Cervical SpineAbstract The cervical spine often becomes involved early in the course of rheumatoid arthritis, leading to three different patterns of instability: atlantoaxial subluxation
Trang 1Cervical Spine
Abstract
The cervical spine often becomes involved early in the course of rheumatoid arthritis, leading to three different patterns of instability: atlantoaxial subluxation, atlantoaxial impaction, and subaxial subluxation Although radiographic changes are common, the prevalence of neurologic injury is relatively low The primary goal of treatment is to prevent permanent neurologic injury while avoiding potentially dangerous and unnecessary surgery Strategies include patient education, lifestyle modification, regular
radiographic follow-up, and early surgical intervention, when indicated Magnetic resonance imaging is indicated when neurologic deficit (myelopathy) occurs or when plain radiographs show atlantoaxial subluxation with a posterior atlantodental interval≤14 mm, any degree of atlantoaxial impaction, or subaxial stenosis with a canal diameter≤14 mm Surgery should be
considered promptly for any of the following: progressive neurologic deficit, chronic neck pain in the setting of radiographic instability that does not respond to nonnarcotic pain medication, any degree of atlantoaxial impaction or cord stenosis, a posterior atlantodental interval≤14 mm, atlantoaxial impaction represented
by odontoid migration≥5 mm rostral to McGregor’s line, sagittal canal diameter <14 mm, or a cervicomedullary angle <135°
Rheumatoid arthritis (RA) is a chronic inflammatory autoim-mune disorder characterized by poly-arthritic disturbance of peripheral joints and early involvement of the cervical spine RA is relatively com-mon, affecting 0.5% to 1.5% of the
US population and twice as many women as men.1The etiology of the disease is unknown but is likely to
be multifactorial, with a relatively strong genetic component RA re-duces life expectancy, and half of all afflicted patients become disabled within 10 years of diagnosis.2 The course of the disease in any given pa-tient, however, is unpredictable and may be relentlessly progressive or
characterized by intermittent flares and remissions Current medical treatment involves early and aggres-sive use of disease-modifying anti-rheumatic drugs, such as methotrex-ate, antimalarial drugs, sulfasalazine, and gold Early clinical studies sug-gest that pharmacologic blockade of tumor necrosis factor-αwith etaner-cept or infliximab can preserve joint function and favorably affect the nat-ural history of the disease.3
Chronic synovial inflammation leads to progressive destruction of the joints, ligaments, and bone, par-ticularly in the atlantoaxial region Eventually, this process leads to clinical manifestations of pain,
de-David H Kim, MD, and
Alan S Hilibrand, MD
Dr Kim is Assistant Clinical Professor of
Orthopaedic Surgery, Department of
Orthopaedic Surgery, Tufts University
School of Medicine, Boston, MA, and
The Boston Spine Group, New England
Baptist Hospital, Boston Dr Hilibrand is
Associate Professor, Departments of
Orthopaedic Surgery and Neurosurgery,
and Director of Medical Education for
the Department of Orthopaedic Surgery,
Jefferson Medical College, Thomas
Jefferson University, Philadelphia, PA,
and The Rothman Institute, Philadelphia.
None of the following authors or the
departments with which they are
affiliated has received anything of value
from or owns stock in a commercial
company or institution related directly or
indirectly to the subject of this article:
Dr Kim and Dr Hilibrand.
Reprint requests: Dr Hilibrand, The
Rothman Institute, 925 Chestnut Street,
Philadelphia, PA 19107-4216.
J Am Acad Orthop Surg
2005;13:463-474
Copyright 2005 by the American
Academy of Orthopaedic Surgeons.
