Andrew Barry

L Deutsch,

J. Rothman,

MD MD

#{149} Jemrold

MD MD

H. Mink,

#{149} David

W. Stoller,

#{149} James #{149} W.

M.

Dilworth

Peripheral Meniscal Tears: after Conservative Treatment or Arthroscoplc Repair’

P

Follow-up knee magnetic resonance (MR) examinations were performed on i7 patients (i8 menisci) with arthroscopically proved tears of the outer third of the meniscus who were treated either conservatively (six patients) or with surgical repair (ii patients). All patients satisfied accepted clinical orthopedic criteria for meniscal healing. MR examinations obtained 3-27 months after injury revealed persistent signal intensity (grade 3), unchanged from that seen on the preoperative study, in all 15 patients in whom both preand postoperative studies were obtamed and in three of four menisci that were proved to be healed at second-look arthroscopy. It appears that grade 3 signal from both conservatively treated and repaired menisci may persist long after the tear has become asymptomatic and has presumably healed. The presence of such signal should not be interpreted as necessarily indicating meniscal retear in these patients. Persistent signal intensity at the site of previous injuries may account for some reported cases of disagreement between MR and arthroscopic findings.

MR

ERIPHERAL

tomy, with its documented deleterious effects on articular cartilage (16), increasing attention has been directed by orthopedic surgeons to-

ward

meniscal

preservation

(7-16).

Small tears within the vascularized peripheral third of the rneniscus can be treated conservatively, and arthnoscopically guided repair techniques have been developed for larger peripheral tears. Repair of these peripheral meniscal tears has, to date, mesulted in a high reported rate of success, although assessment has been largely limited to subjective clinical evaluation on occasional “secondlook” arthroscopy. This study was undertaken to characterize the appearance of rnenisci in which documented peripheral tears were treated either conservatively on with operative repair and to assess whether magnetic resonance (MR) imaging could provide assessing the operatively.

PATIENTS

a reliable method status of the repair

AND

for post-

METHODS

A computer

search of medical records was undertaken to identify patients who had sustained tears involving the periphenal (outer) one-third of either meniscus and who had been successfully treated conservatively (brace immobilization for 4-6 weeks) on had undergone arthno-

1990; 176:485-488

I From the Department of Radiology, Division of Musculoskeletal Imaging, Cedars-Sinai Medical Center, 8700 Beverly Blvd. Los Angeles, CA 90048 (A.L.D., J.H.M., B.J.R.); Department of Radiology, University of California, San Diego (A.L.D.); Southern California Orthopedic Institute, Cen-

ter for Disorders Hospital (D.W.S.);

From vision

of the Knee,

Van

Nuys,

for Special Surgery, New York and Department of Orthopedic

the 1989 RSNA received

RSNA,

March

1990

scientific 15; accepted

assembly. March

Calif

(J.M.F.);

(SPA.); Surgery,

Received 23.

Laboratory

Advanced University

Address

of Comparative

Diagnostic Imaging, of California, San

Orthopedics,

San Francisco Francisco (W.D.C.).

January 9, 1990; revision requested reprint requests to A.L.D.

March

#{149} Steven

P. Arnoczky,

DVM

#{149}

Jr, MD

Findings

meniscal teams represent an important subgroup of meniscal injuries because of their proximity to the synovial blood supply and consequent ability to heal. As an alternative to partial meniscec-

Index terms: Knee, arthrography, 452.122 #{149} Knee, injuries, 452.4852 #{149} Knee, ligaments and menisci, 4524.4852, 4525.4852 #{149} Knee, MR studies, 452.1214 #{149} Knee, surgery, 452.459 Radiology

