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Lumbar Spinal Stenosis
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46
JasonPuiYinCheung andKennethM.C.Cheung
46.1 Definition
Lumbar spinal stenosis should be differentiated into clinical and/or radiological stenosis. Clinical stenosis refers to the presence of radiculopathy, neurogenic claudication, or lower limb neurological decit. Radiological stenosis refers to narrowing of
the spinal canal with the compromise of the dural sac and the nerve roots, due either
to developmental narrowing or progressive degeneration or a combination of both.
Developmental stenosis (Fig.46.1) is due to maldevelopment of the neural arch,
while degenerative stenosis is a result of progressive spinal segment degeneration,
starting with the loss of disc height, disc bulging, facet joint, and ligamentum avum hypertrophy. These features contribute to canal stenosis, and the location of
pathology can be classied and is illustrated in Tab le46.1 (Ta b le 46.1).
46.2 Natural History
The natural history of spinal stenosis is quite variable. Radiological stenosis is not
necessarily accompanied by symptoms. A general trend observed is that over a
period of 2 to 5 years after the initial presentation of symptoms secondary to spinal
stenosis, approximately 20% of patients worsen with nonoperative treatment, 40%
Supplementary Information The online version contains supplementary material available at
[https://doi.org/10.1007/978- 3- 030- 80356- 8_46].
J. P. Y. Cheung · K. M. C. Cheung (*)
Department of Orthopaedics and Traumatology, The University of Hong Kong,
Hong Kong, China
e-mail: cheungmc@hku.hk
© The Author(s), under exclusive license to Springer Nature
Switzerland AG 2022
A. Şenköylü, F. Canavese (eds.), Essentials of Spine Surgery,
https://doi.org/10.1007/978-3-030-80356-8_46
275
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Fig. 46.1 Developmental
spinal stenosis as
evidenced by multilevel
short pedicles
J. P. Y. Cheung and K. M. C. Cheung
Tab le 46.1 Classication of spinal stenosis by location
Classication
Central
stenosis
Lateral
recess
stenosis
Foraminal
stenosis
Location Compression
Narrowed central zone of the
spinal canal
Narrowing of the subarticular
recess causing nerve root
compression
Neuroforamen anteriorly
bounded by the disc and end
plate, posteriorly by the pars
interarticularis, and superiorly
and inferiorly by the pedicles
Pathology
Dural sac Anterior: central disc
herniation
Posterior: inferior articular
facet hypertrophy and
ligamentum avum
hypertrophy
Traversing
nerve root
Exiting nerve
root
Anterior: posterolateral disc
herniation
Posterior: Superior articular
facet and ligamentum avum
hypertrophy
Far lateral disc herniation,
overriding superior articular
process
46 Lumbar Spinal Stenosis
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Tab le 46.2 Pain generators in lumbar spinal stenosis
Leg pain/
radiculopathy
Neurogenic
claudication
Direct mechanical compression of nerve root by osteophyte or disc herniation
Vascular embarrassment of blood supply
Cauda equina irritation from exercise-induced ischemia
Small intraneural arterial occlusion
Venous congestion
277
stay the same, and 40% improve [1]. Typically, over a period of 2–3 years, patients
with moderate stenosis may be treated without surgery, because acute deterioration
is uncommon. Regardless of the decreased walking tolerance and gait disturbances,
most patients still lead active lives.
46.3 Physical Examination
Patients may present with a combination of radiating leg pain and/or back pain,
weakness, and sensory change, with loss of ankle or knee jerk reexes due to compression of segmental nerve roots (Tab le46.2) (Video 46.4) [2]. Lumbar extension
on physical examination can elicit back or leg pain, but the extension position
should be held for at least 30s in order to provoke such symptoms. Objective motor
and sensory loss should pinpoint the specic nerve root involved.
