RESEARCH ARTICLE
Mirror Therapy and Transcutaneous Electrical Nerve Stimulation for Management of Phantom Limb Pain in Amputees — A Single Blinded Randomized Controlled Trial Merlyn Tilak*, Serin Anna Isaac, Jebaraj Fletcher, Lenny Thinagaran Vasanthan, Rajalakshmi Sankaran Subbaiah, Andrew Babu, Rohit Bhide & George Tharion Christian Medical College, Vellore 632002, India
Abstract Background and Purpose. Phantom limb pain (PLP) can be disabling for nearly two thirds of amputees. Hence, there is a need to find an effective and inexpensive treatment that can be self administered. Among the nonpharmacological treatment for PLP, transcutaneous electrical nerve stimulation (TENS) applied to the contralateral extremity and mirror therapy are two promising options. However, there are no studies to compare the two treatments. The purpose of this study is to evaluate and compare mirror therapy and TENS in the management of PLP in subjects with amputation. Methods. The study was an assessor blinded randomized controlled trial conducted at Physiotherapy Gymnasium of Physical Medicine and Rehabilitation Department, Christian Medical College, Vellore. Twenty-six subjects with PLP consented to participate. An initial assessment of pain using visual analogue scale (VAS) and universal pain score (UPS) was performed by a therapist blinded to the treatment given. Random allocation into Group I-mirror therapy and Group II-TENS was carried out. After 4 days of treatment, pain was re-assessed by the same therapist. The mean difference in Pre and Post values were compared among the groups. The change in pre–post score was analyzed using the paired t test. Results. Participants of Group I had significant decrease in pain [VAS ( p = 0.003) and UPS ( p = 0.001)]. Group II also showed a significant reduction in pain [VAS ( p = 0.003) and UPS ( p = 0.002)]. However, no difference was observed between the two groups [VAS ( p = 0.223 and UPS ( p = 0.956)]. Discussion. Both Mirror Therapy and TENS were found to be effective in pain reduction on a short-term basis. However, no difference between the two groups was found. Substantiation with long-term follow-up is essential to find its long-term effectiveness. Copyright © 2015 John Wiley & Sons, Ltd. Received 23 June 2014; Revised 21 January 2015; Accepted 25 February 2015 Keywords mirror therapy; phantom limb pain; transcutaneous electrical nerve stimulation *Correspondence Merlyn Tilak, Christian Medical College, Vellore 632002, India. Email: [email protected]
Published online 1 April 2015 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/pri.1626
Introduction Phantom limb pain (PLP) occurs when a person feels pain in the area of the limb that has been amputated. It is severe and disabling and continues to be experienced by 60–80% of amputees (Gallagher and Maclachlan, 2001). Nearly Physiother. Res. Int. 21 (2016) 109–115 © 2015 John Wiley & Sons, Ltd.
75% of patients develop pain within the first few days after amputation and 70% of phantoms remain painful several years after amputation (Nikolajsen and Jensen, 2001). The occurrence of PLP is explained by the peripheral and central mechanisms that have gained consensus as 109
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proposed mechanisms over the recent years. The most cited reason among these is the central mechanism, which explains cortical reorganization, where the areas representing the amputated extremity are eventually invaded by the neighbouring representational zones in both the primary somatosensory and the motor cortex (Subedi and Grossberg, 2011). Transcutaneous electrical nerve stimulation (TENS) applied to contralateral extremity and mirror therapy are non-invasive, non-pharmacological treatment options, which have shown promising results in management of PLP. The contralateral limb application of TENS sends afferent impulses, which passes through the transcallosal fibres and activates cortical areas, which represent the de-afferented limb (Giuffrida et al., 2010). Mirror training is thought to reverse the cortical reorganizational changes related to PLP (Flor et al., 1995; McCabe et al., 2005). Since phantoms remain painful several years after the loss of the limb, there is a need to find an effective, homebased, easily administered treatment for amputees. TENS, although it is inexpensive and can be administered at home, needs training and skill of the patient to learn the technique as it involves specific parameters of electrical current, whereas mirror therapy is an easyto-use and low-cost therapeutic technique, which can be performed at home without any supervision. Several studies have shown the effectiveness of contralateral limb application of TENS extremity (Carabelli and Kellerman, 1985; Katz et al., 1989; Giuffrida et al., 2010) and mirror therapy (MacLachlan et al., 2004; Chan et al., 2007) in management of PLP. But to date, no randomized control trial has been carried out to compare these two treatments for management of PLP in amputees. This study, as the need suggests is a single blinded randomized control trial comparing contralateral limb application of TENS and mirror therapy in the management of PLP in amputees.
