Hip and knee flexion contractures occur when patients compensate for loss of sagittal balance by assuming a crouched position.. Deformity resulting from inflammation and fusion of the sacr
Trang 1Erik N Kubiak, MD, Ronald Moskovich, MD, Thomas J Errico, MD, and Paul E Di Cesare, MD
Abstract
Ankylosing spondylosis (AS) is a
se-ronegative inflammatory disease of
unknown etiology characterized by
inflammation in the axial skeleton
The sacroiliac joints are often
in-volved initially, followed by
enthe-sopathy in the paravertebral
zyga-pophyseal joints and disk spaces
Enthesopathy is inflammation at the
site of tendon insertions that
predis-poses to the development of fibrosis
and calcification; left untreated, it
leads to fusion of the zygapophyseal
joints and intervertebral disk space
This fusion in turn can lead to a
fixed, hyperkyphotic posture and
compromised sagittal balance Hip
and knee flexion contractures occur
when patients compensate for loss
of sagittal balance by assuming a
crouched position Degeneration
and ankylosis of peripheral joints,
such as the hip, knee, and shoulder,
may ensue Deformity resulting from inflammation and fusion of the sacroiliac joints, spine, and hips leads to severe functional impair-ment in approximately 30% of pa-tients.1Several diagnostic and treat-ment strategies are available for early and late manifestations of AS
Epidemiology
AS typically affects young adults, most commonly males (M:F = 3:1) in their second through fourth de-cades The incidence of AS in North America is reported to be 1 to 2 per 1,000.2Worldwide prevalence is up
to 0.9%.3Fifteen percent to 20% of patients with AS have a positive family history of the disease AS
is linked to HLA-B27; 80% to 95%
of patients with AS are
HLA-B27–positive.2Carriers of this gene have a 16% to 50% increased risk of developing AS, but other genetic factors are likely involved as well.4 HLA-B27 is present among the in-habitants of Eurasia, North Africa, and North America; it is virtually absent among the aboriginal pop-ulations of Australia and South America.2 Although both HLA-B27–negative and HLA-B27–posi-tive AS patients have similar artic-ular manifestations, the former usually develop the disease at an older age and lack a positive family history AS tends to occur at a later age in females than in males, and di-agnosis is often delayed.2
Dr Kubiak is Resident, Musculoskeletal Research Center, NYU–Hospital for Joint Diseases Depart-ment of Orthopaedic Surgery, New York, NY Dr Moskovich is Associate Chief, Spine Service, Mus-culoskeletal Research Center, NYU–Hospital for Joint Diseases Department of Orthopaedic Sur-gery Dr Errico is Chief, Spine Service, Muscu-loskeletal Research Center, NYU–Hospital for Joint Diseases Department of Orthopaedic Sur-gery Dr Di Cesare is Chief, Adult Reconstruc-tive Service, Musculoskeletal Research Center, NYU–Hospital for Joint Diseases Department of Orthopaedic Surgery.
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 com-pany or institution related directly or indirectly
to the subject of this article: Dr Kubiak, Dr Mos-kovich, Dr Errico, and Dr Di Cesare Reprint requests: Dr Di Cesare, Musculoskele-tal Research Center, NYU–HospiMusculoskele-tal for Joint Dis-eases, 301 E 17th Street, New York, NY 10003 Copyright 2005 by the American Academy of Orthopaedic Surgeons.
Ankylosing spondylitis is an inflammatory disease of unknown etiology that affects
an estimated 350,000 persons in the United States and 600,000 in Europe,
pri-marily Caucasian males in the second through fourth decades of life Worldwide, the
prevalence is 0.9% Genetic linkage to HLA-B27 has been established Ankylosing
spondylitis primarily affects the axial skeleton and is characterized by inflammation
and fusion of the sacroiliac joints, spine, and hips The resultant deformity leads to
severe functional impairment in approximately 30% of patients Orthopaedic
man-agement primarily involves correction of hip deformity through total hip
arthro-plasty and, less frequently, correction of spinal deformity with spine osteotomy.
Closing wedge osteotomies have the lowest incidence of complications Whether
pa-tients with ankylosing spondylitis are at increased risk for heterotopic ossification
remains controversial, but comparison with age- and sex-matched counterparts
suggests no dramatically higher risk Because of the high rate of missed fractures
and complications after minor trauma in patients with ankylosing spondylitis,
plain radiographs are usually not sufficient for evaluation Thorough patient
as-sessment should include a comprehensive history, physical examination, and
lab-oratory studies.
