Alternative
Strategies for Lumbar Discectomy: Intradiscal Electrothermy and Nucleoplasty
The general trend in spinal surgery has been one of
reductionism and minimalization, and has been driven by a number of factors,
including surgeons' desires to reduce surgery-related trauma, patients'
awareness of alternatives to open surgical procedures, and the development of
new technologies. To this end, a number of techniques have been developed that
are applicable to the treatment of lumbar disc herniation and discogenic pain
due to degenerative disc disease.
These techniques have been designed either to shrink
or remove disc material believed to be causing lumbar pain and/or radiculopathy.[9]
The most commonly examined and applied percutaneous techniques include
arthroscopic microdiscectomy, automated percutaneous lumbar discectomy, and
chymopapain, as well as other procedures.[3,4,7,15,17] The purpose
of this document is to examine two newer percutaneous disc treatment
techniques, intradiscal electrothermal therapy (IDET) anuloplasty and
nucleoplasty. This is a review of the appropriate clinical treatment criteria,
techniques, and lessons learned.
The IDET involves the percutaneous insertion of a
specially designed thermal resistance probe followed by controlled heating of
the intervertebral disc. This may result in disc shrinkage and reduction in
pain. The nucleoplasty procedure involves the percutaneous removal of disc
material by using a low-temperature resister probe to disintegrate and evacuate
disc material, followed by thermal treatment of adjacent residual disc
material. To date, no study has been published in which investigators examine
the outcomes of this procedure for the treatment of radicular leg pain and
low-back pain.
Both IDET and nucleoplasty appear to be safe
procedures. The IDET procedure may be an alternative to lumbar interbody
fusion. Although its long-term role is being defined, this technique appears to
provide intermediate-term relief of pain in a population of patients with
discogenic low-back pain. Nucleoplasty may provide a percutaneous alternative
to microdiscectomy in selected cases.
Indications for Treatment
The IDET procedure involves the percutaneous placement of a specially designed thermal resistance probe, which is inserted through a cannula that is coiled into the selected area of the targeted disc. After the location is confirmed using fluoroscopy, controlled heating of the disc material is performed[5,10-12] which may result in disc-related shrinkage and reduction in pain (Fig. 1).[2,13,16] This procedure is supported by basic science research performed by investigators who assessed in vitro temperature mapping and demonstrated that thermal resistance catheter heating conducted temperatures sufficient to coagulate nerve endings and to contract collagen.[1]
A number of clinical studies have been
performed, and are ongoing, to assess the efficacy of this device and
procedure. These studies have included preclinical trials to examine the
feasibility of the technique, as well as formal clinical trials[2,5,10,11,12,14,17]
(JA Saal, et al., unpublished data). We generally view IDET as an alternative
to ALIF and apply the same diagnostic and treatment criteria. As with most
treatments, patient selection may be the single most important criterion for a
successful outcome.
Discogenic low-back pain is the most common
condition treated with IDET, and its presence has been our primary selection
criterion. By discogenic pain, we refer to unremitting, persistent low-back
pain that is worse with axial loading and improved with recumbency. Typically,
the pain has been present for at least 6 months and is continuous in nature.
The low-back pain is greater than leg pain. This is a nociceptive pain and not
a neuropathic pain syndrome.
Neuroimaging studies are necessary in the
diagnostic evaluation process. Magnetic resonance imaging confirms the presence
of disc degeneration, desiccation, high-intensity zones (Moderate endplate
changes), and loss of disc height. Contained disc fragments may also be
present. Extruded and free fragments of disc cannot be effectively treated
using this procedure, but patients with these lesions may be treated for
discogenic low-back pain with the proviso that the fragments will be unchanged
after treatment.
Provocative discography, conducted by an
unbiased interventional neuroradiologist, is performed in most cases. This
diagnostic study is used to confirm our clinical suspicions, and its results
may be used as exclusionary criteria for patients with multilevel disease.
Discography also provides the surgeon with technical information regarding
placement of the intradiscal catheter. Specifically, if a skilled
neuroradiologist has difficulty placing a 20-gauge needle into the L5-S1 disc
space, the surgeon can reasonably expect to have similar difficulties placing
an even larger needle into the same intervertebral space.
Candidates for IDET will have undergone at
least 6 months of nonsurgical treatments including physical therapy and
nonsteroidal antiinflammatory drug therapy. Most patients will have undergone
epidural steroid treatments and narcotic therapies prior to our evaluation. In
summary, patients who generally meet all criteria for ALIF are offered IDET as
a treatment alternative.
