The goal of this article is to pro-vide the reader with an under-standing of lumbar stenosis as an element of the degenerative pro-cess of aging commonly seen in the older population, as
Trang 1The earliest description of lumbar
stenosis is attributed to Antoine
Portal, who in 1803 described
Òtoo-narrow vertebral canalsÓ in
hunch-backs with rickets The concept of
acquired lumbar spinal stenosis
was popularized in the 1950s by
Verbiest Since then, advances in
diagnostic and therapeutic
modali-ties, coupled with the extension of
life expectancy, have increased the
rate of detection and subsequent
operative intervention
The general incidence of
degen-erative lumbar spinal stenosis
ranges from 1.7%1to 8%.2
Symp-toms typically develop in the fifth
or sixth decade of life in association
with osteoarthritic changes in the
lumbar spine No sex
predomi-nance has been found, although degenerative spondylolisthesis associated with lumbar spinal stenosis is four times more com-mon acom-mong women.3 No associa-tion has been found with occupa-tion or body habitus
The goal of this article is to pro-vide the reader with an under-standing of lumbar stenosis as an element of the degenerative pro-cess of aging commonly seen in the older population, as well as an overview of treatment options
Basic Science
Anatomically, lumbar stenosis is usually caused by a reduction in
the space available for the neural elements due to variant osseous anatomy or filling of the spinal canal with hypertrophic tissue Three typical canal shapes have been described: round, ovoid, and trefoil (Fig 1) Trefoil canals have the smallest cross-sectional area and are associated with the highest incidence of symptomatic lumbar stenosis.4 Arnoldi et al5 classified lumbar stenosis as congenital, ac-quired, or combined (Table 1) The term Òcentral stenosisÓ is used when compression of the dural sac
is the main component ÒLateral stenosisÓ refers to compression of the nerve root in the lateral recess,
in the neural foramen, or lateral to the neural foramen.6,7
The pathophysiology of degener-ative lumbar stenosis usually begins with disk dehydration, resulting in
a loss of disk height and bulging of the anulus fibrosus and ligamentum flavum into the spinal canal These
Dr Hilibrand is Assistant Professor of Orthopaedic Surgery, Rothman Institute at Thomas Jefferson University, Philadelphia
Dr Rand is Adjunct Professor of Orthopaedic Surgery and Spine Fellow, Vanderbilt Univer-sity, Nashville, Tenn.
Reprint requests: Dr Hilibrand, Rothman Institute, 5th Floor, 925 Chestnut Street, Philadelphia, PA 19107.
Copyright 1999 by the American Academy of Orthopaedic Surgeons.
Abstract
Degenerative lumbar stenosis is a common cause of disabling back and lower
extremity pain among older persons The process usually begins with
degenera-tion of the intervertebral disks and facet joints, resulting in narrowing of the
spinal canal and neural foramina Associated factors may include a
developmen-tally narrow spinal canal and degenerative spinal instability Nonoperative
management includes restriction of aggravating activities, physical therapy, and
anti-inflammatory medications If nonoperative treatment has failed, surgical
treatment may be appropriate Decompression should be performed so as to
ad-dress all clinically relevant neural elements while maintaining spinal stability If
instability is present, autogenous intertransverse bone grafting is recommended.
There may be an advantage to augmenting some of these procedures with
in-ternal fixation Surgical success rates as high as 85% have been reported, but
may be compromised by inadequate decompression, inadequate stabilization, or
medical comorbidities Short-term follow-up data indicate that operative
man-agement provides more effective relief than nonoperative treatment, but
prospec-tive studies comparing the effects of nonoperaprospec-tive and operaprospec-tive interventions on
the long-term natural history of lumbar spinal stenosis are needed.