J Am Acad Orthop Surg 2005;13:267-278
Trang 2Not everyone who is HLA-B27–
positive develops AS; it is likely that
other genetic and/or environmental
factors play a role in the etiology.5
One recent theory is that AS is an
autoimmune disorder that occurs
subsequent to a Klebsiella pneumoniae
infection in HLA-B27–positive
indi-viduals, with molecular mimicry
be-tween HLA-B27 and K pneumoniae
bacterial antigens.6 Elevated levels
of antibodies to K pneumoniae have
been noted in AS patients Elevated
IgA levels in AS patients may reflect
mucosal immunity to a persistent
bacterial infection and may be the
autoimmune trigger for AS,
idio-pathic bowel disease, and other
re-active arthritides No causal
rela-tionship has been established
between AS and other autoimmune
diseases, but the incidence of AS in
patients with idiopathic bowel
dis-ease is approximately 3.7%.7
Pathophysiology
The pathognomonic feature of AS is
a combination of inflammation and
bony destruction at the site of
ten-don insertion (ie, enthesopathy)
Pannus or fibroblastoid tissue and
inflammatory cell infiltrates invade
the bone adjacent to entheseal
at-tachments; new bone formation in
response to inflammation leads to
ankylosis of affected joints
Preferen-tial involvement of the
zygapo-physeal joints has been noted on
magnetic resonance imaging (MRI)
Ankylosis and subsequent loss of
motion of the zygapophyseal joints
leads to syndesmophyte formation,
resulting in the characteristic
“bam-boo spine” of individuals with AS
(Fig 1) Enthesopathy also can occur
in peripheral joints, leading to
sy-novitis-like symptoms and joint
de-generation.8Other manifestations of
AS include inflammatory bowel
dis-ease, psoriasis, uveitis/iritis (25%),9
pulmonary fibrosis, aortitis, and genitourinary problems, with prev-alence up to 40%.10,11
Clinical History
Patients usually present with symp-toms and physical findings consistent with the nonmechanical and inflam-matory nature of AS Onset is often insidious; patients typically cannot give the precise time of onset or even pinpoint the initially affected site
These individuals frequently present
in the second through fourth decades
of life with low back pain and stiff-ness, particularly in the morning, at night, or after prolonged periods of sitting and/or recumbency Chest wall pain is a frequent complaint, par-ticularly with deep inhalation Back pain not relieved by recumbency and the persistent discomfort may com-pel the individual to leave the bed at night.12Patients also may have but-tock pain that radiates down the pos-terior thigh Enthesopathy involving the Achilles and plantar tendon inser-tions with associated symptoms also
is common Some patients experience
no pain but present with increasing stiffness in the hips and spine As with other inflammatory diseases, symp-toms often improve with exercise
Physical Examination
A systematic examination of the en-tire patient is imperative Ocular pain, scleral redness, and photophobia are often indicative of acute anterior uve-itis and may be clinically apparent be-fore other symptoms or signs of AS appear Chest expansion measured at the fourth intercostal space typically
is limited to <2.5 cm after fusion of the costovertebral joints; the patient then becomes an obligate diaphrag-matic breather Total lung volume and vital capacity usually are preserved;
the diaphragm excursion is affected only in the patient with severe
tho-racic kyphosis Patients become tachypneic when the degree of ky-phosis compresses the abdominal cavity, thereby limiting
diaphragmat-ic excursion Pulmonary function test-ing should be performed before sur-gery on all patients with AS Aortic and mitral regurgitation murmurs can occur as a consequence of aorti-tis in patients with long-standing dis-ease Right bundle branch block and varying degrees of atrioventricular block occur in up to 30% of patients
as a result of fibrosis extending from the aorta to the intraventricular sep-tum.13
Early in the disease, examination
of the sacroiliac joints may reveal ten-derness to palpation, which can be
ex-Figure 1 Lateral radiograph of the lumbar spine in a 46-year-old man demonstrating the flowing syndesmophytes and posterior ele-ment fusion consistent with bamboo spine Disk spaces are often maintained, especially
in the lumbar spine Anteriorly, osteophytes are often oriented vertically rather than hor-izontally, which is common in spondylitis and diffuse idiopathic skeletal hyperostosis.
Trang 3acerbated by hyperextension of the
hips Patients with hip involvement
develop hip flexion contractures
Some patients exhibit loss of
lordot-ic curvature of the lumbar spine and
loss of spine movement in all planes
Patients with decreased mobility of
the thoracolumbar spine have an
ab-normal Schober sign—that is, lack of
at least a 5-cm increase in distance
from a midline point 5 cm below and
10 cm above the posterior superior
il-iac spine, measured in both the erect
standing position and full forward
flexion Late in the disease, the
cer-vical spine can become rigid, with
loss of flexion and extension
Chin-brow angle, occiput-to-wall distance,
and gaze angle are used to evaluate
functional deformity involving the
cervical spine (Fig 2) Most patients
are neurologically normal, with
pres-ervation of deep tendon reflexes A
slow, progressive cauda equina
syn-drome may appear late in the course
of the disease
Assessment of Deformity
Correction of deformity most often
is performed to improve the
pa-tient’s visual field, respiratory
func-tion,14 balance, sitting position,
swallowing function, or ambulation
Determining the site of deformity is
critical before surgically treating the
deformity Flexion contracture of the
