MR imaging. The MR images were interpreted by means of consensus of three radiolo ...... tears diag- nosed with MR imaging versus arthros- copy: how reliable.
Patrick Kevin
A. Ruwe, MD Lynch, MD
J.
Can MR Diagnostic
James Wright, Peter Joki, MD
#{149} #{149}
MD, MPH, FRCSC Shirley McCarthy,
R. Lawr Randall, MD, PhD
#{149}
#{149}
Imaging Effectively Arthroscopy?’
T
Replace
A study was performed to determine whether magnetic resonance (MR) imaging is cost-effective and reduces the need for diagnostic arthroscopy of the knee. During a 9-month period, 103 consecutive patients with knee injury that justified diagnostic ar-
with abnormalities of the knee are known to be nonspecific in the determination of the cause of internal derangement. Physical examination of the knee was evaluated in a recent
throscopy
study
underwent
MR
imaging.
HE clinical
physical
history
and
findings
examination
of i61
patients
with
knee
pain
of at least
sports
Apley grind, joint line tenderness,
medicine
orthopedists.
After
the examination, 44 patients (42.7%) underwent immediate arthroscopy. The 59 other patients (57.3%) did not undergo arthroscopy; follow-up was performed in 55 of these 59 patients (93%) at a mean of 22 months. The outcome was successful in 49 of 55 patients
(89%);
40 patients
had
nor-
mal
function and no limitation in activity, six patients with chronic injury of the anterior cruciate ligament Underwent reconstruction, and three patients underwent arthroscopy with negative findings. Without the use of MR imaging, all patients in this study
would
nostic
arthroscopy.
diagnoses
have
undergone
diag-
Because
of the
based on MR images, 53 (51.4%) avoided a potentially diagnostic arthroscopy,
patients unnecessary
and, as a result, $103,700 in the
the net savings 103 patients.
Index terms: 452.485 452.485
Arthroscopy Cost effectiveness #{149}Knee, MR, 452.1214 #{149}
Athletic
#{149}
Knee,
#{149}
was
injuries, injuries,
and
1 years
duration
(1). The
value of five common clini(McMurray, flexion pinch,
extension
block)
for detection
of
meniscal tears was evaluated in a prospective fashion and compared with arthroscopic findings. None of the clinical tests were predictive for the presence of meniscal tears; this finding indicates that the clinical examination has considerable limitations
whenever presence
it is used
knee (i). In patients
in whom
is uncertain,
fore
to confirm
of meniscal
turn
physicians
to other
the
lesions
in the
the
diagnosis
must
diagnostic
there-
modali-
ties to select the appropriate treatment. Amthrognaphy has been shown to be highly accurate; however, it is invasive, technically demanding, ne-
cessitates
exposure
to ionizing
expensive
and
invasive,
1992;
183:335-339
I From the Departments of Orthopedics and Rehabilitation (PAR., R.L.R., J.K.L., P.J.) and Diagnostic Imaging (SM.) and the Robert Wood Johnson Clinical Scholars Program Q.W.), Yale University School of Medicine, 333 Cedar St, New Haven, CT 06510. From the 1990 RSNA scientific assembly. Received October 1, 1991; revision requested October 31; revision received January 8, 1992; accepted January 16. Address reprint requests to SM. RSNA, 1992
multiple
studies
has
sensitivity
high
particularly
have
shown and
that
it
specificity,
for meniscal
injury (9-13). enables evaluation of extracapsular tissues and may enable distinction between patients without internal derangements and those who would benefit Furthermore,
from 15).
MR
imaging
therapeutic
The judged come
arthroscopy
(9,14,
success of MR imaging by two criteria: patient and
cost-effectiveness.
