Download Catastrophic Failure of a Boston Scientific Artisan

Neuromodulation: Technology at the Neural Interface
Received: January 25, 2013
Revised: February 9, 2013
Accepted: March 21, 2013
(onlinelibrary.wiley.com) DOI: 10.1111/ner.12066
LETTER TO THE EDITOR
Catastrophic Failure of a Boston Scientific
Artisan Spinal Cord Stimulator
To the Editor:
INTRODUCTION
The most common reasons for revision or removal of permanent
spinal cord stimulator leads are infection and mechanical failure.
Most mechanical failures involve displacement of an intact lead or a
fracture of the wires within one or both electrodes. This is the report
of a case of catastrophic failure of a paddle lead. The implications
regarding certain fixation techniques and the information that is
lacking in the literature will be discussed.
electrodes were found to have completely pulled out of the paddle,
which had displaced from the epidural space into the muscular
layer. The silastic anchor sleeves were still sutured to the spinous
process of T9, although they were both empty. Consistent with the
x-ray, the electrodes were found wrapped around the IPG in the
subcutaneous pocket over the left hip. A new Boston Scientific
Artisan lead was inserted through a laminectomy at T8 and was
connected to the original IPG.
One week later, the stimulator was programmed, and the patient
reported satisfactory coverage and pain control. Figure 3 shows his
final x-ray.
CASE REPORT
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A 43-year-old white male developed neck and back pain with
radiation to the left lower extremity after helping a neighbor move
a refrigerator in September 2004. He underwent a transforaminal
lumbar interbody fusion at L5-S1 by another spine surgeon on June
30, 2008, without improvement in his pain. At the time of presentation, his back pain radiated to the left posterolateral thigh, leg, and
foot. His pain increased with all activities. He obtained relief from
lying down. He had numbness and paresthesias along the lateral
aspect of the left thigh, leg, and foot, and weakness in his left knee.
He had been treated with anti-inflammatories, muscle relaxants,
pain medications, epidural blocks, and physical therapy without
improvement. A computed tomography (CT) myelogram of his
lumbar spine showed no evidence of herniated disc or stenosis at
any level. He had a spinal cord stimulator trial with greater than 50%
improvement in his pain. On March 16, 2010, he underwent implantation of a Boston Scientific Artisan spinal cord stimulator through a
laminotomy at T8 and placement of a rechargeable battery over the
left hip. The lead was secured to the spinous process of T9 with two
sutures of 2-0 Ethibond tied over silastic anchor sleeves, which had
been placed over each electrode. Strain reliefs were created caudad
to the paddle and behind the implanted pulse generator (IPG). The
last intraoperative x-ray is shown in Figure 1.
At one week post-op, the patient’s surgical pain was improving,
his incisions were healing well, and his stimulator was programmed.
He was getting satisfactory coverage and pain relief until four weeks
post-op when he fell in his bathtub at home. When he was seen
again six weeks after implantation, he was getting no coverage or
pain relief. He was able to charge and program his IPG. His incisions
were well healed with no swelling or tenderness. Figure 2 shows the
x-ray obtained that day. The electrodes had retracted into the
pocket over the left hip and were wrapped around the IPG. Multiple
loose contacts can be seen in the subcutaneous tract between the
laminotomy site and the IPG pocket.
The patient underwent revision of the Boston Scientific Artisan
spinal cord stimulator paddle lead on June 2, 2010. At surgery, the
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DISCUSSION
Mechanical failure of the permanent spinal cord stimulator device
has been reported in most series of neuromodulation. Kemler (1)
implanted permanent percutaneous spinal cord stimulators in 24
patients. One patient had a “defective lead” and five others had
“complications related to unsatisfactory position of the electrode.”
Kumar (2) implanted various leads into 121 patients and noted electrode displacement or fracturing among the notable complications.
North’s (3) analysis of 298 permanent spinal cord stimulator
implants revealed that clinical and technical failures were significantly less when multichannel devices were substituted for singlechannel implants. Cameron (4) culled 68 studies on spinal cord
stimulation and found that the most common form of mechanical
failure was lead migration at 13%. The incidence of lead breakage
was 9%.