hips, loss of lumbar lordosis, and
progressive thoracic and cervical
ky-phosis all may contribute to the
functionally disabling stooped
pos-ture of patients with AS Deformity
must be assessed both clinically and
radiographically as part of
preoper-ative planning The level of
defor-mity will aid in determining the
benefit of total hip arthroplasty
(THA) and/or the level of corrective
spine osteotomy and degree of
cor-rection necessary
The chin-brow angle is the angle
formed by the vertical line drawn
from the chin to the brow with the
pa-tient’s hips and knees fully extended (Fig 2) Occiput-to-wall distance is measured to grossly determine the patient’s sagittal balance The hori-zontal distance from the occiput to the wall is measured with the patient’s buttocks and heels against the wall, with hips and knees extended Clin-ically, occiput-to-wall distance should
be 0 to 2 cm The degree of hip flex-ion contracture is determined by placing the patient supine with the lumbar spine pressed flat to the ex-amining table, then measuring the angle that each femur makes with the horizontal
Normal sagittal balance places the center of mass just in front of the S1 vertebral body Radiographically, a plumb line drawn from the center of the C7 vertebral body should just touch the anterior edge of the body
of S1 on the lateral radiograph Nor-mal individuals are able to compen-sate for small changes in sagittal bal-ance through changes in sacral inclination; hip, knee, and ankle flex-ion; or extension In patients with AS, these normal compensatory changes are ameliorated by loss of motion in these areas.15
Laboratory Evaluation
Baseline laboratory investigation in pa-tients suspected of having AS should include a basic metabolic panel, com-plete blood count, erythrocyte sedi-mentation rate (ESR), C-reactive pro-tein (CRP) level, and rheumatoid factor
Although routine HLA-B27 status is not required to make a diagnosis of
AS, it is helpful in the differential di-agnosis The clinician should be sus-picious of a diagnosis of AS in patients who are HLA-B27–negative Patients
in the active phase of the disease have mildly elevated ESR, CRP level, and white blood cell count In most cases, rheumatoid factor is negative and HLA-B27 is positive Patients with chronic AS may have a normocytic, normochromic anemia
Imaging Studies
The sacroiliac joints usually are the first joints affected in patients with
AS Sacroiliitis initially presents as a widening of the sacroiliac joints with progressive sclerosis of the joint margins, leading to eventual bony fusion across the joints with subsequent loss of sclerosis Care must be taken to disregard congen-ital deformities and degenerative changes as well as osteitis conden-sans ilii (symmetric sclerosis on the iliac sides of both sacroiliac joints without erosions, seen in women who have borne children) Standard anteroposterior radiographs of the pelvis are inadequate to fully eval-uate the sacroiliac joints For accu-rate diagnosis, a Ferguson view of the pelvis (anteroposterior with the x-ray tube tilted 30° cephalad) and oblique radiographs are required Hip involvement presents as ossifi-cation of the ligamentous origins and insertions about the trochanters, iliac crests, and ischial tuberosities Late findings include loss of joint
Figure 2 Measurement of occiput-to-wall distance, gaze angle, and chin-brow angle.
Trang 4space, sclerosis, and fusion with loss
of sclerosis at the hips
The ascending osseous changes of
the cervical, thoracic, and lumbar
spine lead to the characteristic
bam-boo spine in advanced stages of the
disease The erosive sclerotic
process-es that occur in the spine are
differ-ent from those that occur in diffuse
idiopathic skeletal hyperostosis
(DISH, also known as Forestier’s
dis-ease) AS can be erroneously
diag-nosed in patients who have
ankylo-sis of the spine for other reasons
Spine lesions in AS are the result of
wedging of vertebral bodies and
os-sification of disk spaces leading to a
rigid kyphotic spine Enthesopathy of
the zygapophyseal joints leads to
fu-sion of the posterior elements The
bone loss and reabsorption that lead
to these deformities occur early in
young persons with active disease.16
Erosions at the discovertebral
junc-tions are called Romanus lesions;
scle-rosis in this region gives rise to
so-called “shining corners.” In AS, the
syndesmophytes are bilateral and
have their insertions at the upper and
lower margins of adjacent vertebrae;
in DISH, the syndesmophytes are
larger and asymmetric, with
nonmar-ginal vertebral insertions consistent
with their status as ligamentous
os-sifications Additionally, DISH spares
the sacroiliac joints and is not
asso-ciated with HLA-B27 In patients with
AS, the zygapophyseal joints are
pre-dominantly involved and frequently obliterated by fusion Four other spondyloarthropathies—psoriatic ar-thritis, reactive arar-thritis, arthritis as-sociated with inflammatory bowel disease, and undifferentiated spondy-loarthropathy—can have
radiograph-ic changes similar to those of AS
Both computed tomography (CT) and MRI are more sensitive than plain radiographs for detecting early dis-ease In a review of imaging tech-niques for sacroiliitis, Braun et al17 ad-vocated the use of CT for evaluation
of erosions and regional ankylosis
MRI is the most sensitive instrument for detecting early disease, with a sen-sitivity of 95% and a specificity of 100%.18Early detection may be im-portant in determining which pa-tients would likely benefit from immune-modulating medication reg-imens when radiographic evidence is lacking Bone scans are unreliable, al-though a negative bone scan should create suspicion of an AS diagnosis
