It has been suggested that patients with axial low back pain who experience a concordant pain response during diskography are more likely to respond favorably to surgical intervention..
Trang 1Evaluation of Low Back Pain
Abstract
Diskography is evolving to play a crucial role in the evaluation of axial low back pain, especially in regard to surgical decision making Despite advances in other forms of imaging, diskography remains unique in that it is the only test that seeks to provoke a pain response during the study It has been suggested that patients with axial low back pain who experience a concordant pain response during diskography are more likely to respond favorably
to surgical intervention However, the efficacy of using this potential correlation is dependent on the technical application and interpretation The validity of diskography remains controversial,
in part because postdiskography surgical outcomes have been inconsistent Therefore, in select patients with recalcitrant back pain, diskography remains a second-line diagnostic modality that is used to clarify surgical indications Despite well-defined guidelines, the technical aspects of diskography and its interpretation are still evolving
Low back pain (LBP) occurs fre-quently and, in some cases, may become chronic.1 Many causes of LBP remain poorly understood Al-though the disk is Al-thought to be a pain generator, establishing a disco-genic origin for LBP in a specific pa-tient can be challenging
Evidence supports the concept that the intra-vertebral disk is a po-tential pain generator The nucleus pulposus, the central core of the disk, is composed of type II collagen fibers, along with various muco-polysaccharides and glycosami-noglycans This composition sup-ports the high water content of the nucleus, which behaves biomechan-ically as a fluid cushion that trans-mits its loading forces to the outer anulus fibrosus as well as to the ver-tebral end plate.2,3The anulus is dis-tinct from the nucleus and is prima-rily composed of type I collagen
arranged in multiple concentric lay-ers This fiber arrangement allows the anulus to optimally resist ten-sile, radial, and torsional forces With acute trauma or the degener-ative changes associated with time and repetitive microtrauma, the fi-bers of the anulus may be disrupted Although the nucleus pulposus has
no nerve supply, the outer third of the anulus is innervated It receives supply from both the sinuvertebral nerve, which innervates the posterior and posterolateral regions, and the gray ramus, which is distributed pri-marily laterally and anteriorly.4 Pro-liferation of nerve fibers containing substance P have been found in the anuli of degenerative disks and in the disks of patients undergoing spinal fusion for back pain.5,6These findings suggest that the anulus fibrosus may play a role in neuromodulation of pain and, more specifically, that the
Spiros G Pneumaticos, MD, PhD
Charles A Reitman, MD
Ronald W Lindsey, MD
Dr Pneumaticos is Assistant Professor,
Department of Orthopedic Surgery,
Baylor College of Medicine, Houston,
TX Dr Reitman is Assistant Professor,
Department of Orthopedic Surgery,
Baylor College of Medicine Dr Lindsey
is Professor and Chair, Department of
Orthopedic Surgery, University of Texas
Medical Branch, Galveston.
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 Pneumaticos, Dr Reitman, and Dr.
Lindsey.
Reprint requests: Dr Lindsey,
Department of Orthopaedic Surgery,
University of Texas Medical Branch,
Rebecca Sealy Hospital, 2316
University Boulevard, Galveston, TX
77555.
J Am Acad Orthop Surg 2006;14:
46-55
Copyright 2006 by the American
Academy of Orthopaedic Surgeons.