Nadu, India, between April 2013 and September 2013. Approval for the study was obtained from the Institutional Review Board (Research and Ethics Committee) of the Christian Medical College, Vellore. The subjects with amputation, who registered for the Amputee Clinic in Physical Medicine and Rehabilitation (PMR) Department, at Christian Medical College, Vellore, from April 2013 to June 2013, were assessed for eligibility, following which a written consent was obtained by the principal investigator in their regional language. To be eligible for inclusion, the subjects had to present with PLP of any duration with unilateral upper limb or lower limb amputation, between the age of 18 and 60 years of any gender. Subjects with visual and sensory impairment, bleeding disorders and those with bilateral amputation were excluded from the study.
Random allocation and interventions A computer generated simple randomization sequence was carried out by a biostatistician who was not directly involved in the treatment and the assessment of the subjects. Subjects were evaluated at baseline and at the end of treatment in the PMR Department, by the physical therapist (PT 1), who was blinded to the treatment given to the subjects. The baseline assessment included level of amputation, duration since surgery and pain assessment using visual analogue scale (VAS) and universal pain score (UPS). The randomization allocation was concealed using sequentially numbered opaque sealed envelopes, which were prepared by the biostatistician. The envelope was given by the principal investigator to each subject immediately after the baseline assessment. The subjects were randomly allocated to Group I (mirror therapy) or Group II (TENS), and the treatment was given for 4 days by another physical therapist (PT2) in the physical therapy outpatient unit. A detailed diagrammatic algorithm of the study is shown in Figure 1.
Method Design overview
Mirror therapy group
This study was a single blinded randomized controlled trial in which the outcome assessor was blinded to the treatment received by the subjects.
Mirror therapy is a concept, proposed by Ramachandran et al. (1995) to reduce PLP in amputees (Michielsen et al., 2011). The subject views the reflection of their intact limb moving in a mirror placed parasagittally between the arms or legs as it appears to be the missing limb (Weeks et al., 2010). The subject performs simple movements for a period of 20 minutes with their intact limb, and views the virtual image in the mirror (Figure 2).
Setting and participants The study was carried out in the physiotherapy outpatient unit of Christian Medical College, Vellore, Tamil 110
Physiother. Res. Int. 21 (2016) 109–115 © 2015 John Wiley & Sons, Ltd.
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Mirror Therapy Versus TENS for Phantom Limb Pain
Figure 1. Consort flow diagram of participants. TENS, transcutaneous electrical nerve stimulation
Subjects allocated to this group received one session of mirror therapy for 4 consecutive days. Transcutaneous electrical nerve stimulation group TENS is a form of electrical stimulation with surface electrodes to modulate pain perception. The electrodes were fixed on the contralateral leg at the site exactly where they
Figure 2. Subject receiving mirror therapy
Physiother. Res. Int. 21 (2016) 109–115 © 2015 John Wiley & Sons, Ltd.
have PLP on the amputated leg. Burst TENS was used and the intensity of current (mA) was a strong but comfortable sensation without visible muscle contraction for duration of 20 minutes (Figure 3). Subjects allocated to this group received one session of TENS for 4 consecutive days. Measurement instruments and outcome measures The participants’ data sheet included demographic data, details related to amputation including cause, level of
Figure 3. Subject receiving contralateral limb TENS. TENS, transcutaneous electrical nerve stimulation
111
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amputation and date of surgery. The primary outcome measure was pain intensity, which was measured using VAS and UPS. The description of each scale is given in the following. Visual analogue scale It is a 10 cm line labelled ‘no pain’ at one end and ‘severe pain’ in the other end. The subjects were given an explanation of the line and asked to mark a point upon it which corresponded to their pain (Keele, 1948). Higher score indicates greater intensity of pain. Universal pain score This combines six hand drawn faces from the Wong–Baker Pain assessment tool with activity tolerance. Tolerance statements are provided in a variety of languages. Six faces scores on a scale of 1–10. An explanation is given to the subjects that each face is a person who feels happy because he has no pain or sad because he has some or a lot of pain. The subject is then asked to choose the face that best describes how they feel. Blinding The assessor was blinded to the treatment allocation. The therapy room and the assessment room were located at different areas, but because of the nature of the interventions, it was not possible for the therapist or the subjects to be blinded. Sample size estimation As there were no prior studies to calculate sample size, we conducted a pilot study of eight participants and the sample size was calculated to include a minimum of eight participants in both groups. The sample size was calculated based on the pilot study. Statistical analysis The data collected was checked for normality using the Kolmogrov–Smirnov test. The difference in median between the groups was assessed using Mann–Whitney U-test. The difference in median in the groups between the pre and post measurement of the pain scores were tested using Wilcoxon-signed rank test. The statistical software used was SPSS version 17.0. 112