in a patient with sacroiliitis or low back pain
Diagnostic Criteria
The Rome criteria for AS, established
in 1961, were modified by the Amer-ican Academy of Rheumatology in
1966 and renamed the New York clas-sification The New York criteria were modified in 1984 by van der Linden
et al19to improve sensitivity and re-tain specificity (Table 1) The modi-fied New York criteria combine clin-ical and radiographic findings for the diagnosis of AS Radiographic eval-uation (eg, Ferguson’s view, oblique views) of the sacroiliac joints is used
to determine the degree of the sacro-iliitis, which is graded 0 (normal), 1 (suspicious), 2 (minimal sacroiliitis),
3 (moderate sacroiliitis), and 4 (anky-losis) Limitations of this system are
an inability to detect all sacroiliac and/or spinal involvement on plain radiographs, failure to include pa-tients with other forms of spondyloar-thropathy, and an assumption that the duration of inflammatory back pain has exceeded 3 months The presence
of HLA-B27 is not necessary to make the diagnosis
Nonsurgical Management
Nonsteroidal anti-inflammatory drugs (NSAIDs)—specifically, in-domethacin—remain the mainstay of medical therapy Cyclooxygenase-2 inhibitors offer the potential benefits
of decreased gastrointestinal morbid-ity, but their efficacy in the treatment
of AS remains to be proved Sulfasala-zine, methotrexate, thalidomide, and anti–tumor necrosis factor (TNF)-α agents (infliximab, etanercept, adal-imumab) are frequently used in long-term AS management.20 Indometha-cin and radiation therapy have been employed to manage ankylosis and myositis ossificans In 2003, the As-sessment in Ankylosing Spondylitis Working Group recommended that anti–TNF-α be used to treat patients with AS when any of the following exists: (1) a definitive diagnosis of AS; (2) presence of the disease for at least
4 weeks; (3) presence of refractory dis-ease (defined by the failure of two types of NSAIDs during a single 3-month period); (4) failure of local corticosteroid injection into inflamed sacroiliac joints; (5) failure of sul-fasalazine in patients with
peripher-Table 1
The Modified New York Criteria for Diagnosing Ankylosing Spondylitis19
Clinical Criteria
1 Low back pain of at least 3 months’ duration improved by exercise and
not relieved by rest
2 Limitation of lumbar spine motion in sagittal and frontal planes
3 Chest expansion decreased relative to normal values for age and sex
Radiographic Criteria
4 Bilateral sacroiliitis, grade 2-4
5 Unilateral sacroiliitis, grade 3-4
Trang 5al disease; and (6) no medical
con-traindications to the initiation of
treatment.21Braun et al22summarized
the results of anti–TNF-α medications
in more than 300 patients enrolled in
clinical trials, which indicated
signif-icant (P < 0.0001) short-term
improve-ment in disease activity, function, and
quality of life Long-term efficacy of
these medications is being studied in
ongoing clinical trials Early medical
intervention may improve patient
function, lessen pain, and delay
dis-ease progression
The physician is responsible for
educating the patient about the
dis-ease and its natural history An
activ-ity program of physical exercise,
in-cluding stretching and postural
alignment, should be consistently
fol-lowed A medium-firm mattress is
recommended, and the patient may
benefit from sleeping supine with one
pillow to maintain a more normal
sagittal spinal alignment and prevent
hip flexion contractures Ultimate
ankylosis of the spine in an anatomic
position, an achievable outcome for
patients who receive early diagnosis
and counseling, is far preferable to
progressive kyphosis
Surgical Management
Indications for surgical treatment of
patients with AS are to lessen pain
and to improve function
Addition-ally, the psychosocial effects of severe
deformity are devastating, and
cor-rection may help the patient recover
vital social skills and possibly accept
having the disease THA is the most
common surgical intervention in AS
patients, followed by spinal
osteoto-mies for correction of cervical
defor-mity and thoracolumbar sagittal
bal-ance Few patients require surgical
intervention for correction of
periph-eral joint abnormalities
Hip Deformity
Thirty percent to 50% of patients
with AS exhibit involvement of the
hips; of those, 90% present
bilateral-ly.23 Hip involvement ranges from flexion contractures to complete ankylosis, often in a disabling flexed position THA consistently improves both range of motion (ROM) and function; it also decreases pain in pa-tients with AS
Patients with AS onset at an early age are more likely to require THA
Sweeney et al24reported the mean age
of AS onset in patients undergoing THA to be 19.5 years, an average of 3.5 years younger than matched con-trols with AS who had not undergone THA In addition, 16% of AS patients with onset before age 16 years re-quired THA within 20 years
Indications for THA are correction
of hip flexion contractures and reduc-tion of pain caused by degenerareduc-tion, with the goal of improved function
Patients with AS typically undergo THA at a younger age than do pa-tients having THA for osteoarthritis
THA implant survival in AS patients
is similar to that in other young pa-tients with THA It was previously thought that patients with AS were
at a significantly greater risk of de-veloping disabling heterotopic ossi-fication (HO) than other patients un-dergoing THA; however, careful review of the literature reveals that there may not be dramatically
high-er rates of HO for age- and sex-matched counterparts.25,26
