Myofascial Pain and Treatment
Effect of adjuvant frequency-specific microcurrents on pain and
disability in patients treated with physical rehabilitation for neck and
low back pain*
Gautam M. Shetty a, *
, Pallavi Rawat b
, Anjali Sharma b
a QI Spine Clinic, Mumbai, India
b QI Spine Clinic, Pune, India
ABSTRACT
Objectives: To evaluate the efficacy of adjuvant frequency-specific microcurrent (FSM) application onpain and disability in patients treated with physical rehabilitation for mechanical low back pain (LBP)and neck pain (NP).
Methods: In this retrospective case-control study, pre- and post-treatment numerical pain rating scale(NPRS) score, Oswestry disability index (ODI) score, neck disability index (NDI) score, disability categories, and treatment outcome categories were compared between 213 patients in the FSM group (167patients with LBP, 46 patients with NP) and 78 patients in the control group (61 patients with LBP, 17patients with NP).
Results: In LBP patients, mean post-treatment NPRS score was significantly lower (p 1⁄4 0.02) and asignificantly higher percentage of patients were in the 3 NPRS score (p 1⁄4 0.02), in the minimaldisability (p 1⁄4 0.01), and the full success (p 1⁄4 0.006) categories post-treatment in the FSM group whencompared to the control group. In NP patients, there was no significant difference in the post-treatmentpain intensity, disability or treatment outcome when the 2 groups were compared.
Conclusions: The use of adjuvant FSM application in patients treated with physical rehabilitation for LBPsignificantly improved pain and disability when compared to patients in the control group. Frequencyspecific microcurrent could be a useful adjuvant in the rehabilitation treatment of patients with low backpain.
1. Introduction
Electrophysical modalities such as transcutaneous electrical nerve stimulation (TENS), interferential current stimulation, diadynamic current stimulation, and high-voltage electrical stimulation are used for pain management in patients with musculoskeletal conditions (Almeida et al., 2018; Rajfur et al., 2017; Gibson et al., 2019; Logan et al., 2017; White et al., 2017). However, the evidence is lacking in the literature about the efficacy of such modalities on acute or chronic low back pain (LBP) or neck pain (NP). A recent systematic review and meta-analysis reported inconclusive evidence of benefits of TENS in patients with low backpain patients due to the low quality of studies available in the literature (Resende et al., 2018). However, another systematic review which analyzed 700 patients, reported that although TENS does not improve symptoms of lower back pain, it may offer short-term improvement of functional disability (Wu et al., 2018).
Frequency-specific microcurrent (FSM) is an electrophysicalmodality used in pain management that delivers very low-intensityelectric current to tissues within the microampere (mA) range,approximately 1000 times lower than the current intensity used in TENS (McMakin, 2011, 2017). Microcurrent application is based onthe principle that a current closer to the cellular current of the bodycan overcome electrical resistance of injured or inflamed tissue,restore cellular homeostasis, and facilitate tissue regeneration incontrast to TENS which primarily works by blocking the transmission of pain signals (McMakin, 2011, 2017). Although themechanism of action of FSM is not yet clear, these microcurrents ofphysiological amperage when delivered to damaged or inflamedtissues is said to alter cell membrane function, reduce inflammation, and promote healing by maintaining intracellular Ca2þ homeostasis and upregulating ATP production (McMakin, 2011; Kwonet al., 2014; Fujiya et al., 2015; Lambert et al., 2002).
Although previous studies have reported the efficacy of microcurrent in improving muscle function in musculoskeletal conditions such as delayed onset muscle soreness, congenital musculartorticollis, spastic myocontracture in cerebral palsy, and age-relatedmuscle weakness (Lambert et al., 2002; Curtis et al., 2010; Kimet al., 2009; Maenp € €
aa et al., 2004 € ; Kwon et al., 2017), literature is
lacking on the effect of FSM application on pain and disability inpatients with LBP or NP. Hence, this study aimed to determine theefficacy of adjuvant FSM application on pain and disability in patients treated with physical rehabilitation for LBP and NP. We hypothesized that the use of adjuvant FSM application in patientstreated with physical rehabilitation for LBP and NP will significantlyimprove pain and disability when compared to patients where FSMis not used.