If some
patients avoid arthroscopy, imaging may be beneficial. more, if the cost of diagnostic copy
can be out-
is avoided
then MR Furtherarthros-
in a significant
num-
ber of patients, then MR imaging in all patients may also save money (ie, it may be cost-effective). The purpose of this study was to determine whether MR imaging reduced the number of diagnostic arthroscopies necessary
in patients
with
knee
injury
and whether MR imaging performed in all patients with suspected internal derangement was cost-effective compared with diagnostic arthroscopy in diagnosis
the
of internal
derangement
of
knee.
radia-
tion, and is limited in evaluation of structures external to the capsule (2-5). Because of these and other factons, arthnoscopy has become the diagnostic procedure of choice (6). Although diagnostic arthroscopy is
proponents
point
Radiology
at
in patients
The MR images were interpreted by means of consensus of three radiologists and reviewed with the referring
predictive cal tests
BA
to its accuracy and to the sungeon’s ability to diagnose and treat abnormality with a single procedure (7). Unfortunately, diagnostic arthroscopy sometimes reveals no abnormality or only minor, possibly nonpathologic lesions such as plicae or chondnomalacia patellae (8). Thus, patients may be subjected to an unnecessary surgical procedure with its associated risks and potential morbid-
PATIENTS From
AND
METHODS
March 1989 to December 1989, 103 (61 male patients and 42 female
patients patients)
aged
11-72
years)
underwent
lion
at the sports
years
(mean
consecutive
age,
31
examina-
center of our knees were evaluated by one of two senior specialists in orthopedic sports medicine (J.K.L., P.J.) with particular attention to the range of
motion;
medicine
All affected
institution.
findings
at examination
for effu-
sion and at the McMurray and pinch tests; and the pivot shift line tenderness, and quadriceps All
patients
with
findings
flexion sign, jointatrophy.
sufficient
to jus-
tify diagnostic arthroscopy and compatible with the diagnosis of internal knee de-
ity. Alternatively,
(MR)
imaging
magnetic
is noninvasive,
resonance
and
Abbreviations:
ment,
FOV
ACU =
=
anterior
field of view, SE
=
cruciate ligaspin echo.
335
LONG TERM
SURGERY (n44(
EVALUATION
SURGERY )n.31)
LONG
TERM
EVALUATION
ACL
rALL PATIENTS (n=103)
ACL RECONSTRUCTION (n-5)
RECONSTRUCTION (n-6) ALL PATiENTS (n = 66)
________NEGATIVE
SURGERY (n-li)
_______
SURGERY
NEGATIVE
PLICA )n-2)t
NO INITIAL SURGERY (n - 59)
NO INITIAL SURGERY )n35) NL FUNCTION
NO )n-44( SURGERY
NL FUNCTION
NO (n-27( SURGERY
(n-40(
)n
CONTINUED COMPLAINTS )n-4(t
-
24(
CONTINUED COMPLAINTS (n = 3))
1.
2.
Figures
NL
1, 2.
(1) Flow
normal,
=
*
of outcome
success,
=
or less. One patient
rangement
chart
t
failure.
=
(2) Flow
sign,
were
enrolled
in the study.
results
test, or acute trauma. Patients with tent knee pain complained of pain, ing, locking, or giving-way (16,17).
center,
patients
with
undergo diagnostic meet two conditions:
to respond
physical treatment.
persistent
symptoms
and
with
arthroscopy,
completed
ing the area
who
a questionnaire,
that
performed Patients with from the
and underwent therapeutic without MR examination
spin-echo
(SE) sequence
msec/echo 16-cm trix,
time
field
to evaluate
with
=
(repetition 1,500/20,
orthopedists
signal
intensity
that
patients
therapeutic
arthroscopy
nonsurgical
treatment.
body,
with
or a meniscal
a grade cyst
changes,
tic arthroscopy.
of
with time
80),
a
At this
Patients nonsurgical
of 17 months of a standardized
a gap of 2.5 mm. An axial image was used as a localizer
tionnaire
cartilage,
tears
of the
on either
or continued 3 change,
a loose
underwent
thera-
cyst
on
university,
questions
ment
after
was
MR
classified
a failure
that
limited
if the
arthroscopy persistent
activity.
Outcome
was classified a success if the patient (a) did not undergo subsequent diagnostic arthroscopy with positive findings and was functioning normally without marked limitation in activity or (b) underwent reconstructive surgery for chronic instability to a tear
of the
MR imaging diagnostic ings.
