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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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8.

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Sur-

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for meniscal

of the knee. J Bone Joint Surg 1990;

162:547-551.

Silva I, Silver DM. Tears of the meniscus as revealed by MRI. J BoneJoint Surg 1988; 70:199-202.

13.

Mink JH, Levy T, Crues the anterior of the knee: ology 1988;

study 14.

Boeree

JV III. Tears of cruciate ligament and menisci MR imaging evaluation. Radi167:769-774.

NR, Watkinson

AF, Ackroyd

Johnson C. Magnetic resonance of meniscal injuries of the knee. Joint Surg 1991; 73:452-457.

Volume

in the di-

lesions: a comparison arthrography and J Bone Joint Surg 1979; 61:

Hartzman Duckwiler

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equa-

#{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.

References

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J Bone

Radiology

#{149} 339

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