Trang 2mechanical irritation of the outer
anulus can stimulate these nerve
endings.7Additionally, annular
fis-sures may allow nuclear cytokines
and other inflammatory substrates to
communicate with the nerve endings
and cause a chemical irritation.8-10
Discogenic pain may occur
second-ary to acute disk disruption, from
chronic degenerative processes, or
from conditions that result in
seg-mental spine instability
Although episodes of acute LBP
are prevalent in the general US
pop-ulation, most symptomatic episodes
resolve within a short time Only a
small percentage of these patients
develop chronic symptoms; of this
group, most do not have a clear
diag-nosis It is important for the
clini-cian to differentiate patients with
axial pain or possibly referred pain
syndromes from those who have
true radicular pain In the latter, it is
usually easier to establish specific
diagnosis because the workup,
man-agement, and prognosis of these
tients greatly differ from those of
pa-tients with axial pain syndromes
Individuals with true radicular pain
often have positive neurologic signs;
the goal of treatment, therefore, is to
relieve the cause of the neurologic
disturbance
A thorough history and physical
examination are essential for all
pa-tients Those with discogenic pain
syndromes will have established
ax-ial pain complaints of >3 months
Symptoms typically are aggravated
by weight-bearing activity, and
rela-tive relief can be achieved from
re-cumbency The physical
examina-tion is often nonspecific Lumbar
spine range of motion is usually
re-stricted secondary to pain
Paraspi-nal muscle spasm may be present,
nerve-root tension signs are
nega-tive, and the neurologic examination
is usually normal
Plain radiography also typically is
nonspecific and may demonstrate
disk space narrowing, end plate
scle-rosis, or osteophyte formation
Dy-namic flexion and extension
radio-graphs may detect elements of instability; computed tomography (CT) is rarely enlightening
Magnet-ic resonance imaging (MRI) may be appropriate for acute disk derange-ment; however, it does not consis-tently demonstrate abnormalities in the disk In advanced degenerative conditions, MRI more routinely de-tects degenerative disk morphology
However, the relationship between MRI-depicted disk degenerative changes and LBP remains poorly un-derstood.11Although MRI is highly sensitive in depicting disk disease, its specificity or ability to correlate symptoms with these changes is low This low MRI sensitivity in es-tablishing a discogenic origin for LBP is best reflected by the high in-cidence of disk abnormalities associ-ated with lumbar spine MRI studies
in asymptomatic volunteers.12 Diskography may be considered
to further evaluate the condition of patients diagnosed with discogenic LBP that is not responsive to an ex-tended course of nonsurgical treat-ment Unlike other tests for LBP, diskography has a provocative com-ponent It not only demonstrates ab-normal morphology, but it can also assist in localizing the disk as a pain generator Diskography can be ap-plied to determine the presence of a painful disk despite normal noninva-sive imaging studies, to identify the painful disk or disks amid multiple degenerative disks, and to assist in defining the extent of surgery when multiple levels of potential pain gen-erators exist However, the efficacy
of diskography is controversial, and appropriate interpretation requires
an in-depth appreciation of the pa-tient, the pathologic condition or conditions, and the proper technique for its application
History
Lindblom,13stimulated by the
earli-er work of Schmorl and Lindgren, first reported a novel technique for the direct evaluation of potentially
symptomatic lumbar disks The test consisted of a diagnostic disk punc-ture and injection, which was called diskography Lindblom noted that the use of diskography was indicated based on its ability to distinguish be-tween normal and ruptured disks and to reproduce pain concordant with symptoms in symptomatic disks This was corroborated by Hirsch,14who successfully provoked pain in 16 patients by injecting sa-line solution into the disk
Although diskography initially was sparingly used, its popularity further decreased in 1968, when Holt15 demonstrated a 37% inci-dence of positive diskograms in a group of asymptomatic prison vol-unteers Almost two decades later, Simmons et al16deemed Holt’s study
to be flawed in its methodology However, when Walsh et al17 later duplicated Holt’s study with im-proved methodology, they reported
no false-positive results
The sensitivity of diskography has been considerably enhanced by the advent of CT Bernard18 demon-strated that plain diskography in combination with postdiskography
CT improved diagnostic accuracy More recently, interest has devel-oped in the degree of intradiskal pressure and its relationship to prov-ocation during diskography The use
of manometry allows for the mea-surement and correlation of incre-mental injectable pressure with the resultant pain response There is early evidence that this may permit more specific interpretation and di-agnosis and thus may more accu-rately guide treatment.19,20