J Am Acad Orthop Surg 1999;7:239-249 Diagnosis and Management
Alan S Hilibrand, MD, and Nahshon Rand, MD
Trang 2changes alter the loading of the
facet joints, which together with the
intervertebral disk form the
three-joint spinal motion segment
Further degeneration leads to facet
arthrosis with sclerosis and
osteo-phytic overgrowth The most
com-mon result is that as the nerve roots
traverse the lateral recesses, they
may be encroached on by
hyper-trophic facet joints, infolded
liga-mentum flavum, and a bulging
anu-lus These degenerative changes
can also cause root stenosis in the
neural foramen The
anteroposteri-or diameter of the fanteroposteri-oramen is
reduced by the bulging anulus
ante-riorly and the hypertrophic facets
posteriorly, while the foraminal
height is reduced by the loss of
intervertebral disk height and
asso-ciated facet subluxation.8
The degenerative process is
sometimes accompanied by the
development of segmental
instabil-ity Degenerative changes in the
supporting structures of the spinal
motion segment, including
com-promise of the facet joints and
cap-sular ligaments, may cause higher
mechanical stress across the degen-erated anulus, leading to the devel-opment of dynamic subluxation or spondylolisthesis.6 As abnormal motion develops within a degener-ated motion segment, it exacerbates nerve root irritation in the stenotic lateral recess and foramen
The sequence of
neuropatholog-ic changes that result from stenosis
of the lumbar spinal canal have been investigated in animal stud-ies Delamarter et al9employed a dog model in which they created varying degrees of stenosis and demonstrated deleterious effects on the neural elements by increasing the degree of the stenosis They found that cortical evoked poten-tials were highly sensitive to this compression and were affected long before any clinical signs oc-curred They also demonstrated venous congestion and arterial con-striction around compressed nerve roots and dorsal root ganglia The result was blockage of axoplasmic flow, with resulting edema, demye-lination, and wallerian degenera-tion of motor and sensory fibers
Other authors have shown that sensory fibers are more susceptible
to pressure and slower to recover than motor fibers,10 which may explain the presence of subjective sensory changes in the absence of objective physical findings
The mechanism of pain produc-tion in lumbar spinal stenosis re-mains unclear Although many older patients have degenerative changes in their lumbar spines, few have any symptoms Arnoldi et al5
suggested that increased venous pressure may explain the symp-toms of neurogenic claudication Others have suggested that narrow-ing of the spinal canal may lead to a reduction in blood supply to the cauda equina, resulting in ischemic changes from the diffusion of metabolites.11 These changes may stimulate the sinuvertebral nerve or lead to secretion of pain mediators, such as substance P, from the dor-sal root ganglion Perineural in-flammation of unknown origin may also result in pain generation
Clinical Presentation
Symptomatic degenerative lumbar stenosis usually has an insidious onset and a slow rate of
progres-Round
Trefoil
Ovoid
Fig 1 The three typical shapes of the spinal canal Trefoil canals have the smallest
cross-sectional area.
Table 1 Classification of Lumbar Spinal Stenosis
Congenital (developmental) stenosis Chondrodystrophy
Idiopathic Acquired stenosis Degenerative Spondylolytic Iatrogenic Posttraumatic Miscellaneous Combined (degenerative changes superimposed on a congenitally narrow spinal canal)
Trang 3sion At initial presentation, most
patients have a long history of back
pain in the lumbar region with
recent development or progression
of lower-extremity pain
Discom-fort in the back, buttocks, and/or
lower extremities is the most
com-mon complaint Symptoms are
usually exacerbated by standing,
walking, and exercising in an erect
posture, which results in the
devel-opment of pain, tightness,
heavi-ness, and subjective weakness in
the legs.12 This symptom complex,
referred to as Òneurogenic
claudi-cation,Ó is rapidly relieved by
sit-ting down or leaning forward
Cycling, which involves forward
flexion, is usually tolerated by
pa-tients with lumbar stenosis
Pain-less motor claudication, deficits in
proprioception leading to gait
dis-turbances, and bowel and bladder
dysfunction are relatively
uncom-mon
Amundsen et al12reported that
the most common symptoms in
pa-tients with lumbar spinal stenosis
were back pain (prevalence of 95%),
claudication (91%), leg pain (71%),
weakness (33%), and voiding
dis-turbances (12%) In 70% of the
patients in their study, the pain
intensity was equally distributed
between the back and the lower
extremities; 25% had
predominant-ly leg pain Radicular pain was
unilateral in 58% and bilateral in
42% The radicular pattern
corre-sponded to the L5 root in 91%, S1 in
63%, L1-L4 in 28%, and S2-S5 in 5%
In that study, 47% of the patients
had double-root involvement, 35%
had single-root involvement, 17%
had triple-root involvement, and
1% had quadruple-root
involve-ment
Even in the presence of
symp-toms, there may be few associated
physical findings A thorough
examination is required, however,
to rule out other conditions that
