Orthopedics

Tips & Techniques 

Clinical and Economic Impact of TENS in Patients With Chronic Low Back Pain: Analysis of a Nationwide Database

Robert Pivec, MD; Michael Stokes, MPH; Abhishek S. Chitnis, MPharm, PhD; Carl B. Paulino, MD; Steven F. Harwin, MD; Michael A. Mont, MD

Abstract

This study evaluated patients who were given transcutaneous electrical nerve stimulation (TENS) compared with a matched group without TENS prior to intervention and at 1-year follow-up. Patients who were treated with TENS had significantly fewer hospital and clinic visits, used less diagnostic imaging (31 vs 46 events per 100 patients), had fewer physical therapy visits (94 vs 107), and required less back surgery (7.5 vs 9.2 surgeries) than patients receiving other treatment modalities. Total annual costs for chronic low back pain patients without neurological involvement were lower in TENS patients ($17,957 vs $17,986 for non-TENS), even when the cost of the device was taken into account. [Orthopedics. 2013; 36(12):922–928.]

The authors are from the Department of Orthopaedic Surgery (RP, CBP), SUNY Downstate Medical Center, Brooklyn, New York; Health Economics and Epidemiology (MS, ASC), Evidera, Lexington, Massachusetts; the Department of Orthopaedic Surgery (SFH), Beth Israel Medical Center, New York, New York; and the Rubin Institute for Advanced Orthopedics (MAM), Sinai Hospital of Baltimore, Baltimore, Maryland.

Drs Pivec and Mont are consultants to DJO. Messrs Stokes and Chitnis are employees of Evidera. Drs Paulino and Harwin have no relevant financial relationships to disclose.

Correspondence should be addressed to: Michael A. Mont, MD, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore, 2401 W Belvedere Ave, Baltimore, MD 21215 (mmont@lifebridgehealth.org).

Received: October 25, 2013
Accepted: November 11, 2013
Posted Online: December 13, 2013

Abstract

This study evaluated patients who were given transcutaneous electrical nerve stimulation (TENS) compared with a matched group without TENS prior to intervention and at 1-year follow-up. Patients who were treated with TENS had significantly fewer hospital and clinic visits, used less diagnostic imaging (31 vs 46 events per 100 patients), had fewer physical therapy visits (94 vs 107), and required less back surgery (7.5 vs 9.2 surgeries) than patients receiving other treatment modalities. Total annual costs for chronic low back pain patients without neurological involvement were lower in TENS patients ($17,957 vs $17,986 for non-TENS), even when the cost of the device was taken into account. [Orthopedics. 2013; 36(12):922–928.]

The authors are from the Department of Orthopaedic Surgery (RP, CBP), SUNY Downstate Medical Center, Brooklyn, New York; Health Economics and Epidemiology (MS, ASC), Evidera, Lexington, Massachusetts; the Department of Orthopaedic Surgery (SFH), Beth Israel Medical Center, New York, New York; and the Rubin Institute for Advanced Orthopedics (MAM), Sinai Hospital of Baltimore, Baltimore, Maryland.

Drs Pivec and Mont are consultants to DJO. Messrs Stokes and Chitnis are employees of Evidera. Drs Paulino and Harwin have no relevant financial relationships to disclose.

Correspondence should be addressed to: Michael A. Mont, MD, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore, 2401 W Belvedere Ave, Baltimore, MD 21215 (mmont@lifebridgehealth.org).