Trang 2formity, instability, and neurologic
deficits Three characteristic
pat-terns of instability resulting from
rheumatoid involvement of the
cer-vical spine have been described; each
may occur in isolation or in
combi-nation: atlantoaxial subluxation,
at-lantoaxial impaction, and subaxial
subluxation Each form of
instabili-ty can lead to compression of or
in-jury to the spinal cord or brainstem
and can progress to paralysis or
death Treatment strategies for the
rheumatoid cervical spine include
patient education and lifestyle
mod-ification, periodic assessment for
ra-diographic signs of increased risk of
neurologic injury, and early surgical
intervention to prevent permanent
neurologic injury
Epidemiology
After the hands and feet, the cervical
spine is the most common site of
disease involvement in RA.4
De-pending on the population and
diag-nostic criteria, between 17% and
86% of patients with RA have
evi-dence of cervical spine disease.5
Sev-eral studies of patients with RA
sug-gest that the cervical spine becomes
involved early in the course of the
disease, often within the first 2 years
following diagnosis.6A prospective
study of 103 Finnish patients with
rheumatoid factor–positive RA
re-vealed a 20-year incidence of
atlan-toaxial subluxation of 23%,
atlanto-axial impaction of 26%, and subatlanto-axial
subluxation of 19%.7
Pathophysiology
The cervical spine is composed of 22
separate synovial joints, all potential
targets of rheumatoid disease.5The
synovial joints between the
trans-verse atlantal ligament and the
odon-toid process, as well as those between
the anterior atlas arch and the
odon-toid, are frequently involved The
oc-cipitoatlantal and atlantoaxial
artic-ulations are the only segments in the
spine without intervertebral disks,
which may account for the high prev-alence of disease in the upper cervi-cal spine in patients with RA
Atlantoaxial Subluxation
Rheumatoid involvement of the synovial joints in the cervical spine
is characterized by formation of pan-nus, an inflammatory tissue with variable fibrous content Synovitis and pannus formation can weaken the transverse, alar, and apical liga-ments The weight of the head, par-ticularly with neck flexion, contrib-utes to the repetitive strain of these ligaments, leading to stretching or rupture and the onset of
atlantoaxi-al subluxation Transverse ligament weakening and rupture occur most commonly at the site of a synovial bursa separating the ligament from the posterior surface of the odontoid
Inflammation also leads to decalcifi-cation and occasional rupture of the ligamentous insertion sites on the atlas
Erosion of the odontoid process, a hallmark of RA, may occur
anterior-ly at its synovial joint with the arch
of C1, posteriorly at its synovial joint with the transverse ligament, and at the tip of the odontoid in re-lation to the apical ligament inser-tion Asymmetric patterns of ero-sion can lead to various radiographic instability patterns, including an-teroposterior, rotatory, or lateral sub-luxations (Table 1) Both rotatory and lateral subluxation patterns can result in torticollis
Atlantoaxial subluxation may oc-cur in up to 49% of RA patients and usually manifests as anterior sub-luxation of the atlas (C1) on the
ax-is (C2).8This increased anterior at-lantodental interval and decreased posterior atlantodental interval is apparent on lateral cervical spine ra-diographs, particularly with the neck in flexion (Figure 1) As sublux-ation increases with time, the space available for the spinal cord
decreas-es, which may compress or injure the spinal cord However, in patients with a large spinal canal, an anterior
atlantodental interval >10 mm may
be seen without any apparent neuro-logic sequelae
The reducibility of atlantoaxial subluxation, either with extension positioning or external traction, is important in planning treatment Initially, subluxation may be purely dynamic, appearing only on flexion views Eventually, pannus may be-come interposed between the
anteri-or atlas arch and the odontoid, con-verting a dynamic subluxation into a fixed one
Atlantoaxial Impaction
Involvement of the atlanto-occipital and atlantoaxial joints can lead to weakening and collapse of the lateral masses, with rostral mi-gration of the odontoid process and atlantoaxial impaction Atlantoaxial impaction also has been referred to
as superior migration of the odon-toid, cranial settling, and basilar in-vagination The prevalence of atlan-toaxial impaction is reportedly between 5% and 32% and generally
is thought to follow the appearance
of atlantoaxial subluxation.5 Com-pared with other instability patterns, atlantoaxial impaction appears to carry the worst prognosis and a much higher risk of myelopathy The symptomatology of atlanto-axial impaction is highly variable Compression of the C1 and C2 nerve roots leads to occipitocervical pain Ventral pressure on the medulla ob-longata can injure local cranial nerve nuclei or cause sudden death by
Table 1 Patterns of Rheumatoid Arthritis in the Cervical Spine
Atlantoaxial subluxation Anterior
Posterior Lateral Rotatory Atlantoaxial impaction Subaxial subluxation
Trang 3compressing the respiratory center.