may cause referred pain to the
lum-bar region or lower extremities
Abnormalities in gait may be related
to the lumbar stenosis, although the possibility of cervical myelopa-thy or an intracranial disorder should also be considered, espe-cially in patients with a positive Romberg test Patients frequently assume a ÒsimianÓ posture, with translation of the shoulders anterior
to the pelvis
Tenderness, if present, is usually noted on palpation of the sciatic notches or the lumbosacral or sacroiliac region Lumbar lordosis
is generally reduced, and range of motion is diminished There are usually no signs of nerve root ten-sion, although lower-extremity pain may be reproduced by forci-ble lumbar extension The straight-leg-raising test may be positive if a concurrent disk herniation or nerve root entrapment is present The remainder of the neurologic exami-nation is usually normal, at least when the patient is at rest If mus-cle weakness is present, it is most often in the L5 root distribution
Postexercise examination may reveal greater motor weakness and help establish the diagnosis of lum-bar stenosis
Sensory examination should include vibration and propriocep-tion testing in addipropriocep-tion to pin-prick testing Responses may be altered
by spinal stenosis or peripheral neuropathy, as may be seen in dia-betic patients Deep tendon reflexes may be diminished due to involve-ment of the L3, L4, or S1 nerve roots Loss of deep tendon reflexes
is common among the elderly
Evaluation of hip and knee range of motion, joint irritability, and peripheral pulses should be documented Amundsen et al12
reported sensory changes in 51% of patients with lumbar stenosis; re-flex changes in 47%; lumbar ten-derness in 40%; reduced spinal mobility in 36%; positive straight-leg-raising test in 24%; weakness in 23%; and perianal numbness in 6%
Differential Diagnosis
It is essential to rule out other con-ditions that may present with pain
in the low back and/or lower extremity (Table 2) Peripheral vas-cular claudication should be differ-entiated from neurogenic claudica-tion Both conditions are most prevalent in the older population and may coexist Symptoms of vas-cular claudication are reproduced at
a consistent level of exertion (e.g., walking two blocks) These symp-toms are most commonly described
as cramping or tightness in the large muscle groups of the buttock, thigh, and leg Peripheral vascular disease will result in diminished peripheral pulses; therefore, in patients with buttock, thigh, or leg pain, vascular studies should be obtained, with determination of ankle and brachial indices Aortic aneurysms are a less common source of low back pain but have serious consequences They may be palpable on examina-tion, and can be assessed with abdominal ultrasonography The
Table 2 Differential Diagnosis of Lumbar Spinal Stenosis
Vascular conditions Peripheral vascular disease Aortic aneurysm
Musculoskeletal diseases Degenerative arthritis of the hip Degenerative arthritis of the knee Pelvic and sacral disorders Neurologic disorders Diabetic neuropathy Peripheral compressive neuropathy Cervical myelopathy
Amyotrophic lateral sclerosis Demyelinating disease Other
Renal disorder Retroperitoneal tumors Depression
Litigation-related issues
Trang 4aorta can frequently be visualized
on axial spinal imaging
Osteoarthritis of the hip may be
associated with buttock pain, a
com-mon complaint in patients with
lum-bar stenosis These patients most
commonly relate their symptoms to
weight bearing on the affected limb,
although radiation therapy to the
groin or the anterior aspect of the
thigh may be a factor with both hip
arthritis and stenosis of the upper
lumbar spine Hip irritability and
diminished range of motion,
espe-cially in internal rotation and
abduc-tion, are commonly seen with
degenerative arthritis of the hip
Peripheral neuropathy, most
commonly the result of diabetes
mellitus, is another cause of
lower-extremity complaints in the elderly
Generally, peripheral neuropathy
presents with dysesthesias and
paresthesias rather than
activity-and position-related claudication
The anatomic distribution of
symp-toms may help distinguish these two
entities: in stenosis, sensation is
more likely to be diminished in a
dermatomal distribution; in contrast,
diabetic neuropathy is characterized
by a Òstocking/gloveÓ distribution
Electromyography and nerve
con-duction studies are helpful in
differ-entiating the two entities
Less common diagnoses, such as
renal infections and fevers,
retro-peritoneal tumors, and sacral or
presacral lesions should be
consid-ered as well It should also be
borne in the mind that certain
nonorganic factors, such as
depres-sion and involvement in litigation,
may enhance the pain response
Diagnostic Modalities
The primary role of imaging studies
is to confirm the clinical diagnosis
of lumbar stenosis, although
ad-vanced imaging studies are also
essential for preoperative planning
Upright plain radiographs are
nec-essary to exclude pathologic condi-tions of the spine, such as tumor, infection, and fracture The films may demonstrate hypertrophic facet joints narrowing the interlaminar space, but these plain-radiographic findings are not diagnostic of spinal stenosis Dynamic views should be obtained to identify associated in-stability, such as that due to spon-dylolisthesis, scoliosis, or other spinal deformity
