Abstract Hemilaminectomy with diskectomy, the original surgical option to address intervertebral disk herniation, was superseded by open microdiskectomy, a less invasive technique recogn
Trang 1Open hemilaminectomy to treat
symptomatic intervertebral disk
her-niation, described by Mixter and
Barr in 1934,1set the standard for
subsequent surgical techniques The
trend since has been to develop less
invasive surgical procedures for the
treatment of radiculopathy
second-ary to herniated disk The concept
of minimally invasive spine surgery
is to provide surgical options that
optimally address the disk
pathol-ogy without producing the types of
morbidity commonly associated
with open surgical procedures
Min-imally invasive techniques are not,
however, a panacea for all lumbar
disk pathology These techniques
are designed to treat nerve root
com-pression alone as the source of
ra-diculopathy in patients with acute
primary disk herniations
Radiculopathy has been
attrib-uted to the production of chemical
mediators that result from the com-pression and/or leakage of degen-erative nuclear material through annular tears These chemical me-diators may result in inflammation and may affect the large and small sensory afferent nerve fibers.2,3
Phospholipase A2 and nitric oxide synthase from extruded or migrated disk fragments have been specifi-cally cited as possible agents related
to the pathophysiology of radicu-lopathy.4
Minimally Invasive Techniques: An Overview
First-generation minimally invasive methods were blind percutaneous techniques, including chemonucleo-lysis, percutaneous nucleotomy, automated percutaneous nucleot-omy, and laser disk decompression
The development of fiberoptic visu-alization with rigid discoscopes and flexible endoscopes allowed more advanced methods to be
undertak-en, including biportal arthroscopic intradiscal diskectomy and percuta-neous intradiscal and epidural uni-portal techniques through postero-lateral, posterior interlaminar, or foraminal approaches The stan-dard for evaluation of percutaneous techniques became open microdisk-ectomy, considered the benchmark for comparison A recently devel-oped percutaneous variation of the standard laminotomy technique is endoscopic diskectomy Laparo-scopic transperitoneal and retroperi-toneal approaches to herniated nuclear pathology also have been introduced
Dr Mathews is Associate Clinical Professor, Department of Orthopaedic Surgery, Virginia Commonwealth University, Medical College of Virginia, Richmond, VA Ms Long is Clinical Researcher, MidAtlantic Spine Specialists, Richmond.
One or more of the authors or the departments with which they are affiliated has received something of value from a commercial or other party related directly or indirectly to the sub-ject of this article.
Reprint requests: Dr Mathews, Suite 200,
7650 Parham Road, Richmond, VA 23294 Copyright 2002 by the American Academy of Orthopaedic Surgeons.
Abstract
Hemilaminectomy with diskectomy, the original surgical option to address
intervertebral disk herniation, was superseded by open microdiskectomy, a less
invasive technique recognized as the surgical benchmark with which minimally
invasive spine surgery techniques have been compared as they have been
devel-oped These minimally invasive surgical techniques for patients with herniated
nucleus pulposus and radiculopathy include laser disk decompression,
arthro-scopic microdiskectomy, laparoarthro-scopic techniques, foraminal endoscopy, and
microendoscopic diskectomy Each has its own complications and requires a
long learning curve to develop familiarity with the technique Patient selection,
and especially disk morphology, are the most important factors in choice of
tech-nique The optimal candidate has a previously untreated single-level herniation
with limited migration or sequestration of free fragments.
