diagnostic pitfalls mimicking meniscal tears: mr … · the medial and lateral oblique...

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Diagnostic pitfalls mimicking meniscal tears: MR imagingevaluation with arthroscopic correlation

Poster No.: C-611

Congress: ECR 2009

Type: Educational Exhibit

Topic: Musculoskeletal

Authors: I. Tsifountoudis, I. Kalaitzoglou, A. Haritanti, I. Economou, A. S.Dimitriadis; Thessaloniki/GR

Keywords: MRI, Meniscus, Diagnostic pitfalls, Postoperative meniscus

DOI: 10.1594/ecr2009/C-611

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Learning objectives

MRI has been established as a very sensitive method for the diagnosis ofmeniscal tears. To maintain high accuracy, radiologists should be aware ofpotential pitfalls in interpretation. Our purpose is to review these potentialcauses of confusion, to describe the mechanisms by which they may createfoci of pathologic signal intensity similar to meniscal tears and to recommendmethods to avoid false-positive and false-negative interpretations.

Background

The findings from MRI examinations of 310 knees were retrospectivelyinterpreted and correlated with prospectively recorded results fromarthroscopic examinations performed between 2006 and 2008.

The imaging protocol consisted of: a) T1-weighted fast spin-echo (FSE), b)proton density (PD)-weighted and T2-weighted FSE, c) T2 gradient (GRE)-weighted and d) short-tau inversion recovery (STIR) sequences.

Of the knees examined, 255 meniscal tears were identified. Furthermore, 27false-positive and 14 false-negative findings were detected.

Imaging findings OR Procedure details

False-positive and false-negative findings were attributed to pitfalls ininterpretation which may be caused by: (a) normal structures of theknee which project in close relationship to the menisci, such as anteriortransverse ligament, meniscofemoral ligaments, oblique menisco-meniscalligament and popliteal tendon and bursa, (b) normal variants of themenisci such as meniscal flounce, speckled anterior horn of the lateralmeniscus and Wrisberg's variant of a discoid lateral meniscus, (c) MRIartifacts created by the pulse sequences used, such as magic anglephenomenon, volume averaging, motion and truncation artifacts, (d) variouspathologic conditions of different etiology, such as chondrocalcinosis,meniscal ossicles and gas within the joint and (e) postoperative changesof the menisci.

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NORMAL ANATOMIC STRUCTURES

Normal anatomic structures that lie in close proximity to the meniscus andshow similar MR signal intensity to the meniscus are common mimickers ofmeniscal pathology.

The anterior transverse ligament attaches the anterior margin of lateralmeniscus to the anterior horn of medial meniscus (Fig.).

Fig.: The anterior transverse ligament is clearly demonstrated on coronal PD-W fatsat (a) and T1-W images (b) and on axial PD-W fat sat (c) and T1-W images (d) asit courses from the anterior margin of lateral meniscus to the anterior horn of medialmeniscus.

On sagittal images, a linear band of increased signal is present betweenthe anterior horn of lateral meniscus and the anterior transverse ligament,occasionally simulating an oblique meniscal tear (Fig.) [1].

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Fig.: A linear band of increased signal intensity (arrowhead) is noticed on a sagittalPD-W fat sat image (j), between the anterior horn of lateral meniscus and the anteriortransverse ligament (arrow), simulating an oblique meniscal tear. The course ofthe ligament is clearly demonstrated on adjacent sagittal PD-W fat sat images (e-j). Osgood-Schlatter disease is also present with patellar tendon thickening, deepinfrapatellar bursitis and tibial tubercle fragmentation.

By the same mechanism, increased linear MR signal in the medial aspectof the posterior horn of lateral meniscus at the attachment site of themeniscofemoral ligament can mimic the appearance of a vertical meniscaltear. The meniscofemoral ligament originates from the lateral meniscusposteriorly and inserts on the medial aspect of medial femoral condyle. Theligament is composed of 2 separate branches, the ligament of Humphry andthe ligament of Wrisberg (Fig.).

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Fig.: Diagram showing the origin of meniscofemoral ligaments from the medial aspectof the posterior horn of lateral meniscus.

On sagittal MR images, these are seen as low signal intensity ovoidstructures anterior and posterior to the posterior cruciate ligament (PCL) andmay be mistaken for meniscal fragments (Fig.) [2].