In patients with signs and symp-toms consistent with spinal steno-sis, magnetic resonance (MR) imag-ing or postmyelographic computed tomography (CT) is needed to con-firm neural element compression
Until the advent of MR imaging, the most widely utilized radiologic technique for evaluating spinal stenosis was myelography in com-bination with CT On the myelo-gram, nerve root entrapment in the lateral recess or central canal steno-sis is demonstrated by the level of cutoff of contrast material The postmyelographic CT images can then be used to identify the bone or soft tissue at each level that must
be removed for decompression
Using myelography and CT, Bolen-der et al4 correlated the degree of symptomatic lumbar stenosis with the anteroposterior diameter of the dural sac A sac narrower than 10
mm was usually associated with clinical symptoms Herno et al13
also found that myelographic evi-dence of complete cutoff of contrast material and severe stenosis corre-lated with better surgical outcome
A disadvantage of myelography is that it requires injection of contrast medium into the spinal canal; post-injection spinal headache is rela-tively common
Magnetic resonance imaging is a noninvasive technique that can also define neural element compression through cross-sectional axial and sagittal imaging This very sensitive method of evaluation should be used to confirm a clinical diagnosis
of lumbar stenosis In one study,14
21% of asymptomatic individuals aged 60 to 80 years had MR imaging evidence of lumbar stenosis Modic
et al15 prospectively found 79% agreement between the severity of lumbar spinal stenosis noted at surgery and the postmyelographic
CT findings, compared with 77% agreement with MR findings Two advantages of plain myelography over MR imaging include the ability
to evaluate dynamic neural element compression on flexion-extension views and the improved definition
of nerve root anatomy in scoliotic patients
Riew et al16 recently compared the relative contributions of MR imaging and postmyelographic CT
in surgical planning for patients with lumbar stenosis The four academic spine surgeons who par-ticipated expressed a general pref-erence for MR imaging over post-myelographic CT for preoperative planning However, the surgical plans derived from review of the postmyelographic CT study alone were much closer to those derived from both studies together than were the plans derived from a review of the MR study alone Although the authors noted that the two modalities provided com-plementary information and were both important, they concluded that postmyelographic CT is supe-rior to MR imaging as a single study for the preoperative plan-ning of decompression for lumbar spinal stenosis
Electrophysiologic studies are rarely useful, except in identifying the presence and source of a peripheral neuropathy About 80%
of patients with symptomatic lum-bar stenosis will demonstrate elec-tromyographic changes,17 usually consistent with single or multiple radiculopathies The presence of these changes supports the diagno-sis of lumbar spinal stenodiagno-sis, al-though their absence does not
Trang 5exclude the diagnosis
Somato-sensory evoked potentials (SSEPs)
and dermatomal SSEPs may
pro-vide additional information by
identifying changes in the sensory
component of peripheral nerves or
in the dermatomes of the lower
ex-tremities.10
Overview of Treatment
Options
The prevalence of lumbar spinal
stenosis is increasing with the aging
of the population However, many
persons who have degenerative
changes consistent with lumbar
stenosis are asymptomatic For
those with symptomatic lumbar
stenosis, the natural history has been
shown to be relatively stable in mild
to moderate cases Johnsson et al18
studied the progression of
symp-toms over 4 years in 32 patients with
lumbar stenosis who either refused
or were not medically cleared for
decompressive surgery The
symp-toms of 70% of the patients were
un-changed at follow-up, with half of
the remainder better and half worse
Although the physical findings were
improved in almost half of the
pa-tients, 38% had progression of
elec-tromyographic changes In the
shorter term, patients in the Maine
Lumbar Spine Study (Part III) who
were treated nonoperatively
re-mained symptomatically stable but
did not show any significant clinical
improvement.19
Appropriate candidates who do
not improve with nonoperative
in-terventions are likely to realize
major benefits from decompressive
surgery if they have moderate to
severe lumbar stenosis The
litera-ture supporting operative treatment
of lumbar stenosis has been shown
to have many methodologic flaws
with respect to indications for
surgery, surgical approaches, and
long-term outcome.20 Recently,
however, the results in the Maine
Lumbar Spine Study (Part III) pro-spectively demonstrated superior outcomes at 1 year for operative treatment of symptomatic lumbar stenosis compared with continued nonoperative management The preliminary results in the same co-hort demonstrated that the opera-tively treated patients maintained their superior status compared with nonoperatively treated patients even at 3-year follow-up.19 Longer prospective follow-up is needed to prove the long-term superiority of operative treatment of lumbar ste-nosis
