Article

Chronic low back pain (CLBP) is one of the main causes of disability in the
western world with a huge economic burden to society. As yet, no specific
underlying anatomic cause has been identified for CLBP. Imaging often reveals
degenerative findings of the disc or facet joints of one or more lumbar motion
segments. These findings, however, can also be observed in asymptomatic people.
It has been suggested that pain in degenerated discs may be caused by the
ingrowth of nerve fibers into tears or clefts of the annulus fibrosus or nucleus
pulposus, and by reported high levels of pro-inflammatory mediators. As this
so-called discogenic pain is often exacerbated by mechanical loading, the concept
of relieving pain by spinal fusion to stabilise a painful spinal segment, has
been developed. For some patients lumbar spinal fusion indeed is beneficial, but
its results are highly variable and hard to predict for the individual patient.
To identify those CLBP patients who will benefit from fusion, many surgeons rely
on tests that are assumed to predict the outcome of spinal fusion. The three most
commonly used prognostic tests in daily practice are immobilization in a
lumbosacral orthosis, provocative discography and trial immobilization by
temporary external transpedicular fixation. Aiming for consensus on the
indications for lumbar fusion and in order to improve its results by better
patient selection, it is essential to know the role and value of these prognostic
tests for CLBP patients in clinical practice. The overall aims of the present
thesis were: 1) to evaluate whether there is consensus among spine surgeons
regarding the use and appreciation of prognostic tests for lumbar spinal fusion;
2) to verify whether a thoracolumbosacral orthosisis (TLSO) truly minimises
lumbosacral motion; 3) to verify whether a TLSO can predict the clinical outcome
of fusion for CLBP; 4) to assess whether provocative discography of adjacent
segments actually predicts the long-term clinical outcome fusion; 5) to determine
the incidence of postdiscography discitis, and whether there is a need for
routine antibiotic prophylaxis; 6) to assess whether temporary external
transpedicular fixation (TETF) can help to predict the outcome of spinal fusion;
7) to determine the prognostic accuracy of the most commonly used tests in
clinical practice to predict the outcome of fusion for CLBP. The results of a
national survey among spine surgeons in the Netherlands were presented in Study
I. The surgeons were questioned about their opinion on prognostic factors and
about the use of predictive tests for lumbar fusion in CLBP patients. The
comments were compared with findings from the prevailing literature. The survey
revealed a considerable lack of uniformity in the use and appreciation of
predictive tests. Prognostic factors known from the literature were not
consistently incorporated in the surgeons' decision making process either. This
heterogeneity in strategy is most probably caused by the lack of sound scientific
evidence for current predictive tests and it was concluded that currently there
is not enough consensus among spine surgeons in the Netherlands to create
national guidelines for surgical decision making in CLBP. In Study II, the
hypothesized working mechanism of a pantaloon cast (i.e., minimisation of
lumbosacral joint mobility) was studied. In patients who were admitted for a
temporary external transpedicular fixation test (TETF), infrared light markers
were rigidly attached to the protruding ends of Steinman pins that were fixed in
two spinal levels. In this way three-dimensional motion between these levels
could be analysed opto-electronically. During dynamic test conditions such as
walking, a plaster cast, either with or without unilateral hip fixation, did not
significantly decrease lumbosacral joint motion. Although not substantiated by
sound scientific support, lumbosacral orthoses or pantaloon casts are often used
in everyday practice as a predictor for the outcome of fusion. A systematic
review of the literature supplemented with a prospective cohort study was
performed (Study III) in order to assess the value of a pantaloon cast in
surgical decision-making. It appeared that only in CLBP patients with no prior
spine surgery, a pantaloon cast test with substantial pain relief suggests a
favorable outcome of lumbar fusion compared to conservative treatment. In
patients with prior spine surgery the test is of no value. It is believed by many
spine surgeons that provocative discography, unlike plain radiographs or magnetic
resonance imaging, is a physiologic test that can truly determine whether a disc
is painful and relevant in a patient's pain syndrome, irrespective of the
morphology of the disc. It has been suggested that in order to achieve a
