Indications for repair are acute root avulsions as well as selected chronic root avulsions in the absence of osteoarthritis [12]. Meniscus tear MRI is a common imaging technique used when patients have knee pain. ?weighted (B) MR images show signal to surface (arrow, A) on sagittal proton density?? In most patients, meniscal signal to the surface on MRI of a frayed meniscus will be present on only one MR image, which I would diagnose as a possible tear and not as a definite tear. This finding may represent recurrent tear or granulation tissue from healed repair. Posterior Medial Meniscus Root Ligament Lesions: MRI Classification and Associated Findings. Recently developed techniques now also allow repair of posterior meniscus root tears. meniscal tear [24]. This type of fraying is most common on the free edge of the body of the lateral meniscus but occasionally causes MR signal abnormalities in other areas of both menisci. Fig. B, Coronal (A) and sagittal (B) reformatted images with bone kernel from CT arthrography. 3A —14-year-old boy with knee twisting injury and locking 6 months after medial meniscus repair. On T2-weighted imaging, a parameniscal cyst is a high-signal-intensity fluid collection either directly overlying a meniscus or adjacent to a meniscus with a fluid track connecting to the periphery of a meniscus (Fig. ?weighted image shows linear internal meniscal signal likely contacting meniscal surface (arrow). Parameniscal cysts are a very common finding on a knee MRI. Horizontal Meniscal Tear: Pearls. When evaluating a knee MR examination, I study the medial and lateral menisci first on the sagittal images and then on the coronal images because sagittal images are the most useful in diagnosing meniscal tears. 10 ?? However, we identified three studies that compared conventional MRI with second-look arthroscopy. Normally the superior and inferior surfaces of the menisci are equal in length. Menisci should have low signal intensity on MR images because of their fibrocartilage composition, but they may have central globular or linear increased signal intensity secondary to internal mucinous degeneration [3]. Sagittal proton density?? Medial root tears are usually radial in type and are often associated with meniscal extrusion as noted earlier. B, Sagittal proton density?? This booklet gives information on the different types of meniscus problems, the evidence-based management options, and how physiotherapy can help. Medial and lateral oblique meniscomeniscal ligaments have been identified with the ligament named according to its anterior attachment. Fig. These criteria are, first, contact of intrameniscal signal with the superior or the inferior surface of a meniscus (or with both surfaces) and, second, distortion of the normal appearance of a meniscus [7]. However, in my experience, 0.8- to 1.0-mm axial images have been useful primarily in confirming radial tears suspected but not definitively diagnosed on coronal and sagittal images (Fig. 1A). 18 and 19). To begin, we start with a sagittal view on the lateral side. In contrast, if there was surface contact on two or more images, there was a 90?? Routine total meniscectomy was later abandoned, on the basis of the observation that it led to accelerated osteoarthritis as a result of increased contact pressures on the tibial and femoral articular cartilage proportional to the amount of meniscus removed [4, 5]. Partial meniscectomy—After débridement, the postoperative meniscus will typically appear truncated along its free edge. ?weighted MR image shows irregularity of meniscal undersurface (arrow). In our study, 94.4% of tears located at the meniscocapsular junction of the medial meniscus were found to be healed at surgery. ?17-year-old boy with bucket-handle lateral meniscal tear. Meniscus repair—Conventional MRI is the least invasive modality for the evaluation of evaluate meniscus repair, but it has lower sensitivity, specificity, and accuracy than direct MR arthrography or indirect MR arthrography. The major landmark that can be used to identify these fascicles is the popliteal hiatus. ?weighted images show normal variant (arrows). ?weighted image. A, Coronal proton density?? The transverse meniscal ligament, also called the ?? ?weighted images show fibrous strand (arrows) arising from anterior horn (A) and extending to attach to ACL. B, Coronal (A) and sagittal (B) proton density?? Copyright © 2013-2020, American Roentgen Ray Society, ARRS, All Rights Reserved. The signal to the surface must be in the same area of the meniscus on the two images, but one image can be in the coronal plane and one, in the sagittal plane. In recent years, posterior root tears have received increasing attention in both the arthroscopic and MR literature [48]. A ring medial meniscus is even more rare and has been reported in only one patient to date [27]. As an extension of these two studies [56], investigators first noted in 1993 [1] and confirmed in 2006 [58] and 2009 [59] that if intrameniscal signal contacted the surface of the meniscus on only one MR image, there was only an 18?? Technologic innovations have improved MRI field strength, surface coils, and pulse sequences. 