Nonoperative Management
Nonsteroidal anti-inflammatory drugs (NSAIDs) should be part of the initial management of sympto-matic lumbar stenosis (Fig 2) At lower doses, the analgesic effect reduces musculoskeletal pain; at higher doses, NSAIDs provide an anti-inflammatory effect on nerve root and joint irritation Unfortu-nately, many elderly patients can-not tolerate the gastrointestinal and renal side effects Another option is enteric-coated aspirin, which may
be as effective, at lower cost and with fewer gastrointestinal side effects Patients taking any of these medicines should have their hepatic and renal function monitored
For patients with severe radicu-lar complaints, corticosteroids are potent anti-inflammatory agents that may reduce nerve root irrita-tion However, their benefits must
be weighed against the potential side effects, such as osteonecrosis
of the femoral head, hypergly-cemia, and gastritis In addition, steroids may adversely affect the mental status of elderly patients
Many physicians continue to prescribe narcotic analgesics for the treatment of chronic back pain and neurogenic claudication These medications are analgesic but not
anti-inflammatory They are addic-tive and have depressant effects on mood and energy level In the ab-sence of an acute fracture or meta-static cancer, they have a limited role in the treatment of patients with lumbar stenosis
Other medications used to treat stenotic symptoms include muscle relaxants, antidepressants, and calci-tonin Muscle relaxants may pro-vide short-term relief of muscle spasm, but geriatric patients may have adverse reactions Tricyclic antidepressants are useful in the treatment of chronic numbness and dysesthetic leg pain, and help estab-lish an effective sleep pattern Salmon calcitonin has been reported
as a medical treatment for neuro-genic symptoms of stenosis Al-though it may be indicated in the management of spinal stenosis re-lated to Paget disease, its efficacy has not been demonstrated in double-blinded studies.21
Physical therapy is another com-mon nonoperative intervention for symptomatic lumbar stenosis A modification of the standard low-back-pain exercise program may be used, wherein postural exercises in flexion are combined with pelvic stabilization and aerobic condition-ing The stabilization exercises are utilized to strengthen the abdomi-nal and lumbodorsal muscle groups and unload the spinal elements A program of aerobic conditioning can improve overall muscle tone and truncal balance as well as assist
in weight loss, which is important
in the treatment of lumbar stenosis
in obese individuals Patients with lumbar stenosis are ideally suited to the exercise bicycle We also en-courage walking, if tolerated by the patient Aquatic therapy can be beneficial for some patients limited
by medical comorbidities
Brace or elastic-corset immobi-lization for low back pain due to spinal stenosis is another available treatment The support from a
Trang 6brace may provide short-term relief
when back pain is related to
seg-mental instability or
spondylolisthe-sis, although it can prevent lumbar
flexion, which may limit its regular
use An elastic corset may also
assist the posterior musculature by
providing a counterforce to
contrac-tions, reducing strain Long-term
brace wear leads to truncal
decondi-tioning, however, and has therefore
fallen out of favor
Epidural steroid injection (ESI)
is an invasive modality that may be
used to treat patients with lumbar
stenosis It involves delivery of a corticosteroid preparation, such as methylprednisolone, around the stenotic cauda equina and nerve roots in order to relieve lower-extremity pain and neurogenic claudication Numerous articles have been written regarding the efficacy of ESI in the treatment of lumbar radicular syndromes; how-ever, only a few of these studies included patients with degenera-tive lumbar stenosis
Cuckler et al22performed a pro-spective, randomized, double-blind
study of epidural steroids in pa-tients with lumbar radicular syn-dromes, approximately half of whom had diagnoses of lumbar spinal stenosis In the patients with spinal stenosis, no statistically sig-nificant difference was seen in symptomatic improvement be-tween steroid and placebo injec-tions at 24-hour and 1-year
follow-up However, a similar study in
1973 by Dilke et al23demonstrated a
significant (P<0.05) improvement in
short-term pain and functional measures
In a study restricted to patients with symptomatic lumbar stenosis, Hoogmartens and Morelle24 found that 48% of patients treated with ESI demonstrated functional im-provement from their preinjection status approximately 2 years after treatment However, the patients were evaluated retrospectively and were not compared with a control group Furthermore, the authors conceded that the improvement rate was close to that of the placebo effect Nevertheless, they suggested that ESI is a good alternative to sur-gical treatment in older patients with medical comorbidities