The anterior spinal artery and
verte-bral arteries also can be
compro-mised, leading to neurologic deficits,
vertebrobasilar insufficiency, or
tran-sient ischemic attacks.9,10With
pro-gression of atlantoaxial impaction
and greater penetration of the
odon-toid process into the foramen
mag-num, the degree of atlantoaxial
sub-luxation may decrease in a process
referred to as “pseudostabilization.”5
However, any reduction in
atlan-toaxial subluxation with the
pro-gression of atlantoaxial impaction
actually carries a worse prognosis
because of the increased risk of
brainstem injury and sudden death.11
Subaxial Subluxation
Destabilization of the facet joints
as a result of weakening of the facet
capsules and interspinous ligament
results in anterior subaxial
sublux-ation Although marked
degenera-tive disk changes are consistently
present, synovitis has not been
ob-served in disk or annular tissue
Therefore, anterior spinal disease
does not appear to contribute
direct-ly to the development of subaxial
subluxation This instability pattern
is a relatively late manifestation of
cervical spine disease and is
ob-served in 20% to 25% of patients with RA.5 It is also the most fre-quently observed new instability pattern following upper cervical fu-sion in RA patients Subaxial sub-luxation occurs most frequently at the C2-3 and C3-4 levels and
typical-ly affects multiple adjacent levels, yielding a characteristic “staircase”
deformity and associated kypho-sis.6,12 Spinal cord compression oc-curs anteriorly from the proximal edge of the vertebral body distal to the slip or posteriorly from the neu-ral arch of the slipped vertebrae Sub-axial subluxation may not be appar-ent on radiographs with the patiappar-ent
in neutral position but should be-come apparent, when present, on flexion or extension views
Clinical Presentation
Rheumatoid involvement of the cer-vical spine is often asymptomatic
Neck pain, the most frequent com-plaint, may be present in 40% to 80%
of patients.5 Characteristically, pa-tients describe the pain as a deep ache radiating into the occipital, retro-orbital, or temporal areas The tem-poral pattern is typically mechanical and readily distinguishable from the typical pain of rheumatoid synovitis
Pain referred to the face, ear, or sub-occiput originates from irritation of the C2 nerve root supply to, respec-tively, the nucleus of the spinal trigeminal tract, greater auricular nerve, or greater occipital nerve.13 Some patients with atlantoaxial subluxation report the sensation of the head falling forward during neck flexion.14A clunking sensation also can occur during neck extension with spontaneous reduction of atlan-toaxial subluxation; this has been la-beled a positive Sharp-Purser test.15 Stiffness, crepitus, and painful range
of motion also are common com-plaints Sleep apnea may be caused
by brainstem compression
associat-ed with atlantoaxial impaction.16 Objective neurologic signs are present less frequently than pain but may be found in 7% to 34% of pa-tients.17,18In contrast to
radiograph-ic changes, whradiograph-ich appear early in the course of RA, neurologic deficits usually appear later, most
common-ly in late middle-age patients They may be difficult to elicit in patients with more advanced disease Ex-tremity weakness is thought to re-sult from advancing joint involve-ment with neurologic symptoms Signs of cervical myelopathy, the clinical manifestation of spinal cord
Figure 1
A 65-year-old woman with rheumatoid arthritis and progressive cervical myelopathy A, Lateral radiograph of the cervical spine
reveals atlantoaxial subluxation The anterior atlantodental interval measures 4 mm and the posterior atlantodental interval
measures 14 mm Sagittal (B) and axial (C) T2-weighted MRI scans reveal significant additional reduction in space available for
the cord to 7 mm because of a large soft-tissue pannus posterior to the odontoid process
Trang 4compression, should be sought,
in-cluding a wide-based spastic gait,
clumsy hands, a visible change in
handwriting, or difficulty
manipu-lating buttons or handling coins
Other classic physical findings
asso-ciated with myelopathy include
hy-perreflexia, a positive Babinski test,
and a positive Hoffmann sign Mild
motor and reflex deficits may be
im-possible to identify in patients with
significant pain and deformity of
ex-tremity joints Lhermitte’s sign, the
sensation of electric shocks traveling
down the torso or upper extremities
on neck flexion, suggests
myelopa-thy Urinary retention, followed by
overflow incontinence, is a
symp-tom of severe myelopathy
Occa-sionally, injury to the pyramidal
tract decussation can manifest as a
“cruciate paralysis,” with varying
degrees of upper extremity weakness
that may be symmetric or
asymmet-ric.10This injury pattern is often
dif-ficult to distinguish from central
cord syndrome
Radiographic
Evaluation
Plain Radiography
Appropriate preoperative
screen-ing for cervical spine disease in
pa-tients with RA is a controversial
subject No radiographic screening
protocol is universally accepted
Nevertheless, certain groups of
pa-tients should be considered strong
