Spinal cord stimulators (SCS) for injured workers
with chronic low back and leg pain after lumbar
surgery – A prospective pilot study to describe
costs, complications, and patient outcomes
William Hollingworth, PhD (PI)
Richard Deyo, MD MPH (Co-investigator)
Judith Turner, PhD (Co-investigator)
University of Washington
Study Protocol
Human Subjects Review Committee Application No. 04-3479-G 01
Approved 3rd November 2004
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Specific aims
1. To determine the proportion of Workers Compensation claimants with chronic
low back and leg pain (LBP) despite previous spine surgery who show
improvement (defined as 50% or greater leg pain reduction and 2 point or greater
reduction in the Roland Scale of back pain-related physical disability and less
than daily narcotic analgesic use) one year and two years after Spinal Cord
Stimulator (SCS) implantation.
2. To compare these outcomes to those of other claimants with chronic LBP and
prior spine surgery who receive: a) usual care; or b) multi-disciplinary pain clinic
treatment†.
3. To estimate the per-patient direct cost of medical care and time loss
compensation (wage replacement payments for lost work time) to the
Department of Labor and Industries (DLI) over a period of 18 months in the SCS
and comparison groups.
4. To describe the types of complications and adverse events associated with SCS,
and their prevalence, in the first 18 months after SCS implantation in a group of
DLI claimants with chronic LBP and prior spine surgery.
Background
Spinal cord stimulation (SCS) has been used since the late 1960s to treat patients with
intractable pain syndromes, most commonly, chronic low back and leg pain that has
failed to respond to spine surgery and complex regional pain syndrome (CRPS) Type I
(formerly known as reflex sympathetic dystrophy). SCS devices and implantation
methods vary widely; however, all involve the insertion into the epidural space of
electrodes that are connected to an internal or external electrical pulse generator1.
Based on the gate control theory of pain proposed by Melzack and Wall,2 electrical
impulses generated by the SCS are thought to inhibit the conduction of pain signals to
the brain. A randomized controlled trial of SCS in patients with CRPS concluded that
SCS combined with physiotherapy reduced pain significantly more than physiotherapy
alone, but did not improve functional status at 6 months and 2 years post-implantation3,4.
Researchers have also estimated that, if pain reduction is maintained in the long term,
then SCS might be a cost-effective intervention5-8. With the exception of the CRPS
randomized trial, the evidence supporting the efficacy of SCS is poor, most reports have
been case series9. Due to the paucity of the evidence, several reviewers have
concluded that, although SCS may be associated with pain relief in many patients, the
efficacy of SCS for chronic low back and leg pain remains unproven1,10-15
Methods
Study design:
We propose a non-randomized prospective study of spinal cord stimulation (SCS) for
Workers’ Compensation claimants with chronic low back and leg pain despite previous
lumbar spine surgery. The SCS intervention group will be prospectively recruited and
compared to two comparison groups. The first comparison group (C1) will comprise
Workers’ Compensation patients with chronic LBP who meet inclusion and exclusion
criteria for SCS (described below), but who have not been offered SCS by their
physician. This group will be prospectively identified from DLI administrative databases
† Based on the numbers provided by the DLI, approximately 70 Workers with back injury claims and 1 or 2
previous lumbar surgeries participate in pain clinics each year. We will monitor recruitment of pain clinic
patients over the first 6 months of the study. If after this period we have recruited 15 or more patients we will
continue recruitment throughout the first year of the study. If there are insufficient numbers, the pain clinic
comparison group will be dropped and the remaining budget reduced accordingly
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and will receive usual care for their symptoms. The second comparison group (C2) will
be prospectively identified on an ongoing basis as requests are made for authorization
for treatment at a multi-disciplinary pain clinic. The inclusion and exclusion criteria for
each group are described below:
Inclusion criteria:
 Patient has an open, compensable Washington State Workers Compensation
state fund claim for a back injury and is receiving time loss compensation (SCS,
C1, C2)
 Low back pain radiating into one or both legs for more than 6 months(SCS, C1,
C2)
 Radicular pain greater than axial pain (SCS, C1, C2)
 * Patient has undergone one, two or three open lumbar spine surgeries within the
past 3 years (SCS, C1, C2)
 Average leg pain in the last month rated as greater than 5 on a (0-10) numerical
rating scale (SCS, C1, C2)
 Patient is able and willing to use the SCS (SCS)
 Patient understands the limits and risks of the therapy (SCS)
Exclusion criteria:
 Age < 18 years (SCS, C1, C2)
 Age > 60 years (SCS, C1, C2)
 Claim covered by self-insured employer (SCS, C1, C2)
 Prior SCS trial or implantation (SCS, C1, C2)
 Current diagnosis of cancer (SCS, C1, C2)
 * Diabetes (SCS, C1, C2)
 * More than 3 prior open lumbar spine surgeries
 Progressive motor deficit (SCS)
 Progressive bony deformity (SCS)
 Contraindication for surgery (SCS)
 Inability to complete interviews in English or Spanish (SCS, C1, C2)
 Patient does not have access to a telephone (SCS, C1, C2)
 Patient does not consent to participate in the study (SCS, C1, C2)
* These criteria are included in order to target SCS therapy at the group of patients most
likely to benefit. We will review these criteria after 3 months of enrollment and, if
necessary, relax these criteria to enhance patient enrollment.