Received: October 25, 2013
Accepted: November 11, 2013
Posted Online: December 13, 2013

Chronic low back pain continues to be one of the conditions most commonly presenting to orthopedic surgeons, who, following primary practitioners, are the most common physicians patients seek.1,2 It is the fifth most frequent indication for a physician visit.2 Up to 85% of the population will experience an episode of nonspecific low back pain during their lifetimes, but the vast majority (more than 90%) will have a self-limited disease that resolves within 3 months.1,3,4 However, due to the large number of patients presenting with this condition annually, it represented a substantial fiscal burden estimated to be $26 billion in 1998 and nearly $100 billion in 2007.5,6

Chronicity is less common, but the prevalence of chronic low back pain in the United States rose from 3.9% in 1992 to 10.2% in 2006.7,8 These patients in particular may be drivers of cost because they often require substantial medical intervention and have high pharmacologic costs.5,9 Low back pain is associated with substantial direct (eg, cost of medical care) and indirect (eg, lost productivity due to time off work) costs. A study of Swedish patient data by Ekman et al10 demonstrated that direct costs represented only 15% ($2200) of the total annual cost, with 85% ($16,600) consisting of indirect costs.

Patients with chronic low back pain who do not also have neurological deficits represent a treatment dilemma with multiple nonoperative treatment modalities proposed.11 However, combined guidelines from the American College of Physicians and the American Pain Society,12 which were also adopted by the American Academy of Orthopaedic Surgeons in 2010,13 have given nonoperative modalities a weak recommendation due to the poor level of evidence for the supporting studies. One potential treatment modality for chronic low back pain is transcutaneous electrical nerve stimulation (TENS). This functions by delivering a localized voltage of varying intensity and frequency, which has been shown to inhibit normal nociceptive fiber signaling.14–16 The literature has reported mixed results regarding the efficacy of TENS. Recent meta-analyses by Brosseau et al17 and Khadilkar et al18 demonstrated no evidence for or against the use of this treatment modality. The primary reason for this lack of consensus is interstudy heterogeneity, which is due to a lack of a standardized treatment protocol (eg, different TENS device settings, duration of treatments, and adjuvant therapies).19,20 However, no study has evaluated the clinical and economic effects of the use of TENS for the treatment of chronic low back pain without neurological symptoms using a nationwide administrative claims database.

The purpose of this study was to evaluate the clinical and economic effects among patients who were given TENS for chronic low back pain compared with a matched group of patients who were not given TENS, both prior to intervention and at 1-year follow-up. The primary outcome measures of this study were whether the use of TENS resulted in differences between (1) hospital and clinic visits; (2) use of diagnostic imaging; (3) use of physical therapy; (4) incidence of back surgery; and (5) treatment costs.

Materials and Methods

The costs and clinical effects of TENS for patients with chronic low back pain, compared with those who were not treated with TENS, were evaluated using a commercial and Medicare supplemental administrative claims database (MarketScan; Truven Health Analytics, Ann Arbor, Michigan). This database contained claims and eligibility records for approximately 30 million enrollees in distinct sets of files for commercially insured individuals (ie, working-aged adults and their dependents), and 3 million enrollees for Medicare supplemental insurance. Patients were selected if they had at least 2 ICD-9-CM coded claims for low back pain during a 3-month period anytime between January 1, 2008, and September 30, 2010. Patients were then divided into groups based on those who received TENS and those who did not receive TENS during the follow-up period (Table 1). For TENS patients, the date of the first TENS procedure was set as the study index date. The index date for the non-TENS patients was the date of the first claim for procedures other than TENS (eg, physical therapy, opioids, back surgery, or diagnostic imaging).

Inclusion and Exclusion Criteria

Table 1:

Inclusion and Exclusion Criteria

Patients in each group were matched using a 1:1 greedy propensity score matching algorithm to ensure patient groups were comparable regarding baseline clinical and demographic characteristics. Logistic regression models were used to calculate a predicted probability of group membership (eg, receiving TENS vs not receiving TENS), or propensity score, based on the observed predictors. The following variables were included in the logistic regression model: age, sex, geographic region of residence, indicators of individual comorbidities, medication use, back surgery, and surrogate low back pain baseline severity measures. These predictor variables were measured during the 12-month pre-index period. Following matching, there were 22,913 patients in each group (Figure). Patients with low back pain findings without neurological involvement were further selected using ICD-9 diagnosis codes to isolate patients with purely mechanical low back pain (as opposed to patients with neurological symptoms or those with congenital or acquired spinal disorders). After final selection, there were 16,593 patients available for analyses.