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Fig.: A linear band of increased signal intensity (arrowheads) is noticed on sagittal PD-W fat sat images (e, f), between the posterior horn of lateral meniscus and the ligamentof Humphry, simulating a vertical meniscal tear. The anterior meniscofemoral ligament(arrows) is clearly demonstrated on adjacent sagittal PD-W fat sat images (a-f).

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Fig.: The anterior meniscofemoral ligament (arrows) is depicted on adjacent coronalPD-W fat sat images (g, h) as it courses from the medial aspect of medial femoralcondyle to the medial aspect of the posterior horn of lateral meniscus. A horizontal tearof the posterior horn of medial meniscus (arrowheads) is also noticed.

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Fig.: The ligament of Humphry (arrows) is demonstrated on adjacent axial PD-W fatsat images (i-l) as it courses from the medial aspect of medial femoral condyle to themedial aspect of the posterior horn of lateral meniscus.

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Fig.: A linear band of increased signal intensity (arrowhead) is noticed on a sagittalPD-W fat sat image (e), between the posterior horn of lateral meniscus and theligament of Wrisberg, simulating a vertical meniscal tear. The posterior meniscofemoralligament (arrows) is clearly demonstrated on adjacent sagittal PD-W fat sat images (a-e).

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Fig.: The ligament of Wrisberg (arrows) is depicted on adjacent coronal PD-W fatsat images (f, g) as it courses from the medial aspect of medial femoral condyle tothe medial aspect of the posterior horn of lateral meniscus. A horizontal tear of theposterior horn of medial meniscus (arrowheads) is also noticed.

The medial and lateral oblique menisco-meniscal ligaments have a reportedincidence of 1% to 4% and are an uncommon source of diagnostic difficulty.These ligaments extend obliquely from the anterior horn of one meniscus tothe posterior horn of the opposite meniscus (Fig.).

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Fig.: Diagram showing the medial oblique menisco-meniscal ligament as itcourses from the anterior horn of medial meniscus to the posterior horn oflateral meniscus.

As the ligament traverses the intercondylar notch, it passes between anteriorcruciate ligament (ACL) and PCL, mimicking the appearance of a "doublePCL sign" (Fig.).

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Fig.: Sagittal T1-W (a) and PD-W fat sat images (b) through the intercondylar notchat the level of PCL demonstrate the medial oblique menisco-meniscal ligament as athin linear structure of low signal intensity (arrows) mimicking a displaced meniscalfragment. A Baker's cyst is also noticed (arrowheads). Coronal PD-W fat sat image (c)shows the ligament as it passes through the intercondylar notch.

Knowledge of the normal course of these ligaments, as well as the ability totrace them on consecutive MR images, allows distinction of these ligamentsfrom a meniscal bucket-handle tear (Fig.) [3].

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Fig.: Bucket-handle meniscal tear of medial meniscus. The thin linear structure of lowsignal intensity (arrow) which courses under the PCL (arrowheads) on a sagittal T2-Wimage (a) represents a displaced meniscal fragment ("double PCL sign"). The meniscalfragment (arrow) is also demonstrated as it passes through the intercondylar notchunder the PCL (arrowheads) on a coronal PD-W fat sat image (b).

The bursa of the popliteus tendon, which lies close to the posterolateralmeniscus, may also be mistaken for a meniscal tear. Fluid within the bursaappears as high-signal intensity on T2-weighted MR images and gives theappearance of a vertical or slightly diagonal tear in the posterior horn oflateral meniscus (Fig.) [4, 5].

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Fig.: Fluid within the bursa (arrowhead) appears as high-signal intensity on a sagittalPD-W fat sat image (e) and gives the appearance of a vertical or slightly diagonal tearin the posterior horn of lateral meniscus. The popliteus tendon and bursa (arrows) areclearly demonstrated on adjacent sagittal PD-W fat sat images (a-e).

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Fig.: Fluid within the bursa (arrowhead) appears as high-signal intensity on a coronalPD-W fat sat image (f) and resembles a vertical or slightly diagonal tear in the posteriorhorn of lateral meniscus. The popliteus tendon and bursa (arrows) are demonstratedon adjacent coronal PD-W fat sat images (f, g).

The lateral inferior genicular artery arises from the popliteal artery at the levelof the tibiofemoral joint and courses laterally to the anterior aspect of theknee where it and other arteries compose the genicular anastomosis. Unlikethe superior genicular arteries and the inferior medial genicular artery, thelateral inferior genicular artery is closely applied to the meniscus as it wrapsaround the knee, lying in a periarticular fat pad between the meniscus andlateral collateral ligament (LCL) (Fig.).