Results From a total of 59 subjects with amputation who registered for the Amputee Clinic at Christian Medical College, 32 had complaints of PLP, but only 26 were considered eligible. The reasons for ineligibility were age over 60 years (n = 3), bilateral lower limb amputation (n = 1) and sensory deficit (n = 2). All 26 consented, and therefore sequentially numbered opaque sealed envelopes were prepared by the biostatistician for a total of 26 subjects (n = 13 in each group). All participants received the treatments as allocated, except for one dropout in Group I (n = 12). The characteristics of the participants at baseline are shown in Table 1. The demographic characteristics and the outcomes of both groups were similar at baseline. Among the subjects who underwent the treatment, the proportion of men were higher than women, 88% (n = 23 out of 26). The mean age of participants was 39 years, and the average duration of amputation period before initiating treatment was 45 days. The effect of mirror therapy and TENS on pain intensity was measured by VAS and UPS. A comparison between initial and final pain intensity using these scales for both groups is shown in Table 2. Following mirror therapy there was a significant reduction in PLP. The VAS value went down from 5.46 to 2.08
Table 1. Demographic characteristics of participants at baseline (N = 26) Variable
Mirror therapy TENS group group
Sex Male 12 (92.3) 11 (84.6) Female 1 (7.7) 2 (15.4) Age (years) 42.62 ± 10.69 36.38 ± 9.55 Onset of PLP from date of surgery (days) 13 (1.414) 13 (1.640) Type of amputation Upper limb 4 (30.8) 3 (23.1) Lower limb 9 (69.2) 10 (76.9) Level of amputation Trans humeral 2 (15.4) 0 (0) Trans radial 2 (15.4) 3 (23.1) Trans femoral 7 (53.8) 7 (53.8) Trans tibial 2 (15.4) 3 (23.1) Pain intensity VAS 5.46 ± 1.671 5 ± 1.63 UPS 5.50 ± 2.576 5.69 ± 2.136 TENS, transcutaneous electrical nerve stimulation; VAS, visual analogue scale, UPS, universal pain score. Categorical variables are expressed as number (%), continuous variables are expressed as mean (SD).
Physiother. Res. Int. 21 (2016) 109–115 © 2015 John Wiley & Sons, Ltd.
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Table 2. Within group differences for pain intensity Intervention
Table 3. Comparison between groups
Outcome measure
Initial
Final
p value
VAS UPS VAS UPS
5.46 ± 1.671 5.50 ± 2.576 5 ± 1.63 5.69 ± 2.136
2.08 ± 1.621 1.83 ± 1.267 2.46 ± 1.561 2.08 ± 1.115
0.003 0.003 0.001 0.002
Mirror therapy TENS
TENS, transcutaneous electrical nerve stimulation; VAS, visual analogue scale, UPS, universal pain score. The variables are expressed in mean (SD).
( p value = 0.003) and a reduction of UPS from 5.50 to 1.83 ( p value = 0.003) was observed. Participants allocated to TENS also had a significant reduction in PLP and the VAS value reduced from 5.00 initially to 2.46 finally ( p value = 0.001) and UPS reduced from 5.69 to 2.08 ( p value = 0.002). When the pre and post-treatment pain scores were compared between the two groups, the mean difference of VAS and UPS were not found to have a significant difference (VAS, p value = 0.223 and UPS, p value = 0.956).
Discussion The objective of this randomized control trial was to evaluate and compare mirror therapy and TENS in the management of PLP in subjects with amputation. After 4 days of treatment, we observed a significant reduction in PLP in both groups. In Group I, which received mirror therapy, there was significant reduction in PLP, which is consistent with the findings of Chan et al. (2007), in which, PLP decreased significantly in eight out of nine patients (89%) who received mirror therapy. Furthermore, case study carried out by MacLachlan et al. (2004), in which the PLP reduced from 6 out of 10 on the VAS to 0 after, mirror therapy also supports these findings. Group II, which received Contralateral limb TENS, also showed a significant reduction of PLP, which is consistent with the results of previous studies (Carabelli and Kellerman, 1985; Katz et al., 1989; Giuffrida et al., 2010). However, no between groups statistically significant differences were detected in pain intensity using either outcome (Table 3). The current study, together with the previous studies, suggests that TENS and mirror therapy are promising interventions for management of PLP. However, the theoretical explanation is not very obvious from this clinical finding alone. There have been some studies in Physiother. Res. Int. 21 (2016) 109–115 © 2015 John Wiley & Sons, Ltd.