5 Horizontal tears, the most common meniscal tear pattern, lie parallel to the tibial plateau and separate the meniscus into upper and lower parts (4a,4b). Patients with horizontal meniscal tears often recall no specific episode of trauma but report new or increased knee pain after increased physical activity. Meniscal ossicles may be asymptomatic or may be symptomatic because of mass effect or an associated meniscal tear. The most commonly described popliteomeniscal fascicles are the anteroinferior, posterosuperior, and posteroinferior [16]. ?96% likelihood that a meniscal tear would be identified at that location on subsequent knee arthroscopy [1, 58]. Common anatomic structures that can mimic a tear include the transverse meniscal ligament, meniscofemoral ligaments (MFLs), popliteomeniscal fascicles, and meniscomeniscal ligament. ?weighted image with ill-defined free edge (arrow, B) on coronal proton density?? If you have advanced, degenerative … Such arti- 3A and 3B). Similar to the potential error when interpreting MR images of a ring lateral meniscus, a potential error in MR diagnosis is mistaking this central low-signal-intensity structure for a displaced meniscal fragment. I had an accident to my left knee and the pain was pretty unbearable for a few weeks. 6 ?? ?28-year-old woman with normal lateral meniscus. Clinical series report better outcomes and a lower risk of progressive radio-graphic osteoarthritis among patients who have undergone root repair, compared with those whose meniscus tear is managed non-surgically [33]. 6). In severe injuries, other parts of the knee may also be damaged in addition to a meniscal tear. The term ?? ?42-year-old man who injured knee 6 weeks earlier. When there is an ACL tear, particular attention should be paid on MRI to the lateral meniscus because in one study lateral meniscal root tears were found in 8% of patients with ACL tears but in only 0.8% of patients without an ACL tear [21]. These are different than the more common Bakers Cyst we tend to get in the back of our knee. B, Coronal T2-weighted fat-suppressed unenhanced knee MR image shows fluid signal intensity (arrow) at same location in medial meniscus shown in A. ?s symptoms. Some authors advise that the term should be reserved for arthroscopy reports, and not used in MRI reports as a meniscal tear pattern descriptor 1. Those who interpret knee MR examinations need to be aware of the MR appearance of each type of tear to increase their accuracy of diagnosis of meniscal tears and to precisely describe the tear for the treating orthopedic surgeon [30]. Types of Tear In addition, I discuss my experience with the causes of errors in the MR diagnosis of meniscal abnormalities and the nuances of meniscal abnormalities that can mimic a meniscal tear. The posterior root of the lateral meniscus is a particularly difficult area to assess on MRI for a tear. Conventional MRI and direct MR arthrography had equivalent accuracy (89%) when less than 25% of the meniscus has been resected. Although the normal meniscus is triangular in cross section with a C-shaped configuration, occasionally an individual may have a meniscus that extends farther onto the articular surface of the tibia. 2B —36-year-old man with injury from martial arts sparring and recurrent knee pain 5 years after medial meniscus repair. These variants include a discoid meniscus, ring lateral meniscus, meniscal ossicle, and oblique meniscomeniscal ligament. The next image is a sagittal view, which shows fluid in the back of the knee where a Baker’s cyst is developing. This attachment is visualized on MRI only occasionally; however, when it is thick, it may appear to be a displaced meniscal fragment (Figs. A, Coronal (A) and sagittal (B) proton density?? An ACL tear may cause a "popping" sound or sensation and will often cause immediate swelling. However, changes in the appearance of the meniscus caused by surgery can mimic or obscure recurrent or residual meniscus tears. This subluxation is a normal variation without proven clinical significance. B, Arthroscopic photograph shows intact inner portion of ring meniscus (arrow) within central portion of joint. Hallmarks of Cancer in the Reading Room: A Guide for Radiologists, Pictorial Essay. Fig. ?weighted image shows tear (arrow) confirmed on five other sagittal images. They found that clinical examination findings had an accuracy of 73% for recurrent tear. ?weighted images show increased signal at root (arrows). However, no tests of statistical significance were reported, and the authors acknowledged that it may be impractical to perform both examinations in most situations. ?complex tear??? The transverse meniscal (geniculate) ligament is a thin fibrous band that is present in 90% of dissection specimens and 83% of MR imaging studies. 