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Microwave diathermy for treating nonspecific chronic neck pain: a randomized controlled trial
The Spine Journal
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(2013)
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Clinical Study
Microwave diathermy for treating nonspecific chronic neck pain: a randomized controlled trial on Cer on Fernandez, PTb, Juan Alfonso Andrade Ortega, MD, PhDa,*, Encarnaci Rosario Garcıa Llorent, PTb, Marisa Ribeiro Gonzalez, PTb, Alberto Damian Delgado Martınez, MD, PhDc,d a
Department of Physical Medicine and Rehabilitation, Complejo Hospitalario de Jaen, Avenida del Ejercito Espa~nol, s/n, 23005 Jaen, Spain b Physiotherapy Unit, Complejo Hospitalario de Jaen, Avenida del Ejercito Espa~nol, s/n, 23005 Jaen, Spain c Department of Orthopedic Surgery, Hospital ‘‘San Agustın’’, Avenida de San Cristobal, s/n, Linares, 23700 Jaen, Spain d University of Jaen, Campus de las Lagunillas, s/n, 23071 Jaen, Spain Received 27 May 2012; revised 12 September 2013; accepted 17 October 2013
Abstract
BACKGROUND CONTEXT: Although the use of deep heat therapy is widespread, there is scant literature available on its effectiveness in treating back or neck pain. PURPOSE: The purpose of this study was to determine the efficacy of microwave diathermy to treat nonspecific chronic neck pain. DESIGN: The study was designed as a double-blind, randomized controlled trial. PATIENT SAMPLE: The patient sample consisted of 149 patients with nonspecific chronic neck pain in a hospital of the Andalusian Public Health Care System, Spain OUTCOME MEASURES: The study outcome measures are as follows: at baseline, pain intensity (using a visual analogue scale), disability (Neck Disability Index), and health-related quality of life (36-item short form health survey [SF-36]); at 3 weeks, baseline measures and patients’ perceived overall outcome and satisfaction with the treatment; and at 6 months, 3–week measures, therapeutic co-interventions, and adherence to exercises. METHODS: Patients were allocated randomly to three groups. The first group received continuous microwave diathermy, the second group was administered pulsed microwaves, and the third group (the control group) received unplugged microwaves. All three groups received the same general treatment: range of motion, isometric exercises, and transcutaneous electrical nerve stimulation. RESULTS: The three groups had reduced pain and disability, and improvement was seen in some dimensions of the SF-36. However, there were no differences found in any of the parameters measured among the three therapeutic groups. CONCLUSIONS: Microwave diathermy does not provide additional benefit to a treatment regimen of chronic neck pain that already involves other treatment approaches. Ó 2013 Elsevier Inc. All rights reserved.
Keywords:
Neck pain; Microwaves; Diathermy; Physical therapy modalities; Exercise; Transcutaneous electrical stimulation
Introduction Neck pain is a common and expensive condition [1]. Its age-adjusted prevalence ranges from 67% to 86% [2,3]. FDA device/drug status: Approved (microwave diathermy and TENS [transcutaneous electrical nerve stimulation]). Author disclosures: JAAO: Support for travel to meetings for the study or other purposes: Instituto de Salud ‘‘Carlos III’’ (B); Provision of writing assistance, medicines, equipment, or administrative support: Instituto de Salud ‘‘Carlos III’’ (B). ECF: Nothing to disclose. RGL: Nothing to disclose. MRG: Nothing to disclose. ADDM: Nothing to disclose. 1529-9430/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.spinee.2013.10.025
Neck pain increases with age and is more frequent in women than men, although such bias is not accepted unanimously by all experts [3]. About 50% to 80% of neck
The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com. This study was supported by a research project from the Instituto de Salud Carlos III (PI11/087). There is no topic-specific conflict of interest related to the authors of this study. * Corresponding author. C/Dr Federico del Castillo, 8, 1 E, 23005Jaen, Spain. Tel.: 34679650663. E-mail address: [email protected] (J.A. Andrade Ortega)
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pain cases are not fully resolved, and thus become chronic and cause significant direct and indirect costs [4–6]. Most direct costs are generated by physical treatments, including patient education and counseling, exercises, manual therapies, and electrothermal therapies [6,7]. However, only physical exercise—alone or combined with manual therapies—is supported by solid scientific evidence [8]. Although the use of electrophysical agents is widespread, little evidence is available on its effectiveness in neck pain [5,9]. Kroeling et al. [5] concluded there is no scientific evidence—either limited or contradictory—on the effectiveness of galvanic currents, iontophoresis, transcutaneous electrical nerve stimulation (TENS), pulsed electromagnetic fields, electrical muscle stimulation, and permanent magnets. Considering the number of patients seeking treatment for neck pain, surprisingly few studies have addressed the physical interventions used in such cases, especially for heat therapy, for which there is a great variability in use [10]. A lack of uniformity in heat use for this patient population is illustrated by several studies. From the report by Jette and Jette [11] in 1996 to the report by Boissonnault and Badke [10] in 2008, ‘‘usual treatment’’ for patients with neck pain provided by physiotherapists includes the use of heat modalities in a range that goes from 91% of the first to less than 17% of the latter. From a recent survey in North Carolina, Goode et al. [12] found that heat was used by 57% of people with neck pain. These authors note that, based on current evidence for best practice, their findings indicate overuse of modalities and underuse of effective treatments such as therapeutic exercise. A cross-sectional study [13] of the Spanish National Health Service in the Canary Islands, where the public health service covers a total population of two million people, showed that as much as 60% of the resources spent on physical treatments for nonspecific chronic neck pain, back pain, and shoulder pain between 2004 and 2007 were allocated to treatments that were found to be either ineffective or for which there was no evidence of effectiveness. Heat therapy was a major part of these physical treatments. Microwave diathermy once had a place in therapy, but since the 1980s, interest in its use has declined in many countries, more than shortwave diathermy or ultrasound [14–16]. The Food and Drug Administration [14] differentiates between diathermy devices according to their thermal or nonthermal mechanism of action. Specifically, it separates diathermy devices into ‘‘diathermy for use in applying therapeutic deep heat for selected medical conditions’’ and ‘‘diathermy intended to treat medical conditions by means other than the generation of deep heat.’’ Today, most commercial devices allow both types of application. Microwave diathermy is a form of electromagnetic energy that uses its conversion to thermal energy, which is produced by increased kinetic energy of molecules within the microwave field; radiation is absorbed selectively by water, and muscle
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should be heated preferentially. Fourteenth Federal Communications Commission-approved frequencies for therapeutic microwave are 915 MHz and 2,450 MHz. The lower frequency has the advantage of increased depth of penetration but also the disadvantages of greater beam dispersion and the requirement of larger applicators [14]. Microwaves do not penetrate tissue as deeply as shortwave diathermy and ultrasound. Shortwave therapy is generally preferred over microwave because it has a more predictable heat distribution pattern [14,15]. Recently, particularly in Europe, microwaves are being used at 434 MHz and, therefore, are realizing increased penetration [17–20]. Because of this, microwave diathermy seems to have become popular again, as evidenced by trials looking at its effectiveness in knee osteoarthritis [17] and other musculoskeletal conditions [18–20]. Indications and contraindications of microwave and shortwave therapy are practically the same [15,16]. In a trial conducted with patients with nonspecific neck pain (most of them chronic), the use of pulsed shortwave diathermy in combination with physical exercise and patient counseling did not improve patients’ health status [21]. Consequently, the efficacy of pulsed shortwave diathermy has been questioned by some authors [22]. Studies on the efficacy and cost-effectiveness of the therapies used to treat neck pain are required [23]. Because of the significant lack of supporting studies about diathermy and the considerable economic burden for many health systems [13], it is important to clarify the role to be played by these physical modalities. No trials have been conducted on the effectiveness of microwaves in patients with neck pain. This study is intended to determine the effectiveness of microwave diathermy in treating nonspecific chronic neck pain.