Variable VAS UPS
Group I difference
Group II difference
p value
3.38 ± 1.896 3.67 ± 2.498
2.54 ± 1.45 3.62 ± 2.022
0.223 0.956
VAS, visual analogue scale, UPS, universal pain score. The variables expressed in mean (SD).
the past which state that cortical remapping takes place following amputation (Halligan et al., 1993; Flor et al., 1995). It has been suggested that this cortical remapping could alter the pain gate mechanism that causes an eventual amplification of the pain associated with the missing limb (Melzack, 1990). The application of TENS in the contralateral leg is believed to make up for the lack of afferent signals caused by the amputation, as described in previous studies (Melzack, 1990; Giuffrida et al., 2010). This may activate the cortical areas representing the de-afferented limb, through the transcallosal fibres, which link the homotopic parts of the brain, thereby reversing the cortical reorganization and subsequently reducing the PLP (Melzack, 1990). Mirror training is also thought to reverse cortical reorganizational changes following an amputation (Flor et al., 1995; McCabe et al., 2005). A correlation between cortical reorganization and occurrence of PLP, and a significant decrease in PLP with reduction of cortical reorganization has been shown by MacIver et al. (2008), in a controlled neuro imaging study of motor imagery in PLP. Therefore, together with the previous studies, our study results show that there is sufficient clinical evidence to warrant rigorous evaluation, using more objective measures to assess the effectiveness of mirror therapy. No increase in the phantom pain or any other adverse effects were reported by any of the subjects in both groups. Nearly 70% of phantoms remain painful for several years after the loss of the limb (Nikolajsen and Jensen, 2001). Hence, the finding of an effective, easily accessible and self-administered treatment for amputees is a necessity for the interest of amputees. Thus, we conclude that mirror therapy can be used as a safe and cost-effective alternative to contralateral limb TENS for the management of PLP in subjects with amputation. TENS, although effective and can be administered at home, needs training and skill of the patient to learn the technique as it involves specific parameters of electrical current, whereas mirror therapy is an easy-to-use 113
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and low-cost therapeutic technique which can be performed at home without any supervision, and it does not need any special skill or training to learn the technique.
Limitations of the study All possible measures were taken to ensure the study had low level of bias including randomization, allocation concealment, blinding of the outcome assessor, similar baseline characteristics and sample size calculation. However, the present study had a few limitations. Firstly, the blinding of the therapist or the study subjects was impossible because of the nature of the intervention given. Secondly, the homogeneity in the two groups using stratified randomization was not followed with respect to the level of amputation, because of lack of vast samples. Thirdly, the treatment period was very short (4 days) for subjects in both groups, because of practical difficulty of subjects coming for treatment to the hospital. Other limitations include duration and frequency of PLP among the subjects, lack of placebo or non-treatment group and lack of long-term followup. These factors may have limited the response of these interventions.
Conclusions Subjects allocated to mirror therapy and TENS experienced significant reduction in PLP. However, there was no difference between the two groups in the reduction of pain.
Implications for physiotherapy practice Our study shows that both mirror therapy and TENS are comparable in the reduction of PLP in subjects with amputation. Therefore, the clinicians and physical therapists should explain and inform their patients regarding both the treatment techniques in order to define which method to use, taking into account accessibility as well as patient preferences.
Recommendations for research Our study results show effectiveness of mirror therapy and TENS in a short duration. However, it is not known whether the effectiveness lasts for a longer duration. Therefore, substantiation with long-term followup is necessary to find its long-term effectiveness. 114
Acknowledgements Monetary support was taken from the institutional research grant, which is an internal fund from Christian Medical College, Vellore. We would like to thank Ms Anumeha Srivastava and Mr Arun Paul, Physical Therapists from Christian Medical College, Vellore, for their intellectual contribution and help in reviewing the body of the paper.
REFERENCES Carabelli RA, Kellerman WC. Phantom limb pain: relief by application of TENS to contralateral extremity. Archives of Physical Medicine and Rehabilitation 1985; 66(7): 466–467. Chan BL, Witt R, Charrow AP, Magee A, Howard R, Pasquina PF, Heilman KM, Tsao JW. Mirror therapy for phantom limb pain. The New English Journal of Medicine 2007; 357: 2206–2207. Flor H, Elbert T, Knecht S, Wienbruch C, Pantev C, Birbaumer N, Larbig W, Taub E. Phantom-limb pain as a perceptual correlate of cortical reorganization following arm amputation. Nature 1995; 375(6531): 482–484. Gallagher P, Maclachlan M. Adjustment to an artificial limb: a qualitative perspective. Journal of Health Psychology 2001; 6(1): 85–100. Giuffrida O, Simpson L, Halligan PW. Contralateral stimulation, using TENS, of phantom limb pain: two confirmatory cases. Pain Medicine 2010; 11(1): 133–141. Halligan PW, Marshall JC, Wade DT, Davey J, Morrison D. Thumb in check? Sensory reorganization and perceptual plasticity after limb amputation. Neuroreport 1993; 4: 233–236. Katz J, France C, Melzack R. An association between phantom limb sensations and stump skin conductance during transcutaneous electrical nerve stimulation (TENS) applied to the contra lateral leg: a case study. Pain 1989; 36(3): 367–377. Keele KD. The pain chart. Lancet. 1948; 2(6514): 6–8. MacIver K, Lloyd DM, Kelly S, Roberts N, Nurmikko T. Phantom limb pain, cortical reorganization and the therapeutic effect of mental imagery. Brain 2008; 131: 2181–2191. MacLachlan M, McDonald D, Waloch J. Mirror treatment of lower limb phantom pain: a case study. Disability and Rehabilitation 2004; 26(14–15): 901–904. McCabe CS, Haigh RC, Halligan PW, Blake DR. Simulating sensory-motor incongruence in healthy volunteers: implications for a cortical model of pain. Rheumatology (Oxford) 2005; 44(4): 509–516. Physiother. Res. Int. 21 (2016) 109–115 © 2015 John Wiley & Sons, Ltd.
