Meniscal Tears with Fragments Displaced: What you need to know.

Transcription

1 Meniscal Tears with Fragments Displaced: What you need to know. Poster No.: C-1339 Congress: ECR 2015 Type: Authors: Keywords: DOI: Educational Exhibit M. V. Ferrufino, A. Stroe, E. Cordoba, A. Dehesa, O. D. Laffite Licona; Burgos/ES Image verification, Diagnostic procedure, MR, Musculoskeletal joint, Extremities /ecr2015/C-1339 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 14

2 Learning objectives The purpose of our educational exhibit is to: Evaluate magnetic resonance (MR) imaging findings of meniscal tears with meniscal fragments displaced. Show illustrative examples and schemes with a didactic approach. Page 2 of 14

3 Background MR Imaging-based diagnosis of Meniscal Tears The prevalence of meniscal tears increases with age, and meniscal tears are often associated with and contribute to degenerative joint disease. Tears are more common in the posterior horn of the menisci, particularly favoring the more constrained medial meniscus (MM). However, in younger patients with an acute injury, lateral meniscus (LM) tears are more common. MR imaging is a proved, highly accurate modality for detection of meniscal injuries, with excellent arthroscopic correlation. The most commonly used sequences include spinecho or fast spin-echo (FSE) proton density (PD) with or without fat saturation (FS), T1, and gradient echo (GRE). The sagittal plane is the most frequently used; however, studies have reported that the coronal imaging plane improves the detection and characterization of radial, bucket-handle, horizontal, and displaced tears of the meniscal body, and that the axial plane assists in diagnosing radial, vertical, complex, displaced, and lateral meniscal tears. Normal menisci should have low signal intensity at MR imaging; however, globular or linear increased intrameniscal signal intensity can be seen in children (due to normal vascularity), in adults with internal mucinous degeneration, and after trauma due to acute contusion. MR imaging criteria for diagnosing a tear include meniscal distortion in the absence of prior surgery or increased intrasubstance signal intensity unequivocally contacting the articular surface. The findings must be identified in the same area on any two consecutive MR images. In contrast, increased intrasubstance signal intensity without extension to the articular surface is often not associated with a tear at surgery, nor has this finding been shown to progress to a tear. Meniscal Tear Classification An accurate description of a meniscal tear has become increasingly important, with the emphasis on meniscal preservation and repair, because of the known, longterm complications of complete meniscectomy. Currently, there is no standard tear classification system. The most common tear patterns described are horizontal, longitudinal, radial, root, complex, displaced, and bucket-handle tears. Page 3 of 14

4 Meniscal tears with partially detached, displaced fragments are defined as unstable meniscal tears that cause a fragment that is still attached to the torn meniscus to be subluxated at a distance from the parent meniscus. These tears represent a subset of meniscal lesions that are clinically important and can be treated successfully with reattachment or resection. Displaced tears include free fragments, displaced flap tears, and bucket-handle tears. Page 4 of 14

5 Findings and procedure details We reviewed 30 cases of displaced meniscal tears and found several types: Bucket-handle tears: 10 cases. Anteriorly flipped meniscus: 5 cases Parrot-beak tears: 3 cases. Flap tears with displacement: 7 cases Root tears and full-thickness radial tears with displacement: 5 cases Bucket- handle tears: The central fragment of a meniscus with a peripheral longitudinal tear may displace centrally into the intercondylar notch creating a bucket-handle tear. The displaced fragment maintains anterior and posterior attachments to meniscal horns and is considered to resemble the lifted up handle of a bucket. If the anterior or the posterior attachment is disrupted it s a broken bucket-handle tear. This tear pattern occurs seven times more frequently in the MM and has at least five different MR imaging signs: an absent bow tie (when the meniscus body is not identified), a fragment within the intercondylar notch, a double posterior cruciate ligament (PCL) sign (displaced meniscal fragment in intercondylar notch roughly parallel to the PCL) and a double delta sign (visualization of flipped meniscal fragments posterior to the anterior horn) (Fig. 1). Flipped meniscus: A flipped meniscus is a special form of bucket-handle tear. It occurs when the ruptured fragment of the posterior horn is flipped anteriorly so the anterior horn of the meniscus appears to be enlarged. Most commonly involves displacement of posterior horn of lateral meniscus anteriorly. MR findings: Page 5 of 14