Correction of hip flexion contrac-ture with THAcan restore sagittal bal-ance in patients with AS Tang and Chiu27noted that, because of the pres-ence of relative hyperextension of the hips after THA, AS patients are more prone to anterior dislocation when ac-etabular components are placed in their normal position relative to the pelvis When positioning the acetab-ular component in a patient with AS, one must account for the relationship
of the pelvis to the lumbar spine in the sagittal plane in order to avoid an excessively hyperextended hip once the patient resumes an upright posi-tion In patients with severe spinal
de-formity, corrective spinal osteotomies should be performed before THA to prevent future acetabular component malposition However, many sur-geons still concur with Lee,28who as early as 1963 stated that THA should
be performed before considering spi-nal osteotomy because improvement
in hip ROM and pain relief may ob-viate the need for spinal osteotomy
in patients with severe hip flexion de-formity Determining surgical se-quence should be based on patient circumstances
Several studies indicate that THA
is beneficial in AS patients (Table 2) The studies listed in Table 2
evaluat-ed a total of 524 THAs performevaluat-ed in
320 patients with AS Ambulatory sta-tus improved in all patients Sixty per-cent to 97% of patients reported no pain after THA.23,25,27,29-31Fifteen-year survival (ie, time to THA failure) ranged from 66% to 81.4%.23,27,31 Av-erage age at time of surgery was 38 years.23,25,27,29-31 Thirty patients had Brooker33 class 3 or 4 HO.27,29,32 Eighty-six revision THAs were performed.23,27,29-32Sweeney et al24 re-viewed charts and questionnaires of
340 patients with AS who were
treat-ed with THA Survival rates of pri-mary THA were 90%, 78%, and 64%
at 10, 15, and 20 years, respectively Survival rates of revisions were 73%, 55%, and 55% at 10, 15, and 20 years, respectively These THA survival rates and those listed in Table 2 are not dissimilar to survival rates in other young patients requiring THA.34-40
The majority of revisions in the studies listed in Table 2 were per-formed for aseptic loosening of both the femoral and acetabular compo-nents.27,30Tang and Chiu27used both uncemented and cemented implants
in their series of THA in patients with AS; they reported loosening rates of 5% and 28% in uncemented and ce-mented implants, respectively The short duration of follow-up in pa-tients receiving uncemented implants prevented Tang and Chiu from fully
Trang 6advocating their use However, more
recent preliminary clinical data39,40
support the use of uncemented
ace-tabular and femoral components in
young, active patients, including
those with AS
The level of risk for heterotopic
bone formation after THA in
pa-tients with AS remains
controver-sial Previous reports have resulted
in the impression that the rates of
postoperative HO are unacceptably
high after THA in AS patients
How-ever, careful review of the
previ-ously reported high rates of HO
af-ter THA in patients with AS shows
rates not unlike those seen in other
young patients undergoing THA
Additionally, patients with
preoper-ative ankylosis often experience
sig-nificant improvement in function
af-ter THA.23,30,41The proportion of AS
patients with functional ankylosis
secondary to HO following THA is
likely substantially lower than
pre-viously thought Patients with class
3 HO, nevertheless, experienced
sig-nificant (P < 0.01) improvement in
ROM, pain relief, and independent ambulation after THA.41 Higher rates of HO after THA have been re-ported in AS patients who have un-dergone repeat operations, who have experienced postoperative in-fection, who were treated with a transtrochanteric approach, and/or who had an active disease (reflected
by elevated ESR or CRP level)
Brinker et al25found similar rates of
HO in 12 patients with AS and in an age-matched control group without
AS who underwent THA High-risk patients with preoperative ankylo-sis, with previous hip surgery, with previous infection, and/or in whom
a transtrochanteric approach to the hip was used should be considered for HO prophylaxis with indo-methacin or low-dose radiation The benefits of HO prophylaxis in other patients with AS has not been defin-itively determined
Other Peripheral Joint Involvement
The rate of shoulder and knee in-volvement in AS ranges from 25% to 70%.42Although little has been
report-ed on managing the shoulder and knee in patients with AS, Finsterbush
et al32noted marked improvement in walking, function, and pain in 21 of
23 patients with severe hip, knee, and ankle involvement who were treated with surgery and rehabilitation They did not address survivorship or the treatment of knee or ankle involve-ment Parvizi et al43recently
report-ed on 30 total knee arthroplasties in
20 patients (mean age, 55 years) who were followed for a mean of 11.2 years Knee Society pain scores
im-proved significantly (P < 0.0001), from
a mean of 14 preoperatively to a mean
of 76.3 at final follow-up Knee Soci-ety function scores improved from 16.3 to 58.7 There was essentially no improvement in ROM (84.8° to 86.7°)
In both series,32,43severe preoperative
Table 2
Review of Total Hip Arthroplasty in Patients With Ankylosing Spondylitis
Study
Patients/
Hips (N)
Ce-mented/
Unce-mented
Preop-erative Anky-losis (N)
Mean Age at Surgery (yrs)
Mean Follow-up (yrs [range])
HO:
Brooker Class 1-2/3-4
Mean Survival at 10/15/20
yr (%)
Revi-sions (N)
Patients With-out Pain (%)
Ambu-lation Status
Finster-bush et
al32
Shih
Brinker
Sochart
and
Porter30
(1
mo-30 yr)
Tang
and
Chiu27
49 U
(2-28)
Lehti-mäki
et al31
Joshi
— = no data, C = cemented, HO = heterotopic ossification, I = improved, U = uncemented
Trang 7morbidity justified total knee
arthro-plasty as a reliable means of