46.4 Imaging
Plain standing radiographs can demonstrate spondylolisthesis, disc space narrowing, end plate sclerosis, osteophytes, and facet hypertrophy. Lateral dynamic exion
and extension radiographs can determine whether spondylolisthesis (Chap. 47) is
demonstrating instability. Whole spine standing radiographs are also used to assess
the sagittal alignment. Lateral recess and central canal stenosis can be easily
assessed on axial T2-weighted magnetic resonance imaging as a trefoil-shaped spinal canal (Fig.46.2). Foraminal nerve root compression is identied as a complete
obliteration of the fat in the foramen on T1-weighted images. Nerve root sedimentation (Fig.46.3) to the dorsal section of the dural sac as a result of gravity is expected
for a patient in supine. The lack of sedimentation is a positive sign of lumbar spinal
stenosis.
46.5 Differential Diagnosis
Lower limb ischemia is an important differential diagnosis. The vascular examination should be performed including observation for trophic changes in the skin and
nails of the lower limbs and diminished distal pulses. Other conditions such as cervical myelopathy (Chap. 43) and hip osteoarthritis should be ruled out. Examination
of the upper limb neurology, gait instability, and brisk reexes should distinguish
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Fig. 46.2 Obliterated
cerebral spinal uid signal
with a trefoil-shaped canal.
Compression is by disc
herniation anteriorly and
hypertrophic ligamentum
avum posteriorly
Fig. 46.3 Nerve root
sedimentation sign
J. P. Y. Cheung and K. M. C. Cheung
46 Lumbar Spinal Stenosis
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279
any cervical cord lesions. Patients should be observed while walking to detect any
unusual limping, and the hip should be examined.
46.6 Treatment Options
Management of spinal stenosis involves relief of back and leg pain, prevention of
deterioration and recurrence of symptoms, and improvement of function such as
quality of life and walking distance. Conservative management is commonly offered
rst, and surgery is indicated if conservative measures fail to improve symptoms or
if they persist and in cases of cauda equina syndrome where a delay of treatment
may cause irrecoverable neurological, bladder, and bowel decits.
Nonoperative management includes avoidance of spine extension posture, core
muscle strengthening, and physiotherapy. Some well-known physiotherapy treatment regimens include elastic lumbar binder, physical therapy, cryotherapy, heat
therapy, acupuncture, ultrasound, transcutaneous electrical nerve stimulation, and
lumbar traction, although most only provide temporary relief. Medications include
nonsteroidal anti-inammatory drugs (NSAIDs), gabapentin, vitamin B12, and calcitonin, but evidence for their utility is weak. Epidural and selective nerve root
blocks can be diagnostic and therapeutic.
Surgery is usually helpful for leg symptoms, but back pain associated with spondylosis or root compression may not always improve. The actual surgical procedure
is dependent on the pathoanatomy. Decompression is by laminotomy or laminectomy. Removal of the ligamentum avum, medial facetectomy, and removal of
osteophytic ridge adjacent to the disc space is usually sufcient to decompress the
central canal and traversing nerve roots (Fig.46.4). Usually, the medial one-third to
half of the facet is removed. Any further lateral can result in instability of the spinal
segment. Discectomy is also performed for extrusion or protrusion that compresses
the neural elements. Foraminal decompression is achieved by undercutting hypertrophic facet joints. The nerve root and thecal sac should be visualized to avoid
nerve root or dural injury. Patency of the entire nerve root should be conrmed
through the neuroforamen.
Fig. 46.4 Ligamentum
avum excision with its
characteristic yellow
appearance in the lower
right corner
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J. P. Y. Cheung and K. M. C. Cheung
46.7 Expected Outcomes
Nonoperative management is helpful for symptom control, especially pain. Surgery
is often required in patients with neurogenic claudication and neurological decit.
Surgery usually leads to good improvement of pain, function, and quality of life
(Video 46.1).
46.8 Potential Complications
Inadequate decompression and wound infections are the most common complications. Dural tears may occur and should be managed intraoperatively. Injury to the
nerve root is rare. Reoperation rates at the adjacent segment are common (21.7%) in
patients with developmental spinal stenosis [3].
46.9 What Should Patient andFamily Know?
Lumbar spinal stenosis is a common disease affecting an aging population. Many
patients lead functional lives despite the disease. Surgery is recommended if there
are neurological decits or if conservative treatment fails. Surgical treatment is not
complex, and patients often experience good relief of symptoms.