J Am Acad Orthop Surg 2002;10:80-85
Minimally Invasive Techniques for the Treatment of
Intervertebral Disk Herniation
Hallett H Mathews, MD, and Brenda H Long, MS, RN
Trang 2Advances in minimally invasive
surgery relate to a number of factors:
understanding of a technique’s
abili-ty to effect nerve root
decompres-sion, development of approaches
that are based on the location of the
disk pathology, and the refinement
of diagnostic modalities to aid in
lo-cating specific disk pathology
Ad-vances in fiberoptic visualization
have been a factor, as has refined
surgical instrumentation Better
patient selection has resulted from
experience with individual
tech-niques as well as an appreciation of
technique-related complications and
outcomes In addition, improved
fluoroscopic imaging and navigation
systems have enhanced the safety
and predictability of minimally
inva-sive techniques when performed by
experienced endoscopic surgeons
Perhaps the most notable
advan-tage of minimally invasive
tech-niques is the ability they provide to
surgically address and resolve
her-niated nuclear pathology without
the morbidity associated with
inci-sion of the paraspinal muscle in
tra-ditional open techniques Enhanced
visualization of the surgical field
allows the pathology to be seen and
permits both identification and
avoidance of injury to the
neurovas-cular structures The surgical field
can be surveyed before conclusion of
the procedure, and the diskectomy
itself can be inspected and
docu-mented on videotape In addition,
these procedures generally are done
on an outpatient basis Patients
usu-ally require minimal analgesic
med-ication and have a timely return to
activities of daily living, including
work Little, if any, postoperative
rehabilitative therapy is necessary
Consequently, the overall economic
impact of minimally invasive
tech-niques in most instances is less than
that of open techniques
Disadvantages to minimally
invasive surgery for the herniated
disk are few Primarily, the
learn-ing curve for the surgeon and his
or her staff is steep Mastery of the neurovascular anatomy is required, and familiarity with the spatial ori-entation of the endoscopic field is critically important
The goal of minimally invasive techniques is either disk debulking
or selective fragment removal to alter disk morphology and subse-quently abate nerve root compres-sion Selective fragmentectomy may remove an obstructive disk herniation mechanically However, intradiscal depressurization and lavage also may improve symptoms without significant change in neural anatomy Good results have been achieved without significant change
in neural anatomy following the procedure The governing factor in considering a minimally invasive procedure is patient selection.5
Indications for Minimally Invasive Spine Surgery
Except in emergent circumstances, such as rapidly progressive neuro-logic deficits or the threat of cauda equina syndrome, 6 to 8 weeks of nonsurgical treatment with appro-priate medication and conservative care is routine before proceeding with surgical intervention The ideal candidate should have unilateral radicular pain radiating into the foot, with leg pain greater than back pain Positive straight leg raising is often present The radicular pain may be described as lancinating and/or aching Other complaints can include numbness, tingling, and weakness, along with decreased sen-sation to light touch and pin prick
Because herniation can result in canal stenosis relative to the size of the herniation, some patients com-plain of pseudoclaudication
Location of the herniation dic-tates the appropriate minimally invasive approach Magnetic reso-nance imaging is the most effective radiologic test for visualizing disk
pathology and achieving a defini-tive correlation with patient presen-tation Diskography, although con-troversial, may be especially helpful
in the diagnosis when symptoms are equivocal and the pain genera-tor can be isolated through symp-tom provocation.6
Optimal candidates for
minimal-ly invasive access are those with a single-level herniation that has not previously undergone surgery and occupies <50% of the spinal canal, with limited migration or sequestra-tion of free fragments Scarring or other deviations in normal anatomy that may have resulted from previ-ous surgical intervention at a de-fined level are a relative contrain-dication to minimally invasive revi-sion surgery for disk herniation recurrence Developmental spinal stenosis and minimal disk hernia-tion presenting as only a small bulge also are relative contraindications
Techniques, Complications, and Results
Early Techniques
Open microdiskectomy, the benchmark procedure with which percutaneous and minimally inva-sive techniques are compared, uti-lizes a small incision and a micro-scope or loupe magnification rather than an endoscope The technique is similar to minimally invasive tech-niques in regard to patient selection and indications Compared with percutaneous techniques, especially foraminal epidural endoscopy, diskectomy is limited in its ability to address sequestered free fragments with significant migration Open diskectomy allows the surgeon to visualize the pathology and neu-rovascular anatomy, but in this tech-nique, the anatomic structures often must be gently manipulated (rather than avoided) for optimal access to the disk–nerve root compression interface The overall rate of