At our center, we reserve ESI for patients with mild to moderate stenosis and major medical comor-bidities for whom medical treat-ments and physical therapy have not been efficacious If the first in-jection provides symptomatic relief, one or two additional injections are prescribed We use ESI to facilitate
a return to more aggressive truncal strengthening and aerobic condi-tioning, which may provide longer-term relief of symptoms There are, however, potential complications of ESI, including meningitis, para-paresis, arachnoiditis, and epidural hematoma.25
Other invasive modalities con-tinue to be widely used despite a lack of scientific support Facet-joint injections may provide tempo-rary relief in select patients with
Successful
Unsuccessful Successful
No further workup
No further workup
Referrals
No further workup
Advanced imaging studies
Severe
stenosis
Mild to moderate stenosis
Minimal stenosis
Unsuccessful at 6-12 weeks
Patient with lumbar stenosis
NSAIDs Physical therapy Weight loss
NSAIDs Physical therapy Weight loss
Operative
intervention
Operative intervention
Epidural steroids
Reevaluate for other causes
Fig 2 Algorithm for nonoperative management of degenerative lumbar stenosis.
Trang 7low back pain, although their
effi-cacy in lumbar stenosis has not
been shown.26 Manipulation is
another common treatment
modali-ty for back pain that has not been
proved efficacious in treating
patients with degenerative lumbar
stenosis
Operative Treatment
Not all patients for whom
nonopera-tive treatment has failed will be
sur-gical candidates However, when
nonoperative intervention cannot
restore the patient to a tolerable
quality of life, operative treatment
can be considered (Fig 3) A
thor-ough workup should identify any
associated degenerative pathologic
changes, such as spondylolisthesis,
segmental instability, or scoliosis,
that might require stabilization in
addition to decompression
Decom-pressive surgery is clearly indicated
in cases of progressive neurologic
deficit, cauda equina syndrome, and
disabling lower-extremity weakness
In addition, decompressive
treat-ment is appropriate for patients with
neurogenic claudication and/or
pain that significantly affects the
patientÕs quality of life
Previous reviews have
suggest-ed that surgical treatment of
lum-bar stenosis is successful (defined
as significant pain relief with a
return to activities of daily living)
in 80% to 85% of cases.17,27
How-ever, other authors have found a
much lower rate of successful
results, perhaps attributable to
dif-fering definitions of a Òsuccessful
result.Ó In a retrospective review 4
years after lumbar decompression,
Katz et al28 found Òsuccessful
out-comesÓ (defined as relief of pain
and no reoperation) in only 57% of
cases Factors associated with
un-successful outcomes were multiple
comorbidities, single-level
decom-pressions, and a 5% annual
inci-dence of degeneration at levels
ad-jacent to the decompression In another shorter-term follow-up study of patients who underwent surgery for lumbar stenosis, the authors identified predominating low back pain as another factor associated with poor outcomes after surgical treatment of lumbar stenosis.29
Katz et al28 have suggested that surgical results deteriorate with time However, Herno et al30 ob-served 67% and 69% successful outcomes in their patients at 7 and
13 years after lumbar decompres-sion, respectively
Preoperative planning for lum-bar decompression begins with a review of the clinical findings and evaluation with MR imaging or postmyelographic CT to precisely identify areas of neural element compression by articular processes, capsular tissue, bulging anulus, and ligamentum flavum in the lateral recesses and foramina Patients will sometimes present with multi-level disease despite well-defined neurologic deficits referable to one
or two motor roots (Fig 4) Several
authors have suggested that pro-duction of symptomatic disease may require compression of the cauda equina at more than one level.11,31,32 As a result, in some centers it is routine to address all levels of moderate or severe steno-sis visualized with postmyelo-graphic CT at the time of surgical decompression
For surgical decompression, the patient is placed in the prone knee-chest position, although the more lordotic position of the Jackson spinal table may be preferred when internal fixation is planned The lumbar spine is exposed through a midline incision of skin, subcuta-neous tissue, and thoracolumbar fascia Subperiosteal exposure is carried out laterally to the facet joint capsules, which are preserved, and the lateral extent of the pars interarticularis is identified
Compressive elements are re-moved by undercutting the facet joints and pars interarticularis, tak-ing care to preserve at least 50% of the facet joint surface area and approximately 1 cm of the dorsal
No spondylolisthesis Spondylolisthesis
Stable
Fusion ± instrumentation
Fusion ± instrumentation
Fusion ± instrumentation
No or minimal scoliosis
Significant scoliosis
Lumbar decompression only
Fusion
in situ
Surgical candidate
Unstable (>3 mm on dynamic films)
Stable Unstable (grade II or
higher or >3 mm on dynamic films)
Fig 3 Algorithm for operative management of degenerative lumbar stenosis.
