Use of the one-legged hyperextension test and magnetic resonance imaging in the diagnosis of active spondylolysis * Commentary * Commentary

Abstract

Active spondylolysis is an acquired lesion in the pars interarticularis and is a common cause of low back pain in the young athlete.
To evaluate whether the one-legged hyperextension test can assist in the clinical detection of active spondylolysis and to determine whether magnetic resonance imaging (MRI) is equivalent to the clinical gold standard of bone scintigraphy and computed tomography in the radiological diagnosis of this condition.
A prospective cohort design was used. Young active subjects with low back pain were recruited. Outcome measures included clinical assessment (one-legged hyperextension test) and radiological investigations including bone scintigraphy (with single photon emission computed tomography (SPECT)) and MRI. Computed tomography was performed if bone scintigraphy was positive.
Seventy one subjects were recruited. Fifty pars interarticulares in 39 subjects (55%) had evidence of active spondylolysis as defined by bone scintigraphy (with SPECT). Of these, 19 pars interarticulares in 14 subjects showed a fracture on computed tomography. The one-legged hyperextension test was neither sensitive nor specific for the detection of active spondylolysis. MRI revealed bone stress in 40 of the 50 pars interarticulares in which it was detected by bone scintigraphy (with SPECT), indicating reduced sensitivity in detecting bone stress compared with bone scintigraphy (p = 0.001). Conversely, MRI revealed 18 of the 19 pars interarticularis fractures detected by computed tomography, indicating concordance between imaging modalities (p = 0.345). There was a significant difference between MRI and the combination of bone scintigraphy (with SPECT)/computed tomography in the radiological visualisation of active spondylolysis (p = 0.002).
These results suggest that there is a high rate of active spondylolysis in active athletes with low back pain. The one-legged hyperextension test is not useful in detecting active spondylolysis and should not be relied on to exclude the diagnosis. MRI is inferior to bone scintigraphy (with SPECT)/computed tomography. Bone scintigraphy (with SPECT) should remain the first-line investigation of active athletes with low back pain followed by limited computed tomography if bone scintigraphy is positive.

Full text

ORIGINAL ARTICLE
Use of the one-legged hyperextension test and
magnetic resonance imaging in the diagnosis of
active spondylolysis
L Masci, J Pike, F Malara, B Phillips, K Bennell, P Brukner
...............................................................................................................................
See end of article for
authors’ affiliations
.......................
Correspondence to:
Dr Masci, Centre for
Health, Exercise and
Sports Medicine,
University of Melbourne,
Melbourne, Victoria 3010,
Australia;
lawrence_masci@hotmail.
com
Accepted 22 August 2006
Published Online First
15 September 2006
.......................
Br J Sports Med 2006;40:940–946. doi: 10.1136/bjsm.2006.030023
Background: Active spondylolysis is an acquired lesion in the pars interarticularis and is a common cause
of low back pain in the young athlete.
Objectives: To evaluate whether the one-legged hyperextension test can assist in the clinical detection of
active spondylolysis and to determine whether magnetic resonance imaging (MRI) is equivalent to the
clinical gold standard of bone scintigraphy and computed tomography in the radiological diagnosis of this
condition.
Methods: A prospective cohort design was used. Young active subjects with low back pain were recruited.
Outcome measures included clinical assessment (one-legged hyperextension test) and radiological
investigations including bone scintigraphy (with single photon emission computed tomography (SPECT))
and MRI. Computed tomography was performed if bone scintigraphy was positive.
Results: Seventy one subjects were recruited. Fifty pars interarticulares in 39 subjects (55%) had evidence
of active spondylolysis as defined by bone scintigraphy (with SPECT). Of these, 19 pars interarticulares in
14 subjects showed a fracture on computed tomography. The one-legged hyperextension test was neither
sensitive nor specific for the detection of active spondylolysis. MRI revealed bone stress in 40 of the 50 pars
interarticulares in which it was detected by bone scintigraphy (with SPECT), indicating reduced sensitivity
in detecting bone stress compared with bone scintigraphy (p = 0.001). Conversely, MRI revealed 18 of
the 19 pars interarticularis fractures detected by computed tomography, indicating concordance between
imaging modalities (p = 0.345). There was a significant difference between MRI and the combination of
bone scintigraphy (with SPECT)/computed tomography in the radiological visualisation of active
spondylolysis (p = 0.002).