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Fig.: Diagram showing the arteries of the knee.

When the lateral inferior genicular artery lies immediately adjacent to theanterior horn of lateral meniscus, the space between the artery and themeniscus can produce the appearance of a tear in the meniscus on sagittalimages. Comparison with a coronal image through the area of suspectedtear may be helpful since the artery does not mimic a tear when viewed inthe coronal plane (Fig.) [6].

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Fig.: Adjacent sagittal T1-W images through the lateral meniscus (a-d) demonstratethe course of the lateral inferior genicular artery (arrows). A narrow separation(arrowhead) between the anterior horn of lateral meniscus and the lateral inferiorgenicular artery (c) can sometimes be mistaken for a meniscal tear.

NORMAL VARIANTS

In addition to normal meniscal structures previously demonstratedradiologists should be familiar with several normal variants of the meniscithat have been described in recent years.

Meniscal flounce is an uncommon variant that can simulate meniscalpathology. It occurs in the absence of a tear and is a single symmetric foldalong the free edge of the meniscus. It is a normal finding that is said tobe present with ligamentous laxity, although it is not necessarily indicativeof a tear in the ligament. The appearance is like that of a carpet that has awrinkled edge and, in fact, presumably has a similar cause-that is, slidingof the tibia on the femur because of ligamentous laxity with resultant foldingor buckling of the inner edge of the meniscus. It has no known significance.

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A flounce results in a wavy S-shaped appearance along the free edge ofthe meniscus on sagittal images and a truncated meniscal appearance oncoronal images that may be mistaken for a meniscal tear or degeneration(Fig.) [7].

Fig.: Meniscal flounce of medial meniscus (arrows) which results in a slight wavy S-shaped appearance along the free edge of the meniscus on adjacent sagittal PD-W fatsat images (a, b).

A speckled appearance of the anterior horn of lateral meniscus is a frequentfinding that has been explained by fibers of the anterior cruciate ligamentinserting into the meniscus. It can be seen on one or two of the most medialsagittal images. The appearance can be mistaken for a torn lateral meniscus(Fig.) [8].

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Fig.: A speckled appearance (white arrows) of the anterior horn of lateral meniscuson adjacent sagittal PD-W fat sat images (a, b), which is caused by the insertion of thefibers of anterior cruciate ligament (black arrow) into the meniscus (c). The finding caneasily be mistaken for a torn lateral meniscus.

A discoid lateral meniscus is a normal variant seen in about 3% of knees.An uncommon variant of a discoid lateral meniscus is a Wrisberg's variant,in which the posterior horn is not attached to the capsule and is, therefore,mobile enough to move freely and sublux into the joint, causing pain and,occasionally, locking. The MR imaging appearance is a discoid lateralmeniscus with no posterior horn attachment or a free-floating posteriorhorn. Unlike the incidental discoid meniscus, which should be asymptomaticunless torn, a Wrisberg's variant can be a source of pain and require surgery.It is most commonly found in children, although it can be seen in patientsat any age [9].

The moderate to high signal intensity seen at the normal capsular attachmentof the posterior horn of medial meniscus may be due to tissue inhomogeneityor peripheral vessels that can mimic a meniscocapsular detachment (Fig.).

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Fig.: The high signal intensity seen at the periphery of the posterior hornof medial meniscus (arrows) on adjacent sagittal (a, b) and coronal PD-Wfat sat images (c) was diagnosed as meniscocapsular detachment. Thefollowing arthroscory for anterior cruciate ligament reconstruction (ACLR),because of torn ACL, revealed absence of meniscal tear.

Usually, the signal intensity of this normal connective tissue at themeniscocapsular junction is less conspicuous, whereas in cases ofmeniscocapsular detachment, there is markedly increased signal intensity(Fig.) [10].

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Fig.: Peripheral tear-meniscocapsular detachment (arrows) of the posterior horn ofmedial meniscus on sagittal (a) and coronal PD-W fat sat images (b). Bone contusionsof the posterior tibial epiphysis are also noticed.

The most significant characteristic in the appearance of pediatric meniscusis the presence of intrasubstance signal that represents perforating vesselswithin the meniscus. This signal has been described in 82% of menisciin children and is considered to be a normal finding that should not bemisinterpreted as mucinous or myxoid degeneration like in adults. The MRcriteria for establishing the diagnosis of a meniscal tear are the same inchildren and adults. The 2 most important criteria are intrameniscal signalthat extends to the surface and abnormal meniscal morphology (Fig.) [11].