Flow diagrams of patient selection based on inclusion and exclusion criteria for patients who received transcutaneous electrical nerve stimulation (TENS) (A) and those who did not receive TENS (B). Abbreviation: LBP, low back pain.

Figure:

Flow diagrams of patient selection based on inclusion and exclusion criteria for patients who received transcutaneous electrical nerve stimulation (TENS) (A) and those who did not receive TENS (B). Abbreviation: LBP, low back pain.

Primary outcomes (hospital and clinic visits; physical therapy use; incidence of back surgery; direct and indirect treatment costs) were compared across treatment groups by measuring the proportion of patients with an outcome for categorical variables (eg, percent of patients having out-patient or inpatient visits) or the means for continuous variables (eg, total medical costs). All outcomes were evaluated at baseline (prior to intervention) and at 1-year follow-up.

All statistical analyses were performed using SAS version 9.1 software (SAS, Cary, North Carolina). The chance of having a type I error used as a cutoff to determine statistical significance was set at alpha=0.05. Continuous study measures were assessed and reported with means and SDs. Categorical variables were reported using frequency distributions. Student’s t test was used to test for statistical differences for continuous variables, chi-square test was used for categorical variables, and the nonparametric Wilcoxon rank sum test was used for ranked data.

Results

Baseline demographic and clinical variables were compared between TENS and non-TENS patients. There were no significant differences between the 2 groups based on mean age, age category, sex, geographic region of residence, major medical comorbidities, Charlson Comorbidity Index, or psychiatric disorders (Table 2). The only significant differences observed were in the type of insurance (13.1% in the TENS group had supplemental Medicare insurance compared with 11.9% in the non-TENS group) and single episodes of low back pain (17.6% vs 16.4%, respectively) (Tables 23).

Comparison of Baseline Demographic Variables Following Matching

Table 2:

Comparison of Baseline Demographic Variables Following Matching

Comparison of Baseline Comorbidities Following Matching

Table 3:

Comparison of Baseline Comorbidities Following Matching

Chronic Low Back Pain Without Neurologic Compromise

Overall, patients with chronic low back pain without neurologic compromise who were treated with TENS had significantly lower proportions of inpatient and outpatient admissions and physician office visits than those who did not receive TENS (all P<.001). Patients who received TENS had higher medical equipment costs (eg, cost of the TENS unit), but lower total annual costs.

Resource use due to any cause between the 2 groups demonstrated that patients who received TENS had lower proportions of emergency department visits (26.9% vs 28.2%; P=.048), inpatient hospital stays (13.7% vs 15.9%; P<.0001), and physician office visits (98.9% vs 99.6%; P<.0001). These differences were maintained when patients were specifically evaluated for visits due to pain alone (Table 4).

Overview of Resource Use Between Groups

Table 4:

Overview of Resource Use Between Groups

Analysis of total annual costs demonstrated that patients who received TENS had significantly lower total costs, although the difference was modest ($17,957 for TENS patients vs $17,986 for non-TENS patients; P<.0001). Transcutaneous electrical nerve stimulation patients were observed to have significantly lower inpatient costs ($4074 vs $4772, respectively; P<.0001), but significantly higher outpatient costs ($10,489 vs $9643, respectively; P<.0001), primarily due to durable medical equipment costs, which incorporate the cost to purchase the TENS device (Table 5).

Overview of Resource Use Costs Between Groups

Table 5:

Overview of Resource Use Costs Between Groups

Overall Cohort

Diagnostic imaging use during the 1-year follow-up period was found to be significantly lower in TENS patients (mean, 31 events per 100 patients) compared with non-TENS patients (mean, 46 events per 100 patients; P<.0001).

Physical therapy use at 1-year follow-up was significantly lower in TENS patients (mean, 94 events per 100 patients) compared with non-TENS patients (mean, 107 events per 100 patients; P<.0001). Of note is that the higher number demonstrates that several patients were prescribed physical therapy on more than 1 occasion.