Conclusions: These results suggest that there is a high rate of active spondylolysis in active athletes with low
back pain. The one-legged hyperextension test is not useful in detecting active spondylolysis and should
not be relied on to exclude the diagnosis. MRI is inferior to bone scintigraphy (with SPECT)/computed
tomography. Bone scintigraphy (with SPECT) should remain the first-line investigation of active athletes
with low back pain followed by limited computed tomography if bone scintigraphy is positive.
S
pondylolysis is an acquired defect in the pars inter-
articularis of the lumbar spine.
1
It is prevalent in the
general population but is often asymptomatic and
detected incidentally on plain radiographs.
1–3
However, it is
the most common cause of persistent low back pain in young
active athletes,
4
whereitisreferredtoas‘‘activespondylolysis’’
in view of the symptomatic nature of the disease process.
5
Active spondylolysis in young athletes has been reported in
almost every sport. However, activity that involves repetitive
lumbar extension and rotation such as gymnastics and diving
pose a higher risk.
6–8
The progression of active spondylolysis to non-union has
been associated with an increased incidence of spondylolisth-
esis and lumbar disc degeneration.
910
Moreover, earlier
recognition of acute spondylolysis is associated with
improved fracture healing
11 12
and is important in preventing
the formation of non-union and its consequences.
Clinical features of active spondylolysis previously
described in the literature do not differentiate this condition
from other causes of low back pain.
341314
In addition, there
are no validated examination findings for active spondylo-
lysis.
15 16
The only reported pathognomonic finding is
reproduction of pain with the performance of the one-legged
hyperextension test.
17 18
However, no formal study of its
validity has been described.
As a consequence of the non-specific nature of clinical
findings of active spondylolysis, radiological visualisation is
important for diagnosis. The current gold standard investiga-
tion for young athletes with low back pain is bone
scintigraphy with single photon emission computed tomo-
graphy (SPECT), with the addition of limited reverse-gantry
axial computed tomography if bone scintigraphy is positive
(fig 1).
19
There are a number of limitations in using this
current diagnostic modality including the intravenous injec-
tion of radioactive tracer and the exposure of young athletes
to ionising radiation.
20
Magnetic resonance imaging (MRI) has been shown to be
as sensitive as bone scintigraphy in detecting lower limb
stress fractures.
21–24
It has many advantages over bone
scintigraphy including the non-invasive nature of the
imaging and the absence of ionising radiation.
20
MRI changes in active spondylolysis include bone marrow
oedema, visualised as increased signal in the pars inter-
articularis on oedema-sensitive sequences, and fracture,
visualised as reduced signal in the pars interarticularis on
T1 and T2 weighted sequences (figs 2 and 3).
25–29
Although
numerous studies have examined MRI changes in active
Abbreviations: MRI, magnetic resonance imaging; SPECT, single
photon emission computed tomography
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spondylolysis,
26–30
only one study comparing MRI with the
gold standard bone scintigraphy (with SPECT)/computed
tomography has been published.
31
This study prospectively
analysed bone scintigraphy (with SPECT), computed tomo-
graphy, and MRI in a cohort of 72 young athletes with low
back pain. Although good agreement was found between the
imaging modalities, there were a number of limitations of the
study that questioned the validity of its findings. These
included lack of reliability testing of the imaging modalities
and significant discordance between bone scintigraphy (with
SPECT) and MRI. Clearly, there is a need to examine further
the role of MRI in investigating young athletes with
suspected active spondylolysis.
The purpose of this study is to (a) evaluate the usefulness
of the one-legged hyperextension test in assisting early
detection of active spondylolysis and (b) evaluate the
effectiveness of MRI in detecting active spondylolysis
compared with bone scintigraphy (with SPECT)/computed
tomography.
METHODS
Subjects
Young active subjects with a history of recent-onset low back
pain were recruited. Referrals were obtained primarily from
sports physicians in sports medicine clinics. The inclusion
criteria of subjects included:
(1) aged 10–30 years
(2) engaged in regular activity
(3) symptoms of low back pain for 6 months or less
(4) had been assessed by a sports physician or sports
medicine practitioner and a provisional diagnosis of
active spondylolysis had been made
(5) had been referred for bone scintigraphy (with SPECT)/
computed tomography as the initial investigation.
For the purpose of this study, ‘‘regular activity’’ was
defined as the participation in sport for leisure or competition
other than activity related to daily living.