ACL
diagnosed
or underwent arthroscopy
Cost-effectiveness mated cost of $1,000
with was
with
subsequent negative
based
on
findthe
esti-
per MR examination of the knee in all patients and a savings of $3,900 in each patient in whom diagnostic arthroscopy was not performed. The cost of the MR examination of the knee was based on a facility fee of $700 and a professional fee of $300. The cost of arthroscopy was composed of the fees of the surgeon ($1,400), facility ($1,500), and anesthesiologist ($1,000). patients with
The cost-effectiveness knee injury who
in all underwent
MR imaging was calculated as follows: The cost of MR examination in all these patients plus the cost of all immediate therapeutic
arthroscopies
plus
the
of
cost
all procedures in patients with outcomes classified as failures was subtracted from the theoretical cost of immediate diagnostic arthroscopy in all patients.
patients
who underwent continued treatment were evaluated
by means
patellar
underwent
with an isolated tear of the anterior cruciate ligament (ACL) generally undergo acute surgical repair only in the presence of an associated meniscal tear. These patients undergo meniscal repair, if possible, along with ACL reconstruction (19).
minimum
x 128
the articu-
or a Baker
masection
128
and 5-mm
P.J.).
On the basis of the findings
images,
MR
contacted
Outcome
patient underwent diagnostic with positive findings or had
due
(J.K.L.,
underwent continued nonsurgical treatment and did not undergo therapeu-
arthros-
obtained
(FOV),
average,
Radiology
#{149}
msec
of view
one signal
thickness 12-weighted
336
images
sub-
images
MR imaging was performed by means of a i.5-T imager (Signa; GE Medical Sys-
axial T2-weighted
in MR imaging and were with the referring
medicine
meniscal
(18).
tems, Milwaukee) with a transmit-receive coil. The first series of images consisted
by
radiologists
peutic arthroscopy. Patients with normal findings on MR images or a diagnosis of an isolated ligament tear, intrasubstance
planned.
who met one of the criteria and in whom arthroscopy
would have been otherwise were enrolled in the study. locked knees were excluded
interpreted
of three
reviewed
Patients
and
were
Meniscal changes and tears were classifled, according to the system of Crues et al (9), in three grades of signal intensity: Grade 1 was defined as an area of globular intrameniscal signal intensity that did not contact the articular margin; grade 2, an area of primarily linear signal intensity that did not contact the articular margin; and grade 3, an area of linear or globular
the
indicatwas
80) obtained
of 0.3 mm.
of consensus
lar margin.
met
abnormality,
arthroscopy
Only patients for arthroscopy
a gap
sequently
herein were schedof the knee. Before the orthopedic sur-
of suspected
confirmed
study copy
with
experienced
that had
patients
the criteria described uled for MR imaging the MR examination, geons
complaints
(SE 1,600-2,300/20,
means
nonsurgical
symptoms
Ti-weighted obtained with
images
The MR images
lasted less than 6 months, the injury was classified as acute; in patients with symptoms that had lasted longer than six months, the injury was classified as chronic. The mean duration of symptoms was 2.0 months (range, 3-6 months) in the group with acute injury and 2.3 years (range, 8 months to 30 years) in the group with chronic injury. Rather than undergo diagnostic
lost to follow-up. In Figures i-3, had symptoms that lasted 6 months
and limitations-level of athletic activity and the presence of pain, swelling, and instability of the knee-and a subjective assessment of their return to normal activities.
sports
In patients
were who
a 14-cm FOV, 192 x 256 matrix, one signal average, and contiguous sections 3 mm thick. The third series of images consisted of coronal intermediate and 12-weighted
ness
conis fail-
of directed
other
consisted of sagittal (SE 600-800/13-20)
with a 14-cm FOV, 192 x 256 matrix, one signal average, and 3-mm section thick-
arthroscopy if they The diagnosis can-
to 6 weeks
therapy
images images
persisswellAt this
not be accurately and reproducibly firmed with other means and there ure
Four patients in the study
medial or lateral patellar retinaculum, and potential Baker cysts. The second series of
of the McMurray of the flexion pinch
presence
positive
chart
was lost to follow-up.