2. Patients and methods
2.1. Study design
In this retrospective analysis, electronic records of routinelycollected data from all patients treated for low back pain (LBP) andneck pain (NP) at 3 outpatient clinics specializing in spine rehabilitation (QI Spine Clinic, Pune) from October 2016 to January 2019were analyzed. The inclusion criterion was all patients with LBP or NP, more than 20 years of age, who underwent physical rehabilitation treatment at our clinics. The exclusion criteria were patientswith inflammatory conditions such as rheumatoid arthritis andspondyloarthropathies, patients where peripheral joints such aship, knee and ankle joints were involved, patients with structuralkyphotic or scoliotic deformities, patients with peripheral neuropathy, patients with complex regional pain syndrome (CRPS),patients with lumbar canal stenosis (LCS) and, patients who didphysiotherapy for less than 1 month or more than 3 months at thecentre.
2.2. Study population
Based on the inclusion criteria, 1187 patients who underwenttreatment for LBP and NP at the outpatient clinics were eligible tobe part of this study. Among the eligible patients, 811 patientsreceived adjuvant FSM therapy (FSM group) whereas 376 patientsdid not receive the adjuvant FSM therapy (control group) duringtheir treatment for LBP or NP. Based on the exclusion criteria, 93patients were excluded due to inflammatory causes of LBP or NP,peripheral neuropathy or joint involvement, associated kyphotic orscoliotic deformities, CPS and LCS and 505 patients were excludedbased on the duration of treatment of less than 1 month or morethan 3 months in the FSM group. Similarly, based on the exclusioncriteria, 48 patients were excluded due to inflammatory causes of LBP or NP, peripheral neuropathy or joint involvement, associatedkyphotic or scoliotic deformities, CPS and LCS and 250 patientswere excluded based on the duration of treatment of less than 1month or more than 3 months in the control group. Hence, datafrom 213 patients in the FSM group and data from 78 patients in thecontrol group were analyzed and compared for this study. Thisstudy was approved by an Institutional Ethics Committee and wasperformed as per the ethical standards laid down in the 1964Declaration of Helsinki and its later amendments or comparableethical standards.
2.3. Outcome measures
All patients were evaluated clinically before and during treatment for their LBP or NP. A thorough history of presenting complaints, past illness, previous surgical or non-surgical treatment orany red flag conditions (recent trauma, night or at rest pain, fever, unexplained weight loss, progressive motor or sensory deficit,bowel or bladder symptoms, history of cancer, chronic steroid use,and immunosuppression) was recorded. All patients were clinically examined for posture, lumbar spine movement, motor and sensoryfunction (myotomal and dermatomal loss) by a physiotherapist inthe clinic. The intensity of LBP or NP was recorded using the numerical pain rating scale (NPRS) with pain intensity ranging from“0” (no pain) to “10” (worst pain imaginable) and functionaldisability was recorded using the Oswestry disability index (ODI) or Neck disability index (NDI) before and after treatment (Childs et al.,2005; Fairbank and Pynsent, 2000; Vernon, 2008). Using the Mechanical Diagnosis and Therapy (MDT) system, all patients wereevaluated by movement testing and diagnosed as reducible
derangement, irreducible degrangement, postural syndrome,
dysfunction syndrome, or others by a senior physiotherapist inthe clinic (McKenzie and May, 2003, 2008).