Indications
The indications for diskography in the management of LBP have been outlined in a position statement from the Executive Committee of the North American Spine Society Diagnostic and Therapeutic Com-mittee21and are described in Table 1 Patients considered for
Trang 3diskogra-phy ideally should have low back
symptoms for a minimum of 4 to 6
months that are nonresponsive to
nonsurgical management, including
physical therapy and medical
treat-ment The potentially painful level
should be consistent with the
find-ings on physical examination, plain
radiographs, and MRI In these select
discogenic back pain patients,
dis-kography serves as a test to confirm,
not determine, the need for surgical
intervention
Procedure
Anesthesia and
Positioning
Because the procedure requires
the patient’s response to pain
provo-cation, it is imperative that only a
mild sedative be administered
intra-venously, such as midazolam 2 mg
with fentanyl 25 µg The merits of
prophylactic antibiotic use
current-ly is controversial.22When
adminis-tered, antibiotics can consist of 1 g
cefazolin given intravenously
with-in 1 hour before the procedure, as
well as cefazolin 0.5 mL added into
the injectate for each disk
Two standard approaches are
ad-vocated for access to the lumbar
disks: the direct posterior or
intra-pedicular approach and the
postero-lateral or extrapedicular approach
The posterolateral approach more
commonly is used.23The patient is
positioned prone on a radiolucent
ta-ble in a manner to accommodate an-teroposterior and lateral
fluoroscop-ic images
The preferred side for injection is that contralateral to the patient’s dominant pain The levels to be eval-uated are determined by the clini-cal presentation of the patient and the results of the imaging studies
A legitimate study always should include at least one control level consisting of a normal-appearing, asymptomatic disk adjacent to the level or levels being evaluated
Posterolateral Techniques
The two-needle technique is pre-ferred to lower the incidence of post-diskography infection The skin is anesthetized with local anesthesia approximately 5 to 6.5 cm from the midline of the level of the interver-tebral disk The initial larger, cannu-lated needle (18-gauge) is first passed through the skin and soft tissue to the anulus of the disk; this needle guides the second, smaller needle (22- or 25-gauge) that actually punc-tures the anulus Fluoroscopy is used
to confirm the disk level and to di-rect the larger needle from the skin puncture toward the anterior margin
of the superior articular process and into the posterolateral aspect of the disk (Figure 1, A) The smaller nee-dle is then directly inserted through the larger needle to puncture each disk and terminate within the
nucle-us pulposnucle-us Proper needle
place-ment in the disk is confirmed by vi-sualizing the tip of the needle in the inner one third of the disk in both the anteroposterior and lateral radio-graphs
Confirmation of optimal needle placement can be challenging at the L5-S1 level, where significant caudal angulation is required for adequate visualization Anatomic landmarks
of the safe zone for needle insertion are the inferior end plate of L5, the superior articulating process of S1, and the iliac crest (Figure 1, B) Most
of the technical difficulties encoun-tered when injecting the L5-S1 space can be avoided by selecting a higher puncture site compared with the other disk spaces When the iliac crest obstructs the approach despite adjusting the angle of trajectory, then alternative approaches, such as
a midline transthecal L5-S1 punc-ture, might be warranted However, this approach clearly carries a
high-er risk for complications and theo-retically may provoke more pain
Assessment
After all needles have been
insert-ed into the levels to be studiinsert-ed, a water-soluble contrast solution is in-jected with the patient unaware of the precise moment of injection, the level or levels injected, and the exact amount of contrast infiltrated Disk pressurization should first be per-formed at the control level to estab-lish the patient’s pain tolerance As other levels are injected, the patient
is asked to determine whether the injection provoked pain and to com-pare these symptoms with his or her usual pain level in both distribution and quality
Digital manometry should be used to measure intradiskal pressure
at the time of the injection and at 0.5-mL injectable increments The static disk pressure (relative to the opening pressure) associated with a pain response is noted, as are the
lev-el of pain intensity and the concor-dance of the provoked symptoms When the test is done properly, a
Table 1
Indications for Diskography in a Position Statement From the Executive
Committee of the North American Spine Society 21
Unremitting spinal pain, with or without extremity pain, of >4 months’
duration, not responsive to all standard methods of conservative treatment