Methods A double-blind, randomized controlled trial was conducted with 149 patients with nonspecific chronic neck pain in a hospital of the Andalusian Public Health Care System in Jaen, Spain. The patients were referred from a primary care setting to the Department of Rehabilitation between September 2008 and December 2010, because of failure of the treatment prescribed by the general practitioner. Subjects were recruited consecutively when they met the requirements described later. Most people in Jaen, a rural area in southern Spain, are covered by the public health care system. Patients’ epidemiological data are shown in Table 1. The trial was approved by the ethics committee of the hospital. The eligibility criteria were patients between 18 years and 65 years with a diagnosis of nonspecific chronic neck pain, ie, 3-month or longer duration, and the absence of red flags (clinical features that indicate an increased risk of specific conditions) such as weight loss, fever, progressive neurologic signs, cancer history, infectious or inflammatory disease history, osteoporosis, or
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major structural abnormalities or neurologic conditions affecting the neck. Exclusion criteria included women who were pregnant, individuals on sick leave or involved in a lawsuit or claim process in which neck pain was the cause, and subjects with a pacemaker, metal implants, or any other device that contraindicated the use of microwaves [15,16]. This study was registered under the unique identifier NCT01487122 (www.clinicaltrials.gov). After informed consent was obtained, patients were randomized to three treatment arms (Group C, continuous microwave; Group P, pulsed microwave; or Group U, unplugged microwave) using a series of random, repeating three possible figures generated by free software. This series was only known by the chief of physiotherapists, who allocated to each figure a treatment group before starting the trial. In the rehabilitation department, the same two physiotherapists delivered 15 physical treatment sessions (five per week for 3 weeks) according to each group schedule. The rationale for the use of 15 sessions in 3 weeks has been reported elsewhere [24]. The comprehensive treatment included, in this order, range of motion and isometric exercises (initially in treatment room and, after 3 weeks, at home), TENS, and diathermy. The latter was provided differently according to the treatment arm. Group C received continuous microwaves, Group P received pulsed microwaves, and Group U received unplugged microwaves. One of the physiotherapists conducted the exercises, and the other administered TENS and microwaves. Exercise included monitored free movements and resisting elastic band isometric exercises of the cervical spine Table 1 Baseline values Variable
Total
N
149
Age, y (SD) Males, n (%) Females, n (%) BMI, kg/m2 (SD) LA, n (%) HA, n (%) VAS, pt (SD) NDI, pt (SD) SF-36, pt (SD) PF, pt (SD) RP, pt (SD) RE, pt (SD) BP, pt (SD) SF, pt (SD) VT, pt (SD) GH, pt (SD) MH, pt (SD)
44.2 36 113 24.9 93 56 53.5 34.4 56.5 72.7 36.9 53.3 42.1 71.5 51.6 47.5 58.5
C
P
50 (10.1) (24.1) (75.9) (3) (62.4) (37.6) (15.8) (12.1) (14.9) (22.9) (42.9) (46.7) (20.8) (22.3) (12.8) (12.6) (8.4)
43.6 13 37 24.6 33 17.0 52.9 34.4 55.4 69.8 31.0 52.7 39.0 72.0 52.0 49.3 60.8
U
48 (11.2) (26) (74) (3.2) (66) (34) (16.7) (11.9) (14.5) (26.3) (42.1) (44.7) (22.5) (20.8) (12.4) (10.2) (6.3)
45.5 10 38 25.2 29 19.0 54.7 33.6 60.1 79.1 46.9 59.8 43.8 76.3 51 47.5 57.1
51 (7.9) (20.8) (79.2) (3.2) (60.4) (39.6) (13.9) (12.5) (15.6) (19.8) (42.1) (48.1) (19.5) (21) (15.7) (14.3) (10)
43.6 13 38 24.9 31 20.0 53 35.2 54.1 69.6 33.3 47.7 43.6 66.4 51.8 45.7 57.5
(10.9) (25.5) (74.5) (2.5) (60.8) (39.2) (16.9) (12.1) (14.3) (21.2) (43.5) (47.3) (20.4) (24.3) (10.2) (13) (8.1)
BP, bodily pain; BMI, body mass index; C, continuous microwave; GH, general health perceptions; HA, heavy activity; LA, light activity; MH, mental health; NDI, Neck Disability Index; P, pulsed microwave; PF, physical functioning; RE, role emotional; RP, role physical; SD, standard deviation; SF, social functioning; SF-36, 36-item short form health survey; U, unplugged microwave; VAS, visual analogue scale; VT, vitality.
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3
(flexion, extension, left and right rotations, and left and right lateral bending), and raising and forward and rearward rotation of the shoulders. Each exercise was performed 10 times with patients sitting in front of a mirror, their back against the backrest of a chair, and their feet touching the ground. The position was maintained for 5 seconds after each exercise. All patients were instructed to perform the learned exercises at home, a minimum of three times per week indefinitely. Transcutaneous electrical nerve stimulation was performed using the Enraf-Nonius Tensmed 911 model (Rotterdam, Netherlands) through four 55-cm square electrodes. One pair was placed between C5 and C7 (on both sides) and the other pair was placed on the upper fibers of the trapezius. We used the continuous mode at a frequency of 80 Hz, with a pulse duration of 150 microseconds. Intensity was adjusted to produce a tingling sensation, and TENS was delivered for 30 minutes. Similar parameters have been used by others [24]. Microwaves were delivered using the Enraf-Nonius Radarmed 12S259 generator (Rotterdam, Netherlands). Group C received continuous microwaves at 80 W for 20 minutes through a large circular electrode placed 15 cm from the neck. Individuals in Group P received pulsed microwaves (mean power, 5 W) using the same conditions as group C. Similar doses have been used elsewhere [25]. Group U was provided with the same therapy, but the device was unplugged and a light-emitting diode induced patients to think that the device was operating. At all times the patients did not know to which treatment arm they were assigned. During the medical consultation before the treatment, patients were informed of the importance of performing their exercises at home. They were allowed to take any pain relief medication as necessary, and were asked to record their analgesic medication intake. Similarly, patients were asked to record any therapeutic co-interventions received during the follow-up, especially if they attended physiotherapy sessions outside the public health system. At all times, except for the therapist who administered electrothermal therapy and the chief of physiotherapists (who did not participate directly in the treatment), all professionals were blinded to treatment allocation. Before the treatment started, the following variables were recorded: age, sex, body mass index, and intensity of work activity (‘‘light’’ for nonphysically demanding jobs, and ‘‘heavy’’ for physically demanding jobs). Housework, which as highly represented in our sample, was included in the ‘‘heavy’’ category. The primary outcome was pain intensity. Secondary outcomes were disability for cervical pain, health-related quality of life, patients’ perceived overall outcome, satisfaction with the treatment, therapeutic co-interventions, and adherence to exercise. Outcome measures were obtained at session 1, session 15, and at 6 months by a physiotherapist blinded with respect to the treatment groups. At three time points (session 1, session 15, and at 6 months), pain
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Figure. Flow of participants through each stage of the trial.
intensity was measured using a visual analogue scale (a tool for measuring pain intensity, the use of which is widespread [26]), disability in terms of cervical pain was measured according to the Neck Disability Index (NDI; the Spanish version of the NDI has been validated [27,28]), and health-related quality of life, which was measured according to the 36-item short form health survey (SF-36).
Respect of this, overall value and each of the eight dimensions values were assessed, including physical functioning, role physical, role emotional, bodily pain, social functioning, vitality, general health perceptions, and mental health. The Spanish version of the SF-36 was validated by Alonso et al. [29]. At session 15, additional parameters assessed were as follows: patients’ perceived overall outcome
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Table 2 Pain at baseline, after treatment, and at 6 months Pain intensity
Total
C
P
U
General linear model
N
141
45
47
49
Within subjects (time)
Between subjects (timegroup)
VAS at baseline pt (SD) VAS after treatment, pt (SD) VAS at 6 mo, pt (SD)
52.9 (15.8) 37.2 (21.5) 37.3 (21.1)
52.8 (17.4) 36.0 (19.8) 36.1 (18.6)
53.7 (13.6) 39.4 (21.3) 37.7 (19.6)
52.1 (16.5) 36.2 (23.4) 38.1 (24.7)
p!.001
p5.420
C, continuous microwave; P, pulsed microwave; U, unplugged microwave; VAS, visual analogue scale. Note: Measures are average values (standard deviation).
according to a 6-point scale for the measures excellent, very good, good, fair, poor, and very bad (a similar scale has been used elsewhere for measuring perceived outcome in neck pain [30]), and satisfaction with the treatment according to a 5-point scale for the measures very satisfied, satisfied, neither satisfied or dissatisfied, dissatisfied, and very dissatisfied. The latter scale is one of the items of an NDI-based satisfaction questionnaire that has been used elsewhere [31]. At 6 months, in addition to the parameters measured at the other two time points, therapeutic cointerventions (narrative description) and adherence to exercises (often, sometimes, or never) were further evaluated. The measurements taken at the beginning and on completion of treatment were collected at the hospital, whereas those taken at 6 months were collected by telephone and by mail. A pilot clinical trial with 64 patients was performed previously. In this study, Groups C, P, and U achieved a mean visual analogue scale pain score relief of 17.76 points, 10.21 points, and 15.95 points after treatment, with an overall standard deviation of 11.73 points. With these data, using the sample size calculator Ene 2.0 (Department of Biometry, Glaxo-Smith-Kline, Barcelona, Spain), it was established that 133 patients were required, with p5.05 and a 0.80 power. Because we predicted a dropout rate of 10%, 148 patients were recruited. Statistical analysis was performed by the first author, who was also blinded to treatment allocation. All quantitative variables were transformed to normal distribution (Kolmogorov-Smirnov test). Analysis was done on an intent-to-treat basis. A repeated-measures general linear model was used to analyze numerical data such as pain, disability, and health-related quality of life; time was within-subject factor and therapeutic groups were the between-subjects factor. The chi-square test was used for categorical data. Statistical significance was set at the 5% level
(two tailed). Analysis of the outcomes was performed using SPSS version 15.0 (SPSS Inc., Chicago, IL, USA).