Further Readings
1. Johnsson KE, et al. The natural course of lumbar spinal stenosis. Clin Orthop Relat Res.
1992;279:82–6.
2. Tomkins-Lane C, etal. ISSLS prize winner: consensus on the clinical diagnosis of lumbar spinal
stenosis: results of an international Delphi study. Spine (Phila Pa 1976). 2016;41(15):1239–46.
3. Cheung PWH, etal. The inuence of developmental spinal stenosis on the risk of re-operation
on an adjacent segment after decompression-only surgery for lumbar spinal stenosis. Bone
Joint J. 2019;101-B(2):154–61.
Degenerative Instability
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47
Yat-WaWong
47.1 Definition
Degeneration of the intervertebral disc reduces its capability to resist loading in all
directions. Extra stress is then imposed on the facet joints, resulting in degeneration.
With the progression of disc and facet joint degeneration, segmental instability
develops, and the proximal vertebra slips anteriorly on the adjacent distal vertebra,
known as degenerative spondylolisthesis. It commonly occurs at L4/L5, but it may
also occur at other segments.
47.2 Natural History
Radiological instability is not necessarily symptomatic. With the same radiological
ndings, patients may be asymptomatic or present with back pain, radicular pain,
spinal claudication, or any of these combinations. Back pain can also be a continuous dull ache or mechanical in character. The latter is more suggestive of instability
but not pathognomonic. Long-term follow-up by Matsunaga (J Neurosurgery 2000)
showed that only 30% had progression of slip and 24% of patients without neurological decit had deterioration of symptoms. Osteophytes, a complete collapse of
Supplementary Information The online version contains supplementary material available at
[https://doi.org/10.1007/978- 3- 030- 80356- 8_47].
Y.-W. Wong (*)
Chief of Spine Division, The University of Hong Kong, Queen Marry Hospital,
Hong Kong, China
e-mail: yatwa@hku.hk
© The Author(s), under exclusive license to Springer Nature
Switzerland AG 2022
A. Şenköylü, F. Canavese (eds.), Essentials of Spine Surgery,
https://doi.org/10.1007/978-3-030-80356-8_47
281
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Y.-W. Wong
the intervertebral disc leading to proximal vertebral body resting on the distal vertebral body, facets hypertrophy, and ligamentum avum hypertrophy may stabilize
the motion segment (Fig.47.1a–d). For severely symptomatic patients, Weinstein
(N Engl Med 2007) reported better outcomes by surgery. In summary, natural his-
tory varies among patients. The treatment given should be tailor-made.
a
b
e
c
d
f
g
Fig. 47.1 (a and b) Standing anteroposterior and lateral radiographs showing degenerative
changes such as reduced intervertebral disc height and osteophytes. (c and d) Standing extension
and exion radiographs demonstrating no signicant instability although there was L4/5 grade II
spondylolisthesis. (e–g) T2-weighted sagittal and axial MRI showing the L4/5 spinal stenosis. The
patient presented with spinal claudication without symptoms at rest. L4/5 decompression without
fusion gave good symptomatic relief with improved walking tolerance (e–g)
47 Degenerative Instability
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47.3 Physical Examination
If patients complain of lower limb pain (or numbness/paresthesia), clinicians should
differentiate whether they are referred pain, radicular pain, or spinal claudication
(most evocative sign). Referred pain does not go beyond the knees. Radicular pain
is distributed along the dermatomes. The pain may be persistent or immediately
after ambulation. For spinal claudication, the pain or paresthesia is also distributed
along the dermatomes, but patients are relatively asymptomatic within claudication
distance. Patients tend to lean forward, and their lumbar extension movement may
be reduced due to customary lumbar exion to relieve claudication. To distinguish
spinal from vascular claudication, patients have palpable peripheral pulses, no skin
ischemic changes at the distal lower limbs, and symptoms (pain or sensory disturbance) in a dermatomal distribution.
Neurological examination is mandatory although the neurological decit is a late
presentation (Video 47.4). Genuine positive nerve tension sign is uncommon in spinal stenosis due to degenerative spondylolisthesis. A positive test suggests the sciatica is due to prolapsed intervertebral disc (Chaps. 44 and 45), which is less
common in the elderly.