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Melzack R. Phantom limbs and the concept of a neuromatrix. Trends in Neurosciences 1990; 13(3): 88–92. Michielsen ME, Smits M, Ribbers GM, Stam HJ, van der Geest JN, Bussmann JB, Selles RW. The neuronal correlates of mirror therapy: an fMRI study on mirror induced visual illusions in patients with stroke. Journal of Neurology, Neurosurgery, and Psychiatry 2011; 82(4): 393–398. Nikolajsen L, Jensen TS. Phantom limb pain. British Journal of Anaesthesia 2001; 87: 107–116.
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Ramachandran VS, Rogers-Ramachandran D, Cobb S. Touching the phantom limb. Nature 1995; 377: 489–490. Subedi B, Grossberg GT. Phantom limb pain: mechanisms and treatment approaches. Pain Research and Treatment 2011; 2011: 864605. doi: 10.1155/2011/864605. Epub 14 Aug 2011. Weeks SR, Anderson-Barnes VC, Tsao JW. Phantom limb pain theories and therapies. The Neurologist 2010; 16(5): 277–286.
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Mirror Therapy and Transcutaneous Electrical Nerve Stimulation for Management of Phantom Limb Pain in Amputees — A Single Blinded Randomized Controlled Trial Merlyn Tilak*, Serin Anna Isaac, Jebaraj Fletcher, Lenny Thinagaran Vasanthan, Rajalakshmi Sankaran Subbaiah, Andrew Babu, Rohit Bhide & George Tharion Christian Medical College, Vellore 632002, India
Abstract Background and Purpose. Phantom limb pain (PLP) can be disabling for nearly two thirds of amputees. Hence, there is a need to find an effective and inexpensive treatment that can be self administered. Among the nonpharmacological treatment for PLP, transcutaneous electrical nerve stimulation (TENS) applied to the contralateral extremity and mirror therapy are two promising options. However, there are no studies to compare the two treatments. The purpose of this study is to evaluate and compare mirror therapy and TENS in the management of PLP in subjects with amputation. Methods. The study was an assessor blinded randomized controlled trial conducted at Physiotherapy Gymnasium of Physical Medicine and Rehabilitation Department, Christian Medical College, Vellore. Twenty-six subjects with PLP consented to participate. An initial assessment of pain using visual analogue scale (VAS) and universal pain score (UPS) was performed by a therapist blinded to the treatment given. Random allocation into Group I-mirror therapy and Group II-TENS was carried out. After 4 days of treatment, pain was re-assessed by the same therapist. The mean difference in Pre and Post values were compared among the groups. The change in pre–post score was analyzed using the paired t test. Results. Participants of Group I had significant decrease in pain [VAS ( p = 0.003) and UPS ( p = 0.001)]. Group II also showed a significant reduction in pain [VAS ( p = 0.003) and UPS ( p = 0.002)]. However, no difference was observed between the two groups [VAS ( p = 0.223 and UPS ( p = 0.956)]. Discussion. Both Mirror Therapy and TENS were found to be effective in pain reduction on a short-term basis. However, no difference between the two groups was found. Substantiation with long-term follow-up is essential to find its long-term effectiveness. Copyright © 2015 John Wiley & Sons, Ltd. Received 23 June 2014; Revised 21 January 2015; Accepted 25 February 2015 Keywords mirror therapy; phantom limb pain; transcutaneous electrical nerve stimulation *Correspondence Merlyn Tilak, Christian Medical College, Vellore 632002, India. Email: [email protected]
Published online 1 April 2015 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/pri.1626
Introduction Phantom limb pain (PLP) occurs when a person feels pain in the area of the limb that has been amputated. It is severe and disabling and continues to be experienced by 60–80% of amputees (Gallagher and Maclachlan, 2001). Nearly Physiother. Res. Int. 21 (2016) 109–115 © 2015 John Wiley & Sons, Ltd.