Results The Figure shows the flow of participants through each stage of the trial. Table 1 shows the distribution of baseline values. Two patients from Group C and another two from Group U dropped out of treatment, so a total of 145 patients completed the treatment. The reasons given were job incompatibility (one patient from Group C and two patients from Group U) or housework incompatibility (one patient from Group C). Another four patients dropped out at 6 months, three of whom could not be contacted (two from Group C and one from Group P), and one patient refused to continue participating in the study (Group C). Consequently, a total of 141 patients completed the study. One patient from Group C and another from Group U experienced dizziness on one occasion after the therapy session. These symptoms were relieved after a few minutes without any intervention. No other adverse reactions or side effects were reported. Tables 2 and 3 show the improvements in pain and disability on treatment completion and after 6 months. Treatment arms did not influence the results. Pain relief was maintained at the 6-month follow-up assessment, and the reduction of disability was even greater after 6 months than on treatment completion. Table 4 shows the results in terms of patient satisfaction on treatment completion and at 6 months after treatment; therapeutic arms did not influence them. In the same way, this table also shows that treatment arms did not influence patients’ adherence to exercises at 6 months. Table 5 shows that health-related quality of life improved by more than 11% in all groups. Again, therapeutic
Table 3 Disability at baseline, after treatment, and at 6 months Disability
Total
C
P
U
General linear model
N
141
45
47
49
Within subjects (time)
Between subjects (timegroup)
NDI at baseline, pt (SD) NDI after treatment, pt (SD) NDI at 6 mo, pt (SD)
33.9 (12.1) 25.8 (14.5) 23.3 (14.2)
34.1 (11.6) 25.2 (14.4) 23.1 (14.6)
32.8 (12.6) 25.3 (14.0) 22.2 (12.9)
34.9 (12.3) 26.8 (15.3) 24.7 (15.3)
p!.001
p5.923
C, continuous microwave; NDI, Neck Disability Index; P, pulsed microwave; U, unplugged microwave. Note: Measures are average values (standard deviation).
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Table 4 Perceived outcome and satisfaction, and adherence to treatment Perceived outcome, satisfaction, and adherence to exercise Initial, N After treatment, N Perceived outcome after treatment, n (%) Excellent Very good Good Fair Poor Very bad Satisfaction after treatment, n (%) Very satisfied Satisfied Neither satisfied or dissatisfied Dissatisfied Very dissatisfied After follow-up, N Perceived outcome at 6 mo, n (%) Excellent Very good Good Fair Poor Very bad Satisfaction at 6 mo, n (%) Very satisfied Satisfied Neither satisfied or dissatisfied Dissatisfied Very dissatisfied Adherence to physical exercise, n (%) Often Sometimes Never
Total
C
P
U
149 145
50 48
48 48
51 49
p (Chi-square)
3 28 62 52 0 0
(2) (19.3) (42.8) (35.9) (0) (0)
1 9 21 17 0 0
(2) (18.8) (43.8) (35.4) (0) (0)
0 9 20 19 0 0
(0) (18.8) (41.7) (39.6) (0) (0)
2 9 22 16 0 0
(4.1) (18.4) (44.9) (32.7) (0) (0)
49 (33.8) 72 (49.7) 24 (16.6) 0 (0) 0 (0) 141
17 24 7 0 0 45
(35.4) (50) (14.6) (0) (0)
17 21 10 0 0 47
(35.4) (43.8) (20.8) (0) (0)
15 27 7 0 0 49
(30.6) (55.1) (14.3) (0) (0)
1 28 60 43 9 0
(0.6) (19.9) (42.6) (30.5) (6.4) (0)
0 9 19 16 1 0
(0) (20) (42.2) (35.6) (2.2) (0)
0 10 30 15 2 0
(0) (21.3) (63.8) (31.9) (4.3) (0)
1 8 22 12 6 0
(2) (16.3) (44.9) (24.5) (12.2) (0)
40 77 24 0 0
(28.4) (54.6) (17) (0) (0)
15 25 5 0 0
(33.3) (55.6) (11.1) (0) (0)
12 24 10 0 0
(25.5) (51.1) (21.3) (0) (0)
12 28 9 0 0
(24.5) (57.1) (18.4) (0) (0)
p5.77
p5.62
p5.91
p5.36
p5.52 30 (21.2) 60 (42.4) 51 (36.2)
9 (20) 22 (48.9) 14 (31.1)
8 (17) 22 (46.8) 17 (36.2)
13 (26.5) 16 (32.7) 20 (40.8)
C, continuous microwave; P, pulsed microwave; U, unplugged microwave.
arms did not influence the results. Improvements in role physical, role emotional, bodily pain, and general health perceptions after treatment and at 6 months were remarkable in all treatment arms. Therapeutic co-interventions during the follow-up are shown in Table 6. Treatment groups did not affect the final outcome. None of the therapeutic co-interventions included the use of any type of diathermy. Discussion The results suggest that continuous microwaves (thermal effect), pulsed microwaves (athermal effect), and unplugged microwaves (placebo) have the same influence in terms of pain or disability reduction. The same can be applied to the patients’ perceived outcome and satisfaction with the treatment. The minimal detectable and minimal clinically important changes have been explored for neck pain severity [32]. Improvements less than or equal to 1.5 points in pain intensity could be seen as irrelevant, so our results suggest that patients experienced significant improvement in pain
relief. The minimal detectable and minimal clinically important changes have also been explored for disability [33]. For NDI, these values were 10.2 and 7.5, respectively. Our results partially meet these requirements after treatment and fully meet them after the 6-month follow-up. The Spanish version of the SF-36 was validated by Alonso et al. [29]. The mean age in their study was 45.52 years, with a slight prevalence of women. The reference values were as follows: physical functioning, 84.7 points; role physical, 83.2 points; role emotional, 86.6 points; bodily pain, 79 points; social functioning, 90.1 points; vitality, 66.9 points; general health perceptions, 58.3 points; and mental health, 73.3 points. Because our study included patients with chronic pain, it is not surprising that the baseline scores obtained were low. As far as we know, minimal clinically important changes have not been explored for health-related quality of life in patients with neck pain. A comparable study could be that of Escobar et al. [34], who determined responsiveness and clinically important differences for the SF-36 after total knee replacement (minimal clinically important differences were at least 10 points). On the basis of this study, our results suggest that
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Table 5 Health-related quality of life at baseline, after treatment, and at 6 months Health-related quality of life
Total
C
P
U
General linear model
After treatment, N
141
45
47
49
Within subjects (time)
Between subjects (timegroup)
SF-36 at baseline, pt (SD) SF-36 after treatment, pt (SD) SF-36 at 6 mo, pt (SD) PF at baseline, pt (SD) PF after treatment, pt (SD) PF at 6 mo, pt (SD) RP at baseline, pt (SD) RP after treatment, pt (SD) RP at 6 mo, pt (SD) RE at baseline, pt (SD) RE after treatment, pt (SD) RE at 6 mo, pt (SD) BP at baseline, pt (SD) BP after treatment, pt (SD) BP after treatment, pt (SD) SF at baseline, pt (SD) SF after treatment, pt (SD) SF at 6 mo, pt (SD) VT at baseline, pt (SD) VT after treatment, pt (SD) VT at 6 mo, pt (SD) GH at baseline, pt (SD) GH after treatment, pt (SD) GH at 6 mo, pt (SD) MH at baseline, pt (SD) MH after treatment, pt (SD) MH at 6 mo, pt (SD)
57.1 63.3 63.3 73.1 75.7 75.5 38.5 47.1 47.2 55.3 68.8 68.4 42.8 53.8 51.9 72.4 77.8 77.7 51.6 51.7 52.4 47.8 60.5 60.4 58.6 59.7 60.8
p!.001
p5.387
p5.011
p5.767
p5.006
p5.070
p!.001
p5.226
p!.001
p5.633
p!.001
p5.303
p5.520
p5.978
p!.001
p5.130
p5.048
p5.188
(15.0) (15.2) (15.1) (23.0) (23.5) (23.3) (43.4) (42.7) (42.8) (46.4) (41.4) (41.2) (20.9) (23.6) (24.9) (22.2) (21.0) (21.0) (12.9) (11.3) (9.9) (12.7) (16.7) (17.0) (8.4) (5.9) (8.0)
55.5 61.9 61.6 69.2 73.7 73.4 31.7 38.3 38.4 53.3 67.4 66.7 38.6 53.6 50.8 72.5 78.3 78.1 51.9 52.8 53.1 49.6 61.0 59.6 61.2 61.2 63.9
(14.3) (13.5) (13.3) (26.6) (23.7) (23.6) (42.4) (38.7) (38.9) (44.6) (40.5) (40.0) (22.1) (21.1) (21.9) (20.2) (18.6) (18.5) (12.1) (10.6) (9.60) (10.6) (14.8) (16.3) (6.3) (6.5) (11.1)
61.2 65.9 65.8 79.8 81.3 81.1 48.9 50.0 50.1 63.2 73.1 72.7 46.0 53.5 52.4 77.9 80.9 80.8 51.4 51.1 52.1 48.2 61.6 62.9 57.3 58.5 58.6
(15.7) (16.2) (16.1) (19.9) (21.4) (21.1) (42.7) (43.9) (44.0) (47.3) (40.9) (40.7) (19.6) (25.6) (28.3) (20.6) (22.1) (20.8) (15.9) (11.9) (10.7) (13.9) (18.6) (18.3) (9.8) (5.6) (5.4)
54.7 62.3 62.4 70.3 72.1 72.0 34.7 52.6 52.6 49.7 66.0 66.0 43.6 54.3 52.3 67.1 74.3 74.2 51.6 51.2 51.9 45.7 59.0 58.8 57.6 59.6 59.9
(14.3) (15.7) (15.7) (21.2) (24.6) (24.6) (43.8) (43.0) (44.8) (47.2) (41.4) (43.3) (20.8) (24.0) (24.3) (24.4) (22.2) (20.8) (10.3) (11.4) (9.5) (13.1) (16.6) (16.5) (8.2) (5.2) (5.6)
BP, bodily pain; C, continuous microwave; GH, general health perceptions; MH, mental health; P, pulsed microwave; PF, physical functioning; RP, role physical; RE, role emotional; SF, social functioning; SF-36, 36-item short form health survey; U, unplugged microwave; VT, vitality. Note: Measures are average values (standard deviation).