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Fig.: The presence of intrasubstance signal in the posterior horns of medial (arrows)and lateral (arrowheads) meniscus represents perforating vessels within the menisci.This signal is considered a normal finding and should not be misinterpreted asmucinous or myxoid degeneration like in adults.

MRI ARTIFACTS

MRI artifacts created by the pulse sequences used can result in imagedegradation and errors in diagnosis.

The magic angle phenomenon occurs on short TE images in fibers that areorientated 55° relative to the static magnetic field. This MRI artifact is a causeof increased signal in the medial segment of the posterior horn of lateralmeniscus. Imaging the knee joint in slight abduction can alter the orientationof the fibers in the posterolateral meniscus and eliminate this artifact [12].

Partial volume averaging is a type of artifact that occurs when 3-dimensionalvolumetric data is used to create a 2-dimensional image. The attachmentof the capsule produces a concavity at the outer margin of the meniscus

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that is filled with periarticular fat and neurovascular structures. When thesignal from a normal dark meniscus is averaged with the bright, fatty tissueadjacent to the outer concave margin of the meniscus, high-signal intensitylinear artifacts that may simulate a tear are created through the periphery ofthe meniscus on sagittal images (Fig.).

Fig.: Diagram of the meniscus showing the concave meniscal edge. Asagittal section through the edge of the meniscus (B) produces a partialvolume averaging linear artifact in the body of the meniscus. A sectionlocated more medially (A) may produce a similar linear artifact in theanterior and posterior horns when the curvature of the meniscus is placedat the edge of the section.

This linear defect is seen only on sagittal images obtained through theperiphery of the meniscus. A coronal image obtained through the meniscuswill show no abnormality and can be used to exclude the presence of a tear(Fig.) [6].

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Fig.: Partial volume averaging produces linear artifacts mimicking horizontal tears(arrows) in the anterior and posterior horns and in the body of lateral meniscus onadjacent sagittal PD-W fat sat (a-c) and T1-W images (d-f).

Motion artifact can be particularly problematic in MRI because of thelong image acquisition times. If a structure moves to different positionsduring image acquisition, the image appears blurred or double exposed.Intrameniscal signal resembling a tear may result. If motion artifact is presenton an MRI scan and a meniscal tear is suspected by imaging criteria, thesequence should be repeated without motion (Fig.) [5].

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Fig.: Motion artifact mimicking a tear (arrow) in medial meniscus on a coronal PD-Wfat sat image (a). The meniscus appears normal on a coronal T1-W image at the samelevel (b), which is obtained without motion.

Truncation error is a type of MRI artifact that occurs at high-contrastboundaries, such as between the articular cartilage and the menisci.Truncation artifact is a result of inherent errors in the Fourier transformationmethod of image reconstruction. It appears as a series of alternating parallelbands of bright and dark signal. When a line of high-signal intensity projectsover a low-signal meniscus, a pseudotear is created [13].

VARIOUS PATHOLOGIC CONDITIONS

Certain pathologic conditions of different etiology may mimic a meniscal tear.Most of them are rare entities and their recognition may help to explain areasof abnormal signal that do not fit well into previously recognized patterns andmay improve interpretation accuracy.

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A meniscal contusion occurs when the meniscus gets trapped between thetibia and the femur during a traumatic event-usually involving ACL tears.Increased signal in the periphery of the meniscus can resemble a tear;however, the signal intensity of a contusion is indistinct and amorphousrather than sharp and discrete. An adjacent bone contusion should alert oneto the possible presence of a contusion rather than a meniscal tear (Fig.)[14].

Fig.: Meniscal contusion with amorphous and indistinct signal in the periphery of theposterior horn of medial meniscus (arrows) on adjacent sagittal (a-c) and coronal PD-Wfat sat images (d-f) after an acute traumatic event with bone contusions, complete ACLand partial medial collateral ligament (MCL) tear. Follow-up MRI 5 months after initialimaging revealed resolution of abnormal meniscal signal.

Grade 2C meniscal signal is an extensive triangular or wedge-shaped signalthat does not reach the surface of the meniscus on more than one images onMRI. It has a low incidence (1,5%) and has been proved to represent a tearin 50% of cases. Most patients with grade 2C meniscal signal are not treated

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with arthroscopy because they do not have symptoms at the site of grade2C signal. Thus, when grade 2C signal is seen on MR imaging, arthroscopicfollow-up is indicated if symptoms referable to the site of abnormal signalare also present (Fig) [15].