47.4 Imaging
Standing anteroposterior and lateral radiographs of the lumbar spine may reveal
degenerative changes, including decreased intervertebral disc height and spondylolisthesis (Fig.47.1a, b). The degree of slip is usually Meyerding classication grade
I (less than 25% slip). Grade II (25–50% slip) is uncommon, and grade III (50% to
75% slip) or above seldom occurs in degenerative spondylolisthesis (Appendix K).
Other important ndings include congenitally short pedicles which reect narrow
spinal canal, pars defect which may indicate additional instability apart from degeneration, and sagittal malalignment; moreover, it is important to rule out rotatory dislocation between two successive spinal units. Rotatory dislocation can be “open”
when facet joints widen on one side or “closed” when facet joints narrow on the
opposite side. For patients with a loss of normal lumbar lordosis, conducting a whole
spine radiographs is important to evaluate the global spinal alignment (Chap. 50).
Dynamic radiographic examination is used to assess the degree of instability
(Fig.47.1c, d). However, there are different ways to take the dynamic views. Lateral
exion/extension radiographs can be taken in recumbent or standing position. Luk
(Spine 2003) demonstrates that the maximal slip occurs at standing exion radiograph, whereas the maximal reduction occurs at prone traction radiograph.
Magnetic resonance imaging is useful for conrming the diagnosis and how the
cauda equina or nerve roots are compressed (Fig. 47.1e–g). It can evaluate disc
pathology, hypertrophy of the ligamentum avum and facets, synovial cyst, and
facet joint inammation. However, correlation with the clinical picture is important
for management since not all patients with positive radiological ndings are
symptomatic.
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Y.-W. Wong
47.5 Differential Diagnosis
Typical spinal claudication due to degenerative spondylolisthesis is not difcult to
diagnose. It can be easily differentiated from vascular claudication. Radicular pain
occurs at rest or immediately after walking without pain-free claudication distance.
Occasionally, it can be caused by acute disc prolapse or inammation of the nerve
root itself. Their natural history and treatment strategies are different from degenerative instability. It is difcult to locate the pain source of patients with predominantly back pain and multilevel degeneration (Chap. 41). Understanding the
characteristics of patients and conducting a careful analysis of the clinical features
are the keys to avoiding poor surgical results.
47.6 Treatment Options
Most patients have the self-limited disease and do not require active intervention.
The majority of symptomatic patients respond to nonoperative treatments, such as
activity modication, simple analgesics, anti-neuropathic pain drugs (such as gabapentin and pregabalin), and physical therapy. Having an appropriate amount of
strengthening exercise, stretching, and mobilization may increase the functional
capability and pain tolerance. Injections such as epidural steroids or facet joints may
serve diagnostic and therapeutic purposes, although controversy exists in the published literature.
Surgery is indicated if there is a signicant neurological decit. Failed nonoperative treatment and severe symptoms are relative indications. Treatment options
include direct decompression, direct decompression plus fusion, and indirect
decompression with fusion. Degenerative instability is a spectrum of disease with a
wide clinical presentation and varying degrees of spinal segmental instability. The
choice is based on patients’ symptoms, radiological ndings, and surgical expertise.
The limitation of published literature is due to the lack of outcome comparison for
cohorts with similar symptoms, radiological ndings, and surgical techniques
(Videos 47.3, 47.4 and 47.7).
Direct decompression by fenestration and preserving more than 50% of facets
does not destabilize the motion segment signicantly. Less invasive techniques such
as unilateral approach with bilateral decompression or endoscopic decompression
further reduce destabilization. Decompression alone is suitable for patients presenting with predominant spinal claudication or radicular pain without signicant
mechanical back pain. It is also suitable for spondylolisthesis slip less than 5mm
from lateral standing radiograph or segments having been self-stabilized
(Fig.47.1c, d).
Decompression with fusion is appropriate for patients with severe mechanical
back pain and gross radiological instability. Since instrumentation improves fusion
rate and sagittal alignment, modern fusion is commonly done with instrumentation.
Common fusion techniques include posterolateral fusion and posterior or transforaminal interbody fusion +/− posterolateral fusion (Fig. 47.2a–f). Indirect
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