health-related quality of life did not improve after treatment or after follow-up, although we could accept that some dimensions, such as role emotional, bodily pain, and general health perceptions, did. Furthermore, allocation to a treatment arm did not influence the variations. With regard to therapeutic co-interventions, allocation to a specific treatment arm did not influence the outcome obtained. Similarly, no differences were found among the three groups in terms of adherence to exercise. The approach to nonspecific chronic neck pain tends to be empirical, and many of the physical therapies provided are of questionable efficacy. Physical treatments for patients with chronic neck pain include exercises, manual therapies, and electrothermal therapies [6,7]. Only physical exercise—alone or combined with manual therapies—is supported by solid scientific evidence [8]. Although the use of electrophysical agents is widespread, little evidence is available on its effectiveness in neck pain [5,8,9]. Transcutaneous electrical nerve stimulation was effective for patients with chronic neck pain in terms of disability, isometric neck muscle strength, and pain [35]. There is some evidence supporting the use of low-level laser therapy for pain reduction and functional improvement in the intermediate term for acute/subacute and chronic mechanical
neck disorders [8]. There is no scientific evidence for using ultrasound and other modalities. Pulsed shortwave diathermy did not provide any additional clinical benefit over a short course of active physical treatment incorporating advice and exercise [21]. Modalities are used mostly in combination with exercise. Of these modalities, shortwave and microwave diathermy are used in different ratios that vary over time from country to country. From several surveys administered to specialists in physical medicine and rehabilitation, rheumatologists, and physiotherapists, the use of microwaves or shortwaves to treat neck or low back pain was advocated by 22% to 47% of respondents [36–38]. In a report published in 1999 [39], the Danish Center for Evaluation and Health Technology Assessment advised against the use of ultrasound and shortwave diathermy in the treatment of low back pain; however, in 2003, of the 12,387 treatments provided by 254 Danish physiotherapists, 22% included ultrasound and shortwave diathermy. The European guide on low back pain [40] concluded that there is no scientific evidence on the effectiveness of thermal therapy compared with placebo or other therapeutic modalities in the treatment of chronic low back pain. Scarce literature is available on electrothermal therapy in the treatment of cervical pain. Dziedzic et al. [21]
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Table 6 Therapeutic co-interventions during the 6-month follow-up Co-interventions
Total
C
P
U
At 6 mo, N None, n Paracetamol or metamizol, n NSAIDs (with or without paracetamol or metamizol), n Tramadol alone or combined with paracetamol, n Physiotherapy without manual therapy*, n Manual therapy*, n
141 41 40 29
45 16 13 8
47 13 14 11
49 12 13 10
15
4
4
7
4
1
1
2
12
4
3
5
p Value p5.93 (chi-square)
C, continuous microwave; NSAIDs, nonsteroidal anti-inflammatory drugs; P, pulsed microwave; U, unplugged microwave. * In all cases, except for two, it was combined with paracetamol and/or metamizol and/or NSAIDs and/or tramadol.
conducted a multicenter trial that included 350 patients (mean age, 51 years) with nonspecific chronic neck pain who were randomized to three groups: manual therapy and exercises/patient counseling (N5114), shortwaves combined with exercises/counseling (N5121), and exercises/counseling (N5115). No differences were found between the latter two groups after 6 months. In other words, the combination of shortwave diathermy with exercise/counseling did not improve outcome. As far as we know, no study about the use of microwaves in neck pain has been published. Ideally, the design of this study should have only included a comparison between microwave diathermy and placebo. However, this posed ethical problems. Physical exercise therapy is usually studied in combination with other physical treatments [21,41–44], so we provided a standardized treatment, including therapies based on solid scientific evidence (physical exercise) [35,45–47], therapies of questionable effectiveness (TENS) [35,46], and the therapy under study—namely, microwave diathermy. However, because of this design, it is possible that exercise and TENS could have masked any positive effects of microwave diathermy. This could be clarified by additional research in a trial in which microwave diathermy is studied as the only treatment. With regard to adherence to exercises, although some studies have reported information about this item [48–50], a recent systematic review [51] noted that few high-quality trials have been conducted on this topic. Furthermore, there is no standardized method for measuring adherence to treatment in the long term. In the study by Kolt and McEvoy [50], conducted in patients with low back pain, the possibility of receiving some compensation was a relevant factor in terms of adherence. Because one of the eligibility criteria in our study was not being on sick leave or involved in a lawsuit, this possible bias is scarcely represented. A frequent limitation of trials conducted with patients with musculoskeletal pain is the fact that professionals and patients are not blinded, and they do not use standardized outcome measures to assess pain, disability, and
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quality of life. Such limitations are common among research studies within the fields of physiotherapy and physical medicine and rehabilitation, and have received criticism by a number of authors [52]. In his systematic review of the use of electrotherapy in the treatment of neck pain, Kroeling et al. [5] made some recommendations for future studies: larger sample sizes, more accurate standardizations, and a thorough description of the treatment are required. In addition, Kay et al. [45] indicated that conducting a comparative study on the relative benefits of physical exercise compared with those of other physical therapies— frequently provided in combination with physical exercise—is still difficult. The reason is that patients and evaluators should be blinded, and adherence to treatment and recourse to therapeutic co-interventions should be controlled. Accordingly, future research—both on neck pain and other musculoskeletal disorders—based on more accurate methodologies is required [53]. Considering the design and features of the current study, we believe our study sheds light on certain aspects that have not yet been evidenced, and that it solves some of the methodological limitations found in previous studies. Considering that treatment arms did not influence the results after the intervention and at 6 months, we did not assess outcomes at time points longer than 6 months. Nevertheless, this could be a limitation in the study design because of the chronic nature of this painful condition.
Conclusions Our study suggests that microwave diathermy provides no additional benefit to a treatment regimen of chronic neck pain that already involves other treatment approaches (eg, exercise, TENS), in terms of pain, disability, patient satisfaction, perceived outcome, quality of life, adherence to exercise, and use of therapeutic co-interventions. Additional research is needed to determine the relative efficacy of diathermy when used as an independent modality.
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[28] Andrade Ortega JA, Delgado Martınez AD, Almecija Ruiz R. Validation of the Spanish version of the Neck Disability Index. Spine 2010;35:E114–8. [29] Alonso J, Prieto L, Anto JM. The Spanish version of the SF-36 health survey (the SF-36 health questionnaire): an instrument for measuring clinical results. Med Clin (Barc) 1995;104: 771–6. [30] Garvey TA, Transfeldt EE, Malcolm JR, Kos P. Outcome of anterior cervical discectomy and fusion as perceived by patients treated for dominant axial–mechanical cervical spine pain. Spine 2002;27: 1887–94. [31] Hessler C, Boysen K, Regelsberger J, et al. Patient satisfaction after anterior cervical discectomy and fusion is primarily driven by relieving pain. Clin J Pain 2012;28:398–403. [32] Kovacs FM, Abraira V, Royuela A, et al. Minimum detectable and minimal clinically important changes for pain in patients with nonspecific neck pain. BMC Musculoskelet Disord 2008;10:43. [33] Young BA, Walker MJ, Strunce JB, et al. Responsiveness of the Neck Disability Index in patients with mechanical neck disorders. Spine J 2009;9:802–8. [34] Escobar A, Quintana JM, Bilbao A, et al. Responsiveness and clinically important differences for the WOMAC and SF-36 after total knee replacement. Osteoarthritis Cartilage 2007;15:273–80. [35] Chiu TT, Hui-Chan CW, Chein G. A randomized clinical trial of TENS and exercise for patients with chronic neck pain. Clin Rehabil 2005;19:850–60. [36] Rush PJ, Shore A. Physician perceptions of the value of physical modalities in the treatment of musculoskeletal disease. Br J Rheumatol 1994;33:566–8. [37] Foster N, Thompson KA, Baxter GD, Allen JM. Management of nonspecific low back pain by physiotherapists in Britain and Ireland: a descriptive questionnaire of current clinical practice. Spine 1999;24:1332. [38] Li LC, Bombardier C. Physical therapy management of low back pain: an exploratory survey of therapist approaches. Phys Ther 2001;81:1018–28. [39] Hamm L, Mikkelsen B, Kuhr J, et al. Danish physiotherapists’ management of low back pain. Adv Physiother 2003;5:109–13. [40] Airaksinen O, Brox JI, Cedraschi C, et al. European guidelines for the management of chronic nonspecific low back pain: COST B13 Working Group on Guidelines for Chronic Low Back Pain. Eur Spine J 2006;15:S192–300. [41] Koes BW, Bouter LM, van Mameren H, et al. Randomised clinical trial of manipulative therapy and physiotherapy for persistent back and neck complaints: results of one year follow up. BMJ 1992;304: 601–5. [42] Koes BW, Bouter LM, van Mameren H, et al. The effectiveness of manual therapy, physiotherapy, and treatment by the general practitioner for nonspecific back and neck complaints: a randomized clinical trial. Spine 1992;17:28–35. [43] Hurwitz EL, Morgenstern H, Harber P, et al. The effectiveness of physical modalities among patients with low back pain randomized to chiropractic care: findings from the UCLA Low Back Pain Study. J Manipulative Physiol Ther 2002;25:10–20. [44] Borman P, Keskin D, Ekici B, Bodur H. The efficacy of intermittent cervical traction in patients with chronic neck pain. Clin Rheumatol 2008;27:1249–53. [45] Kay TM, Gross A, Goldsmith C, et al, Cervical Overview Group. Exercises for mechanical neck disorders. Cochrane Database Syst Rev 2005;CD004250. [46] Chiu TT, Lam TH, Hedley AJ. A randomized controlled trial on the efficacy of exercise for patients with chronic neck pain. Spine 2005;30:E1–7. [47] Hurwitz EL, Carragee EJ, van der Velde G, et al. Bone and joint decade 2000–2010 task force on neck pain and its associated disorders treatment of neck pain: noninvasive interventions: results of the
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bone and joint decade 2000–2010 task force on neck pain and its associated disorders. Spine 2008;33(4 Suppl):S123–52. [48] Bergman P, Grjibovski AM, Hagstr€omer M, et al. Adherence to physical activity recommendations and the influence of sociodemographic correlates: a population-based cross-sectional study. BMC Public Health 2008;8:367. [49] Jack K, McLean SM, Moffett JK, Gariner E. Barriers to treatment adherence in physiotherapy outpatient clinics: a systematic review. Man Ther 2010;15:220–8. [50] Kolt GS, McEvoy JF. Adherence to rehabilitation in patients with low back pain. Man Ther 2003;8:110–6.