Fig.: Grade 2C signal in the posterior horn of medial meniscus (arrows) on adjacentsagittal PD-W (a, b) and coronal PD-W fat sat images (c, d), confirmed as intactmeniscus on arthroscopy.

Chondrocalcinosis is defined as a radiographically visible calcification in thecartilage of a joint. It can occur in the hyaline articular cartilage lining thearticular surface or in the fibrocartilage of a meniscus. Although it canoccur from many types of calcium crystals, the most commonly seen isfrom calcium pyrophosphate dihydrate crystal deposition in pseudogout,which is also known as calcium pyrophosphate dihydrate deposition disease.When MR imaging is performed on a meniscus with chondrocalcinosis, theT1-weighted or PD-weighted sequence shows high signal, which can bemistaken for a meniscal tear. Differentiating a meniscal tear from the high

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signal of chondrocalcinosis can be difficult, if not impossible. Most meniscaltears have a more linear appearance than the globular high signal seen inchondrocalcinosis. Comparison with a conventional radiograph of the kneewill help avoid this pitfall. However, chondrocalcinosis can also obscure atear and result in a false-negative report (Fig) [16, 17].

Fig.: Chondrocalcinosis in medial meniscus. Radiograph of the knee (a) revealsmeniscal calcifications in the posterior horn of the meniscus (arrow). Coronal PD-W (b)and sagittal PD-W images (c, d) show marked high signal throughout the posterior hornof medial meniscus (arrows) that resembles a tear. No meniscal tear was identified onarthroscopy.

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Fig.: Chondrocalcinosis in lateral meniscus. Anteroposterior knee radiograph (a)shows meniscal calcifications in lateral meniscus (arrow). Sagittal PD-W image (b)shows high signal intensity both in the anterior and posterior horn of lateral meniscuswith extension to inferior articular surface (arrowheads), interpreted as meniscal tears.No meniscal tear was found on arthroscopy.

Meniscal ossification is a rare finding of unknown origin with a prevalence of0,15% in MR examinations. Meniscal ossicles are frequently asymptomaticand discovered incidentally. They mimic intra-articular loose bodies andlead to inappropriate surgical treatment. Imaging is required to confirm thediagnosis and assess meniscal integrity. The typical appearance is that ofan intrameniscal lesion which shows central high signal on T1-weightedimages, due to normal fat bone marrow, surrounded by low signal on bothT1-weighted and T2-weighted images related to the cortical rim. The highsignal of the inner portion, which is the same as viable medullary bone,allows differentiation from loose bodies, which may present internal lowsignal. However, loose bodies, if ossified, may present with an internal highsignal [18, 19].

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Gas within the knee joint may represent a vacuum phenomenon or iatrogenicplacement during arthrography or joint aspiration. The low magneticsusceptibility of gas produces a discrete signal void. If the gas collectsadjacent to the meniscus, it can simulate a meniscal tear, abnormal meniscalvolume, or a displaced meniscal fragment (Fig.) [20].

Fig.: Gas within the knee joint (arrows) produces a discrete signal void on adjacentcoronal T2 GRE (a, b) and T1-W images (c, d), as well as on sagittal T2-W images (e-g), that simulates a radial meniscal tear in medial meniscus (arrowheads).

Articular cartilage damage is another potentially confounding pathologicalcondition that can resemble a tear. Articular cartilage defects and chondralfractures of the tibial, femoral, and patellar cartilage in children may mimica bucket-handle meniscal tear on MRI [21].

POSTOPERATIVE CHANGES

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In recent years, there has been increasing demand for postoperativeevaluation of the meniscus because of the increased number of patientswho undergo meniscal surgery. The most common surgical proceduresinclude partial meniscectomy and meniscal repair. Recognition of the normalpostoperative MRI appearance of the meniscus and of abnormalities isessential for the accurate assessment of symptomatic patients [22].

After partial meniscectomy, meniscal morphology may differ from that of anonoperative meniscus with its postoperative appearance depending onthe amount and anatomical location of meniscal tissue resected and themorphology of the previous meniscal tear. On MR imaging, such postsurgicalvariations in meniscal shape typically include diminution in the overall sizeof the meniscus or meniscal horns, blunting of the meniscal apical margin,or variable degrees of meniscal truncation (Fig.) [23].