provid-ing durable pain relief and modest
improvement in function, regardless
of the high incidence of postoperative
stiffness
In their review of 158 patients with
AS, Emery et al44identified 52 with
shoulder involvement, 6 of whom
had acute inflammatory arthropathy
of the sternoclavicular or
acromio-clavicular joints Most symptoms
re-sponded to NSAIDs Forty-one of the
52 patients with shoulder
involve-ment experienced restriction of
scapulothoracic motion, which was
always bilateral; of these, 34 patients
had involvement of the
scapulotho-racic joint with loss of ROM (forward
flexion, abduction, and external
rota-tion), and 7 patients had asymmetric
scapulothoracic and glenohumeral
involvement Most shoulder
involve-ment was minimally disabling and
re-sponded to nonsurgical management
Destructive glenohumeral
involve-ment, although rare, was the most
disabling The presence of limited
scapulothoracic ROM may
compli-cate treatment of AS patients, similar
to the difficulties encountered during
treatment of other patients with
de-structive glenohumeral arthropathy
Spine
In AS, chronic inflammation of the
zygapophyseal joints leads to
pro-gressive fusion of the spine,
typical-ly in a caudal to cranial fashion As
spinal segments become
progressive-ly fused, pain often disappears
Os-teopenia is common in patients with
AS Rigid fused sections of the spine
concentrate and convert compressive
stresses to shear stresses at the
atlanto-occipital, cervicothoracic, and
thoracolumbar junctions This can
lead to fracture, pseudarthrosis, and
spondylodiscitis Additionally,
pro-gressive increases in cervical and
tho-racic kyphosis, combined with loss of
lumbar lordosis and of motion at the
hip joints, can result in loss of
sagit-tal balance The resultant stooped
posture can lead to significant func-tional deficits and a deformed ap-pearance Incapacitating symptoms include the inability to lie in bed or
to look straight ahead Patients with cervical ankylosis may have
difficul-ty with horizontal gaze even after correction of lumbar alignment Sur-gical intervention also may be indi-cated for management of deformity, pseudarthrosis, fracture, and spondy-lodiscitis
Cervical Deformity
Correction of deformity at the
lev-el of the cervical spine is indicated for patients in whom sagittal balance has been maintained or regained
surgical-ly, but whose kyphotic chin-brow an-gle has significantly impaired the vi-sual field or interfered with either hygiene or swallowing These pa-tients may exhibit chin-on-chest de-formity Patients with evidence of fracture, hypermobility of the cervi-cal spine, and subluxation of C1-C2 leading to kyphotic deformity should
be treated with gradual halo traction
to restore accurate alignment of the spinal canal and chin-brow angle Pa-tients with C1-C2 instability should
be treated initially with cervical trac-tion in a halo, followed by posterior arthrodesis Osteotomy of the cervi-cal spine should be limited to patients with rigid deformities Evidence of re-cent fracture, characterized by an overt fracture or by new onset of pain
in the cervical spine of a person pre-viously without pain, is a contrain-dication to osteotomy
Urist45first described extension os-teotomy of the cervical spine for cor-rection of cervical deformity This operation is performed under local anesthesia with the patient awake to facilitate neurologic monitoring dur-ing the reduction The level of correc-tion is centered at C7-T1 because the canal is relatively wide at this level and the cervical cord and nerve roots are relatively mobile In addition, the vertebral vessels do not enter the lat-eral masses at this level In 1998, Liew
and Simmons46recommended resec-tion extension osteotomy followed by posterior fusion and immobilization, with either halo or collar postopera-tively, depending on the fixation method In 1997, McMaster47
report-ed the results of extension osteotomy
at the C7-T1 level in AS patients with severe flexion deformity of the cervi-cal spine All 15 patients (mean age,
48 years) had a mean correction of 54° One patient became
quadriparet-ic, two had unilateral C8 palsies, and four experienced subluxations Neu-rologic problems were attributed to dural traction (ectasia), posterior el-ement impingel-ement of C8 roots, and subluxation Rigid fixation using plates and rod-and-screw constructs may decrease neurologic complica-tions by maintaining stability during and after osteotomy
Thoracolumbar Deformity
Corrective osteotomy of the lum-bar spine is indicated to correct sag-ittal balance when correction of hip flexion contractures does not restore sagittal balance and the patient is markedly disabled For patients with pseudarthrosis, Simmons48
advocat-ed correction of kyphotic deformity
by spine osteotomy to convert trans-lational forces to compressive forces
at the site of pseudarthrosis Van Royen et al15devised an equa-tion correlating sagittal balance and physiological end plate angle Nomo-grams constructed from this informa-tion allow the surgeon to correlate the correction angle, horizontal position
of the C7 plumb line, and the level
of the spinal osteotomy, predicting the optimum level and degree of correc-tion
Most authors advocate general an-esthesia and fiberoptic intubation for thoracic and lumbar deformity cor-rection In a review of 66 spinal os-teotomies, Bridwell et al49stressed the importance of the “wake-up test” for intraoperative patient evaluation Five neurological sequelae were missed by somatosensory evoked
Trang 8po-tentials but were detected by the
wake-up test
The osteotomies can be performed
in either the lateral decubitus or prone
position Initially plaster