candidates for preoperative
radio-graphic screening (Table 2) All
pa-tients with RA should undergo an initial series of cervical spine radio-graphs, including an anteroposterior view and lateral views with the pa-tient in the neutral position as well
as in flexion and extension These radiographs are recommended before any surgical procedure requiring in-tubation One study of 113 RA pa-tients undergoing elective hip or knee arthroplasty found that 61%
demonstrated evidence of
instabili-ty, defined by at least 3 mm of dy-namic atlantoaxial subluxation, by atlantoaxial impaction (according to Ranawat’s method), or by subaxial subluxation, although only 50% of patients were symptomatic.19
Atlantoaxial Subluxation
Traditionally, an anterior atlanto-dental interval >5 mm was consid-ered diagnostic of atlantoaxial sub-luxation However, several studies have demonstrated that the anterior atlantodental interval does not cor-relate with the risk of neurologic injury.19-21Boden et al20showed that measurement of the posterior atlan-todental interval appears to be a more reliable predictor of
neurolog-ic defneurolog-icit in patients with atlantoax-ial subluxation; a value≤14 mm has been suggested as an indication for surgical stabilization (Figure 2) The posterior atlantodental interval also may be used to predict neurologic re-covery after surgery
Atlantoaxial Impaction
Several radiographic
measure-ment techniques have been
suggest-ed as means to gauge the severity of atlantoaxial impaction The original definition of atlantoaxial impaction was protrusion of the odontoid above the margins of the foramen magnum, also known as McRae’s line Because identifying the mar-gins of the foramen magnum on plain radiographs is difficult, alter-native landmarks have been estab-lished (Figure 3) McGregor’s line is defined on a lateral radiograph by the hard palate and the base of the oc-ciput (opisthion) Protrusion of the tip of the odontoid above
McGre-Table 2
Indications for Anteroposterior and Lateral Radiographs of the Cervical
Spine* in Patients With Rheumatoid Arthritis
Prolonged cervical symptoms >6 months
Neurologic signs or symptoms
Scheduled procedures requiring endotracheal intubation in patients who
have not had cervical radiographs in the last 2 to 3 years
Rapidly progressive carpal or tarsal bone destruction
Rapid overall functional deterioration
* Neutral, flexion, and extension
Figure 2
Diagrammatic representation of atlantoaxial subluxation typically seen in patients with rheumatoid arthritis The posterior atlantodental interval (PADI)
is measured from the posterior margin
of the odontoid process to the anterior margin of the posterior arch of C1 (Reproduced with permission from Boden SD, Dodge LD, Bohlman HH, Rechtine GR: Rheumatoid arthritis
of the cervical spine: A long-term analysis with predictors of paralysis
and recovery J Bone Joint Surg Am
1993;75:1282-1297.)
Trang 5gor’s line >4.5 mm is considered diagnostic of atlantoaxial impac-tion.20
The presence of odontoid erosion can make all of these radiographic measurements inaccurate For this reason, other techniques have been developed to diagnose atlantoaxial impaction on plain radiographs, even with significant odontoid ero-sion.22These include the Ranawat method, designed to assess the ex-tent of collapse at the atlantoax-ial articulation, and the Redlund-Johnell method, which uses the dis-tance between the anterior axis base and McGregor’s line22(Figure 4)
Subaxial Subluxation
The radiographic appearance of subaxial subluxation is characteris-tic and includes not only sagittal plane listhesis of sequential verte-bral bodies but also posterior ele-ment changes, including facet joint erosions and widening, whittling, or spindling of the spinous processes (Figure 5) There are multiple def-initions of subaxial subluxation
Figure 3
Radiographic landmarks for assessing atlantoaxial impaction in patients with
rheumatoid arthritis On a lateral radiograph, atlantoaxial impaction is diagnosed by
protrusion of the odontoid tip proximal to McRae’s line or 4.5 mm above
McGregor’s line (Adapted with permission from Riew KD, Hilibrand AS, Palumbo
MA, Sethi N, Bohlman HH: Diagnosing basilar invagination in the rheumatoid
patient: The reliability of radiographic criteria J Bone Joint Surg Am
2001;83:194-200.)
Figure 4
Methods to assess atlantoaxial impaction on plain radiographs A, Ranawat method A line (a) is drawn across the transverse
axis of the atlas, and a connecting line (b) is drawn through the vertical axis of the odontoid from the center of the C2 pedicle
radiographic shadow Values (x)<15 mm in men and <13 mm in women are diagnostic for atlantoaxial impaction B,
Redlund-Johnell method A line (a) is drawn between McGregor’s line (b) and the midpoint of the inferior end plate of C2 (c) A value (x)<34 mm in men and <29 mm in women is diagnostic for atlantoaxial impaction (Adapted with permission from Riew KD, Hilibrand AS, Palumbo MA, Sethi N, Bohlman HH: Diagnosing basilar invagination in the rheumatoid patient: The reliability of
radiographic criteria J Bone Joint Surg Am 2001;83:194-200.)