Persistent disk-related pain, suspected when other evaluation modalities are
equivocal
Persistent pain in the postoperative period as a result of suspected
intervertebral disk degeneration, recurrent herniation, or a pseudarthrosis
Disk space evaluation in a spine segment considered for fusion to determine
whether it is a pain generator
Determination of the primary symptom-producing level or levels when
chemonucleosis or other intradiskal procedures are being contemplated
Trang 4morphologically normal disk should
not produce pain It is imperative to
avoid excessively high intradiskal
pressures, which may precipitate
false-positive results.20The normal
disk accepts a fluid volume of
be-tween 1.5 and 2.5 mL; more than 3
mL is abnormal Increased
intradis-kal contrast volume often suggests a
complete annular tear with leakage
of fluid into the epidural space Once
the disk has been injected, images
are recorded with high-quality
bipla-nar radiographs, followed by CT
ax-ial scans
Interpreting the Results
An accurate diskogram
interpreta-tion requires the documentainterpreta-tion and
analysis of several vital pieces of
in-formation: (1) the disk pressure and
the volume of fluid accepted by the
disk; (2) the pattern of the contrast
distribution or morphology of the
in-jected disks; and (3) the subjective pain response of the patient to the in-jection, compared with the absence
of a pain response in an adjacent con-trol level.21 One classification for morphologic pattern of progressive degeneration is shown in Figure 2
Additional information on disk morphology and stage of degenera-tion can be obtained from the post-diskography axial CT images (Figure 3) The nature and extent of the pa-thology are better defined, and some lesions, such as annular fissuring and lateral disk herniations, are more clearly delineated A disko-gram is considered positive when it depicts an abnormal disk and con-cordant pain is reproduced during an injection with reasonable disk pres-sures (Table 2)
O’Neill and Kurgansky20
conclud-ed that disk pressures >50 psi were likely to result in a false-positive pain response Furthermore, they
identified two distinct subgroups of true-positive disks on diskography: contact-sensitive and pressure-sensitive In contact-sensitive disks, simple contact between the contrast and the disk was sufficient to pro-voke pain True-positive pressure-sensitive disks demonstrated a con-cordant pain response between and
10 and 50 psi The investigators were unable to differentiate false-positive from true-positive disks when the disk pain threshold was <10 psi Derby et al19also identified a low-pressure–sensitive group of patients with positive diskography They
not-ed that pressures <15 psi were insuf-ficient to cause significant mechan-ical deformation; patients who had positive diskography with pressures
<15 psi were termed to have chemi-cally sensitive disks The authors postulated that the level of pain-provoking pressure may be related to specific surgical indications
Figure 1
A,Proper positioning for L4-5 diskogram The superior articular process of L5 (S) is positioned midway in the superior end plate
of L5 (SEP) Correct needle placement is shown by the black target I = inferior articular process of L4; P = pedicle of L4, L5
B,Proper positioning for L5-S1 diskogram The small inverted triangle defined by the superior articular process of S1 (SAP), the iliac crest (IC), and the inferior end plate of L5 (IE) marks correct needle placement
Trang 5Complications resulting from dis-kography are rare; among the most serious is diskitis The reported inci-dence of diskitis is 0.1% to 0.2%24 and reflects a steady decrease in oc-currence since 1980 This decline can be attributed to the use of the two-needle technique, prophylactic antibiotics, improved fluoroscopic equipment, and use of smaller nee-dles.25
Other reported complications, al-though less prevalent, include tem-porary headache, nausea, meningi-tis, epidural abscess, arachnoidimeningi-tis, intrathecal hematoma, and intradu-ral injection of contrast.26 In addi-tion, there have been isolated reports
of urticaria, retroperitoneal
hemato-ma, cauda equina syndrome, and acute disk herniation Perhaps the most frequent complaint is pain ex-acerbation for 1 to 2 weeks, which resolves with short-term adminis-tration of analgesics and muscle re-laxants Early concerns regarding the long-term adverse effects of diskog-raphy on disk viability have not ma-terialized In an up to 20-year clini-cal follow-up study, Flanagan and Chung27reported no radiographic ev-idence of progressive disk degenera-tion following diskography
Validity
Diskography initially was devel-oped as a provocative test for assess-ing patients with disk herniation As experience with this modality in-creased, it became evident that dis-kography also could provide mor-phologic details about the internal
Figure 2
Classification of stages of disk degeneration (Reproduced with permission from
Adams MA, Dolan P, Hutton WC: The stages of disc degeneration as revealed by
diskograms J Bone Joint Surg Br 1986;68:36-41.)