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[51] Jordan JL, Holden MA, Mason EE, Foster NE. Interventions to improve adherence to exercise for chronic musculoskeletal pain in adults. Cochrane Database Syst Rev 2010;20: CD005956. [52] Fregni F, Imamura M, Chien HF, et al. Challenges and recommendations for placebo controls in randomized trials in physical and rehabilitation medicine: a report of the International Placebo Symposium Working Group. Am J Phys Med Rehabil 2010;89: 160–72; discussion 1045–6; reply 1046–7. [53] Roques CF. Analgesic physical therapy: present clinical data. Ann Readapt Med Phys 2003;46:565–77.
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Clinical Study
Microwave diathermy for treating nonspecific chronic neck pain: a randomized controlled trial on Cer on Fernandez, PTb, Juan Alfonso Andrade Ortega, MD, PhDa,*, Encarnaci Rosario Garcıa Llorent, PTb, Marisa Ribeiro Gonzalez, PTb, Alberto Damian Delgado Martınez, MD, PhDc,d a
Department of Physical Medicine and Rehabilitation, Complejo Hospitalario de Jaen, Avenida del Ejercito Espa~nol, s/n, 23005 Jaen, Spain b Physiotherapy Unit, Complejo Hospitalario de Jaen, Avenida del Ejercito Espa~nol, s/n, 23005 Jaen, Spain c Department of Orthopedic Surgery, Hospital ‘‘San Agustın’’, Avenida de San Cristobal, s/n, Linares, 23700 Jaen, Spain d University of Jaen, Campus de las Lagunillas, s/n, 23071 Jaen, Spain Received 27 May 2012; revised 12 September 2013; accepted 17 October 2013
Abstract
BACKGROUND CONTEXT: Although the use of deep heat therapy is widespread, there is scant literature available on its effectiveness in treating back or neck pain. PURPOSE: The purpose of this study was to determine the efficacy of microwave diathermy to treat nonspecific chronic neck pain. DESIGN: The study was designed as a double-blind, randomized controlled trial. PATIENT SAMPLE: The patient sample consisted of 149 patients with nonspecific chronic neck pain in a hospital of the Andalusian Public Health Care System, Spain OUTCOME MEASURES: The study outcome measures are as follows: at baseline, pain intensity (using a visual analogue scale), disability (Neck Disability Index), and health-related quality of life (36-item short form health survey [SF-36]); at 3 weeks, baseline measures and patients’ perceived overall outcome and satisfaction with the treatment; and at 6 months, 3–week measures, therapeutic co-interventions, and adherence to exercises. METHODS: Patients were allocated randomly to three groups. The first group received continuous microwave diathermy, the second group was administered pulsed microwaves, and the third group (the control group) received unplugged microwaves. All three groups received the same general treatment: range of motion, isometric exercises, and transcutaneous electrical nerve stimulation. RESULTS: The three groups had reduced pain and disability, and improvement was seen in some dimensions of the SF-36. However, there were no differences found in any of the parameters measured among the three therapeutic groups. CONCLUSIONS: Microwave diathermy does not provide additional benefit to a treatment regimen of chronic neck pain that already involves other treatment approaches. Ó 2013 Elsevier Inc. All rights reserved.
Keywords:
Neck pain; Microwaves; Diathermy; Physical therapy modalities; Exercise; Transcutaneous electrical stimulation
Introduction Neck pain is a common and expensive condition [1]. Its age-adjusted prevalence ranges from 67% to 86% [2,3]. FDA device/drug status: Approved (microwave diathermy and TENS [transcutaneous electrical nerve stimulation]). Author disclosures: JAAO: Support for travel to meetings for the study or other purposes: Instituto de Salud ‘‘Carlos III’’ (B); Provision of writing assistance, medicines, equipment, or administrative support: Instituto de Salud ‘‘Carlos III’’ (B). ECF: Nothing to disclose. RGL: Nothing to disclose. MRG: Nothing to disclose. ADDM: Nothing to disclose. 1529-9430/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.spinee.2013.10.025
Neck pain increases with age and is more frequent in women than men, although such bias is not accepted unanimously by all experts [3]. About 50% to 80% of neck
The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com. This study was supported by a research project from the Instituto de Salud Carlos III (PI11/087). There is no topic-specific conflict of interest related to the authors of this study. * Corresponding author. C/Dr Federico del Castillo, 8, 1 E, 23005Jaen, Spain. Tel.: 34679650663. E-mail address: [email protected] (J.A. Andrade Ortega)
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pain cases are not fully resolved, and thus become chronic and cause significant direct and indirect costs [4–6]. Most direct costs are generated by physical treatments, including patient education and counseling, exercises, manual therapies, and electrothermal therapies [6,7]. However, only physical exercise—alone or combined with manual therapies—is supported by solid scientific evidence [8]. Although the use of electrophysical agents is widespread, little evidence is available on its effectiveness in neck pain [5,9]. Kroeling et al. [5] concluded there is no scientific evidence—either limited or contradictory—on the effectiveness of galvanic currents, iontophoresis, transcutaneous electrical nerve stimulation (TENS), pulsed electromagnetic fields, electrical muscle stimulation, and permanent magnets. Considering the number of patients seeking treatment for neck pain, surprisingly few studies have addressed the physical interventions used in such cases, especially for heat therapy, for which there is a great variability in use [10]. A lack of uniformity in heat use for this patient population is illustrated by several studies. From the report by Jette and Jette [11] in 1996 to the report by Boissonnault and Badke [10] in 2008, ‘‘usual treatment’’ for patients with neck pain provided by physiotherapists includes the use of heat modalities in a range that goes from 91% of the first to less than 17% of the latter. From a recent survey in North Carolina, Goode et al. [12] found that heat was used by 57% of people with neck pain. These authors note that, based on current evidence for best practice, their findings indicate overuse of modalities and underuse of effective treatments such as therapeutic exercise. A cross-sectional study [13] of the Spanish National Health Service in the Canary Islands, where the public health service covers a total population of two million people, showed that as much as 60% of the resources spent on physical treatments for nonspecific chronic neck pain, back pain, and shoulder pain between 2004 and 2007 were allocated to treatments that were found to be either ineffective or for which there was no evidence of effectiveness. Heat therapy was a major part of these physical treatments. Microwave diathermy once had a place in therapy, but since the 1980s, interest in its use has declined in many countries, more than shortwave diathermy or ultrasound [14–16]. The Food and Drug Administration [14] differentiates between diathermy devices according to their thermal or nonthermal mechanism of action. Specifically, it separates diathermy devices into ‘‘diathermy for use in applying therapeutic deep heat for selected medical conditions’’ and ‘‘diathermy intended to treat medical conditions by means other than the generation of deep heat.’’ Today, most commercial devices allow both types of application. Microwave diathermy is a form of electromagnetic energy that uses its conversion to thermal energy, which is produced by increased kinetic energy of molecules within the microwave field; radiation is absorbed selectively by water, and muscle
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should be heated preferentially. Fourteenth Federal Communications Commission-approved frequencies for therapeutic microwave are 915 MHz and 2,450 MHz. The lower frequency has the advantage of increased depth of penetration but also the disadvantages of greater beam dispersion and the requirement of larger applicators [14]. Microwaves do not penetrate tissue as deeply as shortwave diathermy and ultrasound. Shortwave therapy is generally preferred over microwave because it has a more predictable heat distribution pattern [14,15]. Recently, particularly in Europe, microwaves are being used at 434 MHz and, therefore, are realizing increased penetration [17–20]. Because of this, microwave diathermy seems to have become popular again, as evidenced by trials looking at its effectiveness in knee osteoarthritis [17] and other musculoskeletal conditions [18–20]. Indications and contraindications of microwave and shortwave therapy are practically the same [15,16]. In a trial conducted with patients with nonspecific neck pain (most of them chronic), the use of pulsed shortwave diathermy in combination with physical exercise and patient counseling did not improve patients’ health status [21]. Consequently, the efficacy of pulsed shortwave diathermy has been questioned by some authors [22]. Studies on the efficacy and cost-effectiveness of the therapies used to treat neck pain are required [23]. Because of the significant lack of supporting studies about diathermy and the considerable economic burden for many health systems [13], it is important to clarify the role to be played by these physical modalities. No trials have been conducted on the effectiveness of microwaves in patients with neck pain. This study is intended to determine the effectiveness of microwave diathermy in treating nonspecific chronic neck pain.