Reasons for exclusion were a contraindication to MRI and
a recent history of bone scintigraphic evidence of active
spondylolysis (within the preceding 12 months). As bone
scintigraphic evidence of bone stress may remain for up to
12 months after diagnosis,
32
excluding these subjects would
eliminate those with asymptomatic bone scintigraphic
changes and back pain with other causes.
AB
C
Figure 1 (A,B) Coronal and axial
single photon emission computed
tomography images showing bilateral
increased tracer uptake at the 5th
lumbar vertebra; (C) axial computed
tomography image confirming bilateral
stress fractures of the pars
interarticularis. Permission for
publication of this figure has been
given.
Figure 2 Reduced signal surrounded by increased bone marrow signal
on a sagittal T2-weighted image: consistent with right L5 pars
interarticularis stress fracture. Permission for publication of this figure
has been given.
Diagnosis of active spondylolysis 941
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Ethical approval was obtained from the University of
Melbourne human research ethics committee. All subjects
provided written informed consent.
Procedure
Once enrolled in the study, subjects:
(a) completed a study questionnaire supervised by the main
investigator relating to individual anthropometric mea-
sures and sports participation
(b) had a one-legged hyperextension test performed by the
main investigator
(c) underwent both bone scintigraphy (with SPECT) and
MRI of the lumbar spine concurrently; computed
tomography was only performed if bone scintigraphy
revealed changes consistent with active spondylolysis.
For bone scintigraphy, a standard dose (800 MBq) of
technetium 99 methylene diphosphonate (Mallinckrodt
Medical) was injected. Angiographic and soft tissue planar
bone scan images were obtained about 5 s and 3 min after
injection. Delayed planar and SPECT images were obtained
about 3 h after injection. Images were acquired using a GE
Starcom 3200i single head (rectangular) gamma camera
fitted with a low-energy-resolution collimator. Projection
data were acquired for 25 s per view on a 128 6128 matrix. A
total of 64 images were acquired over a 360
˚
elliptical
rotation. Tomographic reconstruction was performed on the
raw data using filtered back-projection producing axial,
sagittal, and coronal slices.
For computed tomography, images were performed on a
GE Light Speed scanner. Images were acquired in the reverse-
gantry axial plane at the area corresponding to increased
radioactive tracer uptake on bone scintigraphy.
Approximately six contiguous slices were acquired at each
area with 3-mm slice thicknesses (table index 3 mm, 140 kV,
250–300 mA). The ‘‘effective dose’’ of the computed tomo-
graphy was about 1 mSv per area scanned.
For lumbar spine MRI, all examinations were performed
on a GE Sigma 1.5 T scanner using a phased-array spinal coil.
Multisequence fast spin echo scans were obtained for all MRI
examinations. The four sequences consisted of:
(1) sagittal T1-weighted images (TE 14/TR 475/3.5 mm slice
thickness/interslice gap 1 mm)
(2) sagittal T2-weighted pre-saturated images (TE90/
TR3300–4000/3.5 mm slice thickness/interslice gap
1 mm)
(3) axial T2-weighted fat pre-saturated images (TE90/
TR3300–4000/3.5 mm slice thickness/interslice gap
1 mm)
(4) reverse-gantry oblique axial short tau inversion (STIR)
images (TE 85/TR4000/3 mm slice thickness/interslice
gap 1 mm).
The axial images were acquired through the lower two
lumbar levels only. The acquisition matrix ranged from 256 6
192 to 512 6 256 mm.
Outcome measures
One-legged hyperextension test
The one-legged hyperextension test was performed using a
protocol previously described.
17
While standing, facing away
Figure 3 Break in cortical ring shown by reduced signal (dark line)
consistent with pars interarticularis stress fracture on T2-weighted axial
image. Permission for publication of this figure has been given.
Figure 4 One-legged hyperextension
test. Permission for publication of this
figure has been given.
942 Masci, Pike, Malara, et al
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from the tester, subjects were asked to stand on their left leg
and raise their right leg with their right hip slightly flexed
and their right knee flexed to 80
˚
. They were asked to actively
extend their lumbar spine (fig 4). The main investigator then
asked if this active manoeuvre reproduced their pain. The
manoeuvre was repeated on the right side by standing on the
right leg.
The test was considered positive if it reproduced the
subject’s pain.