Fox, MD Cannon,

5; re-

scopically guided suture meapposition (mepain). We identified 17 patients who met these criteria and were willing to undergo follow-up MR imaging of their knees. The ages of the 1 1 male and six female patients ranged from 16 to 41 years. One patient had sustained tears involving both the medial and lateral menisci; thus, there were a total of 18 menisci available for evaluation. Thirteen tears involved the medial meniscus, and five tears involved the lateral meniscus. Clinical assessment was performed by an experienced subspecialist knee anthroscopist. All patients were considered to be in clinically stable condition. Their meniscal tears were presumed to be healed on the basis of commonly accepted clinical orthopedic criteria (eg, the patients were asymptomatic, had a negative McMumray test result, had full range of motion, and had returned to work and pneinjury athletic activity). Second-look amthnoscopy was performed 6 months aften repair in two patients and 9 months after repair in a third patient (total of four menisci). The results of all MR examinations were reviewed by two musculoskeletal radiologists with experience in MR evaluation. A peripheral meniscal tear was considened to be present if (a) a focus of intrameniscal signal intensity identified within the outer third of the meniscus unequivocally extended to an articular surface (grade 3) or (b) fluid could be demonstrated throughout the entire intenface between the meniscus and its capsular attachment. Fourteen patients underwent preoperative MR imaging, and lesions that conformed to the criteria were identified in all patients and were subsequently confirmed anthroscopically. All preoperative MR examinations were performed on a 1 .5-T imager (Signa; GE Medical Systems, Milwaukee). Images were obtained by using a protocol that has been described in detail previously (17-19). Briefly, all studies were penformed by using a dedicated surface coil. Coronal 800/20 (repetition time msec/ echo time msec) and sagittal 2,000/20, 80 sequences were used in all cases. A 16-cm field of view, a 5-mm section thickness, no intersection gap, and a 128 X 256 matnix acquisition were used to provide images with a spatial resolution of 1.25 mm

485

in the phase-encoded direction and 0.6 mm in the frequency-encoded direction. Postoperative examinations were performed in all cases. Images were obtained 3-27 months after injury (mean, 8 months). All postoperative images were obtained by using the previously descnibed protocol except in two patients, in whom gradient-recalled sagittal 600/30 sequences (flip angle 30#{176}) were used.

cus. In one bar separation virtue

of the

of the

In

the

five

superior

and

py

recesses

Repair

Eleven

patients

scopicably

underwent

guided

One both

patient medial

tears;

thus,

there

the

underwent

anterior

a total

of 12

sociation

reconstruction

cruciate with

Preoperative

the

MR

tients

were

available.

486

#{149} Radiology

of

ligament meniscab

images

patients

(total

menis-

second-look patient (one

b.

anthroscomeniscus),

MR examination grade of the

3 signal tear. The

intensiother

performed

of three

in two

menisci)

patients

at 6 months

repair

as part of an ongoing prostudy. The follow-up MR examinations in these patients were performed within 2 weeks of the amthroscopic procedure. The other patient underwent second-look arthmoscopy 9 months after repair. The tears in all patients were considered to be healed at inspection and probing at the time of the second-book pmocedune. In the one patient for whom both pre- and postoperative studies were available for review, no significant change in the appearance of the meniscus was identified, and pemsistent grade 3 signal intensity was apparent on the MR examination. In two other menisci, both considered to be healed at second-look inspection, persistent grade 3 signal intensity was evident on the follow-up study (Fig 3). In one meniscus, intrameniscal signal not extending to an articubar surface (grade 2) was identified on the postrepair study. No preoperative study of this patient was available for comparison.

DISCUSSION

menisci available for evaluation. Antenor cnuciate ligament tears were present in six patients; all of these patients

of four

Arthroscopy

in asrepair.

of nine In all

Figure

1.

al tear.

(a) Sagittal

small

Conservatively

focus

of

treated

800/20

signal

periphery

of the

medial

meniscus

(arrow).

peripher-

image

depicts

intensity

treme

a

within

posterior

the

horn

At

ex-

of the

arthroscopy

4

weeks after this study, a peripheral tear with partial healing was noted. (b) Sagittal 800/ 20 image obtained 8 months after initial examination.

Image,

centrally

than

equivocal (arrow). this

obtained the

meniscus,

persistent The patient

time

slightly

a, through

of the medial

and

had

more

posterior

horn

demonstrates

un-

grade 3 signal was asymptomatic

intensity at

returned

to

full

activity.

pa-

of these

a.

b. Figure

The deleterious effects of partial or total meniscectomy on the knee joint, with subsequent accelerated degenerative changes, have been documented by numerous investigators (1-6). Increasingly, the attention of orthopedic surgeons has been directed toward meniscab preservation and, in selected instances, meniscal repair (7-16). Tears that involve the outer,

2.

sagittal posterior

Repaired

800/20 horn

ripheral

tear

identified

at

the

months

not clinical

This with

800/20 after

the

the

initial 3 signal

significantly for

use

(a) On the a pe-

of

is

repaired two

sutures.