Methods A double-blind, randomized controlled trial was conducted with 149 patients with nonspecific chronic neck pain in a hospital of the Andalusian Public Health Care System in Jaen, Spain. The patients were referred from a primary care setting to the Department of Rehabilitation between September 2008 and December 2010, because of failure of the treatment prescribed by the general practitioner. Subjects were recruited consecutively when they met the requirements described later. Most people in Jaen, a rural area in southern Spain, are covered by the public health care system. Patients’ epidemiological data are shown in Table 1. The trial was approved by the ethics committee of the hospital. The eligibility criteria were patients between 18 years and 65 years with a diagnosis of nonspecific chronic neck pain, ie, 3-month or longer duration, and the absence of red flags (clinical features that indicate an increased risk of specific conditions) such as weight loss, fever, progressive neurologic signs, cancer history, infectious or inflammatory disease history, osteoporosis, or
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major structural abnormalities or neurologic conditions affecting the neck. Exclusion criteria included women who were pregnant, individuals on sick leave or involved in a lawsuit or claim process in which neck pain was the cause, and subjects with a pacemaker, metal implants, or any other device that contraindicated the use of microwaves [15,16]. This study was registered under the unique identifier NCT01487122 (www.clinicaltrials.gov). After informed consent was obtained, patients were randomized to three treatment arms (Group C, continuous microwave; Group P, pulsed microwave; or Group U, unplugged microwave) using a series of random, repeating three possible figures generated by free software. This series was only known by the chief of physiotherapists, who allocated to each figure a treatment group before starting the trial. In the rehabilitation department, the same two physiotherapists delivered 15 physical treatment sessions (five per week for 3 weeks) according to each group schedule. The rationale for the use of 15 sessions in 3 weeks has been reported elsewhere [24]. The comprehensive treatment included, in this order, range of motion and isometric exercises (initially in treatment room and, after 3 weeks, at home), TENS, and diathermy. The latter was provided differently according to the treatment arm. Group C received continuous microwaves, Group P received pulsed microwaves, and Group U received unplugged microwaves. One of the physiotherapists conducted the exercises, and the other administered TENS and microwaves. Exercise included monitored free movements and resisting elastic band isometric exercises of the cervical spine Table 1 Baseline values Variable
Total
N
149
Age, y (SD) Males, n (%) Females, n (%) BMI, kg/m2 (SD) LA, n (%) HA, n (%) VAS, pt (SD) NDI, pt (SD) SF-36, pt (SD) PF, pt (SD) RP, pt (SD) RE, pt (SD) BP, pt (SD) SF, pt (SD) VT, pt (SD) GH, pt (SD) MH, pt (SD)
44.2 36 113 24.9 93 56 53.5 34.4 56.5 72.7 36.9 53.3 42.1 71.5 51.6 47.5 58.5
C
P
50 (10.1) (24.1) (75.9) (3) (62.4) (37.6) (15.8) (12.1) (14.9) (22.9) (42.9) (46.7) (20.8) (22.3) (12.8) (12.6) (8.4)
43.6 13 37 24.6 33 17.0 52.9 34.4 55.4 69.8 31.0 52.7 39.0 72.0 52.0 49.3 60.8
U
48 (11.2) (26) (74) (3.2) (66) (34) (16.7) (11.9) (14.5) (26.3) (42.1) (44.7) (22.5) (20.8) (12.4) (10.2) (6.3)
45.5 10 38 25.2 29 19.0 54.7 33.6 60.1 79.1 46.9 59.8 43.8 76.3 51 47.5 57.1
51 (7.9) (20.8) (79.2) (3.2) (60.4) (39.6) (13.9) (12.5) (15.6) (19.8) (42.1) (48.1) (19.5) (21) (15.7) (14.3) (10)
43.6 13 38 24.9 31 20.0 53 35.2 54.1 69.6 33.3 47.7 43.6 66.4 51.8 45.7 57.5
(10.9) (25.5) (74.5) (2.5) (60.8) (39.2) (16.9) (12.1) (14.3) (21.2) (43.5) (47.3) (20.4) (24.3) (10.2) (13) (8.1)
BP, bodily pain; BMI, body mass index; C, continuous microwave; GH, general health perceptions; HA, heavy activity; LA, light activity; MH, mental health; NDI, Neck Disability Index; P, pulsed microwave; PF, physical functioning; RE, role emotional; RP, role physical; SD, standard deviation; SF, social functioning; SF-36, 36-item short form health survey; U, unplugged microwave; VAS, visual analogue scale; VT, vitality.
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3
(flexion, extension, left and right rotations, and left and right lateral bending), and raising and forward and rearward rotation of the shoulders. Each exercise was performed 10 times with patients sitting in front of a mirror, their back against the backrest of a chair, and their feet touching the ground. The position was maintained for 5 seconds after each exercise. All patients were instructed to perform the learned exercises at home, a minimum of three times per week indefinitely. Transcutaneous electrical nerve stimulation was performed using the Enraf-Nonius Tensmed 911 model (Rotterdam, Netherlands) through four 55-cm square electrodes. One pair was placed between C5 and C7 (on both sides) and the other pair was placed on the upper fibers of the trapezius. We used the continuous mode at a frequency of 80 Hz, with a pulse duration of 150 microseconds. Intensity was adjusted to produce a tingling sensation, and TENS was delivered for 30 minutes. Similar parameters have been used by others [24]. Microwaves were delivered using the Enraf-Nonius Radarmed 12S259 generator (Rotterdam, Netherlands). Group C received continuous microwaves at 80 W for 20 minutes through a large circular electrode placed 15 cm from the neck. Individuals in Group P received pulsed microwaves (mean power, 5 W) using the same conditions as group C. Similar doses have been used elsewhere [25]. Group U was provided with the same therapy, but the device was unplugged and a light-emitting diode induced patients to think that the device was operating. At all times the patients did not know to which treatment arm they were assigned. During the medical consultation before the treatment, patients were informed of the importance of performing their exercises at home. They were allowed to take any pain relief medication as necessary, and were asked to record their analgesic medication intake. Similarly, patients were asked to record any therapeutic co-interventions received during the follow-up, especially if they attended physiotherapy sessions outside the public health system. At all times, except for the therapist who administered electrothermal therapy and the chief of physiotherapists (who did not participate directly in the treatment), all professionals were blinded to treatment allocation. Before the treatment started, the following variables were recorded: age, sex, body mass index, and intensity of work activity (‘‘light’’ for nonphysically demanding jobs, and ‘‘heavy’’ for physically demanding jobs). Housework, which as highly represented in our sample, was included in the ‘‘heavy’’ category. The primary outcome was pain intensity. Secondary outcomes were disability for cervical pain, health-related quality of life, patients’ perceived overall outcome, satisfaction with the treatment, therapeutic co-interventions, and adherence to exercise. Outcome measures were obtained at session 1, session 15, and at 6 months by a physiotherapist blinded with respect to the treatment groups. At three time points (session 1, session 15, and at 6 months), pain
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Figure. Flow of participants through each stage of the trial.
intensity was measured using a visual analogue scale (a tool for measuring pain intensity, the use of which is widespread [26]), disability in terms of cervical pain was measured according to the Neck Disability Index (NDI; the Spanish version of the NDI has been validated [27,28]), and health-related quality of life, which was measured according to the 36-item short form health survey (SF-36).