Figure 3
A,Lateral CT image of a lumbar spine immediately following a diskogram at the
L3-4, L4-5, and L5-S1 segments The upper level (L3-4) is normal, with a cottonball
appearance Contrast material remains central The middle level (L4-5) is irregular,
with the majority of the contrast in the central nucleus and a focal area of contrast
extension in the anulus The lower level (L5-S1) is an example of an annular fissure,
with contrast extending to the posterior annular margin The upper level is normal,
the middle level shows some degeneration, and the lower level is incompetent with
advanced degeneration B, Axial CT image of the middle level in panel A, showing
an annular tear with dye tracking to the posterolateral anulus
Table 2 Criteria for Establishing a Positive Diskogram
Abnormal disk morphology, including posterior annular disruptions Pain concordant to the patient’s usual pain
Pain limited to 1 or 2 disk levels Negative control
Trang 6architecture of the disk Although
the association of diskography
find-ings with symptoms is not well
un-derstood, some early investigators
did manage to correlate back pain
with disk morphology
The issue of disk morphologic
change and its association with pain
became extremely controversial
when Holt15in 1968 performed
mul-tilevel lumbar diskograms in 30
asymptomatic volunteer inmates and
reported a 37% false-positive rate
(pain provocation in asymptomatic
participants) In this study, a positive
disk was designated by either
provo-cation of pain or the presence of a
morphologically abnormal disk
When Holt’s study was later
reas-sessed by Simmons et al,16 it was
noted that diatrizoate (the contrast
medium used) was more irritating
than currently available contrast
me-dia Furthermore, Holt claimed that
his patients were asymptomatic
vol-unteers, yet the selection process was
not detailed Additionally, the
imag-ing equipment and lumbar puncture
technique employed were
substan-dard, and at least some of the
injec-tions were done through inaccurately
placed needles Finally, a positive
dis-kogram was not clearly defined; this
was most evident in the diskography
interpretation made in patients with
a positive response of concordant
pain without initial symptoms
Walsh et al17evaluated the results
of diskography in 10 asymptomatic
volunteers as well as in 7
symptom-atic patients Morphologically
abnor-mal disks were observed in 17% of
the injected disks in the
asympto-matic volunteers and in 65% of the
symptomatic patients None of the
diskograms in the asymptomatic
group was associated with significant
pain, whereas typical pain was
repro-duced during the injection in six of
the seven symptomatic patients The
authors concluded that the single
most important determinant of
accu-rate sensitivity was a subjective
pa-tient pain response
In three recent diskography
stud-ies, Carragee and colleagues28-30 made several important observa-tions (Table 3) In the first study, a group of patients (mean age, 43 years) without LBP was studied by diskography.28 Ten were asympto-matic, 10 had chronic neck pain, and
6 had a somatization disorder The authors determined that disks with annular disruption were more likely
to be painful However, this associa-tion was considerably more com-mon in the group with an associated chronic pain syndrome In this study, 10% of the asymptomatic group, 40% of the chronic neck pain group, and 83% of the somatization group experienced painful lumbar diskograms
In the second study, Carragee et
al29 studied 24 disks in 8 patients who had previously undergone iliac crest bone grafting for a non-thora-columbar–related disorder Disko-grams were performed in all disks 2
to 4 months following iliac crest sur-gery Because these patients had no lumbar spine symptoms, concor-dance was determined as reproduc-tion of their familiar bone graft site pain Four of the eight patients
dem-onstrated concordant iliac crest pain, and the authors concluded that dif-ferentiating between spinal and non-spinal origins of pain was difficult Again, intensity of pain response was greater in disks with annular disruption compared with disks clas-sified as normal or intermediate