Trang 6Yonezawa et al12described subaxial
subluxation as >4 mm or 20%
listhe-sis of vertebral body diameter
Magnetic Resonance
Imaging
Although plain tomography,
cine-radiography, computed tomography
(CT), and CT myelography have
been used to follow the rheumatoid
cervical spine, these studies have
been supplanted by the use of
mag-netic resonance imaging (MRI) MRI
provides the most detailed
defini-tion of the craniocervical juncdefini-tion,
including the size of rheumatoid
pannus The finding of odontoid
ero-sion on MRI is considered highly
specific for RA and may clarify the
diagnosis in otherwise nonspecific
cases.23
The space-occupying effect of the
periodontoid pannus can be
visual-ized clearly on MRI Both T1- and
T2-weighted images provide
excel-lent visualization of brainstem or
spinal cord contour Increased signal
intensity within the spinal cord on
T2-weighted images may represent
edema, gliosis, or myelomalacia and
has been associated with poor
neuro-logic recovery following surgery.24
The cervicomedullary angle can
be measured on MRI by drawing a
line along the anterior aspect of the
cervical spinal cord and the medulla
This angle normally is between 135°
and 175° (Figure 6) With progressive
craniocervical disease, the
brain-stem angulates ventrally over the
displaced odontoid process, leading
to increased obliquity of the
cervi-comedullary angle One study
re-ported a 100% correlation between a
cervicomedullary angle <135° and
neurologic signs of cervicomedullary
compression, myelopathy, or C2
ra-diculopathy.25
The utility of flexion-extension
or so-called dynamic MRI evaluation
has been debated.26A theoretic
ad-vantage is the ability to identify,
when the patient is in the neutral
position, potentially significant
dy-namic cord compression before
sta-tic compression is apparent One study suggested that cord diameter
in cervical flexion <6 mm is a risk factor for neurologic deficit.27 How-ever, a theoretic risk of sudden death exists as a result of prolonged cervi-cal flexion in a patient with severe instability; therefore, the recommen-dation for routine dynamic MRI in these patients may need to change
Natural History
Understanding of the natural
histo-ry of the rheumatoid cervical spine
is limited Most studies have been handicapped by small sample size or retrospective design Oda et al28 re-viewed the records of 49 patients fol-lowed radiographically for a mini-mum of 5 years and identified a progressive pattern of cervical sub-luxations The earliest instability pattern is most often a reducible at-lantoaxial subluxation.6 Transition from reducible subluxation to an ir-reducible subluxation often ac-companies atlantoaxial impaction, which appears, on average, 6 years after atlantoaxial subluxation.11 Sub-axial subluxation occurs less
fre-quently than do the other two pat-terns and generally develops after atlantoaxial impaction.29
Forty percent to 80% of patients with rheumatoid subluxations dem-onstrate radiographic progression.17 Neurologic deficits occur much less frequently and do not correlate well with radiographic progression.17 Rana30retrospectively reviewed the records of 41 patients with atlanto-axial subluxation who were followed for 10 years; 61% of patients had no change, 27% had progressive sublux-ation, and 12% had improvement at final follow-up Boden et al20 retro-spectively reviewed the records of 73 patients followed for an average of 7 years In 31 patients, all treated non-surgically, no significant neurologic deficit developed during the observa-tion period Of the 42 patients (58%)
in whom paralysis developed, 7 were managed nonsurgically Six of the
Figure 5
Lateral radiograph demonstrating subaxial subluxation across the C3 through C5 segments, with associated facet joint erosions and spinous process changes
Figure 6
Midsagittal T-2-weighted MRI scan of the craniocervical junction in a patient with atlantoaxial impaction The cervicomedullary angle (CMA) is defined by the angle subtended between a line parallel to the long axis
of the brainstem (a) and a line parallel
to the cervical spinal cord (b)
Trang 7seven patients treated nonsurgically
experienced progressive neurologic
deterioration, and all seven died
within 4 years of the onset of
paral-ysis, five from cord compression Of
the 35 patients who underwent
sur-gery, 25 (71%) experienced marked
neurologic improvement
Despite the general impression
that rheumatoid involvement of the
cervical spine does not contribute to
increased mortality in this patient
population, the high rate of sudden
death observed in patients with
un-treated myelopathy argues against
this conclusion.31When myelopathy
appears, the mortality rate increases
dramatically; without surgery, most
patients die within 1 year.32An
au-topsy study of 104 patients with RA
identified 11 with atlantoaxial
sub-luxation and notable spinal cord
compression; most had experienced
sudden death.33 This finding
sug-gests that the mortality rate from
cervical spine instability in patients
with RA may be as high as 10%
Grading systems have been
