments (who was a physiatrist) were unaware of patients’ allocation. The researcher responsible for patient assessment had no contact with the patients during their treatment, and patients were instructed not to make any comment that was not strictly related to the questionnaire administered. To maximize allocation concealment, the researcher had no access to the previous evaluations at follow-up visits.

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Statistical analysis

Assuming that the two treatments would be equally effective in determining a 15-point increase (minimal clinically important difference, MCID) in the WOMAC and VAS summed scores, a sample size of 53 cases was calculated as necessary using an a priori model of power analysis and a two-sided alternative hypothesis, given an α = 0.05 and a power (1−β) = 0.80. Continuous variables were tested in each group for normal distribution, using the Kolmogorov–Smirnov test. The mean differences between the two groups of WOMAC, VAS and MRC scores were calculated by a mixed analysis of variance for repeated measures. Bonferroni corrected post-hoc tests and the Wilcoxon test were performed for pairwise comparisons. Missing data at follow-up were managed through the last observation carried forward method. Analyses were performed according to the intention-to-treat principle. All tests were considered significant if P values were less than 0.05. Statistical analysis was performed using the software SPSS version 19.0 (SPSS Inc., Chicago, Illinois, USA).

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Results

The overall sample consisted of six males and 47 females (age range: 44–84 years).

All the participants have a radiographic diagnosis of KOA with a Kellgren–Lawrence grade’s distribution between the groups substantially symmetrical (study group: 10 patients with grade I, 14 with grade II and seven with grade III; control group: six with grade I, 12 with grade II and four with grade III). At T0, participants of the two groups did not differ in terms of any demographic or anthropometric parameters, or baseline scores at WOMAC, VAS and MRC (Table 2). No adverse events were observed in either group. Four patients of the study group and five of the control group were excluded as they missed the last follow-up trial before the end of the evaluation (Fig. 1). Descriptive statistics for the primary and secondary outcome measures in the two groups are shown in Figs 2–4.

Table 2

Table 2

Fig. 1

Fig. 1

Fig. 2

Fig. 2

Fig. 3

Fig. 3

Fig. 4

Fig. 4

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Discussion

Despite the large popularity and nearly 100 years of use of physical therapy modalities, there is still doubt about the appropriateness of these conservative therapies to treat KOA (McAlindon et al., 2014). In contrast, important reviews have stated that some diathermic therapies, such as ultrasound (Rutjes et al., 2010) or short-wave diathermy (Wang et al., 2017), may be beneficial for patients with KOA. Moreover, in the recent literature other types of physical therapy based on diathermy have been demonstrated to be effective in patients with KOA with satisfactory results. Giombini et al., 2011, in a RCT, investigated the effectiveness of microwave diathermy treatment for functional limitations and pain secondary to KOA. Their study demonstrated a significant improvement in WOMAC scores in patients with KOA compared with the control group. In another RCT, Zhao et al., 2013, demonstrated that a protocol of 4000 pulses of shockwave at 0.25 mJ/mm weekly for 4 weeks is effective in reducing pain and improving knee function, with better results than placebo. Similarly, Rabini et al. (2012), demonstrated that deep heating therapy through microwave diathermy induced a change of −18.7 points in the WOMAC score at 6 months in patients with KOA.

Previous studies showed that CRET acts by generating a warming up of deep tissues that promote cellular metabolism and oxygen delivery to tissues by increasing vascular circulation, facilitating catabolites elimination in metabolism (Tashiro et al., 2017) and stimulating the proliferation of stem cells to repair injured tissues (Hernández-Bule et al., 2014). Our prospective RCT showed that treatment based on CRET can reduce pain, stiffness and functional limitations in patients with KOA.

In the indexed literature, no previous studies exist demonstrating the effectiveness of CRET in the treatment of pain related to KOA. We found only five articles showing its effectiveness in pain treatment for other orthopedic diseases, that is, neck pain (Raffaetà et al., 2007), cervico-omo-brachial pain (Takahashi et al., 2000), back pain (Stagi et al., 2008; Notarnicola et al., 2017), postoperative-surgical pain after femoral fracture surgery (Terranova et al., 2008), shoulder pain secondary to impingement syndrome (Sanguedolce et al., 2009) and insertional tendonitis (Costantino et al., 2005). Our study showed that a 2-week program of CRET was able to significantly improve strength, physical function and pain in a sample of patients with KOA. In the study group, a reduction in the WOMAC and VAS scores compared with T0 was observed at each follow-up evaluation. In particular, differences in the WOMAC score between T0 and T1 and between T2 and T3 were greater than 15 points, which is the MCID for this tool (Tubach et al., 2005). No significant changes of WOMAC and VAS scores were observed in the control group across all time points. In the study group, a significant increase in the MRC score relative to T0 was observed at T2 and T3, but not at T1. In contrast, in the control group, a significant reduction in the MRC score relative to T0 was observed at each follow-up. These results might be explained by the fact that moderate and severe pain is associated with reduced quadriceps strength in KOA (Riddle and Stratford, 2011).

CRET treatment was well tolerated by patients; indeed, no adverse effects were observed or reported in the study group during the treatment and at the follow-up visits.

Our study has three main limitations: (i) patients recruited were affected by mild and moderate KOA (grades I–III of the Kellgren–Lawrence scale) but not severe, (ii) the follow-up duration of 3 months might be not have been completely sufficient for evaluating long-term response to the treatment, and (iii) the number of drop outs. A further possible limitation might be the impossibility to completely standardize the treatment provided, as the intensity of power provided had to be tailored to the patient’s need, compliance and tolerance (Pavone et al., 2013). However, in rehabilitation, this is a common issue, as it is not possible to standardize intensity of exercises, functional training and manual therapy (Kersten et al., 2010).

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Conclusion

The application of CRET seems to improve functional outcome and pain control in patients with KOA. Furthermore, CRET is well tolerated by patients, as shown by the excellent compliance to the treatment. In conclusion, considering the small number of sessions required, low cost and long-term benefits, CRET might represent a useful therapeutic option for the conservative management of KOA patients to reduce pain, stiffness and functional limitation.

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Acknowledgements

Conflicts of interest

There are no conflicts of interest.

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Keywords:

elderly; pain; physical modalities; rehabilitation

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