In the last study, 25 patients with mild persistent LBP were evaluated with diskography.30None of the sub-jects was limited functionally, nor were any seeking medical attention for their symptoms Nine of 25 pa-tients (36%) had fully concordant diskography with negative control levels These results imply that dis-kography may not be specific in dif-ferentiating clinically relevant pa-thology Fifty-two patients being considered for surgery had diskogra-phy as part of their preoperative evaluation and were used as control subjects; in this group, 73% had pos-itive diskograms Low-pressure in-jections made no significant differ-ence in the percentage of positive diskograms among the two groups;
in the experimental group, a positive response was more likely in patients with a history of chronic pain.30
Table 3 Cumulative Results of Diskography28,30-32
Patient Group
Patients Reporting Pain (%)
HIZ lesion: asymptomatic with normal psychometrics
HIZ lesion: asymptomatic with abnormal psychometrics
Posterior disk surgery: symptomatic with normal
Posterior disk surgery: symptomatic with abnormal
HIZ = high-intensity zone
Trang 7Other diskography studies by
Car-ragee and colleagues31,33,34have
con-clusively demonstrated that
assess-ment of the patient’s psychometric
profile is critical in the
comprehen-sive evaluation of LBP These
charac-teristics are shown to be predictors of
the development of LBP as well as of
the patient’s response to diskography
These studies challenge the
abil-ity of structural variables such as
dis-kography (or even MRI) to detect
clinically relevant disk pathology.33
However, clinically useful
informa-tion can be obtained with the careful
analysis of specific pain-response
pat-terns in subgroups of patients with
LBP Chronic LBP patients with
ab-normal psychometric evaluations
and/or somatization features
demon-strated notably higher painful
re-sponses.31,33,34These facts should be
determined, understood, and
appro-priately factored into the
interpreta-tion of provocative diskography
Diskography Versus Magnetic Resonance Imaging
Prior to the advent of magnetic resonance imaging (MRI) in the 1980s, diskography was the only means available of depicting the de-generative quality of the disk Ini-tially, MRI was considered to be at least as accurate as diskography in the assessment of an abnormal disk while maintaining all of the benefits
of a noninvasive procedure that did not require ionizing radiation.35This position was supported by Schnei-derman et al,36who reported MRI to
be accurate in predicting normal ver-sus abnormal disk morphology in
100 of 101 disks compared with dis-kography Later studies, however, demonstrated that diskography may detect abnormal disks in the pres-ence of a normal MRI and that many abnormal disks on MRI are not pain-ful with provocative
diskogra-phy.18,37 Furthermore, it has been suggested that there are no MRI fea-tures that can reliably predict posi-tive provocation during diskogra-phy.38
Aprill and Bogduk39were the first
to describe the high-intensity zone (HIZ) (Figure 4), which was detected
in the MRI scans of 28% of 500 pa-tients with back symptoms without radiculopathy In addition, they re-viewed a subset of 41 patients with HIZs who also were studied with CT diskography The presence of an HIZ correlated notably with high-grade annular tears and was strongly
relat-ed to concordant pain patterns The authors suggested that the HIZ was pathognomonic of an internally dis-rupted and symptomatic disk Oth-ers have since verified the high sen-sitivity of an MRI-depicted HIZ in predicting an annular tear.40 Several other studies, however, have not supported the high correla-tion of an HIZ to a diskographically concordant disk.41,42 Horton and Daftari43studied 63 disks in 25 pa-tients with LBP; they evaluated spe-cific MRI patterns and their associa-tion with results of diskography The authors identified consistently be-nign patterns that had a strong neg-ative correlation, as well as other ad-vanced degenerative or disrupted patterns that had a strong positive correlation with concordant pro-voked pain
Carragee et al32also studied the prevalence and significance of the HIZ in an asymptomatic population prone to degenerative changes, as well as in a group of patients with LBP In 50% of disks with an HIZ and with normal psychometrics (based on a Modified Zung Depres-sion Test and a Modified Somatic Pain Questionnaire), the diskogram was positive, whereas it was positive