2.4. Treatment protocol
A multimodal, active rehabilitation protocol involving a combination of patient education, pain management using directionalmovements with or without application of frequency-specificmicrocurrents (FSM), and strength and stabilization exercises wasadministered to all patients in an outpatient clinic. Rehabilitationprotocol was varied and personalized based on the severity of painon NPRS and response to movement testing. All patients, during thefirst consultation, were educated about and recommended application of FSM as an adjuvant to physical therapy to improve painand function, especially when the NPRS score was >3 by the
consulting physiotherapist. However, the decision to use FSMapplication was left to the patient. Based on the severity of LBP or NP on NPRS during the first assessment, patients were advised lightextension/flexion mobilization exercises for muscle activation,maintaining proper posture and rest (breaking posture and going toa non-loading position like lying supine) when required duringactivities of daily living for a maximum of 1 week if NPRS score was7. Patients who opted for FSM therapy were administered FSM asa 30-min session, every day during the first 1 week of treatment.
Once the pain on NPRS score was 4e7 or in patients presenting withpain on NPRS score 4e7, movement testing was done using the MDT method to determine directional preference. Patients werethen advised directional movements that were performed undersupervision by the treating physiotherapist and advised to becontinued at home at frequent intervals. Patients were reviewedevery week for progress or improvement in pain and function. Oncethe pain on NPRS was <4, paraspinal muscle strengthening andstabilization exercises were administered.
All patients underwent a minimum rehabilitation treatment of30 days and a maximum of 90 days. A minimum of 6 supervisedphysiotherapy sessions at the clinic was advised to all patients.
Post-treatment clinical assessment was performed at the time ofdischarge to determine NPRS score, ODI/NDI score and disabilitycategory. Treatment outcome was considered a full success if thepatient shifted to a disability category of “minimal” and had painimprovement on NPRS of >80%, a partial success if the patientimproved in disability by one category (e.g.: a shift from severe tomoderate category) and pain improvement on NPRS of 30%e80% ,and a failure if patients did not fall into the full or partial successcategory at the end of treatment.
2.5. Statistical analysis
Pre-treatment baseline parameters such as gender ratio, age,lifestyle, history of night pain, response of pain to movementtesting, anatomical case type, treatment sessions done and totaltreatment period were analyzed. Similarly, clinical outcome datasuch as NPRS score, percentage of NPRS score improvement, ODI/NDI score, disability category, and treatment outcome categorywere analyzed. Clinical outcome parameters such as NPRS score,ODI/NDI score, change in disability category and treatment
outcome category were compared before and after treatment between the FSM and control groups to determine the effectiveness ofadjuvant FSM therapy. The Fisher’s test or Chi-square with Yates’
was used to compare categorical data whereas the t-Test was usedto compare continuous data within and between the 2 groups.
Statistical significance was accepted for p values less than 0.05 in alltests. Statistical analysis was performed using the SPSS (ver. 20.0)statistical analysis software (SPSS Science Inc, Chicago, IL).
3. Results
3.1. Comparison of baseline parameters between FSM vs controlgroups
The baseline characteristics of the 213 patients in the FSM groupand 78 patients in the control group are compared in Table 1. Themean age (p 1⁄4 0.15), mean BMI (p 1⁄4 0.83), gender ratio (p 1⁄4 0.88),anatomical case type (p 1⁄4 1.00), lifestyle (p 1⁄4 0.43), presence ofnight pain (p 1⁄4 0.88), diagnosis based on MDT (p 1⁄4 1.00), responseto movement testing (p 1⁄4 1.00), mean treatment duration
(p 1⁄4 0.85) and the mean number of treatment sessions done by thepatients (p 1⁄4 1.00) were not significantly different when the 2groups were compared (Table 1).