devel-oped to assess disease severity as well as treatment outcomes The Ranawat grading system is widely used in clinical studies but has been criticized for lacking the ability to discriminate mild degrees of myel-opathy34(Table 3) The Zeidman and Ducker modification of the Nurick myelopathy scale provides more dif-ferentiation, with an assessment of gait and hand function, and may be more useful10(Table 4) However, its failure to account for severity of ra-diculopathic complaints
significant-ly limits this system for guiding sur-gical decision making
Risk Factors and Predictors of Recovery
Several risk factors for progression of atlantoaxial subluxation have been suggested, including male sex, rheu-matoid factor seropositivity, higher initial C-reactive protein level, presence of subcutaneous nodules, and advanced peripheral joint dis-ease, specifically rapid loss of carpal
height.6,18,28,36,37HLA-DR4 and B-27 seropositive antibodies do not ap-pear to be significant risk factors.6 Whether corticosteroid treatment represents an independent risk fac-tor remains controversial.38Patients with any degree of atlantoaxial im-paction or cord compression on MRI are at significant risk of neurologic injury and should be considered strong candidates for prophylactic decompression and/or stabiliza-tion.37,39
Plain radiography is an efficient and inexpensive means of monitor-ing disease progression Boden et
al20found that the posterior atlanto-dental interval and subaxial sagittal canal diameter correlated with the presence and severity of paralysis, whereas the anterior atlantodental interval did not Using a standard tube distance of 6 feet (1.8 m), 96%
of patients with atlantoaxial sublux-ation and paralysis demonstrated a posterior atlantodental interval≤13
mm In contrast, 60% of the same patients had an anterior atlantoden-tal interval <9 mm All patients with subaxial subluxation and paralysis demonstrated a subaxial sagittal ca-nal diameter≤13 mm
Boden et al20found the posterior atlantodental interval to be a predic-tor of surgical outcome Postopera-tively, no patient experienced signif-icant neurologic recovery when the preoperative posterior atlantodental interval measured <10 mm In pa-tients with isolated atlantoaxial sub-luxation, a posterior atlantodental interval of at least 10 mm predicted improvement of at least one Rana-wat class In the setting of atlanto-axial subluxation and atlantoatlanto-axial impaction, recovery required a pre-operative posterior atlantodental in-terval≥13 mm All patients with a preoperative posterior atlantodental interval and subaxial sagittal canal diameter measuring at least 14 mm experienced complete motor recov-ery
Multiple studies have suggested that the degree of preoperative
neu-Table 4
Zeidman and Ducker Modification of Nurick Grading Scale for
Myelopathy10
Grade Radiculopathy Myelopathy Gait Hand Function
0 Present Absent Normal Normal
I Present Present Normal Slight
II Present Present Mildly abnormal Functional
III Present Present Severely abnormal Unable to button
IV Present Present With assistance
only
Severely limited
V Present Present Nonambulatory Useless
Table 3
Ranawat Grading Scale for Myelopathy35
II Weakness, hyperreflexia, altered sensation
IIIA Paresis and long-tract signs, ambulatory
IIIB Quadriparesis, nonambulatory
Trang 8rologic deficit is also a strong
predic-tor of postoperative neurologic
re-covery.40,41Factors with no apparent
predictive value in terms of recovery
include age, sex, duration of
paraly-sis, and preoperative anterior
atlan-todental interval.42
Nonsurgical Treatment
Patients with rheumatoid
involve-ment of the cervical spine benefit
from early, aggressive medical
inter-vention as well as regular follow-up
Because of the prevalence and early
appearance of cervical spine
involve-ment, screening cervical spine
radio-graphs should be considered in all
patients with RA Regular follow-up
radiography should then be
per-formed in patients with any
evi-dence of cervical spine involvement,
especially when they have advanced
peripheral joint disease At least one
study has demonstrated that early,
aggressive combination
disease-modifying antirheumatic drug
ther-apy can prevent or delay
develop-ment of atlantoaxial subluxation.43
Soft cervical collars are
appropri-ate treatment of symptomatic
pa-tients with relatively minor
occipi-tocervical pain and may occasionally
represent the treatment of choice in
elderly or debilitated patients who
are poor surgical candidates.44
Unfor-tunately, orthoses may be
problem-atic in patients with
temporoman-dibular joint involvement Although
they offer excellent relief of
symp-tomatic neck pain, soft cervical
col-lars do not provide much limitation
of motion and probably do not alter
the natural history of cervical spine
disease.5Progressive neurologic
de-terioration has been observed in
pa-tients with spinal cord myelopathy
treated with a soft collar.20
A comprehensive program of
pa-tient education, physical therapy,
collars, practical aids, symptomatic
treatment, and disease-modifying
antirheumatic drugs achieves
signif-icant (P < 0.001) lasting pain relief in
most patients.45Patients should be
taught to avoid cervical flexion