Trang 3suc-cessful outcomes for diskectomy has
been reported to range from 76% to
100%.7 Other studies demonstrate
that the rate and type of
complica-tions are similar to those of
mini-mally invasive spine surgery.8 The
most common complications are
neurovascular trauma, diskitis, and
cerebrospinal fluid leak.8,9
Diskec-tomy, like minimally invasive
tech-niques used to treat lumbar disk
herniations, has a learning curve
that, once achieved, must be
main-tained through regular application
Percutaneous techniques currently
have few applications, given the
more advanced procedures now
ac-cepted These early blind techniques
addressed central and posterocentral
pathology and were nonselective:
their basic mechanism of action was
a debulking of the nucleus pulposus
without directly addressing the
her-niation The result was
depressur-ization and relief of tension on
annu-lar fibers as well as involution of the
nucleus, essentially withdrawing the
compressive nerve pathology back
into the annular confines.10
Chemonucleolysis caused
dena-turization of the intervertebral
nucleus and a relative disk
debulk-ing Allergic reactions and even
anaphylaxis occurred in
approxi-mately 1% of patients treated with
chymopapain.11 Postoperatively,
radiographs of treated patients
often demonstrated disk space
col-lapse.12 In some centers,
chemo-nucleolysis currently is used in
con-junction with epiduroscopy in the
treatment of migrated or
seques-tered free fragments The technique
is more popular in Europe than in
the United States.11 Gogan and
Fraser13 reported an 80% success
rate at 10-year follow-up with
chemonucleolysis, and similar
suc-cess has recently been reported in a
European study.14 However,
nota-ble neurovascular complications
and transverse myelitis, probably
resulting from the inadvertent
intro-duction of chymopapain
intrathe-cally, has substantially decreased the use of chemonucleolysis
Percutaneous nucleotomy and automated percutaneous nucleotomy are both blind, intradiscal, nonselec-tive techniques for disk debulking
or deflation with disk involution from the site of neural compression
Complications have included
trau-ma or injury to neural or vascular structures, diskitis, and cerebro-spinal fluid leaks, as well as the po-tential for bowel perforation In one multicenter study,15 success rates for automated percutaneous diskec-tomy in carefully selected patients ranged from 55% to 85% Because these results are less satisfactory than those achieved with other tech-niques, this procedure has largely fallen out of favor
Laser disk decompression is a blind, nonspecific disk depressur-ization procedure resulting in grad-ual withdrawal of disk compression
on the nerve root Because it is a blind procedure, complications have paralleled those of the blind nu-cleotomy techniques An additional concern related to complications early in the use of laser disk decom-pression was the heat associated with direct-firing wavelengths
delivered by probes in proximity to neurovascular structures.16 In cen-ters where this technique is still in use, successful outcomes have ranged from 50% to 89%,10,17 imply-ing various outcomes in nonprospec-tive, nonrandomized studies with resulting inconsistent data Recent application of the holmium:YAG cool, side-firing laser in conjunction with endoscopic visualization appears to be a promising option in selected patients.16
Recent Techniques
The combination of fiberoptic technology with arthroscopic can-nulae led to the development of rigid discoscopes and rod-lens endoscopes, and thus to visualized selective microdiskectomy Arthro-scopic microdiskectomy can be either uniportal or biportal (Fig 1), depending on the targeted herniated pathology Small central herniations can be approached uniportally; bi-portal access is dictated for large central herniations and subligamen-tous and sequestered herniations Dedicated instrumentation sized to arthroscopic application allows for manual or automated selective disk decompression at the pathologic
Figure 1 Arthroscopic microdiskectomy technique: the biportal approach to a paracentral
disk herniation The instrument enters through the right foramen to allow access to the disk herniation Triangulation occurs within the disk nucleus (Adapted with permission 12 )
R
Nucleus
L
Trang 4site Complications with this
tech-nique are minimal, but infection
(two cases), transient peroneal
neu-ropraxia (two cases), and transient
skin hypersensitivity (five cases)
have been reported, for a
complica-tion rate of 3% in one large series of
patients spanning 10 years.18
Theo-retic complications related to
trau-ma to neurovascular structures and
perineural/intraneural fibrosis have
not been reported The success rate
for this technique ranges from 75%
to 98%.18-21
The laparoscopic anterior
ap-proach to the lumbar spine for
pri-mary disk herniations began to be
used in the mid-1980s and early
1990s This technique allows access
to contained disk herniations, as
well as to some extruded and
mi-grated fragments, through either a
transperitoneal or retroperitoneal
approach (Fig 2) Complications
including diskitis and segmental
instability have been reported.22
Trauma to major vascular structures
is a potential complication that can
result in marked morbidity This
laparoscopic procedure requires an
approach surgeon as well as unique,
expensive instrumentation