3.2. Comparison of clinical outcomes between FSM vs controlgroups
Clinical outcomes in patients in the FSM group and patients inthe control group are compared in Table 2. Pre-treatment, the mean NPRS score (p 1⁄4 0.44), mean ODI/NDI score (p 1⁄4 0.16), distributionof patients in NPRS categories (p 1⁄4 0.37), and distribution of patients in disability categories (p 1⁄4 0.66) were not significantlydifferent when the 2 groups were compared (Table 2). Post-
treatment, the mean NPRS score was significantly lower
(p 1⁄4 0.01) in the FSM group compared to the control group whereasthe distribution of patients in NPRS categories was not significantlydifferent (p 1⁄4 0.10) when the 2 groups were compared. The posttreatment mean ODI/NDI score was not significantly different(p 1⁄4 0.10) when the two groups were compared whereas a significantly higher percentage of patients (p 1⁄4 0.03) were in the minimal disability category in the FSM group when compared to
patients in the control group (Table 2). Overall, in terms of treatment outcome, a significantly higher percentage of patients were inthe full success (p 1⁄4 0.03) and the partial success (p 1⁄4 0.04) categories in the FSM group when compared to the control group.
3.3. Comparison of clinical outcomes between FSM vs controlgroups in patients with low back pain (LBP)
A total of 167 patients (78.5%) in the FSM group had LBP whereas61 patients (78%) in the control group had LBP. Pre-treatment, themean NPRS score (p 1⁄4 0.49), mean ODI score (p 1⁄4 0.25), distribution of patients in NPRS categories (p 1⁄4 0.37), and distribution ofpatients in disability categories (p 1⁄4 0.66) were not significantlydifferent when the 2 groups were compared (Table 3). Post-
treatment, the mean NPRS score was significantly lower
(p 1⁄4 0.02) in the FSM group compared to the control group and asignificantly higher percentage of patients (p 1⁄4 0.02) were in the3 NPRS score category in the FSM group when compared to thecontrol group (Fig. 1). Similarly, a significantly higher percentage ofpatients (p 1⁄4 0.01) were in the minimal disability category in the FSM group when compared to the control group (Fig. 2). However,the post-treatment mean ODI score was not significantly different(p 1⁄4 0.09) when the two groups were compared (Table 3). Overall,in terms of treatment outcome, a significantly higher percentage ofpatients were in the full success (p 1⁄4 0.006) category in the FSMgroup when compared to the control group (Fig. 3).
3.4. Comparison of clinical outcomes between FSM vs controlgroups in patients with neck pain (NP)
A total of 46 patients (21.5%) in the FSM group had NP whereas17 patients (22%) in the control group had NP. Pre-treatment, themean NPRS score (p 1⁄4 0.35), mean NDI score (p 1⁄4 0.50),
distribution of patients in NPRS categories (p 1⁄4 0.37), and distribution of patients in disability categories (p 1⁄4 0.66) were notsignificantly different when the 2 groups were compared (Table 3).
Post-treatment, the mean NPRS score (p 1⁄4 0.17) mean NDI score(p 1⁄4 0.87), percentage of patients in the 3 NPRS score category(p 1⁄4 0.07) (Table 3), and percentage of patients in the minimaldisability category (p 1⁄4 0.73) were not significantly different whenthe 2 groups were compared (Figs. 4 and 5). Overall, in terms oftreatment outcome, there was no significant difference in thepercentage of patients (p 1⁄4 1.00) who had full success treatmentoutcome category when the 2 groups were compared (Fig. 3).
4. Discussion
The results of this study show that the use of adjuvant FSMtherapy along with an active rehabilitation protocol significantlyreduced pain and disability when compared to patients treatedwith active rehabilitation protocol alone for low back pain. However, the addition of FSM did not appear to significantly affectclinical outcomes of pain and disability in patients with neck pain.
The effectiveness of FSM application in patients with othermusculoskeletal conditions has been previously reported in theliterature (Lambert et al., 2002; Curtis et al., 2010; Kim et al., 2009;Maenp € a€a et al., 2004 € ; Kwon et al., 2017). A previous study had reported that the application of FSM helped in preventing delayedonset muscle soreness (DOMS) up to 72 h post-exercise when
compared to sham treatment (Curtis et al., 2010). Similarly,microcurrent electrical neuromuscular stimulation (MENS), hasbeen reported to enhance muscle function and improve physicalactivity in elderly patients (Kwon et al., 2017). Furthermore,microcurrent application has been reported to be more effectivethan placebo or sham treatment in the treatment of musculoskeletal conditions (Maul et al., 2019; Naclerio et al., 2019; Kwon et al.,2017; Curtis et al., 2010; Koopman et al., 2009; Bertolucci and Grey,1995) and faster acting with lower complication rate when
compared to transcutaneous electric nerve stimulation (TENS)(Saranya et al., 2019; Bertolucci and Grey, 1995).