Fig.: Diagram of medial meniscus (a) illustrating the two types of partialmeniscectomy: circumferential (b)-where the posterior horn and anchor, and therefore

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the meniscal "hoop" has been preserved and segmental (c)-where the posteriorattachment has been resected and the load transmitting function has been sacrificed.

Fig.: Normal appearance of a partially resected meniscus. Adjacent coronal PD-W fatsat images from anterior to posterior (a-c) demonstrate a small blunted body of medialmeniscus (arrow) following circumferential partial meniscectomy.

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Fig.: Normal appearance of a partially resected meniscus. Adjacent coronal PD-W fatsat images from anterior to posterior (a-c) demonstrate a resected posterior horn ofmedial meniscus (arrows) following segmental partial meniscectomy.

Increased short TE intrameniscal signal extending to the meniscal articularsurface after the operation may also be seen as a normal finding on MRimaging and may not be indicative of a recurrent tear (Fig.) [24].

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Fig.: Diagram illustrating the potential of creating an intrasubstance grade 3 signalintensity abnormality after meniscectomy. The dotted lines (a) show the plannedincision in a torn meniscus. The surgeon resects the torn portion of the virgin meniscusafter probing it. The resected fragment usually does not contain the entire linear areaof abnormal signal intensity (straight line) seen on MRI. A grade 3 signal intensityabnormality extends to the articular surface after the operation (b) and mimics a tear inthe untorn postoperative meniscus.

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Fig.: Diminutive morphology of the posterior horn of medial meniscus on adjacentcoronal PD-W fat sat (a, b) and sagittal PD-W images (c, d) following priormeniscectomy with intrameniscal increased signal intensity extending to theinferior meniscal surface (arrows), which was interpreted as new tear. Second-lookarthroscopic evaluation revealed an intact meniscus.

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Fig.: Intrameniscal increased signal intensity (arrows) on adjacent coronal PD-Wfat sat (a-c) and sagittal PD-W images (d, e) in the resected posterior horn of medialmeniscus after partial meniscectomy was interpreted as new tear. Second-lookarthroscopy revealed normal signal postoperative changes.

What is more, studies on meniscal repair have shown that linear increasedsignal intensity extending to the surface, which is indicative of healingprocess, can persist at the site of surgery for at least 1 year after repair (Fig.)[22].

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Fig.: Coronal PD-W fat sat image demonstrates linear increased signal(but not synovial fluid) (arrow) corresponding to a scar mimicking a newtear, 2 years after repair of a peripheral vertical tear in lateral meniscus.

Thus, diagnosis of meniscal tears by using the usual criterion of linearincreased signal intensity extending to the surface on conventional shortecho time MR images may lead to a false-positive diagnosis in patients aftermeniscal repair. Use of the stricter criterion of fluid signal intensity within alinear defect in the meniscus on T2-weighted images has been shown toprovide high specificity (88%-92%) but low sensitivity (41%-69%) for tears.Thus, the use of this stricter criterion with conventional MR imaging will resultin fewer false-positive diagnoses; however, many tears will be missed [25].

For patients who have undergone partial meniscectomy, the accuracy ofconventional MR imaging for detection of a tear is 66%-82%. Studieshave shown accuracy similar to that found for evaluation of preoperativemenisci in cases when only a small resection (less than 25%) is performed.Unfortunately, most resections are not small [25].

In an attempt to improve the accuracy of MR imaging for diagnosing retornmenisci, the use of direct MR arthrography, which involves the injectionof intraarticular contrast material, has been proposed. MR arthrographyis approximately 90% sensitive and specific for detecting retear of thepostoperative meniscus. Advantages of MR arthrography over conventionalMR imaging include the ability to obtain adequate joint distension, greater

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penetration of contrast material and the ability to use T1-weighted images.On MR arthrograms, meniscal tears are diagnosed as areas of increasedsignal intensity (equal to that of intraarticular gadolinium contrast material)within the meniscus (Fig.) [26, 27].

Fig.: Sagittal T1-W fat-sat MR arthrography image following intra-articular injection ofgadolinium demonstrates contrast extending into a subtle cleft (arrow) in the posteriorhorn of medial meniscus corresponding to a peripheral vertical tear, which waspreviously missed on conventional MRI.

Conclusion

MRI is a valuable tool for the evaluation of meniscal pathology. A thorough knowledgeof potential pitfalls mimicking meniscal tears is essential if one is to maximize diagnosticaccuracy.

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Personal Information

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