Another group of patients considered for IDET
are those with multilevel degenerative disc disease in whom multilevel ALIF is
being considered. These patients may benefit from combined-modality treatment
including ALIF and IDET performed at selected levels. The use of IDET in this
manner may avoid the need to fuse multiple levels of the lumbar spine
sequentially.
Exclusion criteria include lumbar spinal
instability that would require fusion, the presence of infection or malignancy
at the level requiring treatment, severe psychosocial issues, or evidence of
substance diversion. Multilevel disease (that is, three or more levels of disc
disease documented on magnetic resonance imaging and discography) is a relative
but not necessarily absolute contraindication to IDET anuloplasty. Greater than
75% loss of normal disc height is also a relative contraindication to the
procedure.
Treatment Technique
We have used a standardized IDET technique in
our last 75 patients. All procedures are performed in an operating room suite
with the patient placed in a prone position on a Jackson table (Orthopedic
Systems, Inc., Union City, CA) or standard operating table with bolster support
(Fig. 2). This allows the use of fluoroscopy in which there is little
radiographic obstruction. An anesthesiologist sedates the patient throughout
the procedures. We use C-arm fluoroscopy to obtain anteroposterior, oblique
("needle eye view"), and lateral images (Fig. 3). The treatment level
is localized, and a local anesthetic is applied to the skin 6 to 9 cm lateral
to the midline on the side contralateral to the patient's pain. This approach
provides excellent access to the disc space in most patients (Fig. 4). In this
approach the anatomical triangular working zone described by Kambin,[4]
Parke,[8] and O'Neill, et al.,[6] is used (Fig. 5). This
"working triangle" avoids the exiting nerve root. Access to the L5-S1
intervertebral space may be difficult if high iliac crests or a very collapsed
disc space are present. Difficulty at this level may be predicted based on the
neuroradiologist's difficulty in accessing this space during preoperative
discography.
The IDET set includes a 17-gauge needle and
stylet (SpineCath; Smith & Nephew Endoscopy [formerly ORATEC Interventions,
Inc.], Menlo Park, CA). These are directed toward the center of the disc under
fluoroscopic guidance. The annulus is punctured, and the thermal resistance
catheter is inserted through the needle into the disc (Fig. 6). The catheter is
coiled within the disc under fluoroscopic guidance (Fig. 7). The tip of the
catheter is directed toward the posterior aspect of the disc in such a manner
that the heating elements of the catheter remain on the symptomatic side (Fig.
8). Once the catheter is successfully placed and its location is confirmed
fluoroscopically, the catheter temperature is increased along an electronically
programmed 13-minute protocol to 90°C and allowed to remain at that temperature
for 4 minutes. Antibiotic agents are not injected into the disc space. The
catheter and needle are then removed as a single unit.
In patients with multilevel disease we follow
the same protocol and treat each level with new catheters and needles. It has
also been our routine to perform bilateral thermoplasty procedures in patients
with only back pain at the diseased level. The patients are discharged after 2
hours of observation. Following the procedure, patients are instructed to
resume, to the extent they can tolerate, their usual activities after 24 hours.
We do not prescribe postoperative brace therapy, although this is recommended
by other authors.[12]
Treatment Difficulties and Complications
Intradiscal electrothermal therapy appears to
be a very safe procedure. Few complications have been reported, and our own
experience has reflected this. The most common difficulty has been inserting
the needle into the L5-S1 disc space. In only rare cases can this level not be
treated and the procedure aborted. In our experience there have been no
postoperative infections or nerve root injuries.
Another treatment-related problem that may
occur is difficulty in threading the catheter into the disc space once the
needle is adequately positioned. Threading the catheter may be difficult if the
needle tip is positioned against the endplate or if the disc is extremely
degenerated. Should this difficulty arise, it is extremely important not to
force the catheter into the disc space because the catheter can be sheared off
by the needle tip. Additionally, the catheter and needle must be removed as a
single unit once the catheter is extended past the needle tip.
Treatment-Related Results
Presentations and publications in which
authors have reviewed clinical outcomes of IDET-treated patients have shown
favorable results depending on their criteria. In most studies the
investigators have used VAS scores, functional tolerance levels, and/or the
SF-36 questionnaire. In most studies improvement in VAS scores, increase in
functional tolerance levels, and improvements in SF-36 subscale scores have
been demonstrated.
Generally positive outcomes in sitting scores
and ability to work may be indicated post-treatment (Wetzel, et al.,
unpublished data). Some authors have demonstrated greater than 70% improvement
in VAS pain scores and sitting tolerance in treated patients.[2,12]
Our favorable results (unpublished data) were similar to the those reported by
others.[2,11]
In an initial 1-year follow-up evaluation of
27 patients who underwent IDET at our institution, the Oswestry Low Back Pain
Disability Index scores improved in 75%. The SF-36 Bodily Pain Subscale scores
at 1 year improved in 52%. We found no relationship between outcome and
duration of symptoms, the number of levels treated, or receipt of Workers'
compensation. No serious complications occurred in our series (unpublished
data).