Imaging
All imaging modalities were analysed by experienced radi-
ologists. One radiologist analysed all MRI scans, and a
different radiologist analysed the bone scintigraphy (with
SPECT) and subsequent computed tomography (if per-
formed). The analysis of the MRI scan was conducted in a
separate section of the radiology building to the analysis of
the bone scintigraphy and computed tomography. Therefore,
each radiologist was blinded to the result of the other
imaging modality.
Reporting of images for each modality was based on a
grading system devised by the main investigator. Reliability
studies were performed in a pilot study. For intrarater
reliability, k coefficients were 1.0 for bone scintigraphy and
computed tomography and 0.87 for MRI. For inter-rater
reliability, k coefficients were 0.92 for bone scintigraphy, 0.65
for computed tomography, and 0.68 for MRI. These results
show good to excellent intrarater and inter-rater reliability
for the grading systems used, with bone scintigraphy
showing greater consistency.
Statistical analysis
Statistics were performed using the Statistical Package for
the Social Sciences (SPSS; Norusis/SPSS Inc, Chicago,
Illinois, USA). A two-tailed level of significance was set at
0.05 for all tests unless otherwise specified.
Sample size calculations were based on McNemar’s test for
equivalence of correlated proportions assuming that the
proportion of positive MRI scans equals 0.50 with type 1
error = 0.05 and power = 0.80. These calculations were
based on previous studies.
23 25
At least 63 subjects were
required to provide acceptable power to the study.
x
2
test of independence was used to assess the relationship
between the one-legged hyperextension test and the presence
of active spondylolysis as defined by the gold standard
investigation of bone scintigraphy. In addition, sensitivity,
specificity, negative predictive value, and positive predictive
value of the one-legged hyperextension test in active
spondylolysis were calculated.
McNemar’s test for equivalence of correlated proportions
was used to compare the results of MRI with those of bone
scintigraphy (with SPECT) and computed tomography.
RESULTS
Seventy one subjects were recruited. The most common
sports associated with participating subjects were cricket
(14), gymnastics (14), Australian football (11), hockey (5),
and basketball (5).
Table 3 Analysis of the one-legged hyperextension test
for each side
Left side Right side
Sensitivity (%) 50 55.2
Specificity (%) 67.6 45.5
Negative predictive value (%) 41.3 46.9
Positive predictive value (%) 40.5 53.8
Pearsons x
2
p value 0.132 0.952
Subjects (n = 71)
Bone scintigraphy
Negative (n = 32)
Positive (n = 39)
(50 pars interarticulares)
Active spondylolysis
CT positive
(n = 14; 19= pars)
Stress fracture
CT negative
(n = 25; 31= pars)
Stress reaction
Figure 5 Abnormalities with bone scintigraphy (with SPECT)/computed
tomography.
Table 4 Comparison between bone scintigraphy (with
single photon emission computed tomography (SPECT))
and magnetic resonance imaging (MRI) in detecting bone
stress (n = 710)
Bone scintigraphy
(with SPECT)
TotalGrade 0 Grade 1
MRI grade 0 660 10 670
MRI grade 1 0 40 40
Total 660 50 710
Grade 0, no bone stress; grade 1, bone stress.
Table 1 Analysis of the one-legged hyperextension test
for the left side in 71 subjects
Active
spondylolysis
negative
Active
spondylolysis
positive Total
Test negative 12 17 29
Test positive 25 17 42
Total 37 34 71
Table 2 Analysis of the one-legged hyperextension test
for the right side in 71 subjects
Active
spondylolysis
negative
Active
spondylolysis
positive Total
Test negative 15 17 32
Test positive 18 21 39
Total 33 38 71
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Of the overall cohort, 39 (55%) had evidence of increased
radioactive tracer uptake on bone scintigraphy (with SPECT)
consistent with active spondylolysis. In this group, 29 (78%)
were male, and all were aged 25 or below.
One-legged hyperextension test
Tables 1 and 2 give the results of the one-legged hyperexten-
sion test for each side. From these results, sensitivity,
specificity, negative predictive value, and positive predictive
value were calculated for each side (table 3). There was no
association between the one-legged hyperextension test and
the presence or absence of active spondylolysis on either side.