Patient recruitment:
Patients who are potential candidates for SCS will be identified in the community by their
physicians. Washington State Department of Labor and Industries (DLI) require that
physicians wishing to use SCS receive authorization before the elective procedure. In
addition to the standard information needed for this prospective utilization review (UR) to
begin, physicians will be required to complete a baseline screening form assessing the
criteria above. The physician will also provide the patient with an SCS information sheet
describing this study. The information sheet states that: 1) SCS implants have been
used for many years to treat chronic intractable pain; 2) SCS devices have been
approved by the FDA for pain relief; 3) DLI does not normally cover SCS implants; 4)
The University of Washington (UW) is currently conducting a study of SCS; 5) If the
patient wishes to participate in the UW study, then DLI will pay for the SCS implant; 6)
By participating in the study, the patient agrees to have the UW team review DLI data
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and medical records pertaining to their claim and claim-related medical care and for their
clinician to provide clinical information; 7) If the patient wishes to withdraw from the study
at any stage after implantation, DLI will not be informed and their care and claim status
will not be affected in any way; 8) The information collected by the UW study will be kept
confidential and individually identifiable data will not be released to the DLI.
As part of the prospective utilization review, the UR nurse will review medical records to
confirm that the patient meets all of the SCS inclusion and exclusion criteria. For
patients who meet the inclusion criteria, a copy of the screening form will then be
forwarded to the UW study team and a study ID will be assigned. Once the screening
form has been received and the UR has been provisionally approved, the UW research
team will mail the consent form to the patient and contact them by telephone to complete
the baseline assessment. The completed consent form must be received by the UW
study team before SCS can be approved. The claims manager will review the UR
findings and make a decision to authorize or deny the request. As the DLI has mandated
that SCS procedures will only be reimbursed if performed under the auspices of this
study, the authorization will be contingent upon the patient consenting to participate in
the study, meeting the study inclusion criteria, and completing the baseline assessment.
Workers’ Compensation claimants who have chronic low back and leg pain and prior
lumbar spine surgery and who, based on the criteria described above, are potentially
eligible for the usual care comparison group (C1) will be identified by the DLI from their
administrative database. The DLI will initially contact potentially eligible workers by mail
to inform them about the study and provide them with a copy of the information sheet.
The information sheet will describe the study goals and procedures and inform the
claimants that they will be contacted by a member of the UW research team within 1
week. The information sheet will also provide a UW telephone number which they can
call if they do not wish to be contacted about the study. The DLI will send the UW team
each week name and contact information for potentially eligible workers. A UW research
assistant will mail consent forms to and telephone all claimants who do not actively
refuse to be contacted. Up to 20 attempts over a 6-week period will be made. During
this telephone call, claimants will be given an opportunity to ask questions about the
study, and, if they wish to participate and meet the inclusion and exclusion criteria,
provide verbal informed consent. Eligible claimants who provide informed consent will
then complete the baseline assessment.
The pain clinic comparison group (C2) will be prospectively identified as they are
referred for authorization for multi-disciplinary Pain Clinic treatment. On receipt of a
request for pain clinic treatment, the DLI claims office will inform the UW study team.