Respect of this, overall value and each of the eight dimensions values were assessed, including physical functioning, role physical, role emotional, bodily pain, social functioning, vitality, general health perceptions, and mental health. The Spanish version of the SF-36 was validated by Alonso et al. [29]. At session 15, additional parameters assessed were as follows: patients’ perceived overall outcome
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Table 2 Pain at baseline, after treatment, and at 6 months Pain intensity
Total
C
P
U
General linear model
N
141
45
47
49
Within subjects (time)
Between subjects (timegroup)
VAS at baseline pt (SD) VAS after treatment, pt (SD) VAS at 6 mo, pt (SD)
52.9 (15.8) 37.2 (21.5) 37.3 (21.1)
52.8 (17.4) 36.0 (19.8) 36.1 (18.6)
53.7 (13.6) 39.4 (21.3) 37.7 (19.6)
52.1 (16.5) 36.2 (23.4) 38.1 (24.7)
p!.001
p5.420
C, continuous microwave; P, pulsed microwave; U, unplugged microwave; VAS, visual analogue scale. Note: Measures are average values (standard deviation).
according to a 6-point scale for the measures excellent, very good, good, fair, poor, and very bad (a similar scale has been used elsewhere for measuring perceived outcome in neck pain [30]), and satisfaction with the treatment according to a 5-point scale for the measures very satisfied, satisfied, neither satisfied or dissatisfied, dissatisfied, and very dissatisfied. The latter scale is one of the items of an NDI-based satisfaction questionnaire that has been used elsewhere [31]. At 6 months, in addition to the parameters measured at the other two time points, therapeutic cointerventions (narrative description) and adherence to exercises (often, sometimes, or never) were further evaluated. The measurements taken at the beginning and on completion of treatment were collected at the hospital, whereas those taken at 6 months were collected by telephone and by mail. A pilot clinical trial with 64 patients was performed previously. In this study, Groups C, P, and U achieved a mean visual analogue scale pain score relief of 17.76 points, 10.21 points, and 15.95 points after treatment, with an overall standard deviation of 11.73 points. With these data, using the sample size calculator Ene 2.0 (Department of Biometry, Glaxo-Smith-Kline, Barcelona, Spain), it was established that 133 patients were required, with p5.05 and a 0.80 power. Because we predicted a dropout rate of 10%, 148 patients were recruited. Statistical analysis was performed by the first author, who was also blinded to treatment allocation. All quantitative variables were transformed to normal distribution (Kolmogorov-Smirnov test). Analysis was done on an intent-to-treat basis. A repeated-measures general linear model was used to analyze numerical data such as pain, disability, and health-related quality of life; time was within-subject factor and therapeutic groups were the between-subjects factor. The chi-square test was used for categorical data. Statistical significance was set at the 5% level
(two tailed). Analysis of the outcomes was performed using SPSS version 15.0 (SPSS Inc., Chicago, IL, USA).
Results The Figure shows the flow of participants through each stage of the trial. Table 1 shows the distribution of baseline values. Two patients from Group C and another two from Group U dropped out of treatment, so a total of 145 patients completed the treatment. The reasons given were job incompatibility (one patient from Group C and two patients from Group U) or housework incompatibility (one patient from Group C). Another four patients dropped out at 6 months, three of whom could not be contacted (two from Group C and one from Group P), and one patient refused to continue participating in the study (Group C). Consequently, a total of 141 patients completed the study. One patient from Group C and another from Group U experienced dizziness on one occasion after the therapy session. These symptoms were relieved after a few minutes without any intervention. No other adverse reactions or side effects were reported. Tables 2 and 3 show the improvements in pain and disability on treatment completion and after 6 months. Treatment arms did not influence the results. Pain relief was maintained at the 6-month follow-up assessment, and the reduction of disability was even greater after 6 months than on treatment completion. Table 4 shows the results in terms of patient satisfaction on treatment completion and at 6 months after treatment; therapeutic arms did not influence them. In the same way, this table also shows that treatment arms did not influence patients’ adherence to exercises at 6 months. Table 5 shows that health-related quality of life improved by more than 11% in all groups. Again, therapeutic
Table 3 Disability at baseline, after treatment, and at 6 months Disability
Total
C
P
U
General linear model
N
141
45
47
49
Within subjects (time)
Between subjects (timegroup)
NDI at baseline, pt (SD) NDI after treatment, pt (SD) NDI at 6 mo, pt (SD)
33.9 (12.1) 25.8 (14.5) 23.3 (14.2)
34.1 (11.6) 25.2 (14.4) 23.1 (14.6)
32.8 (12.6) 25.3 (14.0) 22.2 (12.9)
34.9 (12.3) 26.8 (15.3) 24.7 (15.3)
p!.001
p5.923
C, continuous microwave; NDI, Neck Disability Index; P, pulsed microwave; U, unplugged microwave. Note: Measures are average values (standard deviation).
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Table 4 Perceived outcome and satisfaction, and adherence to treatment Perceived outcome, satisfaction, and adherence to exercise Initial, N After treatment, N Perceived outcome after treatment, n (%) Excellent Very good Good Fair Poor Very bad Satisfaction after treatment, n (%) Very satisfied Satisfied Neither satisfied or dissatisfied Dissatisfied Very dissatisfied After follow-up, N Perceived outcome at 6 mo, n (%) Excellent Very good Good Fair Poor Very bad Satisfaction at 6 mo, n (%) Very satisfied Satisfied Neither satisfied or dissatisfied Dissatisfied Very dissatisfied Adherence to physical exercise, n (%) Often Sometimes Never
Total
C
P
U
149 145
50 48
48 48
51 49
p (Chi-square)
3 28 62 52 0 0
(2) (19.3) (42.8) (35.9) (0) (0)
1 9 21 17 0 0
(2) (18.8) (43.8) (35.4) (0) (0)
0 9 20 19 0 0
(0) (18.8) (41.7) (39.6) (0) (0)
2 9 22 16 0 0
(4.1) (18.4) (44.9) (32.7) (0) (0)
49 (33.8) 72 (49.7) 24 (16.6) 0 (0) 0 (0) 141
17 24 7 0 0 45
(35.4) (50) (14.6) (0) (0)
17 21 10 0 0 47
(35.4) (43.8) (20.8) (0) (0)
15 27 7 0 0 49
(30.6) (55.1) (14.3) (0) (0)
1 28 60 43 9 0
(0.6) (19.9) (42.6) (30.5) (6.4) (0)
0 9 19 16 1 0
(0) (20) (42.2) (35.6) (2.2) (0)
0 10 30 15 2 0
(0) (21.3) (63.8) (31.9) (4.3) (0)
1 8 22 12 6 0
(2) (16.3) (44.9) (24.5) (12.2) (0)
40 77 24 0 0
(28.4) (54.6) (17) (0) (0)
15 25 5 0 0
(33.3) (55.6) (11.1) (0) (0)
12 24 10 0 0
(25.5) (51.1) (21.3) (0) (0)
12 28 9 0 0
(24.5) (57.1) (18.4) (0) (0)
p5.77
p5.62
p5.91
p5.36
p5.52 30 (21.2) 60 (42.4) 51 (36.2)
9 (20) 22 (48.9) 14 (31.1)
8 (17) 22 (46.8) 17 (36.2)
13 (26.5) 16 (32.7) 20 (40.8)
C, continuous microwave; P, pulsed microwave; U, unplugged microwave.