in all of the disks with abnormal psychometrics The authors con-cluded that an HIZ does not reliably reflect the presence of internal disk
Figure 4
A,Sagittal T2-weighted MRI scan of the lumbar spine demonstrating high-intensity
zones at the two lower disk levels (arrows) B, Lateral radiograph of the lumbar
spine with a high-intensity zone at L4-5 following an L3-4, L4-5, and L5-S1
diskography Note the leakage of the contrast material at L4-5, the segment
corresponding with the high-intensity zone
Trang 8disruption or a concordantly painful
disk Currently, an HIZ appears to be
most sensitive for an outer annular
disruption or fissure However, the
significance of this finding in regard
to diskogenic LBP is still in dispute
Diskography and
Treatment Outcome
In most studies that have
ad-dressed outcomes related to the
treatment of discogenic back pain as
evaluated by diskography, inclusion
criteria required the presence of
chronic LBP—that is, at minimum,
LBP of more than 1 year’s duration
Furthermore, all patients will have
failed comprehensive nonsurgical
treatment, with many unable to
work as a result of back pain Also,
all patients will have had
preopera-tive diskography to assist with
surgi-cal decision making
The traditional surgical treatment
of discogenic pain has been lumbar
fusion, and several uncontrolled,
ret-rospective studies have evaluated the
results of fusions (anterior interbody,
posterolateral, posterior interbody,
and/or 360°) for diskographically
con-firmed discogenic pain.1,44-46
Clini-cally successful results varied from
approximately 40% to 90%; these
authors noted a 74% functional
suc-cess rate (return to work, no
medica-tion requirements) at approximately
2.5 years postoperatively.44
Blumen-thal et al44analyzed 34 patients with
LBP confirmed by abnormal
diskog-raphy and treated with anterior
interbody fusion Wetzel et al46
re-ported 66% satisfactory clinical
out-comes in 48 patients fused anteriorly
or posteriorly; successful outcome
was strongly correlated with
achiev-ing a solid arthrodesis
Linson and Williams47 reviewed
51 patients with chronic LBP
(dura-tion >1 year) treated with anterior
lumbar interbody fusion or 360°
fu-sion and compared their outcomes
with those of a similar group of 10
patients who could not undergo
sur-gery because of state insurance
reg-ulations According to the Oswestry
Disability Index and patient reports
of pain, the study demonstrated an 80% measurable diminution of pre-operative pain at follow-up of 15 to
36 months The results of anterior versus 360° fusion were similar In the nonsurgical group, by compari-son, only 1 of the 10 improved after
a mean follow-up of 24 months
Colhoun et al48reviewed 162 pa-tients who had preoperative diskog-raphy before anterior or posterior fu-sions This is the only study to date
to compare outcomes in patients un-dergoing fusion for chronic LBP who had normal, nonprovocative disko-grams with those who had concor-dant diskograms In the study, 137 patients had a least one concordant pain level on diskography; 25 had morphologically abnormal disks but were asymptomatic with provoca-tion (diskogram negative) The diskogram-positive group had an 89% clinical success rate compared with only 52% for the diskogram-negative group; follow-up ranged from 2 to 10 years
In the study of Derby et al,1978 subjects were treated for chronic LBP Based on diskographic charac-teristics, several subcategories were defined; these included a group of pa-tients who experienced concordant pain with low-pressure injection
Chemically sensitive disks were demonstrated in 36 patients; treat-ment consisted of anterior interbody
or combined fusion (9 patients), pos-terior intertransverse fusion (10), and nonsurgical management (17) In this subgroup, the most favorable outcome (89% good or excellent re-sults) was observed in the patients treated with fusion (either anterior
or combined) Patients treated non-surgically demonstrated only 12%
good or excellent results Based on these observations, the authors con-cluded that precise categorization of diskogram responses may improve surgical decision making and out-come