75% of patients develop pain within the first few days after amputation and 70% of phantoms remain painful several years after amputation (Nikolajsen and Jensen, 2001). The occurrence of PLP is explained by the peripheral and central mechanisms that have gained consensus as 109
M. Tilak et al.
Mirror Therapy Versus TENS for Phantom Limb Pain
proposed mechanisms over the recent years. The most cited reason among these is the central mechanism, which explains cortical reorganization, where the areas representing the amputated extremity are eventually invaded by the neighbouring representational zones in both the primary somatosensory and the motor cortex (Subedi and Grossberg, 2011). Transcutaneous electrical nerve stimulation (TENS) applied to contralateral extremity and mirror therapy are non-invasive, non-pharmacological treatment options, which have shown promising results in management of PLP. The contralateral limb application of TENS sends afferent impulses, which passes through the transcallosal fibres and activates cortical areas, which represent the de-afferented limb (Giuffrida et al., 2010). Mirror training is thought to reverse the cortical reorganizational changes related to PLP (Flor et al., 1995; McCabe et al., 2005). Since phantoms remain painful several years after the loss of the limb, there is a need to find an effective, homebased, easily administered treatment for amputees. TENS, although it is inexpensive and can be administered at home, needs training and skill of the patient to learn the technique as it involves specific parameters of electrical current, whereas mirror therapy is an easyto-use and low-cost therapeutic technique, which can be performed at home without any supervision. Several studies have shown the effectiveness of contralateral limb application of TENS extremity (Carabelli and Kellerman, 1985; Katz et al., 1989; Giuffrida et al., 2010) and mirror therapy (MacLachlan et al., 2004; Chan et al., 2007) in management of PLP. But to date, no randomized control trial has been carried out to compare these two treatments for management of PLP in amputees. This study, as the need suggests is a single blinded randomized control trial comparing contralateral limb application of TENS and mirror therapy in the management of PLP in amputees.
Nadu, India, between April 2013 and September 2013. Approval for the study was obtained from the Institutional Review Board (Research and Ethics Committee) of the Christian Medical College, Vellore. The subjects with amputation, who registered for the Amputee Clinic in Physical Medicine and Rehabilitation (PMR) Department, at Christian Medical College, Vellore, from April 2013 to June 2013, were assessed for eligibility, following which a written consent was obtained by the principal investigator in their regional language. To be eligible for inclusion, the subjects had to present with PLP of any duration with unilateral upper limb or lower limb amputation, between the age of 18 and 60 years of any gender. Subjects with visual and sensory impairment, bleeding disorders and those with bilateral amputation were excluded from the study.
Random allocation and interventions A computer generated simple randomization sequence was carried out by a biostatistician who was not directly involved in the treatment and the assessment of the subjects. Subjects were evaluated at baseline and at the end of treatment in the PMR Department, by the physical therapist (PT 1), who was blinded to the treatment given to the subjects. The baseline assessment included level of amputation, duration since surgery and pain assessment using visual analogue scale (VAS) and universal pain score (UPS). The randomization allocation was concealed using sequentially numbered opaque sealed envelopes, which were prepared by the biostatistician. The envelope was given by the principal investigator to each subject immediately after the baseline assessment. The subjects were randomly allocated to Group I (mirror therapy) or Group II (TENS), and the treatment was given for 4 days by another physical therapist (PT2) in the physical therapy outpatient unit. A detailed diagrammatic algorithm of the study is shown in Figure 1.
Method Design overview
Mirror therapy group
This study was a single blinded randomized controlled trial in which the outcome assessor was blinded to the treatment received by the subjects.
Mirror therapy is a concept, proposed by Ramachandran et al. (1995) to reduce PLP in amputees (Michielsen et al., 2011). The subject views the reflection of their intact limb moving in a mirror placed parasagittally between the arms or legs as it appears to be the missing limb (Weeks et al., 2010). The subject performs simple movements for a period of 20 minutes with their intact limb, and views the virtual image in the mirror (Figure 2).
Setting and participants The study was carried out in the physiotherapy outpatient unit of Christian Medical College, Vellore, Tamil 110
Physiother. Res. Int. 21 (2016) 109–115 © 2015 John Wiley & Sons, Ltd.
M. Tilak et al.
Mirror Therapy Versus TENS for Phantom Limb Pain
Figure 1. Consort flow diagram of participants. TENS, transcutaneous electrical nerve stimulation
Subjects allocated to this group received one session of mirror therapy for 4 consecutive days. Transcutaneous electrical nerve stimulation group TENS is a form of electrical stimulation with surface electrodes to modulate pain perception. The electrodes were fixed on the contralateral leg at the site exactly where they
Figure 2. Subject receiving mirror therapy
Physiother. Res. Int. 21 (2016) 109–115 © 2015 John Wiley & Sons, Ltd.