arms did not influence the results. Improvements in role physical, role emotional, bodily pain, and general health perceptions after treatment and at 6 months were remarkable in all treatment arms. Therapeutic co-interventions during the follow-up are shown in Table 6. Treatment groups did not affect the final outcome. None of the therapeutic co-interventions included the use of any type of diathermy. Discussion The results suggest that continuous microwaves (thermal effect), pulsed microwaves (athermal effect), and unplugged microwaves (placebo) have the same influence in terms of pain or disability reduction. The same can be applied to the patients’ perceived outcome and satisfaction with the treatment. The minimal detectable and minimal clinically important changes have been explored for neck pain severity [32]. Improvements less than or equal to 1.5 points in pain intensity could be seen as irrelevant, so our results suggest that patients experienced significant improvement in pain
relief. The minimal detectable and minimal clinically important changes have also been explored for disability [33]. For NDI, these values were 10.2 and 7.5, respectively. Our results partially meet these requirements after treatment and fully meet them after the 6-month follow-up. The Spanish version of the SF-36 was validated by Alonso et al. [29]. The mean age in their study was 45.52 years, with a slight prevalence of women. The reference values were as follows: physical functioning, 84.7 points; role physical, 83.2 points; role emotional, 86.6 points; bodily pain, 79 points; social functioning, 90.1 points; vitality, 66.9 points; general health perceptions, 58.3 points; and mental health, 73.3 points. Because our study included patients with chronic pain, it is not surprising that the baseline scores obtained were low. As far as we know, minimal clinically important changes have not been explored for health-related quality of life in patients with neck pain. A comparable study could be that of Escobar et al. [34], who determined responsiveness and clinically important differences for the SF-36 after total knee replacement (minimal clinically important differences were at least 10 points). On the basis of this study, our results suggest that
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Table 5 Health-related quality of life at baseline, after treatment, and at 6 months Health-related quality of life
Total
C
P
U
General linear model
After treatment, N
141
45
47
49
Within subjects (time)
Between subjects (timegroup)
SF-36 at baseline, pt (SD) SF-36 after treatment, pt (SD) SF-36 at 6 mo, pt (SD) PF at baseline, pt (SD) PF after treatment, pt (SD) PF at 6 mo, pt (SD) RP at baseline, pt (SD) RP after treatment, pt (SD) RP at 6 mo, pt (SD) RE at baseline, pt (SD) RE after treatment, pt (SD) RE at 6 mo, pt (SD) BP at baseline, pt (SD) BP after treatment, pt (SD) BP after treatment, pt (SD) SF at baseline, pt (SD) SF after treatment, pt (SD) SF at 6 mo, pt (SD) VT at baseline, pt (SD) VT after treatment, pt (SD) VT at 6 mo, pt (SD) GH at baseline, pt (SD) GH after treatment, pt (SD) GH at 6 mo, pt (SD) MH at baseline, pt (SD) MH after treatment, pt (SD) MH at 6 mo, pt (SD)
57.1 63.3 63.3 73.1 75.7 75.5 38.5 47.1 47.2 55.3 68.8 68.4 42.8 53.8 51.9 72.4 77.8 77.7 51.6 51.7 52.4 47.8 60.5 60.4 58.6 59.7 60.8
p!.001
p5.387
p5.011
p5.767
p5.006
p5.070
p!.001
p5.226
p!.001
p5.633
p!.001
p5.303
p5.520
p5.978
p!.001
p5.130
p5.048
p5.188
(15.0) (15.2) (15.1) (23.0) (23.5) (23.3) (43.4) (42.7) (42.8) (46.4) (41.4) (41.2) (20.9) (23.6) (24.9) (22.2) (21.0) (21.0) (12.9) (11.3) (9.9) (12.7) (16.7) (17.0) (8.4) (5.9) (8.0)
55.5 61.9 61.6 69.2 73.7 73.4 31.7 38.3 38.4 53.3 67.4 66.7 38.6 53.6 50.8 72.5 78.3 78.1 51.9 52.8 53.1 49.6 61.0 59.6 61.2 61.2 63.9
(14.3) (13.5) (13.3) (26.6) (23.7) (23.6) (42.4) (38.7) (38.9) (44.6) (40.5) (40.0) (22.1) (21.1) (21.9) (20.2) (18.6) (18.5) (12.1) (10.6) (9.60) (10.6) (14.8) (16.3) (6.3) (6.5) (11.1)
61.2 65.9 65.8 79.8 81.3 81.1 48.9 50.0 50.1 63.2 73.1 72.7 46.0 53.5 52.4 77.9 80.9 80.8 51.4 51.1 52.1 48.2 61.6 62.9 57.3 58.5 58.6
(15.7) (16.2) (16.1) (19.9) (21.4) (21.1) (42.7) (43.9) (44.0) (47.3) (40.9) (40.7) (19.6) (25.6) (28.3) (20.6) (22.1) (20.8) (15.9) (11.9) (10.7) (13.9) (18.6) (18.3) (9.8) (5.6) (5.4)
54.7 62.3 62.4 70.3 72.1 72.0 34.7 52.6 52.6 49.7 66.0 66.0 43.6 54.3 52.3 67.1 74.3 74.2 51.6 51.2 51.9 45.7 59.0 58.8 57.6 59.6 59.9
(14.3) (15.7) (15.7) (21.2) (24.6) (24.6) (43.8) (43.0) (44.8) (47.2) (41.4) (43.3) (20.8) (24.0) (24.3) (24.4) (22.2) (20.8) (10.3) (11.4) (9.5) (13.1) (16.6) (16.5) (8.2) (5.2) (5.6)
BP, bodily pain; C, continuous microwave; GH, general health perceptions; MH, mental health; P, pulsed microwave; PF, physical functioning; RP, role physical; RE, role emotional; SF, social functioning; SF-36, 36-item short form health survey; U, unplugged microwave; VT, vitality. Note: Measures are average values (standard deviation).
health-related quality of life did not improve after treatment or after follow-up, although we could accept that some dimensions, such as role emotional, bodily pain, and general health perceptions, did. Furthermore, allocation to a treatment arm did not influence the variations. With regard to therapeutic co-interventions, allocation to a specific treatment arm did not influence the outcome obtained. Similarly, no differences were found among the three groups in terms of adherence to exercise. The approach to nonspecific chronic neck pain tends to be empirical, and many of the physical therapies provided are of questionable efficacy. Physical treatments for patients with chronic neck pain include exercises, manual therapies, and electrothermal therapies [6,7]. Only physical exercise—alone or combined with manual therapies—is supported by solid scientific evidence [8]. Although the use of electrophysical agents is widespread, little evidence is available on its effectiveness in neck pain [5,8,9]. Transcutaneous electrical nerve stimulation was effective for patients with chronic neck pain in terms of disability, isometric neck muscle strength, and pain [35]. There is some evidence supporting the use of low-level laser therapy for pain reduction and functional improvement in the intermediate term for acute/subacute and chronic mechanical
neck disorders [8]. There is no scientific evidence for using ultrasound and other modalities. Pulsed shortwave diathermy did not provide any additional clinical benefit over a short course of active physical treatment incorporating advice and exercise [21]. Modalities are used mostly in combination with exercise. Of these modalities, shortwave and microwave diathermy are used in different ratios that vary over time from country to country. From several surveys administered to specialists in physical medicine and rehabilitation, rheumatologists, and physiotherapists, the use of microwaves or shortwaves to treat neck or low back pain was advocated by 22% to 47% of respondents [36–38]. In a report published in 1999 [39], the Danish Center for Evaluation and Health Technology Assessment advised against the use of ultrasound and shortwave diathermy in the treatment of low back pain; however, in 2003, of the 12,387 treatments provided by 254 Danish physiotherapists, 22% included ultrasound and shortwave diathermy. The European guide on low back pain [40] concluded that there is no scientific evidence on the effectiveness of thermal therapy compared with placebo or other therapeutic modalities in the treatment of chronic low back pain. Scarce literature is available on electrothermal therapy in the treatment of cervical pain. Dziedzic et al. [21]
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Table 6 Therapeutic co-interventions during the 6-month follow-up Co-interventions
Total
C
P
U
At 6 mo, N None, n Paracetamol or metamizol, n NSAIDs (with or without paracetamol or metamizol), n Tramadol alone or combined with paracetamol, n Physiotherapy without manual therapy*, n Manual therapy*, n
141 41 40 29
45 16 13 8
47 13 14 11
49 12 13 10
15
4
4
7
4
1
1
2
12
4
3
5
p Value p5.93 (chi-square)
C, continuous microwave; NSAIDs, nonsteroidal anti-inflammatory drugs; P, pulsed microwave; U, unplugged microwave. * In all cases, except for two, it was combined with paracetamol and/or metamizol and/or NSAIDs and/or tramadol.
conducted a multicenter trial that included 350 patients (mean age, 51 years) with nonspecific chronic neck pain who were randomized to three groups: manual therapy and exercises/patient counseling (N5114), shortwaves combined with exercises/counseling (N5121), and exercises/counseling (N5115). No differences were found between the latter two groups after 6 months. In other words, the combination of shortwave diathermy with exercise/counseling did not improve outcome. As far as we know, no study about the use of microwaves in neck pain has been published. Ideally, the design of this study should have only included a comparison between microwave diathermy and placebo. However, this posed ethical problems. Physical exercise therapy is usually studied in combination with other physical treatments [21,41–44], so we provided a standardized treatment, including therapies based on solid scientific evidence (physical exercise) [35,45–47], therapies of questionable effectiveness (TENS) [35,46], and the therapy under study—namely, microwave diathermy. However, because of this design, it is possible that exercise and TENS could have masked any positive effects of microwave diathermy. This could be clarified by additional research in a trial in which microwave diathermy is studied as the only treatment. With regard to adherence to exercises, although some studies have reported information about this item [48–50], a recent systematic review [51] noted that few high-quality trials have been conducted on this topic. Furthermore, there is no standardized method for measuring adherence to treatment in the long term. In the study by Kolt and McEvoy [50], conducted in patients with low back pain, the possibility of receiving some compensation was a relevant factor in terms of adherence. Because one of the eligibility criteria in our study was not being on sick leave or involved in a lawsuit, this possible bias is scarcely represented. A frequent limitation of trials conducted with patients with musculoskeletal pain is the fact that professionals and patients are not blinded, and they do not use standardized outcome measures to assess pain, disability, and
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quality of life. Such limitations are common among research studies within the fields of physiotherapy and physical medicine and rehabilitation, and have received criticism by a number of authors [52]. In his systematic review of the use of electrotherapy in the treatment of neck pain, Kroeling et al. [5] made some recommendations for future studies: larger sample sizes, more accurate standardizations, and a thorough description of the treatment are required. In addition, Kay et al. [45] indicated that conducting a comparative study on the relative benefits of physical exercise compared with those of other physical therapies— frequently provided in combination with physical exercise—is still difficult. The reason is that patients and evaluators should be blinded, and adherence to treatment and recourse to therapeutic co-interventions should be controlled. Accordingly, future research—both on neck pain and other musculoskeletal disorders—based on more accurate methodologies is required [53]. Considering the design and features of the current study, we believe our study sheds light on certain aspects that have not yet been evidenced, and that it solves some of the methodological limitations found in previous studies. Considering that treatment arms did not influence the results after the intervention and at 6 months, we did not assess outcomes at time points longer than 6 months. Nevertheless, this could be a limitation in the study design because of the chronic nature of this painful condition.
Conclusions Our study suggests that microwave diathermy provides no additional benefit to a treatment regimen of chronic neck pain that already involves other treatment approaches (eg, exercise, TENS), in terms of pain, disability, patient satisfaction, perceived outcome, quality of life, adherence to exercise, and use of therapeutic co-interventions. Additional research is needed to determine the relative efficacy of diathermy when used as an independent modality.
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