The efficacy of diskography in treatment outcomes is still in
dis-pute because class I evidence (pro-spective, randomized clinical trials)
is still lacking Although the current diskography literature is extensive,
no standardization exists in the as-sessment of clinical outcomes, the choice of surgical approach, patient selection, and psychometric evalua-tion Furthermore, satisfactory clin-ical outcomes have varied signifi-cantly Nonetheless, for studies in which reasonable comparisons have been possible, the clinical outcomes
in patients with positive diskograms were more favorable than in patients with nonconcordant provocative studies.19,47,48
Other surgical strategies for dis-cogenic pain, such as intradiskal electrothermal therapy (IDET), have recently been developed IDET is a percutaneous technique that in-volves the placement of a heat probe into the disk space The mechanism
by which this affects pain is unclear, but it is thought to be the thermal ablation of pain-sensitive fibers in the outer anulus and/or the change
in the biomechanical properties of the anulus as the structure of col-lagen is altered during heating and subsequent cooling In general, IDET
is considered to be beneficial in a very select group of patients, for which inclusion criteria include pos-itive diskography
Saal and Saal49reported on 58 pa-tients treated with IDET and as-sessed at 2-year follow-up by visual analog scale (VAS) and the Medical Outcomes Study 36-Item Short Form (SF-36) These patients demon-strated significant improvement
in pain (SF-36, P = 0.0017; VAS,
P = 0.4960), quality of life (SF-36,
P= 0.0001), and physical functioning
(SF-36, P = 0.0001) Symptomatic
improvement was maintained at
2 years Bogduk and Karasek50 fol-lowed a group of 53 patients for 2 years after failure of nonsurgical treatment of chronic LBP Although the study was not randomized, 36 patients were treated with IDET, and
17 patients served as control
Trang 9sub-jects None of the control patients
improved, whereas >50% of the
treatment group experienced at least
a 50% pain reduction; 20% were
pain free Both studies49,50concluded
that IDET can be beneficial in a
care-fully selected group of patients with
discogenic pain
More recently, disk arthroplasty
has been employed for the treatment
of discogenic pain Although the
pro-cedure has been employed in Europe
for many years, it has only recently
been approved for use in the United
States Inclusion criteria for the US
Food and Drug Administration
study were very strict and included
positive diskography Two centers
reported on their combined 2-year
results as part of the FDA trial,51
which consisted of a prospective
ran-domized study comparing 100
pa-tients with disk arthroplasty with 44
patients undergoing anterior lumbar
interbody fusion with threaded
cag-es Improvement was reported in
both treatment groups, and their
re-spective outcomes and
complica-tions were similar Disk
replace-ment offers the hypothetical
advantage of maintaining the
mo-tion segment, but how it compares
in the long term with the
tradition-al spine fusion remains to be
learned
Summary
Considerable controversy exists in
reporting on the efficacy of
diskogra-phy Proponents conclude that
dis-kography is essential for the workup
of patients with persistent back pain
because of its ability to designate a
specific disk as a potential pain
gen-erator However, the mechanism by
which pain is reproduced is not well
understood, and the prognostic value
of the symptomatic levels identified
has not been conclusively
demon-strated Opponents of diskography
also conclude that this diagnostic
modality results in unnecessary
sur-gery Diskography should be
consid-ered when all other treatment
mo-dalities have failed and surgery is being contemplated A position statement of the North American Spine Society advocates the use of diskography within strict guidelines
Finally, a positive diskography eval-uation consists of an abnormal disk with a concordant pain response in a patient with an adjacent normal, asymptomatic disk or disks Even in this scenario, however, diskography results must be considered as an ad-junct in the assessment of the indi-vidual patient
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