To the best of our knowledge, this is the first and the largest study in the literature to report efficacy of FSM therapy on pain and disability in patients treated with rehabilitation therapy for low back and neck pain. In the current study, both pain intensity as measuredby NPRS score and disability as measured by the ODI score wassignificantly better in LBP patients in the FSM group when compared to LBP patients in the control group. These findings validate similar findings previously reported by a small pilot study of 10 patients with nonspecific, chronic LBP where microcurrent application usinga patch resulted in significant improvement in pain at the end of treatment (Koopman et al., 2009). In the current study, the beneficialeffect of adjuvant FSM application seen in LBP patients was not seenin patients with neck pain. This could be due to the small number of patients in the NP sub-group when compared to the LBP sub-group.
Electrotherapy modalities such as TENS or interferential current, used in musculoskeletal pain, are based on the gate control theory ofpain. Stimulation of peripheral sensory Ab fibres by TENS inhibits or closes the “gate” (substantia gelatinosa) in the dorsal horn of spinal cord preventing transmission of sensory input from primary afferent neurons to the brain and inhibiting pain perception (Mokhtari et al.,2020; Moayedi and Davis, 2013). However, the clinical effect of FSMoccurs at a cellular level and involves a decrease in electrical resistance, restoration of cellular homeostasis, and facilitation of tissue regeneration in contrast to TENS which primarily works by blockingthe transmission of pain signals (McMakin, 2011, 2017). Hence, improvement in clinical outcomes of patients with LBP treated with FSM in the current study may be primarily due to microcurrents promoting repair and regeneration of paraspinal muscles and reducing local inflammation as previously reported in animal models (Fujiya et al., 2015). Furthermore, we used directional movements using the Mechanical Diagnosis and Therapy (MDT)
technique, and strengthening and stabilization exercises as the maincomponent of physical rehabilitation treatment in all patients with LBP or NP which most likely accounted for the significant clinicalimprovement after treatment. However, the results of the currentstudy indicate that the addition of FSM as an adjuvant therapy helped achieve a better outcome in LBP patients when compared to LBPpatients where FSM was not used.
This study has a few limitations. First, the retrospective designof the study has its inherent biases and limitations which may affect the generalizability of the study. Second, the results reported were reported for a maximum treatment duration of 90days. Hence the medium and long term implications of adjuvant FSM therapy in patients with LBP and NP are unknown and need further validation. Third, pain is a complex phenomenon and patient’s response to physical rehabilitation treatment may be dependent on their neurophysiological and psychosocial makeup(Smeets et al., 2009; Macedo et al., 2014) which was not measured and analyzed in the current study. Hence, future studies evaluating the efficacy of FSM therapy in the treatment of LBP or NPshould take into account the effect of neurophysiological and psychosocial factors on clinical outcomes. Finally, a well-designed, randomized placebo-controlled trial needs to be undertaken to further confirm the benefits of adjuvant FSM therapy as a
component of conservative management of LBP and NP. However,these preliminary, encouraging results of adjuvant FSM therapy in LBP patients could form the basis for a randomized, placebocontrolled trial to investigate the efficacy of adjuvant FSM therapy in a larger number of patients with LBP and NP.
5. Conclusions
The use of adjuvant FSM application in patients treated withphysical rehabilitation for low back pain significantly improved painand disability when compared to patients where FSM was not used.
Frequency specific microcurrent therapy could be a useful adjuvantin the rehabilitation treatment of patients with low back pain.