The criteria for inclusion in the study were the following: persistent knee pain, recurrent knee effusions, repeated episodes of giving-way,
(n = 103) enrolled in the study. of outcome in all patients enrolled
in all patients
at a
MR imaging 18-item
ques-
or telephone interview. The were designed to enable assessof the patients’ functional abilities
RESULTS After tients
MR imaging, (42.7%)
44 of 103 pa-
underwent
surgery
(Fig
1). The
patients Among
are displayed the 34 patients
immediate
findings
in these
in Table in Table
whom the MR imaging protocol followed and who underwent diate therapeutic arthroscopy, agnoses
based
on
findings
on
1. 1 in
was imme32 diMR
May
im-
1992
I- L
LONG TERM EVALUATION
SURGERY )n.13)
ALL PATIENTS (n #{149} 31)
ACL
1
RECONSTRUCTION (n - 1
_______ NEGATIVE
SURGERY )n4)
NO INITIAL
PLICA )n - 2)t
-El
_________
SURGERY
(n-24)
NLFUNCTION )n .
NO
16)
SURGERY )n 17)
CONTINUED COMPLAINTS )n.
Figure
3.
Flow
in the
study
Three
patients
chart of outcome
in all patients
who had symptoms that were lost to follow-up.
lasted
(,i
=
longer
1)t
37) enrolled
than
6 months.
acute symptoms of less than 6 months duration and 37 patients with chronic symptoms. Thirty-one patients with acute symptoms underwent immediate
surgery
and
35 did
not.
Thirty-
four of these 35 patients (97%) were available for follow-up at a mean of 21 months (range of follow-up, 18-28 months). In 31 of these 34 patients (91%) the outcome was classified a success
(Fig
function activity, construction, anthroscopy
ages were (accuracy,
confirmed 94%). The
tients
grade
had
intensity throscopy.
at surgery
two other
pain signal
3 changes
without
confirmation
at ar-
The 59 other patients (57.3%) meceived continued nonsurgical treatment and did not undergo immediate arthroscopy. The diagnoses based on MR imaging findings in these patients are listed in Table 2. Fifty-five of these 59 patients
(93%)
follow-up (range
The
and Two
occasional
thus
months).
the
mild
considered
limitation five
patients
a
sympin activhad
only
in activity and no indicated that they felt of the 44 patients had to moderate
Only one patient, of severe knee outcome
was
pain
in
however, pain, and
considered
a
tients had normal function and no marked limitation in activity, six patients had undergone reconstruction of the ACL, and three had undergone amthroscopy
instability.
55 patients
with
(89%)
(Fig
negative
in 49 of
was
to persistent
marked of the
slight restriction instability and normal. Thirty
17-28
successful
for
outcome
toms,
in this patient. Fifteen of the 44 had periodic swelling in the knee. Of the four patients with longterm follow-up whose outcomes were classified a failure, one had persistent swelling and one complained of knee
these
was
toms ity.
of 22 months
available
of follow-up,
outcome
secondary
the knee. complained
were
at a mean
the
failure
1); 40 pa-
findings.
The outcome in six of the 55 patients (11%) was considered a failure; four of these six patients had continued limitation in activity and two had undergone successful arthnoscopic treatment of a plica. Of the 44 patients in whom longterm follow-up was performed and Volume
183
#{149} Number
2
failure patients
All four
patients
had
normal
and with
two had negative
in re-
undergone findings.
The outcome was a failure in three of the 34 patients (9%); these three patients had continuous limitation in activity. One patient was lost to longterm follow-up. In the group with chronic symp-
who had not undergone arthroscopic surgery, only five reported a limitation in activity. In three of these patients,
2); 24 patients
and no marked limitation five had undergone ACL
indicated
that they did not feel normal. Four other patients indicated that they did not feel normal, but they had no limitation in activity, no swelling, and no instability; therefore, the outcome in these patients was not considered a failure. Sixty-six patients presented with
13 patients
underwent
immedi-
ate surgery and 24 patients did not. Follow-up was performed in 21 of these 24 patients (88%) at a mean of 22 months (range of follow-up, 18-28 months). Of these 21 patients, 18 had successful
outcomes
(88%);
16 pa-
tients had normal function and no marked limitation in activity, one patient had undergone ACL reconstruction, and one patient had undergone arthroscopy with negative findings (Fig 3). In three patients (14%) the outcome was a failure because they had continued limitation in activity. Three patients were lost to long-term follow-up. Cost-effectiveness (Fig 4) was calculated in the following manner: Before the use of MR imaging at our institution, all 103 patients would have undergone diagnostic arthroscopy at a total cost of $401,700. In this study, however, all 103 patients underwent MR imaging of the knee at a cost of $103,000. In addition, 44 patients underwent immediate therapeutic arthnoscopy
at a cost
of $171,600,
Radiology
and
337
#{149}
the outcome was classified a failure in six patients at a cost of $23,400. Therefore, the clinical strategy of performing MR imaging of the knee in all patients and then performing surgery only in patients with indications for surgery $103,700.