The technique manuals for the Boston Scientific and Medtronic
stimulators recommend creating a strain relief loop in the electrode.
Kumar (5) reported an expert panel opinion stating, “A strain relief
loop should be considered after anchoring the lead. . . Biomechanical testing has shown that, with surgical leads, a strain relief loop
should be created.” Henderson (6) performed fatigue testing of
paddle leads. The leads fixed with an anchor failed at an average of
16,000 cycles. Removing the anchor and adding a strain relief loop
“decreased the effective stiffness of the system and thereby the
Address correspondence to: Jacob Amrani, MD, Deer Valley Spine Center,
Phoenix, AZ, USA 85027. Email: [email protected]
For more information on author guidelines, an explanation of our peer review
process, and conflict of interest informed consent policies, please go to http://
www.wiley.com/bw/submit.asp?ref=1094-7159&site=1
Authorship Statement: Dr. Amrani is the sole author.
Conflict of Interest: Dr. Amrani has a licensing agreement with Boston Scientific,
Inc. Dr. Amrani also has a patent for a lead relating to this letter.
© 2013 International Neuromodulation Society
Neuromodulation 2014; 17: 200–201
LETTER TO THE EDITOR
Figure 1. X-ray at implantation. Note the strain relief in the electrode caudad
to the paddle.
Figure 3. Final x-ray.
an acute event (a fall in the bathtub) that resulted in the destruction
of the lead, one would assume that a great deal of force was
involved. The author was surprised to learn from the manufacturer
that no tensile failure testing has been performed on this brand of
lead. To get a general idea of the failure strength of these leads, the
author contacted St. Jude Medical. Such failure testing has been
performed by this manufacturer on their leads, but the data are
considered proprietary. They would not share the information, and
internet searches proved unsuccessful.
CONCLUSION
Although this is an isolated case report, falls are not infrequent,
especially in patients taking chronic narcotic medications. The
author believes that mechanical testing of these implantable
devices deserves further attention. At the very least, the tensile
strength of the implants should be known as this might affect decisions related to the fixation of these devices.
Jacob Amrani, MD
Deer Valley Spine Center, Phoenix, AZ
REFERENCES
Figure 2. X-ray at six weeks showing catastrophic failure of the paddle lead.
peak load.” The test ran for 1,000,000 cycles without failure.
Although anchors were used in this case, strain relief loops were
added at each end of the electrodes. This did not protect the system
from a catastrophic failure when the patient fell. Since the fall and
the implant failure occurred four weeks post-op, it is unlikely that
there was enough scar to negate the electrode motion at both
loops.
To the author’s knowledge, no one has reported the catastrophic
failure of a stimulator as described in this case report. Since this was
1. Kemler M, Barendse G, van Kleef M et al. Spinal cord stimulation in patients with
chronic reflex sympathetic dystrophy. N Engl J Med 2000;343:618–624.
2. Kumar K, Nath R, Wyant G. Treatment of chronic pain by epidural spinal cord stimulation: a 10-year experience. J Neurosurg 1991;75:402–407.
3. North R, Kidd D, Zahurak M, James C, Long D. Spinal cord stimulation for chronic,
intractable pain: experience over two decades. Neurosurgery 1993;32:384–395.
4. Cameron T. Safety and efficacy of spinal cord stimulation for the treatment of chronic
pain: a 20-year literature review. J Neurosurg 2004;100:254–267.
5. Kumar K, Buchser E, Linderoth B, Meglio M, Buyten J. Avoiding complications from
spinal cord stimulation: practical recommendations from an international panel of
experts. Neuromodulation 2007;10:24–33.
6. Henderson J, Schade C, Sasaki J, Caraway D, Oakley J. Prevention of mechanical
failures in implanted spinal cord stimulation systems. Neuromodulation 2006;9:183–
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Keywords: neuromodulation, paddle failure
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© 2013 International Neuromodulation Society
Neuromodulation 2014; 17: 200–201