Trang 8surface of the pars.33 The
effective-ness of the decompression is
checked by carefully mobilizing the
compressed root with a No 4
Penfield elevator and probing the
neural foramen with an angled
dural elevator Foraminotomy is
usually necessary in patients with
significant degenerative stenosis
This may require removal of
por-tions of the superior articular
pro-cess of the caudal vertebra, a portion
of the pars interarticularis, the
anu-lus fibrosus, or the pedicle of the
superior vertebra This aspect of the
decompression may be
accom-plished with a Kerrison rongeur,
small curettes, or a high-speed burr
When the root can be easily
mobi-lized from the pedicle and an angled
dural elevator can be easily passed
out the foramen around the root, the
decompression is adequate In the
absence of instability, posterolateral
grafting has not been shown to
improve outcome.34
Degenerative spondylolisthesis
is a radiographic finding often associated with spinal stenosis at the L4-5 level, especially in women (Fig 5) In 1991, Herkowitz and Kurz35 published a controlled prospective study of patients with lumbar stenosis and degenerative spondylolisthesis who were ran-domized to either decompression alone or decompression with in situ intertransverse autogenous bone grafting The authors demon-strated significantly better out-comes in patients who underwent decompression and grafting
proce-dures (P = 0.0001).
In another study, the same group studied patients with steno-sis and degenerative spondylolis-thesis treated by decompression and grafting, prospectively com-paring outcomes with and without internal fixation.36 Although radio-graphic evidence of arthrodesis was significantly more likely with
internal fixation (P = 0.0015), the
clinical outcome was not improved The authors concluded that even in the absence of a solid fusion, the intertransverse bone grafting pro-cedure stiffened the spine suffi-ciently to relieve nerve root irrita-tion
In some patients with spinal stenosis, dynamic lateral radio-graphs may indicate segmental instability, defined as more than 3
mm of motion between vertebrae on dynamic views.37 We routinely obtain preoperative prone and supine lateral radiographs of all lumbar stenosis patients If the films document segmental instability, decompression with intertransverse bone grafting is recommended The use of internal fixation in this group
of patients remains controversial; some surgeons include fixation in the physically active patient with at least 5 mm of motion and localized mechanical complaints
Fig 4 Images of a patient who presented with chronic neurogenic claudication, bilateral lower-extremity numbness, and significant
weakness of the L4 and L5 muscle groups preventing ambulation A, Lateral radiograph demonstrates anterolisthesis at L4-5 and retrolis-thesis at L3-4 Note obliteration of L3-4 disk space and narrowing of neural foramen (arrow) B, Myelogram shows cutoff of contrast material from the L2-3 level through the L4-5 level C, Postmyelographic CT at L3-4 level shows absence of contrast material secondary to
proximal cutoff, with hypertrophy of the ligamentum flavum, degenerated facets, and congenitally narrow (trefoil-shaped) spinal canal.
D,Anteroposterior radiograph obtained 6 weeks postoperatively demonstrates wide decompression from L2 through L5, with complete resection of the right L3 pars region (arrows) due to severe foraminal stenosis Note early consolidation of autogenous iliac-crest bone graft in intertransverse gutters.