27

examination

shows

intensity,

which

(arrow). and

meniscal

was

obtained

changed

asymptomatic criteria

tear. through meniscus, junction

tear

image

grade was

obtained medial

red-white

(arrow).

(b) Sagittal persistent

peripheral

image of the

arthroscopically

tient

repair.

repair of meniscal

were

was

arthro-

meniscab

underwent and lateral

study,

spective

capsule.

Meniscal

was

after

with

inferior

to

from

2).

preoperative

(total

inter-

patients

patients, judged

changed

preoperative

(Fig

a.

stable condifollow-up MR

two patients (total of three menisci) did not undergo prearthmoscopic MR examination. Second-look amthrosco-

were present on the follow-up examination, but the fluid no longer dernonstrated a continuous line along the entire extent of the meniscus and joint

in the

demonstrated ty at the site

grade 3 signal intensity on the preoperative study, the postoperative examination demonstrated persistent grade 3 signal intensity that was judged not to have changed significantly (Fig 1). In the one patient with a meniscocapsular separation, prorninent

significantly

ci) underwent py. In one

menis-

of fluid

8 consid-

In all of these signal intensity,

Three

a meniscocapsuidentified by

presence

MR ex3-27

(mean, were

to be in clinically at the time of the

the

evident on of grade 3 the periphery

Follow-up obtained

repair patients

Second-Look

posed between the meniscus and joint capsule. The anterior cruciate ligament was intact in all of these patients. Follow-up MR examinations were obtained in all six patients, with a minimum follow-up interval of 3 months and a maximum of 13 months.

after All

evident

third

patient, was

ered tion

that

Treatment

peripheral

months months).

be not

Six patients with peripheral meniscab tears were treated conservatively with brace immobilization for 4-6 weeks. All patients in this group were considered to be clinically stable with presumably healed meniscal tears at the time of the MR examination. All of these patients underwent a preanthroscopic MR examination, and the tears were identified in all cases. In five patients, the tears were identified on the basis of the presence of grade 3 signal intensity within the

of the meniscus. aminations were

examination. persistent

RESULTS Conservative

patients, the tears were the MR studies as areas signal intensity within

The

satisfied

is

paall

healing.

or peripheral, third of the meniscus represent a unique subgroup of meniscab injuries because of their potentiab to heal by means of synovial ingrowth and vascular proliferation. The vascular supply of the meniscus has been recognized as the essential element in determining the potential

August

1990

Figure

3. Healed tear. Sagittal multiplanar gradient-recalled 600/30 image (flip angle 30#{176}) obtained within 2 weeks of a secondlook arthroscopic examination 6 months aften meniscal repair. Unequivocal grade 3 signal intensity ripheral third

was

considered

spection

and

(arrow) of the

is seen meniscus.

healed

within the Meniscus

at arthroscopic

pe-

in-

probing.

for meniscab repair and healing (1416). A perimeniscal capillary plexus, derived from the geniculam arteries, provides an arbonizing network of vessels that supply the peripheral bonder of the meniscus throughout its attachment to the joint capsule. The degree of vascular penetration ranges between 10% and 30% of the meniscal width (14). This region of the meniscus has been termed the “red zone” because of its blood supply, in contrast to the remainder of the meniscus, which is essentially avascular (the “white zone”). Meniscab lesions that connect with the peripheral vascular network demonstrate a capacity to heal through proliferation of vascular scar tissue (14,16). This group of lesions includes meniscal injuries that are entirely within the vascubanized section of the meniscus (the “med-med junction”) and tears that occur at the junction of the vasculanized and nonvasculanized portions of the meniscus (the “red-white junction”). Expenimental studies in animals have shown that complete radial lesions of the meniscus can heal completely with fibmovascular scar tissue by 10 weeks (16). Histologic studies have demonstrated that this scar tissue eventually modulates into a fibmocartilagelike tissue, although differences between this tissue and the native meniscus are recognizable and indude increased cellularity and, at times, increased vascularity of the mepair tissue. Complete maturation of the scan tissue into fibrocantilage that is indistinguishable from normal meniscus has never been demonstrated. Peripheral meniscab tears that are nondisplaced and are bess than 1 cm in length may heal with conservative management. Larger lesions may ne-