Similar trends were seen in back surgery. An evaluation of the entire cohort demonstrated significantly less back surgery in TENS patients (mean, 7.5 episodes per 100 patients) compared with non-TENS patients (mean, 9.2 episodes per 100 patients; P<.0001).

Discussion

The purpose of this study was to evaluate resource use and costs in patients with chronic low back pain who received TENS compared with a matched group of patients with chronic low back pain who did not receive TENS. Few studies have evaluated the effect of TENS use or non-use on resource use and costs using a large administrative claims database.21 The current authors observed that TENS was associated with significantly fewer inpatient visits and less diagnostic imaging, physical therapy, and back surgery. Overall, when all costs were considered, TENS use was cost neutral compared with TENS non-use, although the upfront costs for the unit itself were significantly higher.

Avoiding surgery when it is not clinically indicated is of utmost importance to orthopedic surgeons. However, this may be particularly difficult when patients erroneously believe that surgery in the setting of no neurologic compromise will effectively reduce their pain. Spinal fusion to treat chronic low back pain is controversial, with conflicting data on clinical and disability outcomes. In a randomized, controlled trial performed in Norway comparing surgical outcomes with physical therapy and cognitive intervention for 124 patients with chronic low back pain (symptom duration, more than 1 year) but no neurological symptoms, Froholdt et al22 observed no difference in clinical outcome scores at 9-year follow-up (mean adjusted Oswestry Disability Index treatment effect, 1.9; 95% confidence interval, −7.9 to 11.6). The authors also observed that, compared with prior studies reporting 1- and 4-year follow-up, there was no significant difference in disability, pain, fear avoidance beliefs, trunk muscle strength, and return to work for lumbar fusion compared with structured exercise and cognitive behavioral therapy for treatment of chronic low back pain.23–25 Therefore, the current study provides a potentially compelling treatment alternative and/or adjuvant for patients for whom back surgery is not indicated. The current authors observed that TENS was a noninvasive option that provided clinical and economic advantages compared with non-use of TENS. Interestingly, in the entire cohort, which included patients with neurological symptoms, TENS was observed to result in less back surgery.

The observed reduction in the use of medical imaging and opioids for TENS patients with chronic low back pain is in stark contrast to increases in imaging studies and opioid therapy during the past 20 years. Based on an extensive review of the evidence, the guidelines issued jointly from the American College of Physicians and American Pain Society recommend against routine imaging for patients with nonspecific low back pain.12 Although the current study could not definitively determine the circumstances for imaging in each patient, the observation that fewer imaging studies were done for TENS patients with chronic low back pain is an important factor contributing to lower overall health care costs. Likewise, in the current study, the small reduction in opioid use for TENS patients with chronic low back pain may be important as an overall public health measure in reducing the exposure of chronic low back pain patients to chronic opioid use and the related sequelae. According to the jointly issued American College of Physicians and American Pain Society guidelines, “Failure to respond to a time-limited course of opioids should lead to reassessment and consideration of alternative therapies or referral for further evaluation.”12 Alternative therapies such as TENS for chronic low back pain may provide clinicians with an option that requires less imaging and avoids opioid pain medication in this challenging population.

There were several limitations to this study. First, confounding factors may have occurred as a result of selection bias related to receiving the TENS device. However, the 2 groups were well matched on baseline demographic variables and comorbidities. One potential confounder is that patients in the TENS group had a slightly higher number of low back pain episodes, which can be seen as a surrogate for slightly more severe disease. It is thus possible that the results of this study may have understated the benefits of TENS. One should note that medical conditions were identified based on administrative claims using ICD-9-CM diagnosis codes, which may be susceptible to clerical errors or erroneous reporting. Also, this study was not able to determine indirect costs (eg, missed workdays) because these are not captured in the database. However, because non-TENS patients had more inpatient and physical therapy visits, it can be hypothesized that they may have also had higher indirect costs. Despite these limitations, the authors believe that this study provides important insights regarding the use of TENS for the treatment of chronic low back pain that have not been previously reported.