The DLI will contact potentially eligible pain clinic patients by mail. Patients will be sent
the C2 information sheet. This information sheet will describe the study goals and
procedures and inform the patients that they will be contacted by a member of the UW
research team within 1 week. The information sheet will also provide a UW telephone
number which the patients can call if they do not wish to be contacted about the study. A
UW research assistant will mail consent forms to and telephone all patients who do not
actively refuse to be contacted. During this telephone call, patients will be given an
opportunity to ask questions about the study, and, if they wish to participate and meet
the inclusion and exclusion criteria, provide verbal informed consent. Eligible claimants
who provide informed consent will then complete the baseline assessment.
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Interventions:
The study aims to observe SCS outcomes in routine practice. Therefore, the type of
SCS device, whether the pulse generator is internal or external, and the length of any
trial period in the SCS group will be decided by the individual physicians. This pragmatic
design should increase the generalizability of our findings, but will not allow us to draw
conclusions comparing different SCS techniques or trial periods.
In the two comparison groups, our study is purely observational and will not alter the
course of either the usual care or the Pain Clinic care.
Questionnaires and follow up:
The UW research assistant will contact patients in the SCS and comparison groups by
telephone at baseline, and at 6, 12 and 24 months. We will collect information on:
1) Age (Baseline)
2) Gender (Baseline)
3) Ethnicity / race (Baseline)
4) Marital status (Baseline)
5) Education (Baseline)
6) Number of previous lumbar surgeries (Baseline)
7) Back pain numerical rating scale (0-10) average pain intensity in past month
(Baseline,6,12,24)
8) Leg pain numerical rating scale (0-10) average pain intensity in past month
(Baseline,6,12,24)
9) Roland back-related function (Baseline,6,12,24)
10) Work status (Baseline,6,12,24)
11) Mental Health (Baseline,12,24)
12) Compensation status (Workers comp / SSDI) (Baseline,6,12,24)
13) Worker-perceived change in pain and function compared to baseline interview
date (12,24)
14) Use of analgesics (Baseline,6,12,24)
15) Complications (requiring an office visit, outpatient visit or hospitalization) (SCS
group only 6,12,18,24) – from telephone interviews, medical billing data, and
medical charts
16) Resource utilization and time loss (12,18) – from DLI medical bills data
Primary outcome:
The composite primary outcome will be the proportion of patients who achieve 50% or
greater reduction (relative to baseline) in leg pain AND less than daily narcotic
medication use AND a 2 point or greater improvement on the Roland function scale.
The 12-month follow-up will be the primary outcome, but this composite outcome will
also be calculated at 24-months.
Secondary outcomes:
Secondary outcomes will be baseline to follow-up change in leg pain, back pain, physical
disability (Roland), depressive symptom severity; cumulative number of time loss days;
compensation status at follow-up (on or off time loss); medical costs in the 18 months
after the baseline interview; time loss compensation costs in the 18 months after the
baseline interview; self-reported work status at follow-up; self-reported symptom
satisfaction at follow-up; and self-reported change in pain and function at one year and
two years. We will also examine complications in the SCS group.
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Sample size:
Given the resource constraints, a definitive large randomized study to determine the
efficacy of SCS in chronic low back pain is not achievable. Instead, the goal of this study
is to provide descriptive information on the comparative costs, complications and
outcomes in the SCS and comparison groups to aid policy decisions. We aim to provide
information on 30 patients with permanent SCS implants over a two year period.
Therefore we would need to recruit 50 claimants who undergo a trial of SCS in order to
take into account likely loss to follow up (estimated at 20%) and patients with an
unsuccessful trial of SCS (estimated at 25%). We will also aim to recruit 50 patients
each to the C1 and C2 comparison groups.
Analysis:
In order to minimize selection bias, we will analyze data using an intention to treat
analysis. Therefore patients will remain in the SCS intervention group, even if the SCS
was not permanently implanted after an initial trial period. We will work with a
biostatistician to determine the most appropriate analytic approach to describe the
primary outcome at 12 and 24 months in the SCS, usual care, and pain clinic groups. In
secondary analyses, we will compare patients who have permanent SCS implants with
those who do not receive a permanent stimulator after a trial period. We will also
conduct secondary analyses to describe changes (relative to baseline) in pain,
functioning, and work status at 12 and 24 months in each group.
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