Sur-geons also must anticipate a steep
learning curve These factors
con-tributed to long surgical times
with-out any decrease in hospital lengths
of stay This has led to surgical
costs that far exceed those of other
minimally invasive techniques.23
With an early success rate of only
69% for treatment of disk
hernia-tion, the transperitoneal approach
has now been adapted for use in
anterior lumbar interbody fusion at
L5/S1.22
Foraminal epidural endoscopy is
a diskectomy technique that
ad-dresses paramedian, foraminal, and
extraforaminal disk herniations It
can also access migrated and
se-questered free fragments in the
epidural space when they are
limit-ed to confines of the axilla and the
pedicle Such access is facilitated by
appropriately sized endoscopes with varied lens angles; foraminal and extraforaminal disk herniations are technically demanding for stan-dard microscopic techniques The foraminal endoscopic technique allows visualization of the
patholo-gy and avoidance of neurovascular
structures at risk, as well as visual-ization of the selective diskectomy and documentation of the surgical effect at the time of the procedure (Fig 3) As with arthroscopic micro-diskectomy, manual and automated instrumentation sized to the work-ing channel of the endoscope allows
Figure 2 Laparoscopic diskectomy technique R = retroperitoneal space The instruments
are inserted on the left side, with the smooth pituitary instrument traversing the retroperi-toneum through the psoas muscle The trochar needle is placed through the posterolateral approach (Adapted with permission 22 )
Figure 3 Foraminal endoscopic diskectomy technique compared with the extraforaminal
approach The foraminal approach allows direct dissection and removal of herniated material (Adapted with permission 12 )
R
R
Exiting root Herniated disc
Dura mater
Traversing root Foraminal approach
Extraforaminal approach
Transpsoas retroperitoneal approach Posterolateral
needle
Trang 5for diskectomy or fragment removal
tailored to the morphology
respon-sible for the radiculopathy The
complication rate for endoscopic
foraminal diskectomy in one large
study was 5%.24 There is potential
for trauma to neurovascular
struc-tures, diskitis, and cerebrospinal
fluid leak, although the risk is
mini-mized by the excellent visualization
The success rate has recently been
reported at 78%.25 Key to the
suc-cess of foraminal epidural
endo-scopic surgery are patient selection
and, at surgery, familiarity with the
spatial orientation and with the
anatomy at risk The learning curve
is steep, and success with this
tech-nique requires regular use.26
For-aminal epidural endoscopic surgery
has been equated to open
micro-diskectomy as “microdiscectomy
through a cannula.”26
Microendoscopic diskectomy
through the interlaminar approach
allows endoscopic intervention for a
broad range of disk pathology This
technique is indicated for all forms
of disk herniation (Fig 4) as well as
for associated pathology, such as
lat-eral recess or central canal stenosis
Microendoscopic diskectomy is
per-formed through a slightly larger
tubular distractor and thus closely
approximates open
microdiskec-tomy It requires an approach to the
pathology through the paraspinous
musculature Dilators are placed in
succession until the optimum
win-dow for surgical exposure is
achieved A tubular retractor is then
placed that allows use of a working
channel endoscope, through which
both disk and bony pathology can
be addressed The surgical system
and technique allow for attention
either intradiscally or extradiscally
in an area that can span from the
pedicle to the midline
Complica-tions are similar to those of
arthro-scopic microdiskectomy and
forami-nal epidural endoscopy; in addition,
there is the potential for cauda
equina syndrome, epidural scarring,
and segmental instability This tech-nique is appropriate not only for disk pathology previously not treated surgically but also for recurrence In their preliminary series, the devel-opers of this technique reported a complication rate of one patient in
41 (3%), with all patients reporting good to excellent results in follow-up based on modified MacNab crite-ria.27 This series included patients who underwent surgery for lateral herniations, herniations within the spinal canal, and free-fragment pathology.27
Summary
Early blind, nonspecific intradiscal techniques have been superseded
by a variety of low-morbidity, min-imally invasive surgical options that offer treatment for patients with radiculopathy secondary to disk pathology tailored to their re-spective pathologies These proce-dures provide results comparable
to those of microdiskectomy done with magnification and may poten-tially have advantages for some specific indications
Dural sac
Exiting nerve root Intervertebral
disk
L5
Herniation Central Paramedian Foraminal Extraforaminal
Figure 4 Disk herniations approachable by interlaminar techniques and selectively by other minimally invasive techniques Central: open microdiskectomy, microendoscopic diskectomy, biportal approach Paramedian: open microdiskectomy; microendoscopic diskectomy; uniportal, biportal, or foraminal approach Foraminal: open foraminal approach, microendoscopic diskectomy, endoscopic foraminal approach Extraforaminal: open far lateral approach, microendoscopic diskectomy, extraforaminal endoscopy.
L4
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