thoracolum-bosacral orthosis with one leg
includ-ed was usinclud-ed for postoperative
immo-bilization Since the advent of
segmental pedicle screw fixation,
many surgeons immobilize patients
in custom rigid thoracolumbosacral
orthoses with a hip extension or
fore-go postoperative immobilization
al-together Recommended periods of
immobilization vary from 2 to 4
months for closing wedge
osteoto-mies and 6 to 15 months for opening
wedge and polysegmental
osteoto-mies
The opening wedge,
polysegmen-tal wedge, and closing wedge
osteot-omies (Fig 3) are the three surgical
techniques used for correcting
lum-bar kyphosis In 1945, Smith-Petersen
et al50 first described an opening
wedge osteotomy for correction of
lumbar kyphosis in six patients
Hehne et al51advocated
polysegmen-tal wedge osteotomy (Fig 4), which
was first described by Wilson and
Turkell52 in 1949 In 1985,
Thomas-en53subsequently described a
mono-segmental closing wedge osteotomy
of the lumbar spine, in which the
pos-terior elements, pedicles, and a
por-tion of the vertebral body are
resect-ed to accomplish the correction (the
so-called pedicle subtraction
osteot-omy)
In their meta-analysis of articles published between 1945 and 1998, Van Royen and De Gast14reported on
856 patients with AS who underwent correction of fixed kyphotic thora-columbar deformity There were 451 opening wedge osteotomies, 249 polysegmental wedge osteotomies, and 156 closing wedge osteotomies
Mean patient age was 41 years at the time of operation; mean correction
obtained was 40.3° for opening wedge osteotomies, 40.3° for polyseg-mental wedge osteotomies, and 36.5° for closing wedge osteotomies Of the
856 patients who underwent surgery,
34 (4%) died from intraoperative or postoperative complications The au-thors noted a tendency toward less severe complications with closing wedge osteotomy Jaffray et al54 re-ported that closing wedge osteotomy
Figure 4 Preoperative (A) and postoperative (B) weight-bearing lateral radiographs of a
41-year-old man who underwent polysegmental closing wedge osteotomy of the lumbar spine for correction of severe kyphotic deformity and loss of sagittal balance Lumbar lordosis was corrected from 37° preoperatively to 60° postoperatively, which resulted in a 16-cm correc-tion of the patient’s sagittal balance to neutral.
Figure 3 Bone removed for opening wedge osteotomy (A), polysegmental closing wedge osteotomy (B), and closing wedge osteotomy (C).
Trang 9can be performed even when the
an-terior longitudinal ligament is
com-pletely ossified The anterior column
is not forcibly extended in this
tech-nique, thereby minimizing the risk of
abdominal aortic injury In their
se-ries of 45 patients undergoing
pedi-cle subtraction closing wedge
osteot-omy, Kim et al55 demonstrated an
ability to effect sagittal and coronal
balance correction with one- and
two-level closing wedge osteotomies with
no long-term neurologic sequelae
Berven et al56also reported correction
of sagittal balance with closing wedge
osteotomy Pedicle subtraction
osteot-omy avoids intraoperative nerve root
compression resulting from closing
down the neural foramina as the
spine is extended
Halm et al57collected functional
outcome data from 148 of 175 patients
who had spinal deformity correction
surgery between 1979 and 1988
Im-provement was noted in 47 of the 60
items of the modified Arthritis Impact
Measurement Scales at a mean
follow-up of 4.8 years Eighty-eight
percent of patients were very satisfied
with the results of surgery, and 60.9%
were able to return to work In a
se-ries of 83 patients (5 with AS)
under-going spinal osteotomy to correct
fixed sagittal and/or coronal plane
deformity, Ahn et al58demonstrated
a statistically significant correlation
between patient functional outcome
and satisfaction with sagittal
lordo-sis >25° (P = 0.034) and coronal plumb
alignment <2.5 cm (P = 0.041) Suk et
al59 prospectively evaluated 34
pa-tients with AS after they underwent
pedicle subtraction extension
osteot-omy for correction of sagittal plane
deformity Correction of chin-brow
angle from−10° to 10° resulted in
sig-nificantly (P = 0.000) better
horizon-tal gaze Additionally, the functional
scores of items related to the
horizon-tal gaze were higher than the overall
mean score Because of the neck
stiff-ness of AS patients, correcting the
chin-brow angle is better for them
than absolute correction of coronal
and sagittal balance would be, be-cause correcting the chin-brow angle improves these patients’ visual field
The importance of planning
deformi-ty correction so as to correct visual fields is essential in AS patients
It is unclear which type of spinal osteotomy is most appropriate for the treatment of severe kyphotic
deformi-ty, although closing wedge osteoto-mies appear to have a lower incidence
of complications Deformity correc-tion surgery in AS patients is associ-ated with dural tears secondary to du-ral ectasia, transient nerve root compression, loss of correction, im-plant failure, postoperative spinal in-stability, and aortic injury
Fortunate-ly, the number of patients with severe kyphotic deformity is decreasing be-cause of improved medical manage-ment and earlier detection.60
Fracture
Generalized spinal osteopenia is common in patients with AS Spinal fracture often is caused by minor trauma and can be missed on spine radiographs because of distortion of the normal spinal anatomy by
ectop-ic bone formation, erosions, sclerosis, disk ossification, vertebral wedging,
or difficulty with patient positioning
Onset of pain after even minor
trau-ma should suggest a fracture, which may not be visible on plain radio-graphs.61Fractures frequently occur
at the C7-T1 junction and are difficult