Imaging
A total of 710 pars interarticulares were imaged in 71 subjects
with both bone scintigraphy and MRI. Increased radioactive
uptake on bone scintigraphy was detected in 39 subjects
(55%). Overall, 28 subjects with positive bone scintigraphy
had unilateral uptake, and the remaining 11 had bilateral
uptake—that is, 50 pars interarticulares affected (fig 5).
Of the subjects with positive bone scintigraphy, 25 (31 pars
interarticulares) had a normal computed tomography,
indicating stress reaction, and 14 (19 pars interarticulares)
had a fracture on computed tomography, indicating a stress
fracture. Most abnormalities were observed at the level of the
fifth lumbar vertebra (39/50).
Comparison between bone scintigraphy and MRI
Of the 50 pars interarticulares with increased radioactive
tracer detected by bone scintigraphy, only 40 (80%) were
detected by MRI as bone oedema (table 4). In the 10
abnormalities not detected by MRI, seven (70%) occurred at
the 5th lumbar vertebra, two (20%) at the 4th lumbar
vertebra, and one (10%) at the first lumbar vertebra. There
was a significant difference between bone scintigraphy and
MRI (p = 0.001). These results suggest that MRI is inferior
to bone scintigraphy in its ability to detect bone stress in
active spondylolysis.
Overall, when compared with bone scintigraphy, sensitiv-
ity, specificity, negative predictive value, and positive
predictive value of MRI in detecting bone stress were 80%,
100%, 98.5%, and 100% respectively.
Comparison between computed tomography and MRI
Fifty pars interarticulares were imaged by computed tomo-
graphy. Nineteen revealed evidence of a fracture. Eighteen
(95%) of these fractures were detected by MRI (table 5).
There was no significant difference between computed
tomography and MRI (p = 0.345). These results indicate
that MRI is equivalent to computed tomography in the ability
to visualise fractures in the pars interarticulares.
Overall, when compared with computed tomography for
the visualisation of a fracture, sensitivity, specificity, negative
predictive value, and positive predictive value of MRI were
94.74%, 100%, 96.88%, and 100%, respectively.
Comparison between bone scintigraphy/computed
tomography and MRI
Table 6 summarises the results. There was a significant
difference between changes detected on MRI and those
detected on bone scintigraphy/computed tomography (p =
0.002). These results suggest that MRI is inferior to bone
scintigraphy/computed tomography in its ability to detect the
spectrum of changes in active spondylolysis.
DISCUSSION
In this study, over half of the cohort recruited was found to
have active spondylolysis. This result suggests that active
spondylolysis is a common cause of persistent low back pain
in young active athletes. This is supported by previous
research that has shown a high proportion of active
spondylolysis in a similar population.
4
Thus, it is imperative
that doctors consider active spondylolysis as a likely cause in
all young athletes with persisting low back pain.
The one-legged hyperextension test has been suggested to
be pathognomonic for active spondylolysis.
17
A negative test
was said to effectively exclude this diagnosis negating
radiological investigations.
18
Examination of the one-legged
hyperextension test in the present study showed that this test
is neither sensitive nor specific for active spondylolysis.
Moreover, its negative predictive value was poor. Therefore, a
negative test cannot exclude active spondylolysis as a possible
cause.
Although this is the first study to examine the usefulness
of the one-legged hyperextension test in detecting active
spondylolysis, this result is consistent with other studies
showing lack of concordance between specific lumbar spine
examination tests and lumbar spine pathology.
33 34
The poor result in relation to the one-legged hyperexten-
sion test may be due to a number of factors. The test would
be expected to transfer a significant extension force on to the
lower lumbar spine. Although this force would place
significant pressure on the pars interarticularis, it may also
stress other areas of the lumbar spine such as facet joints and
posterior lumbar discs, and this may subsequently cause pain
in the presence of other pathology such as facet joint
arthropathy and lumbar disc disease. This may explain the
poor specificity of the test.
Conversely, the poor sensitivity of this test may be related
to the subjective reporting of pain by subjects performing the
manoeuvre, which may vary depending on individual pain
tolerance. In addition, this test may preferentially load the
fifth lumbar vertebra, and therefore bone stress located in the
upper lumbar spine may not test positive.
The results of the one-legged hyperextension test were
limited by the absence of reliability testing. Ideally, to
improve the validity of this result, testing of consistency of
the result should be performed.
Overall, this study suggests that the one-legged hyper-
extension test is a poor predictor of active spondylolysis and
therefore does not assist doctors in detecting this condition.