20A, 20B, 21A, and 21B). This improved resolution also allows MR visualization of fraying of a meniscus (Figs. Finally, when normal articular cartilage or treatable chondral defects are present, meniscus allograft transplant can be performed to treat large, symptomatic, irreparable meniscus tears or painful knees after subtotal meniscectomy [15]. To locate the displaced fragment, one needs to be aware of where these fragments are most commonly found. In other patients, MRI may indicate a meniscal abnormality but the appearance of the abnormality is different from that of a definite meniscal tear. Radial tears are vertically oriented tears that arise from the free edge of a meniscus and extend into the meniscus. The tear involving posterior horn of lateral meniscus is a clearly demarcated one with no associated secondary meniscal degeneration. This line represents synovial fluid from … to the sagittal and coronal planes so that any abnormality of the root is not visualized in the optimal right-angle orientation to the image planes [20]. However, it is better to describe the pattern of tear rather than use a term ascribing a cause to the tear. Knowing the distribution of meniscal tears is helpful in assessing the menisci on MRI. Fig. Correct predictions for the specific tear pattern were 76% for vertical, 84% for horizontal, 88% for radial, 86% for … ?80% likely to be torn (Figs. A child’s meniscus has high meniscal vascularity, causing signs of intrameniscal enhancement on MRI, and can consequently present as a meniscal tear leading to false positives.43 Furthermore, according to Bouju et al, MRI overestimates medial and underestimates lateral meniscal lesions when compared with diagnostic arthroscopy .44 Discoid meniscus can be diagnosed by MRI … ?weighted image shows medial meniscus (arrow) is extruded with displacement of more than 3 mm from edge of tibia. Complex meniscus tears are those in which the tear extends in more than one plane creating separate flaps of meniscus [6]. That same study found that the fascicles are best seen on T2-weighted images but that the frequency of visualization was not changed in the presence of an effusion. 1A —24-year-old man with soccer injury and recurrent knee pain 18 months after medial meniscus repair. ?weighted image shows extensive distortion of meniscus (arrows). Starting at the … An incomplete discoid meniscus has a trapezoidal appearance and may involve only one horn of the meniscus or may extend only partly onto the articular surface of the tibia. 4A, 4B, and 4C). The final image is an axial view, which gives the best assessment of a meniscal root tear. A radial tear that passes perpendicular to the circumference will not have a flap, but an oblique radial tear results in a free-edge flap, sometimes called a parrot-beak tear because of the curved beak appearance of the flap noted at arthroscopy. Proper preoperative sizing of the allograft to match the recipient tibia is important because an undersized graft does not achieve joint congruence, whereas an oversized graft overhangs the edges of the tibia and has reduced load-bearing ability. The most common criterion for diagnosing meniscus tear on MRI is an increased signal extending in a line or band to the articular surface. I think he may have a meniscal root tear according to … This variant is called a ?? ?weighted image more medial than A shows anterior root attaches on anterior surface of tibia (arrow) as normal variation. A torn meniscus is one of the most common reasons for knee pain. We focused on 18-month change in bone marrow lesions (BMLs), cartilage thickness, cartilage surface area, osteophytes size, effusion-synovitis, and Hoffa-synovitis. ?19-year-old woman with normal medial meniscal root. terminology of the type of meniscal abnormality [60, 61]. This article is available for CME credit. Most longitudinal tears without T2 signal to the meniscal surface will be found to be stable or completely healed at subsequent arthroscopy. The key MR features that differentiate a ring lateral meniscus from a displaced meniscal fragment are the perfect isosceles triangle appearance of the meniscus within the central portion of the joint and the absence of a defect in the remainder of the meniscus (Figs. Repair techniques include side-to-side repair, stabilization with suture anchors, and the transtibial pull-out technique [13, 14]. ?ghost meniscus??? Practical points. The complexity of the insult is depicted in the posterior horn of medial meniscus in the form of vagueness in the outline of injury, the loss of volume and the diffuse intrasubstance degeneration. 1B and 1C). A, Sagittal proton density?? ?weighted (B) MR images show signal to surface (arrow, A) on sagittal proton density?? Materials and methods: We reviewed the records of 559 patients who underwent knee MR examinations and arthroscopy. 