2
3
4
5
2 3
4
5
2
3
4 5
Trang 9Patients undergoing revision
lum-bar decompression should receive
special attention Frequently, there is
persistent lateral recess and/or
foraminal stenosis not addressed at
the index procedure, which should
be widely decompressed at the
revi-sion operation Some patients may
have iatrogenic spondylolisthesis,
scoliosis, or postlaminectomy
insta-bility This can lead to significant
coronal and/or sagittal
decompensa-tion, which must be addressed at
reoperation We routinely evaluate
candidates for revision lumbar
decompression with 3-ft-long
stand-ing radiographs If patients have
coronal decompensation or loss of
lumbar lordosis, intertransverse
bone grafting and internal fixation
may be helpful to restore anatomic
sagittal coronal alignment
Whether operative treatment of
recurrent lumbar stenosis can be as
successful as primary procedures
continues to be controversial
Herno et al38 found that revision
procedures were as successful as
primary procedures when patients
presented at least 18 months after
the index procedure with few
comorbidities Overall, however, outcomes were significantly worse for revision procedures than for pri-mary procedures in the study
pop-ulation (P<0.0017) Stewart and
Sachs39reported that at an average follow-up of 4 years, 72% of their patients who had undergone repeat decompression were able to return
to their preinjury work status, 83%
of those treated with grafting went
on to a solid arthrodesis, and none
of the 39 patients required another procedure In general, better out-comes are associated with a pain-free interval after the initial proce-dure, and worse outcomes are asso-ciated with periradicular fibrosis
Complications
Although operative treatment can improve the quality of life of patients with lumbar stenosis, it can also be associated with major complications, which should be discussed with the patient Postop-erative complications may include epidural hematoma, instability fol-lowing wide decompression in the
absence of bone grafting, nonunion
of the graft with failure of any con-comitant instrumentation, and the need for future surgery due to the development of new disease at adjacent levels
Any lengthy procedure in an elderly patient under general anes-thesia poses risks to the cardiovascu-lar and respiratory systems These procedures are often associated with major blood loss, which may require transfusion and invasive cardiac monitoring
Despite antibiotic prophylaxis and strict observation of sterile technique, infection and sepsis re-main a risk, especially when inter-nal fixation is applied A recent historical cohort study of patients undergoing lumbar decompression and arthrodesis, with or without internal fixation, revealed an infec-tion rate of 2% to 3% for degenera-tive spondylolisthesis.40
In the same study,40the incidence
of nerve root injury from placement
of bone screws in the pedicle for degenerative spondylolisthesis was 0.4% Nerve root injury can occur as
a result of manipulation of a severely
Fig 5 Images of a patient who presented with lower-back and bilateral lower-extremity numbness with ambulation A, Lateral radio-graph shows grade I degenerative spondylolisthesis at L4-5 B, Myelogram shows truncation of the column of contrast material and bilat-eral fifth-root cutoff (arrows) at the level of the spondylolisthesis C, Postmyelographic CT scan demonstrates severe spinal stenosis at the level of the spondylolisthesis D, Anteroposterior radiograph obtained 6 weeks postoperatively demonstrates L4 decompressive
laminec-tomy and intertransverse bone grafting (arrows) The patient was asymptomatic.
4
5
4
4-5
5
4
5
Trang 10compressed nerve root or the use of
internal fixation Although there are
no large clinical studies that
specifi-cally assess the neurologic
complica-tions of decompressive lumbar
surgery, a recent review by Wang et
al41 of the data on 641 patients
revealed an incidence of dural tears
of 13.7%; however, half of the
opera-tions in that series were revisions
Summary
Degenerative lumbar stenosis is a
common cause of back and leg pain
in older patients It usually results
from degeneration of the lumbar
motion segments, which causes insidious compression of the neural elements Only a small proportion
of the elderly population will have symptoms that merit referral to an orthopaedic surgeon Most patients will obtain symptomatic improve-ment with medication and physical therapy and not require operative intervention However, it has not been shown that any nonoperative treatment can alter the relatively stable natural history of the disease
The findings from the Maine Lumbar Spine Study19 suggest that surgical treatment can improve on the natural history of lumbar steno-sis at short- to intermediate-term
follow-up If nonoperative treat-ment has failed and operative man-agement is elected, it is crucial that all pathologic changes be addressed
at surgery An intertransverse grafting (fusion) procedure should
be included if there is any preoper-ative or intraoperpreoper-ative evidence of instability Although the applica-tion of internal fixaapplica-tion increases the likelihood of successful ar-throdesis, further study is needed
to determine which patients will benefit Questions regarding the long-term clinical outcome of surgi-cal treatment of lumbar spinal stenosis require prospective studies for clarification
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