Table 5 Comparison between computed tomography
(CT) and magnetic resonance imaging (MRI) in detecting
pars interarticularis fractures (n = 710)
CT
TotalGrade 0 Grade 1
MRI grade 0 31 1 32
MRI grade 1 0 18 18
Total 31 19 50
Grade 0, no fracture; grade 1, fracture.
Table 6 Comparison between single photon emission
computed tomography (SPECT)/computed tomography
(CT) and magnetic resonance imaging (MRI) in detecting
the spectrum of changes in active spondylolysis (n = 710)
Bone scintigraphy/CT
TotalGrade 0 Grade 1 Grade 2
MRI grade 0 660 10 0 670
MRI grade 1 0 21 1 22
MRI grade 2 0 0 18 18
Total 660 31 19 710
Grade 0, normal; grades 1 and 2, acute stress reaction.
944 Masci, Pike, Malara, et al
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This emphasises the importance of early radiological visua-
lisation.
The current gold standard investigation for visualisation of
the spectrum of pathology in active spondylolysis is bone
scintigraphy (with SPECT) with the addition of limited
reverse-gantry axial computed tomography if bone scintigra-
phy is positive.
19
MRI shows similar changes in active
spondylolysis.
24–28
However, there has only been one pub-
lished study comparing MRI with bone scintigraphy (with
SPECT)/computed tomography,
31
and the conclusions of this
study are questionable.
In the present study, MRI detected bone stress in 40 out of
the 50 pars interarticulares in which it was detected by bone
scintigraphy (with SPECT). This was significantly fewer than
bone scintigraphy, which suggests that MRI is not as
sensitive as bone scintigraphy (with SPECT) at detecting
bone stress at the pars interarticularis. This result is
discordant with other studies, which have shown similar
sensitivity at other sites and at the pars interarticularis.
21–24 31
There are a number of possible explanations for the
discordant results in this study. The most plausible is that
the inferior MRI results in this study are related to the use of
a particular imaging sequence. Both sagittal and coronal MRI
images used slice thicknesses and interslice gaps that were
comparable to those in previous studies.
25 29
However, one
study
26
used slightly different sequences with a slice
thickness of 3 mm and an interslice gap of 0.3–0.8 mm
compared with the present study which used a slice thickness
of 3.5 mm and an interslice gap of 1 mm. Larger interslice
gaps may reduce the proportion of bone imaged and
potentially reduce the probability of detecting bone
oedema—particularly in cases with subtle changes. It is
possible that a reduction in interslice gap may improve the
ability of MRI to detect bone stress.
Secondly, the difference in results may be related to the
greater difficulty in detecting the changes of active spondy-
lolysis by MRI. Detecting pathology by MRI relies on the
interpretation of different contrasts of signals compared with
normal tissue. Moreover, for active spondylolysis, this
interpretation involves a small area of bone of the pars
interarticularis surrounded by many other structures. Unlike
stress fractures in other parts of the body, the small area of
the pars interarticularis may make detection of these changes
more difficult.
Conversely, in this study, 18 of the 19 fractures detected by
computed tomography were also detected by MRI. There was
no significant difference in the ability to detect fractures in
the pars interarticularis between MRI and computed tomo-
graphy. This suggests that, compared with computed
tomography, MRI is able to detect fractures in active
spondylolysis. Given the limitations of computed tomogra-
phy, including the exposure of subjects to imaging radiation,
it has been suggested that MRI may replace computed
tomography for the detection of pars interarticularis frac-
tures.
However, unlike MRI, computed tomography has the
ability to differentiate between acute and chronic fractures,
and this differentiation may be an important determinant of
fracture healing.
11 12
Therefore, although MRI may be
equivalent to computed tomography in detecting fractures,
its inability to determine fracture age may limit its useful-
ness. Accordingly, in subjects with pars interarticularis
fractures detected by MRI, it may still be necessary to
perform thin computed tomography slices to determine
whether a fracture is acute or chronic—an important factor
in fracture resolution.
The standardised grading systems used for each imaging
modality in this study were found to be reliable. The blinding
of the radiologists was effective, and the sample size
calculations, based on expected outcome from previous
studies,
23 25
indicated recruitment of adequate numbers to
detect statistically significant differences.
CONCLUSION
These results have implications for management of young
active athletes with persistent low back pain.