A few prior studies have attempted to evaluate the effect of TENS on costs and resource use,21,26 but have usually had small sample sizes or limited geographic areas. Lin et al21 attempted to evaluate the cost-effectiveness of several treatment modalities for chronic low back pain present in the American College of Physicians and American Pain Society guidelines12 but noted that much of the currently available data are methodologically inconsistent and use lower levels of clinical evidence. Chabal et al26 attempted to quantify the cost-effectiveness of TENS by surveying 276 patients with unspecified chronic pain who were being treated with TENS. They observed that physical therapy costs could be decreased by 69% with long-term TENS use. However, it is unclear whether these patients had chronic low back pain or other types of chronic pain. Furthermore, many of these conclusions were based on extrapolations of future expected resource use and thus may have been sensitive to bias. Dagenais et al27 attempted to evaluate the cost-effectiveness of several treatments for chronic low back pain but identified few reports of high quality. This general lack of available data should be seen as an opportunity to further understand the interplay between efficacy and cost-effectiveness in the treatment of chronic low back pain that is likely due to heterogeneous causes.

On the basis of the current study, the authors believe that TENS may be a useful adjuvant in the management of chronic low back pain, which may be more difficult to manage than new-onset acute low back pain. Compared with treatment without TENS, the authors’ results demonstrate that TENS is associated with fewer inpatient, outpatient, physician office, emergency department, and physical therapy visits, less diagnostic imaging, and fewer episodes of back surgery and is less costly annually, although these savings may not be clinically compelling. Further studies are needed using a standardized methodology to determine the optimal treatment options for this challenging patient population.

References

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  22. Froholdt A, Reikerås O, Holm I, Keller A, Brox JI. No difference in 9-year outcome in CLBP patients randomized to lumbar fusion versus cognitive intervention and exercises. Eur Spine J. 2012; 21(12):2531–2538. doi:10.1007/s00586-012-2382-0 [CrossRef]
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  24. Brox JI, Reikerås O, Nygaard ØP, et al. Lumbar instrumented fusion compared with cognitive intervention and exercises in patients with chronic back pain after previous surgery for disc herniation: a prospective randomized controlled study. Pain. 2006; 122(1–2):145–155. doi:10.1016/j.pain.2006.01.027 [CrossRef]
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  27. Dagenais S, Roffey DM, Wai EK, Haldeman S, Caro J. Can cost utility evaluations inform decision making about interventions for low back pain?Spine J. 2009; 9(11):944–957. doi:10.1016/j.spinee.2009.07.007 [CrossRef]

Inclusion and Exclusion Criteria

TENS GroupNon-TENS Group


Inclusion Criteria

1. At least 1 claim for a TENS device (HCPCS codes: E0720, E0730) between January 1, 2008, and September 30, 20101. No claims for TENS and received other therapy (including physical therapy, opioids, back surgery, or diagnostic imaging) betweenJanuary 1, 2008, and September 30, 2010
2. At least 2 medical claims with an associated primary or secondary diagnosis of LBP within 90 days and at least 1 of the LBP claims within ±90 days of the TENS index claim2. At least 2 medical claims with an associated primary or secondary diagnosis of LBP within 90 days and at least 1 of the LBP claims within ±90 days of the LBP other therapy (eg, physical therapy, opioids, back surgery, diagnostic imaging) index claim
3. At least 18 years of age as of the study index date3. At least 18 years of age as of the study index date
4. Continuously enrolled in the health plan for 12 months prior to the index date and at least 24 months of continuous enrollment after the index date4. Continuously enrolled in the health plan for 12 months prior to the index date and at least 24 months after the study index date
Exclusion Criteria

Did not have a claim indicating cancer or neurodegenerative disease during the 12-month period prior to the study index date or during the follow-up periodPatient did not have a claim indicating cancer or neurodegenerative disease during the 12-month period prior tothe index date or during the follow-up period post-study index date