have PLP on the amputated leg. Burst TENS was used and the intensity of current (mA) was a strong but comfortable sensation without visible muscle contraction for duration of 20 minutes (Figure 3). Subjects allocated to this group received one session of TENS for 4 consecutive days. Measurement instruments and outcome measures The participants’ data sheet included demographic data, details related to amputation including cause, level of
Figure 3. Subject receiving contralateral limb TENS. TENS, transcutaneous electrical nerve stimulation
111
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Mirror Therapy Versus TENS for Phantom Limb Pain
amputation and date of surgery. The primary outcome measure was pain intensity, which was measured using VAS and UPS. The description of each scale is given in the following. Visual analogue scale It is a 10 cm line labelled ‘no pain’ at one end and ‘severe pain’ in the other end. The subjects were given an explanation of the line and asked to mark a point upon it which corresponded to their pain (Keele, 1948). Higher score indicates greater intensity of pain. Universal pain score This combines six hand drawn faces from the Wong–Baker Pain assessment tool with activity tolerance. Tolerance statements are provided in a variety of languages. Six faces scores on a scale of 1–10. An explanation is given to the subjects that each face is a person who feels happy because he has no pain or sad because he has some or a lot of pain. The subject is then asked to choose the face that best describes how they feel. Blinding The assessor was blinded to the treatment allocation. The therapy room and the assessment room were located at different areas, but because of the nature of the interventions, it was not possible for the therapist or the subjects to be blinded. Sample size estimation As there were no prior studies to calculate sample size, we conducted a pilot study of eight participants and the sample size was calculated to include a minimum of eight participants in both groups. The sample size was calculated based on the pilot study. Statistical analysis The data collected was checked for normality using the Kolmogrov–Smirnov test. The difference in median between the groups was assessed using Mann–Whitney U-test. The difference in median in the groups between the pre and post measurement of the pain scores were tested using Wilcoxon-signed rank test. The statistical software used was SPSS version 17.0. 112
Results From a total of 59 subjects with amputation who registered for the Amputee Clinic at Christian Medical College, 32 had complaints of PLP, but only 26 were considered eligible. The reasons for ineligibility were age over 60 years (n = 3), bilateral lower limb amputation (n = 1) and sensory deficit (n = 2). All 26 consented, and therefore sequentially numbered opaque sealed envelopes were prepared by the biostatistician for a total of 26 subjects (n = 13 in each group). All participants received the treatments as allocated, except for one dropout in Group I (n = 12). The characteristics of the participants at baseline are shown in Table 1. The demographic characteristics and the outcomes of both groups were similar at baseline. Among the subjects who underwent the treatment, the proportion of men were higher than women, 88% (n = 23 out of 26). The mean age of participants was 39 years, and the average duration of amputation period before initiating treatment was 45 days. The effect of mirror therapy and TENS on pain intensity was measured by VAS and UPS. A comparison between initial and final pain intensity using these scales for both groups is shown in Table 2. Following mirror therapy there was a significant reduction in PLP. The VAS value went down from 5.46 to 2.08
Table 1. Demographic characteristics of participants at baseline (N = 26) Variable
Mirror therapy TENS group group
Sex Male 12 (92.3) 11 (84.6) Female 1 (7.7) 2 (15.4) Age (years) 42.62 ± 10.69 36.38 ± 9.55 Onset of PLP from date of surgery (days) 13 (1.414) 13 (1.640) Type of amputation Upper limb 4 (30.8) 3 (23.1) Lower limb 9 (69.2) 10 (76.9) Level of amputation Trans humeral 2 (15.4) 0 (0) Trans radial 2 (15.4) 3 (23.1) Trans femoral 7 (53.8) 7 (53.8) Trans tibial 2 (15.4) 3 (23.1) Pain intensity VAS 5.46 ± 1.671 5 ± 1.63 UPS 5.50 ± 2.576 5.69 ± 2.136 TENS, transcutaneous electrical nerve stimulation; VAS, visual analogue scale, UPS, universal pain score. Categorical variables are expressed as number (%), continuous variables are expressed as mean (SD).
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Table 2. Within group differences for pain intensity Intervention
Table 3. Comparison between groups
Outcome measure
Initial
Final
p value
VAS UPS VAS UPS
5.46 ± 1.671 5.50 ± 2.576 5 ± 1.63 5.69 ± 2.136
2.08 ± 1.621 1.83 ± 1.267 2.46 ± 1.561 2.08 ± 1.115
0.003 0.003 0.001 0.002
Mirror therapy TENS
TENS, transcutaneous electrical nerve stimulation; VAS, visual analogue scale, UPS, universal pain score. The variables are expressed in mean (SD).
( p value = 0.003) and a reduction of UPS from 5.50 to 1.83 ( p value = 0.003) was observed. Participants allocated to TENS also had a significant reduction in PLP and the VAS value reduced from 5.00 initially to 2.46 finally ( p value = 0.001) and UPS reduced from 5.69 to 2.08 ( p value = 0.002). When the pre and post-treatment pain scores were compared between the two groups, the mean difference of VAS and UPS were not found to have a significant difference (VAS, p value = 0.223 and UPS, p value = 0.956).