The authors of two unpublished studies have
examined the potential effect of IDET on spinal stability. In a cadaveric
study, Lee found no significant differences in nondestructive
flexion-extension, lateral flexion, and axial rotation biomechanics before and
after treatment with IDET (unpublished data). In the other unpublished study, a
retrospective clinical trial of 122 patients underwent IDET, the authors found
that fewer than 5% of IDET-treated patients might require open spinal surgery
in the 6 to 18-month follow-up period (FP Laguttula, et al., unpublished data).
These results suggest that IDET does not destabilize the spine.
Summary of Intradiscal Electrothermal Therapy
Intradiscal electrothermal therapy is a safe
procedure that appears to be moderately effective in relieving pain of
discogenic origin. It may be an alternative to lumbar interbody fusion in
patients who cannot or wish not to undergo a major fusion procedure.[9,15,16,18]
The complication rate is very low and recovery time is minimal, especially
compared with an interbody fusion. Outcome in our personal series is comparable
with most of the published results in that IDET was found to be effective in
75% of patients, resulting in improvement in low-back pain based on the
Oswestry Disability Index as well as the SF-36 (unpublished data). Outcome does
not appear to be dependent on the number of levels treated, duration of
symptoms, or Workers' compensation. Finally, there is no evidence to suggest
that IDET is harmful to patients, either clinically or biomechanically.
Review of Nucleoplasty
Another percutaneous alternative procedure in
the treatment of both discogenic low-back pain and radiculopathy due to
contained disc ruptures is nucleoplasty (ArthroCare Corporation, Sunnyvale,
CA). Nucleoplasty involves the percutaneous removal of disc material by using a
low-temperature resister probe to disintegrate and evacuate disc material,
followed by thermal treatment of adjacent residual disc material. No research
has been published to date in which authors have assessed the outcomes of this
procedure for the treatment of radicular leg pain and low-back pain.
Indications for Treatment
The indications for nucleoplasty include
discogenic low-back pain due to disc degeneration, as well as the treatment of
lumbar disc bulges or disc ruptures causing radiculopathy. Contraindications
include complete disc space collapse leading to inaccessibility of the
intervertebral space, active disc space infection, and medical conditions that
would preclude its safe performance.
Treatment Technique
Nucleoplasty involves the percutaneous
insertion of a cannula positioned in the disc space in a manner similar to that
for IDET (Fig. 9 upper). In contrast to IDET, the cannula is inserted on
the same side as the patient's pain (that is, the side ipsilateral to the disc
herniation). A catheter is then inserted via the needle into the disc space
under fluoroscopic guidance and is positioned where the surgeon wants to ablate
disc material (Fig. 9 lower).
The catheter has a low-temperature resister
at its tip (Fig. 10). The resister generates a plasma field that disintegrates
disc material into its hydrogen and oxygen constituents. The gases escape
through the needle (Fig. 11). A localized area of increased temperature may
result in the ablation of adjacent residual disc material. The tissue ablation
and thermal treatment create a series of channels within the disc, reducing the
pressure from the contained disc herniation or the nerve root and other pain
generating structures (Fig. 12).
Treatment-Related Results
No published results were available for
review. We have a personal experience with more than 25 patients who underwent
nucleoplasty (unpublished results). Our preliminary experience is that
nucleoplasty yields very positive results for relief of low-back pain and
radiculopathy. Our best results have been in patients with diffuse disc
protrusion and radicular pain, in whom very good relief of radicular pain
occurs almost immediately after the procedure.
As with IDET, nucleoplasty appears to be
safe. In our hands, there have been no infections, nerve root injuries, or
worsening of symptoms after the procedure.
Summary of Nucleoplasty
Our preliminary experience is quite positive.
Nucleoplasty seems to be a very good alternative to microdiscectomy in selected
cases of contained disc herniations. Currently we are conducting a 1-year
follow-up examination, using a collection of outcomes instruments, to obtain
quality long-term outcome data.
Conclusions
Both IDET and nucleoplasty appear to be safe
and effective procedures. The IDET procedure has gained some popularity and is
being conducted in numerous centers. Its long-term role is being defined, but
this procedure appears to provide successful intermediate-term pain relief in
patients with discogenic low-back pain. Nucleoplasty may be a minimally
invasive percutaneous alternative to microdiscectomy in selected cases.
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