(1) Given the high proportion of active spondylolysis in a
select population of active athletes, doctors should have a
high index of suspicion and low threshold for performing
early imaging of active young athletes with low back pain.
(2) The one-legged hyperextension test is not useful in
detecting active spondylolysis and should not be relied on
to diagnose this condition.
(3) Radiological visualisation is critical for diagnosis. The use
of MRI as the first-line investigation may result in a
significant number of false-negative scans. Despite the
benefits of MRI, such as lack of radiation, we believe
that, at this stage, the investigation of high-risk athletes
remains with the current gold standard of bone
scintigraphy (with SPECT) with the addition of thin
sliced reverse-gantry axial computed tomography if bone
scintigraphy is positive.
Authors’ affiliations
.....................
L Masci, B Phillips, K Bennell, P Brukner, Centre for Health, Exercise and
Sports Medicine, University of Melbourne, Melbourne, Victoria,
Australia
J Pike, F Malara, MIA Radiology, Victoria House, Melbourne, Victoria,
Australia
Competing interests: None declared.
Permission for publication of figures 1–4 has been given.
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What is already known on this topic
N
Active spondylolysis is a common cause of low back
pain in active adolescent athletes
N
Early diagnosis improves prognosis
N
The current investigative algorithm is a SPECT scan
followed by limited computed tomography if the SPECT
scan is positive
N
MRI has been advocated as an alternative to SPECT/
computed tomography because of proposed benefits
including an absence of radiation
What this study adds
N
The one-legged hyperextension test is a poor predictor
of active spondylolysis and should not be used as a
diagnostic tool
N
The use of MRI as a diagnostic tool results in a
significant number of false negative scans compared
with the traditional SPECT/computed tomography
N
The best investigation of high-risk athletes with low
back pain remains SPECT/computed tomography
Diagnosis of active spondylolysis 945
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COMMENTARY
..............
This paper addresses some crucial questions in the assessment
of adolescent athletes with possible spondylolysis. The one-
legged hyperextension manoeuvre, although commonly used
clinically, has never been studied in this manner. It is very
useful to have data on this, and it is important to recognise that
there may be significant limitations in the sensitivity and
specificity of this test, as there are for many other isolated
provocative and subjective physical examination findings. The
authors’ findings on the relative ability of MRI to identify
lesions of the pars compared with SPECT and computed
tomography are, perhaps, more important. There is significant
disagreement among published authors on the relative utility of
different imaging modalities in the diagnosis of spondylolysis.
There are also very few data directly comparing the various
modalities. The study of Campbell et al
1
was the first to directly
compare MRI with SPECT and computed tomography. This
study used non-standard MRI sequences that were intended to
visualise the pars optimally. Although Campbell et al concluded
that MRI was ‘‘an effective and reliable first-line imaging
modality’’ for diagnosing spondylolysis, their data actually
revealed that MRI failed to identify a significant number of
patients diagnosed with a stress reaction without an overt pars
defect. The current study, using more standard MRI sequences
(although still including one relatively non-standard sequence),
showed similar results, with MRI having a reduced sensitivity
for the identification of pars lesions when compared with
SPECT, particularly for stress reactions without a clear fracture.
From a clinical standpoint, it is extremely important to identify
early stage stress fractures promptly, so that appropriate
treatment can be initiated. Failing to identify these early stress
reactions may lead to prolonged symptoms and, possibly, worse
long-term outcomes. The current medical literature would seem
to support the authors’ conclusions that bone scintigraphy with
SPECT and computed tomography remain the optimal way to
diagnose spondylolysis. The role of MRI and the optimal
sequences for computed tomography await further study.
C Standaert
Department of Rehabilitation Medicine, University of Washington,
Seattle, WA 98195, USA; cjs1@u.washington.edu
REFERENCE
1 Campbell R, Grainger A, Hide I, et al. Juvenile spondylosis: a comparative
analysis of CT, SPECT and MRI. Skeletal Radiol 2005;34:63–73.
..............
COMMENTARY
..............
Many of the findings of this study are consistent with our
experience in dealing with large numbers of young athletes
with spondylolysis. We continue to use the hyperextension
test, but interpret a posture test in the absence of pain on
forward flexion as suggestive of some type of derangement of
the posterior elements of the spine, including facets, etc.
L Micheli
Department of Orthopedic Surgery, Children’s Hospital, Boston, MA,
USA; michelilyle@aol.com
946 Masci, Pike, Malara, et al
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