Physical therapy should focus on isometric strengthening of neck muscles and overall postural train-ing Narcotic medication may be ap-propriate for short-term relief of acute pain, but when chronic
narcot-ic use is required for pain relief, then surgical treatment should be consid-ered
Surgical Management
The goals of surgical treatment of rheumatoid disease of the cervical spine are to achieve spinal stability through a solid fusion and to decom-press involved neural structures
The most commonly accepted indi-cations for surgical treatment of RA
in the cervical spine include neuro-logic deterioration and intractable pain with spinal instability (Table 5)
In addition, Boden et al20 proposed surgery, even without neurologic findings, when patients demonstrate one of three radiographic risk fac-tors: (1) atlantoaxial subluxation with a posterior atlantodental inter-val≤14 mm; (2) atlantoaxial impact represented by odontoid migration
≥5 mm rostral to McGregors’s line;
or (3) subaxial subluxation with sag-ittal canal diameter≤14 mm
Patients with RA are a challenging surgical population Those requiring
surgery suffer from a systemic illness and may be significantly malnour-ished and debilitated In addition to cervical spine disease, micrognathia and temporal mandibular disease make standard intubation difficult and anesthesia hazardous Excessive trauma caused by standard intuba-tion has been associated with a 14% incidence of upper-airway obstruc-tion following extubaobstruc-tion.46This rate can be reduced to 1% with fiberoptic assistance Skin lesions and corticos-teroid use notably increase the rate of wound complications and infections Poor structural bone quality may ren-der standard surgical fixation tenu-ous and unreliable
Atlantoaxial Subluxation
When atlantoaxial subluxation is reducible, a variety of posterior fu-sion techniques are possible, includ-ing Gallie or Brooks wirinclud-ing, Magerl transarticular screws, or Harms C1-2 lateral mass fixation.4 Fixa-tion strategies incorporating Magerl screws appear to provide
particular-ly stable fixation; a fusion rate of 95% has been reported with use of transarticular screws.47The need for postoperative halo-vest stabilization depends on the quality of surgical fixation
When atlantoaxial subluxation is nonreducible, transarticular screw
Table 5 Indications for Surgery in Patients With Rheumatoid Arthritis With Cervical Spine Involvement
Progressive neurologic deficit (eg, weakness, gait disturbance, loss of fine motor coordination)
Mechanical neck pain unresponsive to nonnarcotic pain medication (in the setting of radiographic evidence of AAS, AAI, or SAS)
Radiographic risk factors of impending neurologic injury PADI≤14 mm in the setting of AAS
AAI represented by odontoid migration≥5 mm rostral to McGregor’s line Sagittal canal diameter≤14 mm in patients with SAS
Any degree of AAI or cord stenosis
A cervicomedullary angle <135°
AAI = atlantoaxial impaction, AAS = atlantoaxial subluxation, PADI = posterior atlantodental interval, SAS = subaxial subluxation
Trang 9fixation in combination with C1
laminectomy should be considered,
especially when the patient has
pos-terior cord compression An
occipi-tocervical fusion is an alternative
MRI studies revealing significant
pannus resorption after spinal
stabi-lization indicate that, if bone is not
impinging anteriorly on the cord,
then odontoid resection may be
un-necessary.48 Sublaminar wire
fixa-tion is contraindicated when
atlan-toaxial subluxation cannot be
reduced
Atlantoaxial Impaction
Because the risk of neurologic
in-jury is high with atlantoaxial
impac-tion, early surgery following
identi-fication of this condition has been
recommended.41 Neurologic deficit
or evidence by MRI of cord
compres-sion is a strong indication for
sur-gery.13The use of preoperative halo
traction has been recommended to
reduce the degree of atlantoaxial
im-paction and obviate foramen
mag-num decompression or odontoid
re-section An occipitocervical fusion
can be performed using wires or
screws attached to the occiput below
the superior nuchal line and
con-nected to fixation in the subaxial
spine (Figure 7) When traction is
un-successful, symptomatic
decompres-sion with a transoral odontoid
resec-tion or C1 laminectomy, along with
posterior stabilization, is required.4
An alternative technique for
multi-level instability including
atlantoax-ial impaction is a long rod loop fixed
with occipital and cervical laminar
wires without attempted fusion
Subaxial Subluxation
Evidence from clinical studies
suggests that patients with subaxial
subluxation and neurologic deficits,
or asymptomatic patients with a
subaxial canal diameter ≤14 mm,
should be considered for surgical
sta-bilization.20 Preoperative halo-vest
immobilization can provide
tempo-rary stabilization and reduction of
displacement, often with immediate
improvement in neurologic defi-cits.49Reducible subluxations can be fused anteriorly or posteriorly, but optimal treatment of irreducible subluxations is anterior decompres-sion and fudecompres-sion.23,34Posterior fusion should be strongly considered fol-lowing any laminectomy50 (Figure 8) The extent of fusion required is often not apparent but is a critical decision because RA is progressive