resulted
in a net
savings
COST ANALYSIS (103
x
39)
-
of
1(103
ALL PATIENTS
SURGERY
MRI
+ (6 x 3900)]
+ (44 x 3900)
x 1000)
ALL PATiENTS
FORMULA
SURGERY PATIENTS
= 103,700
FAILURES
SAVINGS
DISCUSSION Figure
Before patients dergone this tient
study, MR treatment
with a surgical lesion and an invasive procedure in patients. In addition to guiding treatment, MR imaging helps the surgeon plan therapeutic arthroscopy before surgery. Plans for meniscal repair can be made in appropriate patients on the basis of the MR examination. For example, isolated ACL injuries can be treated electively on the basis of instability patterns, whereas young active patients with combined meniscal tears and ACL disruption can be treated with menisrepair
and
ACL
as the
increased
reconstruction.
from
84%
to 97%,
and
negative predictive value increased from 86% to 96% when a mobile .35-T imager was compared with a stationary 1.5-T imager (22). Using a 1.5-T magnet, Mink et al (13) reported an overall accuracy of 93%, which is very close to our overall accuracy of 94%. They
also
rate the
noted
ranged
that
from
37 general
the
6% to 16%
orthopedic
338
of a tear
Radiology
#{149}
formula
used
in this
can
be
is the failure of the patients
of comparison.
guided strictly
to
For
management but followed by the
treating surgeons for various reasons. According to our protocol, seven patients with complete meniscal tears should have undergone therapeutic anthroscopy (Table 2). Of these patients, four refused surgery despite the recommendations of the treating surgeon and were doing well at longterm follow-up. In the fifth patient, a test for Lyme disease was positive, therapeutic arthroscopy was canceled, and the outcome was good. The sixth patient was doing well 11 months after MR imaging but was not available for long-term follow-up. The seventh patient, who had a combined chronic ACL tear and acute grade 3 meniscal tear, underwent delayed reconstruction
and
niscectomy. Exclusion tients from the group nonsungical treatment increased the frequency the protocol had been formly.
among
surgeons
In 10 patients on MR images
subjective.
Clearly, the accuracy of arthnoscopy highly dependent on this surgeon’s expertise. All prior studies have used arthroscopy as the standard against which MR imaging is compared. The prob-
standard
this study were not
ACL
false-positive
but was only 6% for the arthroscopist subspecialist. Quinn and Brown (23) have shown that some false-positive findings on MR images can be attributed to inadequate visualization of the meniscus at surgery and that diagnosis
analysis
example, patients with a normal MR image could have a plica or degenerative fraying of the meniscus that is discovered at arthroscopy; this finding would suggest that MR imaging did not enable diagnosis. However, if the patient had not undergone arthroscopy on the basis of findings on MR images and the symptoms had disappeared, then the patient would have avoided diagnostic anthroscopy. The final outcome is a more relevant standard of comparison. The MR imaging criteria used in
Diagnostic arthnoscopy is considerably more expensive than MR imaging, and their accuracy is likely very similar. Many studies have evaluated the diagnostic accuracy of MR imaging of the knee (9-15,20,21). The wide range of reported accuracy rates may be due to a number of factors, such as equipment, imaging technique, and the expertise of the radiologist and anthroscopist. For example, accuracy in diagnosis of medial meniscus tears increased from 86% to 93%, sensitivity
Cost
lem with these studies use the final outcome
imaging affected paby enabling selection
of patients obviating the other
cal
4.
study.
the use of MR imaging, all in this study would have undiagnostic arthroscopy. In
is
in our did not
partial
me-
of these pawho underwent should have of success if followed unistudy, justify
findings thera-
peutic arthroscopy on the basis of our protocol, but they underwent surgery anyway (Table 1). Although most patients with acute isolated ACL tears initially undergo nonsurgical treatment at our institution, three patients with such tears underwent immediate arthroscopic reconstruction of the
ACL.