Volume

176

#{149} Number

2

cessitate repair, and a number of procedumes, both anthroscopic and open, have been developed to facilitate sutune placement (7-13,16). Ligamentous stability is considered to be cnitical to successful repair, and ligament reconstruction is commonly performed in association with repair of the meniscal lesion. Peripheral meniscal teams can be demonstrated with the use of MR irnaging (18,19). In this series, most tears were recognized because of the presence of grade 3 signal intensity within the peripheral third of the meniscus, most commonly at the redwhite junction. Red-red teams and true meniscosynovial separations are recognized by virtue of the presence of fluid that is completely interposed between the meniscus and the joint capsule. T2-weighted spin-echo images may be of particular value in the assessment of rneniscocapsulan separation. Incongruence in the alignment of the posterior horn of the medial meniscus and the periphery of the tibial anticubar cartilage of greater than 5 mm has also been proposed as highly suggestive of meniscocapsulam separation, although considerable vaniation in this relationship may be present (18). In this series, grade 3 signal intensity at the site of the meniscal injury was identified in all patients at foblow-up examination. In those patients for whom preoperative studies were available for comparison, no significant change in the appearance of the meniscal tear was observed. The menisci in all of these patients were considered to be clinically stable and presumably healed on the basis of commonly accepted clinical cmitemia. It is recognized, however, that not all patients who meet the clinical criteria for meniscal healing have menisci that are considered healed at the time of second-look anthroscopy. In recognition of this situation, we sought patients who had undergone second-look anthroscopy and whose menisci were considered to be healed at inspection and probing. Four such healed repaired menisci were evaluated with MR imaging, and unequivocab grade 3 signal intensity was demonstrated in three. In another patient, grade 2 signal intensity was present. Since no preoperative study of this patient was available, it is not known whether the team would have been evident as grade 3 signal intensity in this case; therefore, no statement with regard to the interval change in appearance can be made.

The demonstration of persistent signal intensity within these menisci can likely be accounted for by the known histologic differences between the reparative tissue and native fibrocamtilage. The significance of persistent signal intensity with megard to the structural integrity of the reparative tissue and the risk of metear remains unknown; this will be the subject of a prospective animal study. With regard to the diagnostic implications of this persistent signal intensity, it is important that this be recognized as a common occurrence in the knee, and not constitute the sole criterion for the diagnosis of meniscab retear. Persistent signal intensity in healed tears may also underlie some cases of disagreement between MR and anthroscopic findings. In most reported series, the largest number of false-positive MR findings suggestive of meniscal tear have been within the posterior horn of the medial meniscus (17,20,21). Proposed explanations include (a) variation in interpnetive experience of radiologists; (b) widely varying image quality mebated to equipment, coil, and protocol design; (c) operator dependence of arthroscopy; and (d) the presence of contained and true intrasubstance tears that require extensive probing at the time of anthroscopy for detection (21). The posterior horn of the medial meniscus is also a common site of peripheral teams due to the melative immobility of the meniscus secondary to its attachments via the cononary ligaments. On the basis of the findings in this study, in which grade 3 signal intensity indistinguishable from that normally reflective of a meniscab team was commonly seen in patients with stable postoperative menisci, it is possible that some cases of MR-anthroscopic disagreement may be accounted for by the persistence of grade 3 signal intensity in healed injuries. The presence of grade 3 signal intensity not reflective of meniscal teams has previously been reported in a group of symptomatic patients who had undergone partial meniscectomy and who were undergoing MR examination and repeat arthroscopy for possible meniscal retear (22). In conclusion, meniscab repair is being increasingly considered as an alternative to partial meniscectomy for treatment of teams in the peniphemal vasculanized portion of the meniscus. Follow-up MR examination of patients who have undergone successfub

meniscab

repair

has

often

Radiology

me-

#{149} 487

vealed persistence of grade intensity that is indistinguishable from a rneniscal tear. Definite

2.

3 signal

ever

disappears

on significantly

de-

creases in healed menisci remains unknown. At a minimum, however, it is important that persistent signal intensity be recognized as a common occurrence and not be used to provide the basis for the diagnosis of metear in a patient with symptoms. Finally, the possible persistence of grade 3 signal intensity reflecting prior but healed trauma may provide the explanation for some cases of MR-arthroscopic disagreement. U

3.

diagnosis J Bone

of Joint

Jones

4.

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limita-

tions of the present observations with regard to the small number of healed teams identified at second-look arthroscopy should be recognized, however. Several important questions remain unanswered, particularly those regarding the significance of persistent signal intensity with megard to the structural integrity of mepamative tissue and the risk of netear. Also, whether the signal intensity

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August

1990