successful clinical outcome of lumbar fusion, suspect discs should be painful and
adjacent control discs should elicit no pain on provocative discography. For this
reason, a cohort of patients in whom the decision to perform lumbar fusion was
based on an external fixation (TETF) trial, was analysed retrospectively in Study
IV. The results of preoperative discography of solely the levels adjacent to the
fusion were compared with the clinical results after spinal fusion. It appeared
that in this select group of patients the discographic status of discs adjacent
to a lumbar fusion did not have any effect on the clinical outcome. The most
feared complication of lumbar discography is discitis. Although low in incidence,
this is a serious complication for a diagnostic procedure and prevention by the
use of prophylactic antibiotics has been advocated. In search for clinical
guidelines, the risk of postdiscography discitis was assessed in Study V by means
of a systematic literature review and a cohort of 200 consecutive patients.
Without the use of prophylactic antibiotics, an overall incidence of
postdiscography discitis of 0.25% was found. To prove that antibiotics would
actually prevent discitis, a randomised trial of 9,000 patients would be needed
to reach significance. Given the possible adverse effects of antibiotics, it was
concluded that the routine use of prophylactic antibiotics in lumbar discography
is not indicated. In Study VI, the middle- and long-term results of external
fixation (TETF) as a test to predict the clinical outcome of lumbar fusion were
studied in a group of back pain patients for whom there was doubt about the
indication for surgery. The test included a placebo trial, in which the patients
were unaware whether the lumbar segmental levels were fixed or dynamised. Using
strict and objective criteria of pain reduction on a visual analogue scale, the
TETF test failed to predict clinical outcome of fusion in this select group of
patients. Pin track infection and nerve root irritation were registered as
complications of this invasive test. It was concluded that in chronic low back
pain patients with a doubtful indication for fusion, TETF is not recommended as a
supplemental tool for surgical decision-making. In Study VII, a systematic
literature review was performed regarding the prognostic accuracy of tests that
are currently used in clinical practice and that are presumed to predict the
outcome of lumbar spinal fusion for CLBP. The tests of interest were magnetic
resonance imaging (MRI), TLSO immobilisation, TETF, provocative discography and
facet joint infiltration. Only 10 studies reporting on three different index
tests (discography, TLSO immobilisation and TETF) that truly reported on test
qualifiers, such as sensitivity, specificity and likelihood ratios, could be
selected. It appeared that the accuracy of all prognostic tests was low, which
confirmed that in many clinical practices patients are scheduled for fusion on
the basis of tests, of which the accuracy is insufficient or at best unknown. As
the overall methodological quality of included studies was poor, higher quality
trials that include negatively tested as well as positively tested patients for
fusion, will be needed. It was concluded that at present, best evidence does not
support the use of any prognostic test in clinical practice. No subset of
patients with low back pain could be identified, for whom spinal fusion is a
reliable and effective treatment. In literature, several studies have reported
that cognitive behavioural therapy or intensive exercise programs have treatment
results similar to those of spinal fusion, but with considerably less
complications, morbidity and costs. As the findings of the present thesis show
that the currently used tests do not improve the results of fusion by better
patient selection, these tests should not be recommended for surgical decision
making in standard care. Moreover, spinal fusion should not be proposed as a
standard treatment for chronic low back pain. Causality of nonspecific spinal
pain is complex and CLBP should not be regarded as a diagnosis, but rather as a
symptom in patients with different stages of impairment and disability. Patients
should be evaluated in a multidisciplinary setting or Spine Centre according to
the so-called biopsychosocial model, which aims to identify underlying
psychosocial factors as well as biological factors. Treatment should occur in a
stepwise fashion starting with the least invasive treatment. The current approach
of CLBP, in which emphasis is laid on self-management and empowerment of patients
to take an active course of treatment in order to prevent long-term disability
and chronicity, is recommended.

Langue : ANGLAIS

Tiré à part : OUI