Instability patterns can occur in combination at multiple levels of the cervical spine When atlantoax-ial subluxation and subaxatlantoax-ial sublux-ation occur concurrently, fusion should be extended to the lowest in-volved level to minimize the risk of junctional degeneration.51Some in-vestigators recommend more exten-sive fusions, at times including the entire cervical spine and extending caudally to T1 or T2.52,53
The extent of postoperative im-mobilization depends on the type of surgical fixation used Wiring tech-niques typically require rigid
immo-bilization in a halo-vest or four-poster orthosis for 8 to 12 weeks.5 Following plate and screw fixation, a cervical orthosis may be sufficient New plate, rod, and screw instru-mentation techniques with less
rig-id fixation appear to have improved fusion rates and maintenance of alignment but may increase the risk
of neurovascular injury
Outcomes of Surgery
Over the past 10 years, outcomes of surgery on the rheumatoid cervical spine have improved markedly, largely because of earlier diagnosis of myelopathy and surgical referral.54 More aggressive medical manage-ment of RA and a decrease in corti-costeroid use may be additional con-tributing factors
Most studies favor surgery over nonsurgical management for pa-tients with neurologic deficits.55,56 One of the strongest predictors of postoperative neurologic recovery
Figure 7
A 56-year-old woman with rheumatoid arthritis and atlantoaxial impaction
A,Preoperative midsagittal T2-weighted MRI scan demonstrating penetration of the odontoid through the foramen magnum with impingement on the brainstem
B,Postoperative radiograph demonstrating reduction of the occipitoatlantoaxial relationship and occipitocervical instrumented fusion using a plate-and-screw system
Trang 10appears to be preoperative
neurolog-ic status Nonambulatory patients
demonstrate higher complication
rates and lower overall survival.57
Boden et al20reported a retrospective
review of the records of 35 patients
and found that all Ranawat class II
patients had notable neurologic
im-provement after surgery compared
with 62% of class III patients
Casey et al58reported results from
their prospective study of 116
pa-tients with atlantoaxial impaction
Transoral odontoid resection was
performed for anterior bony
com-pression; otherwise, laminectomy
and instrumented fusion were done
A higher revision surgery rate was
noted in patients without fusion to
the occiput Occipitocervical fusions
failed because subaxial instability
below the level of fusion progressed
Satisfactory results were more
like-ly in patients with better
preopera-tive neurologic function Overall,
marked neurologic improvement
oc-curred in 45% and significant pain
relief in 97% of patients A high rate
of perioperative complications was attributed to the general debility of the patient population; the perioper-ative mortality rate was 10%
Surgical results for subaxial sub-luxation may be less favorable
Olerud et al52reported a small retro-spective study of 16 patients with subaxial subluxation and varying de-grees of myelopathy who underwent anterior and/or posterior decompres-sion and fudecompres-sion Although neck pain was typically relieved, arm pain im-proved less reliably Patients with myelopathy had the worst prognosis, and four of five with severe myelop-athy died within 3 months of surgery
The authors recommend early sur-gery for subaxial subluxation, before significant myelopathy develops
The overall complication rate is markedly increased in patients with
RA Wound complications, includ-ing infection, may occur in up to 25% of patients Generalized os-teopenia correlates with systemic disease activity and compromises fixation strength, leading to
in-creased rates of instrumentation fail-ure.52Successful outcomes are pred-icated on achieving solid fusions, and pseudarthrosis has been associ-ated with a less favorable clinical re-sult because of persistent
instabili-ty.20 Recurrent instability in the form of subaxial subluxation at more caudal levels may occur either
as a result of the natural progression
of the disease or as a result of in-creased stress from an adjacent fu-sion Current perioperative
mortali-ty rates have been reported to be between 5% and 10%, with in-creased rates in patients having coin-cident cardiovascular disease or at-lantoaxial impaction.34,41,58,59
Summary
In most patients with RA, neck pain occurs without significant
neurolog-ic defneurolog-icit Multimodality therapy, in-cluding patient education, physical therapy, and active medical treat-ment, can be very effective in con-trolling symptoms and limiting
dis-Figure 8
A,Preoperative lateral cervical radiograph of a 46-year-old woman with RA myelopathy and subaxial subluxation of C4 on C5
B, Preoperative sagittal T1-weighted MRI scan revealing cervical cord compression at level of subluxation C, Postoperative
radiograph following laminectomy and instrumented fusion using C1-2 transarticular screws and lateral mass screws from C3
to C5