In the
seven
other
patients,
am-
throscopy was performed at the insistence of six patients and on the advice of the surgeon in one patient. In these seven patients, MR images were nor-
mal in two grade
patients
and
2 changes
four
patients
which tient,
revealed
in two
patients.
underwent
was negative. chondromalacia
diagnosed
In the fifth papatellae was
on MR images
umented
but
at arthroscopy.
patient
had
grade
a grade
3) change
on the
on
surgeon’s
not
doc-
The
sixth
2 (possibly
a
MR
and,
images
advice,
anthroscopy, which seventh patient had
fracture, throscopy. throscopy
All
arthroscopy,
underwent
was negative. a tibial plateau
The
confirmed by means of arIn view of the fact that anwas performed inappropn-
ately in 10 patients and was, inappropriately, not performed in seven patients, strict compliance with the protocol would have obviated immediate arthroscopy in three patients.
Of the
11 patients
who
underwent
delayed
arthroscopy
derwent underwent
ACL reconstruction, three negative arthroscopy, and
two
underwent
only
the
plica
excision,
failed
excision
two
patients the
to guide
appropriate In a recent concluded
(Fig 1), six un-
of plica.
who initial
MR
imaging
management treatment. study,
Boden
In
underwent toward et al (7)
that
diagnostic arthroscopy would be more cost-effective than MR imaging if 78% of the patients underwent arthnoscopy. In their study, MR imaging was not costeffective because 87% of the patients underwent arthroscopy. However, their study had two major limitations. First, the final outcome of the patients was not ascertained. Second, no crite-
ria for avoiding
copy have
were used
diagnoses nology.
many
arthros-
surgeons may to confirm
or just try out a new In our study, only 43%
tients underwent peutic arthroscopy findings on MR
that
a diagnostic
stated. The MR imaging
patients
techof pa-
immediate theraon the basis of images. Our findings
with
knee
injuries May
1992
show improvement after nonsurgical treatment is consistent with the study by Hede et al (24), who found that 14 of 36 patients
(39%)
decided
not
in centers imaging
with
different
tients who do not have intraarticular lesions. Costs described in the study are specific to this university and cannot necessarily be extrapolated to other sites. Finally, costs associated and
lost
work
time,
arthroscopic
excluded
tions. should
from
A more include
physical
therapy,
complications
were
our
2.
cost
analysis
comprehensive these factors.
The predictive 16.
D.
Precision
arthroscopy.
183
Number
#{149}
2
17.
3. 4.
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Freiberger Arthrography
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Boden SD, Labaopoulos PA, Vailas JL. MR scanning of the acutely injured knee: sensitive, but is it cost effective? Arthros-
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Johnson U. Impact copy on the clinical rienced arthroscopist. 167:75-83.
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19.
arthros-
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DW,Jenrtings
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Silva I, Silver DM. Tears of the meniscus as revealed by MRI. J BoneJoint Surg 1988; 70:199-202.
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in the di-
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#{149}
PJ, UublinerJA.
Chilies H, Seligson
copy
specialized group of patients likely include even more pa-
with
Fowler
value of five clinical of meniscal pathology. 5:184-186.
equipment,
techniques, radiologists, or patient populations. The patients in our study attended a sports medicine tertiary referral clinic with sports medicine subspecialists and may represent a special population. However, a less would
1.
to
undergo arthroscopy of the knee while on the surgical waiting list. Boeree et al (14) have suggested that the accuracy of MR imaging should enable more appropriate selection of patients for whom arthroscopy would be beneficial. The authors postulate that such accuracy would eliminate the need for arthroscopy in one-third to one-half of those considered, on the basis of clinical findings, to have meniscal or cruciate derangement. Their hypothesis correlates well with the results of our study. Finally, when one interprets the results of this study, several limitations should be considered. Reproduction of our results might not occur
15.
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