to visualize radiographically Bone scan, MRI, or fine-cut CT can be used
to evaluate AS patients who present with cervical pain (Fig 5)
The rigid, unsupported, osteo-porotic cervical spine is most suscep-tible to hyperextension injuries, and the cervical spine is the most common site of fracture in patients with AS The drastic increase in stiffness at the cer-vicothoracic junction, combined with the lever arm of the fused cervical spine and weight of the head, makes fractures at the C6-C7 and C7-T1 lev-els most common The lumbar and thoracic spines are more resistant to
fracture because the anterior and pos-terior longitudinal ligaments are more thoroughly ossified than in the cer-vical spine Spinal fractures
typical-ly occur through the ossified disk and vertebral body; vertebral body frac-tures are more common and have a higher risk of neural compromise, partly as a consequence of a higher incidence of epidural hematoma and the possibility of the newly mobile fracture severely translating, result-ing in neural injury.61
AS patients who sustain spinal frac-tures typically have high rates of neu-rologic injury.62Missed fractures are frequent and often present as rapidly progressing cervical kyphosis Surgi-cal treatment is more commonly used, especially in patients with neurologic compromise, obscured visual fields, pseudarthrosis, or recurrent fracture When traction or internal fixation are
Figure 5 T2-weighted sagittal reconstruction magnetic resonance image of a 46-year-old man with a C7-T1 disk space fracture with subluxation and cord compression Fast spin-echo sequences may show edema, thereby al-lowing fracture localization, even without fracture displacement.
Trang 10used to manage these injuries, the neck
should be aligned to prefracture
position, not necessarily to a normal
position (Fig 6) Minor findings in
pa-tients with AS may be associated with
substantial instability in the cervical
spine, secondary to the altered
bio-mechanics of the fused spine in
ad-dition to osteopenia and the
concen-tration of forces at the cervico-occipital
and cervicothoracic junctions
Preoperative evaluation of the
cervical spine is essential when
ma-nipulating the neck during
intuba-tion and patient posiintuba-tioning
Physi-cians also must be aware that,
because the atlanto-occipital joint is
last to fuse, atlantoaxial instability
may occur Instability is usually
demonstrated on lateral
flexion-ex-tension views of the neck, where the
atlantodens and posterior
atlan-todens intervals are measured An
atlantodens interval >3.5 mm is
in-dicative of instability A difference of
7 mm indicates disruption of the
alar ligaments, and a difference >9 to
10 mm or a posterior atlantodens
in-terval >14 mm is associated with an
increased risk of neurologic injury
and usually requires surgical inter-vention
Spondylodiscitis
Spondylodiscitis has been
report-ed to occur in 5% to 23% of patients with AS; 50% of these patients are asymptomatic.63,64Spondylodiscitis, which presents as an erosive
sclerot-ic process, characteristsclerot-ically involves the intervertebral disk and adjacent bone It can be confused radiograph-ically with diskitis and pseudarthro-sis Unlike diskitis, biopsies of these lesions demonstrate chronic inflam-matory changes with no infective or-ganisms.63,64Spondylodiscitis lesions occur at the level of the intervertebral disk rather than through the vertebral body, as in pseudarthrosis Pseudar-throsis often presents as new back pain in a previously asymptomatic in-dividual and often arises after minor trauma Most cases of spondylodis-citis and pseudarthrosis resolve with nonsurgical management Surgical stabilization may be required in pa-tients with intractable pain,
associat-ed posterior element disruption, and fracture It is important to assess
ky-photic deformity before stabilization because deformity can create shear stresses at the site of spondylodisci-tis or pseudarthrosis These transla-tional forces can be converted to com-pressive forces at the time of stabilization, leading to higher rates
of fusion
Summary
AS, which affects approximately 350,000 people in North America and 600,000 in Europe (worldwide prevalence, 0.9%), belongs to a larger group of spondyloarthropa-thies and is characterized predomi-nantly by involvement of the sa-croiliac joints in young men who present with inflammatory low back pain in their third or fourth decade The disease primarily affects the ax-ial skeleton and is characterized by enthesopathy, which leads to fusion
of the sacroiliac joints, hips, and spine Young men presenting with inflammatory back pain and evi-dence of sacroiliitis should be screened for AS; most patients are HLA-B27–positive
Management of AS remains pal-liative, with NSAIDs continuing to
be the mainstay of treatment How-ever, new anti–TNF-α drugs offer the promise of arresting the progres-sion of AS AS patients presenting with back or neck pain after minor trauma should be considered to have spinal fractures until defini-tively proven otherwise with CT or MRI THA can significantly improve function, pain, and deformity in AS patients with severe hip involve-ment Results are comparable to those in other young patients with severe hip pathology Because the incidence of HO in AS patients undergoing THA may not be sig-nificantly more than that of similar non-AS patients undergoing THA, the routine use of HO prophylaxis in
AS patients should be reserved for
Figure 6 Preoperative (A) and postoperative (B) lateral radiographs of a 31-year-old man
who sustained a C5-C6 fracture through the disk space Posterolateral fusion was done with
lateral mass plates and posterior element wiring.