14A, 14B, and 14C). Some studies have reported the diagnostic performance of specific MRI findings for recurrent tear after repair. In some countries, synthetic meniscus implants are used in place of meniscus allograft transplant; however, these implants are considered investigational in the United States and will not be covered. The number of results achieved for each search term was as follows: for “MRI knee meniscectomy,” 360 results; “postoperative knee MRI,” 1148; “MR arthrography knee,” 167; “indirect MR arthrography knee,” 19; “CT arthrography knee,” 182; “meniscus repair MRI,” 333; “meniscus transplantation MRI,” 184; “meniscus root repair,” 136; and “postoperative meniscus,” 273 results. Because blood flow is necessary for healing, a vertical-longitudinal tear (one that parallels the circumferential collagen fibers) within or bordering the red zone, has the potential to heal after meniscus fixation and repair. Then, as the tendon passes laterally, it passes beneath the posterosuperior fascicle and above the anteroinferior fascicle. This is new since the prior MRI examination. In one study, 17% of patients with an acute ACL tear had a medial meniscal peripheral longitudinal tear and 10% had a lateral peripheral longitudinal tear with these tears often having a bucket-handle displacement [35]. These devastating injuries, which are functionally equivalent to the effects of total meniscectomy [9], detach the meniscus from its tibial anchor and impair its ability to withstand hoop stress. A meniscal ossicle is a focal area of ossification within a meniscus that is most common in the posterior horn of the medial meniscus. B, Sagittal T2 image shows tissue (arrow) and not fluid bridging tear site. It is important to recognize that the allograft may decrease in size (less so with frozen donor tissue compared with fresh donor tissue) [45–47] or may extrude (78% on the medial side and 35% laterally) after implantation, and neither shrinkage nor extrusion is associated with clinical outcomes [48, 49]. ?weighted image shows triangular appearance of inner aspect of ring meniscus (arrow) similar in configuration to body of meniscus. The sensitivity is 29%. Sagittal proton density?? MRI . https://drrobertlaprademd.com/how-to-read-a-mri-of-a-medial-meniscus-tear A tear in this location lacks blood supply and intrinsic healing ability, and it is therefore treated with PM. Fluid-sensitive, T2-weighted pulse sequences had a higher specificity (90–99%) and accuracy (85–91%), whereas PD- and T1-weighted sequences had higher sensitivity (83–91%) [29, 30]. A, Sagittal proton density?? 8 ?? In addition to the presence of a torn posterosuperior fascicle, two other MR findings have a high positive predictive value for a meniscal tear: subchondral edema beneath a meniscus and the presence of a parameniscal cyst. C, Arthroscopic photograph confirms 3-mm-deep radial tear (arrow). An additional 270 knees were prospectively evaluated by both CT and magnetic resonance imaging (MRI) to determine the ability of both techniques to characterize knee menisci in patients believed to have meniscal tears. [43] used postoperative 0.5-T MRI and arthroscopy to evaluate 19 allografts in 16 patients treated with meniscus allograft transplant. In some patients, significant fraying of the meniscus may be clinically significant and may be treated by resection as representing free-edge tearing. However, lateral meniscal tears are more varied in location: Investigators who conducted an arthroscopic series of 399 lateral meniscal tears reported that tears involved the posterior horn in 55%, the body or the body and anterior horn in 29%, and the anterior horn alone in 16% [6]. Maceration can occur if there is severe cartilage loss and an unstable knee that result in grinding away of the meniscus by the exposed subchondral bone. Recently with the higher signal-to-noise ratio available on later-generation MR magnets and with the use of eight-channel phased-array coils, I have modified my MR diagnoses of longitudinal tears on the basis of the appearance of the tear on T2-weighted images. B, Axial fat-suppressed gradient-echo image obtained using 0.8-mm slice thickness confirms radial tear (arrow) and shows adjacent parameniscal cyst (arrowhead). In this way, MRI helps to make an accurate assessment of stability and of the likelihood of tear propagation, and it enables one to determine whether the meniscal tear can be repaired. They often tend to be radial tears extending into the meniscal root . Medial meniscal cysts are most commonly located adjacent to the posterior horn and lateral meniscal cysts are most commonly located adjacent to the anterior horn or body. A meniscal root tear is a radial tear located at the meniscal root. An MRI can confirm one or both diagnoses. [22] found that indirect MR arthrography had superior accuracy of 93%, compared with conventional MRI, which had an accuracy of 63% (p < 0.05), and they also found that direct MR arthrography and indirect MR arthrography had comparable accuracies. A more recent retrospective study of 20 patients directly compared conventional 1.5-T and 3-T MRI with second-look arthroscopy [44]. Incidental meniscal findings on MRI scan of the knee are common in the general population and increase with increasing age: in one study of almost 1,000 people, 61% had meniscal tears on MRI but had no knee symptoms in the previous month .
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