Comparison of Baseline Demographic Variables Following Matching

DemographicNon-TENS (n=8286)TENS (n=8307)P
Mean age, y50.0±13.550.3±13.5.1095
Age range, %
  18–3412.7711.66
  35–4420.4921.27
  45–5430.6430.67
  55–6424.6924.05
  65–746.096.89
  75–844.344.49
  ≥850.970.96
Sex, %.8416
  Female65.5165.66
  Male34.4934.34
Region of residence, %.0834
  Northeast10.3110.12
  Midwest22.3623.43
  South47.0947.26
  West16.7116.32
  Unknown3.522.87
Health plan type, %.0236
  Commercial88.1086.94
  Medical supplemental11.9013.06
LBP episodes, %<.0001
  035.2823.62
  116.3617.61
  28.6714.27
  37.1411.06
  ≥432.5533.44

Comparison of Baseline Comorbidities Following Matching

VariableNon-TENS (n=8286)TENS (n=8307)P
CCI component, %
  Myocardial infarction1.181.17.9284
  Congestive heart failure2.863.07.4264
    Peripheral vascular disease4.314.14.5920
  Cerebrovascular disease2.622.89.2875
    Chronic respiratory disease9.299.26.9371
  Rheumatologic disease4.154.08.8187
  Ulcer disease0.721.05.0263
  Mild liver disease2.822.35.0531
  Hemiplegia1.521.60.6761
    Moderate or severe liver disease1.892.09.3573
  Diabetes mellitus13.4713.03.3996
    Moderate or severe liver disease0.760.76.9886
Mean CCI score0.6±1.10.6±1.1.8682
CCI score distribution, %.9233
  067.6067.88
  113.7213.60
  211.1411.18
  34.314.03
  ≥43.233.30
Chronic LBP-related comorbidity, %
  Coronary atherosclerosis5.585.75.6189
  Anxiety7.817.40.3252
  Major depressive disorder6.226.50.4515
  Insomnia/sleep disorder0.820.84.8760
  Kidney stones2.782.73.8652
  Obesity2.152.24.6895
  Myalgia10.3710.32.9153

Overview of Resource Use Between Groups

Variable%
P
Non-TENS (n=8286)TENS (n=8307)
All-cause resource use
  Any emergency department visit28.2326.86.0480
  Any inpatient hospital stay15.8513.72.0001
  Any outpatient claim100.00100.00
    Any outpatient hospital visit76.9076.14.2481
    Any physician office visit99.6498.90<.0001
    Any use of durable medical equipment11.2499.99<.0001
Pain-related resource use
  Any emergency department visit6.795.02<.0001
  Any inpatient hospital stay6.634.90<.0001
  Any outpatient claim98.4697.41<.0001
    Any outpatient hospital visit37.5534.92.0004
    Any physician office visit93.2483.03<.0001
    Any use of durable medical equipment1.9879.21<.0001

Overview of Resource Use Costs Between Groups

ResourceMean±SD Cost, $
P
Non-TENS (n=8286)TENS (n=8307)
All-cause resource use
  Total17986±30,61717,957±25,711<.0001
  Emergency department409±1566399±1530.1335
  Inpatient hospital4772±20,9844074±16,841.0002
  Outpatient services9643±15,48710,489±14,425<.0001
    Outpatient hospital4177±10,6043896±8163.2027
    Physician office3636±38573752±4424.0792
    Durable medical equipment116±597545±785<.0001
    Pharmacy3161±79872996±4455.0345
Pain-related resource use
  Total6193±17,1276331±16,636<.0001
  Emergency department65±56255±722<.0001
  Inpatient hospital2474±14,1591948±13,321<.0001
    Back surgery2066±12,2441717±12,009<.0001
  Outpatient services2998±70213680±7943<.0001
    Back surgery101±114294±960.3144
    Outpatient hospital1235±54421156±4744.0005
    Physician office1324±20601312±2216<.0001
    Durable medical equipment19±249337±484<.0001
    Physical therapy865±1594793±1635<.0001
    Imaging373±910244±756<.0001
Pharmacy656±1574647±1287.002
  Opioids191±1101680±2.0973

10.3928/01477447-20131120-04

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