Discussion The objective of this randomized control trial was to evaluate and compare mirror therapy and TENS in the management of PLP in subjects with amputation. After 4 days of treatment, we observed a significant reduction in PLP in both groups. In Group I, which received mirror therapy, there was significant reduction in PLP, which is consistent with the findings of Chan et al. (2007), in which, PLP decreased significantly in eight out of nine patients (89%) who received mirror therapy. Furthermore, case study carried out by MacLachlan et al. (2004), in which the PLP reduced from 6 out of 10 on the VAS to 0 after, mirror therapy also supports these findings. Group II, which received Contralateral limb TENS, also showed a significant reduction of PLP, which is consistent with the results of previous studies (Carabelli and Kellerman, 1985; Katz et al., 1989; Giuffrida et al., 2010). However, no between groups statistically significant differences were detected in pain intensity using either outcome (Table 3). The current study, together with the previous studies, suggests that TENS and mirror therapy are promising interventions for management of PLP. However, the theoretical explanation is not very obvious from this clinical finding alone. There have been some studies in Physiother. Res. Int. 21 (2016) 109–115 © 2015 John Wiley & Sons, Ltd.
Variable VAS UPS
Group I difference
Group II difference
p value
3.38 ± 1.896 3.67 ± 2.498
2.54 ± 1.45 3.62 ± 2.022
0.223 0.956
VAS, visual analogue scale, UPS, universal pain score. The variables expressed in mean (SD).
the past which state that cortical remapping takes place following amputation (Halligan et al., 1993; Flor et al., 1995). It has been suggested that this cortical remapping could alter the pain gate mechanism that causes an eventual amplification of the pain associated with the missing limb (Melzack, 1990). The application of TENS in the contralateral leg is believed to make up for the lack of afferent signals caused by the amputation, as described in previous studies (Melzack, 1990; Giuffrida et al., 2010). This may activate the cortical areas representing the de-afferented limb, through the transcallosal fibres, which link the homotopic parts of the brain, thereby reversing the cortical reorganization and subsequently reducing the PLP (Melzack, 1990). Mirror training is also thought to reverse cortical reorganizational changes following an amputation (Flor et al., 1995; McCabe et al., 2005). A correlation between cortical reorganization and occurrence of PLP, and a significant decrease in PLP with reduction of cortical reorganization has been shown by MacIver et al. (2008), in a controlled neuro imaging study of motor imagery in PLP. Therefore, together with the previous studies, our study results show that there is sufficient clinical evidence to warrant rigorous evaluation, using more objective measures to assess the effectiveness of mirror therapy. No increase in the phantom pain or any other adverse effects were reported by any of the subjects in both groups. Nearly 70% of phantoms remain painful for several years after the loss of the limb (Nikolajsen and Jensen, 2001). Hence, the finding of an effective, easily accessible and self-administered treatment for amputees is a necessity for the interest of amputees. Thus, we conclude that mirror therapy can be used as a safe and cost-effective alternative to contralateral limb TENS for the management of PLP in subjects with amputation. TENS, although effective and can be administered at home, needs training and skill of the patient to learn the technique as it involves specific parameters of electrical current, whereas mirror therapy is an easy-to-use 113
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and low-cost therapeutic technique which can be performed at home without any supervision, and it does not need any special skill or training to learn the technique.
Limitations of the study All possible measures were taken to ensure the study had low level of bias including randomization, allocation concealment, blinding of the outcome assessor, similar baseline characteristics and sample size calculation. However, the present study had a few limitations. Firstly, the blinding of the therapist or the study subjects was impossible because of the nature of the intervention given. Secondly, the homogeneity in the two groups using stratified randomization was not followed with respect to the level of amputation, because of lack of vast samples. Thirdly, the treatment period was very short (4 days) for subjects in both groups, because of practical difficulty of subjects coming for treatment to the hospital. Other limitations include duration and frequency of PLP among the subjects, lack of placebo or non-treatment group and lack of long-term followup. These factors may have limited the response of these interventions.
Conclusions Subjects allocated to mirror therapy and TENS experienced significant reduction in PLP. However, there was no difference between the two groups in the reduction of pain.
Implications for physiotherapy practice Our study shows that both mirror therapy and TENS are comparable in the reduction of PLP in subjects with amputation. Therefore, the clinicians and physical therapists should explain and inform their patients regarding both the treatment techniques in order to define which method to use, taking into account accessibility as well as patient preferences.
Recommendations for research Our study results show effectiveness of mirror therapy and TENS in a short duration. However, it is not known whether the effectiveness lasts for a longer duration. Therefore, substantiation with long-term followup is necessary to find its long-term effectiveness. 114
Acknowledgements Monetary support was taken from the institutional research grant, which is an internal fund from Christian Medical College, Vellore. We would like to thank Ms Anumeha Srivastava and Mr Arun Paul, Physical Therapists from Christian Medical College, Vellore, for their intellectual contribution and help in reviewing the body of the paper.
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