6 The double anterior horn sign (best seen on sagittal images): 2 triangular meniscal fragments adjacent to one another, where the anterior fragment is normal anterior horn and posterior fragment is displaced posterior horn (Fig. 2). The anterior horn should not measure greater than 6 mm in height; if it does, this should be considered. Severely truncated or absent posterior horn-absent meniscus sign (Fig. 2). Flap Tears: Tear of meniscus in which 1 or more meniscal fragments are displaced from their normal location. Displaced fragments may be difficult to visualize arthroscopically, so preoperative identification is absolutely necessary. Most common in medial meniscus. -Vertical flap tars (Parrot-beak tears): Oblique short-axis tear with displacement, resulting in V-shaped defect of free edge MR findings: Oblique radial tear (centrally) with longitudinal component (peripherally). The torn portion of the meniscus displaces centrally and looks like a parrot's beak (Fig. 3). Signal extends to free edge of meniscus with separation of borders of tear. V-shaped defect best seen on axial images. -Horizontal flap tears (Displaced horizontal tears): Approximately two thirds of medial meniscus displaced fragments are found in the posterior aspect of the joint near or behind the PCL (Fig. 4), whereas the remaining cases are usually in the superior or inferior recesses above and below the body of the medial meniscus (Fig. 5). In contrast to displaced fragments of the medial meniscus, displaced lateral meniscal fragments are seen equally frequently in the recesses of the body of the meniscus and in the posterior aspect of the joint. The posteriorly displaced fragments often extend into the popliteal hiatus. The most common cause for a shortened meniscus on MRI is a meniscal tear with a displaced fragment. Page 6 of 14

7 Root Tears and full-thickness radial tears with displacement: Root tears are usually radial in type and are often associated with meniscal extrusion (76%) (Fig. 6). It has been described only posterior root tears. They are best seen on coronal images as vertical defect through most posterior aspect of meniscus. When a radial tear is present in the posterior root of the lateral meniscus, the appearance may be the same as a radial tear in other locations. However, posterior root tears of the lateral meniscus can be difficult to diagnose because of the oblique orientation of the root to coronal and sagittal images, prominent signal due to the magic angle effect, and arterial pulsation from the popliteal artery partially obscuring the root. These tears are commonly seen in the setting of osteoarthritis and probably occur due to increased axial loading of the meniscus. The MR findings are shortening or absence of the root on sagittal images ("Ghost meniscus" sign) (Fig. 6) and a vertical fluid cleft on coronal fluid-sensitive images. Page 7 of 14

8 Images for this section: Fig. 1: Bucket-handle tear (BHT): Graphic, axial, coronal and sagittal PD FS MR show large intercondylar notch fragments (A-E), creating a "double PCL" sign anterior to the posterior cruciate ligament (D) and a "double delta" sign (D).Broken bucket-handle tear (E). Radiologia, hospital universitario de burgos - Burgos/ES Page 8 of 14

9 Fig. 2: Flipped meniscus: Graphic, axial, coronal and sagittal PD FS MR show a lateral flipped meniscus. In this tear, a large portion of the posterior horn is displaced anteriorly and lies adjacent to the anterior horn. Notice the "double meniscus" sign (D,E). Severely truncated posterior horn (C, D, E). Radiologia, hospital universitario de burgos - Burgos/ES Page 9 of 14

10 Fig. 3: Vertical flap tars (Parrot-beak tears): Graphic and axial PD FS MR show an oblique radial (D) or longitudinal tear entering the free edge of the meniscus with displacement of the edge (A), resulting in a defect shaped like a parrot's beak or the letter "V" (B,C). Radiologia, hospital universitario de burgos - Burgos/ES Page 10 of 14

11 Fig. 4: Horizontal flap tear: Graphic demonstrating displaced horizontal tear. Coronal and sagittal PD FS MR show displaced fragments in the posterior aspect of the joint near the PCL. Radiologia, hospital universitario de burgos - Burgos/ES Page 11 of 14

12 Fig. 5: Horizontal flap tear: Axial and sagittal PD FS MR show displaced fragments in the recesses of the body of the meniscus. Flap of meniscal tissue extending into the inferior recess medially (E,F) and in the superior aspect of the medial recess (G). Radiologia, hospital universitario de burgos - Burgos/ES Fig. 6: Radial tear with truncation of the posterior root of the medial meniscus. Axial, coronal and sagittal PD FS MR show meniscal extrusion (B) and the "ghost meniscus" sign of absent meniscal tissue (C). Radiologia, hospital universitario de burgos - Burgos/ES Page 12 of 14

13 Conclusion MR imaging is the preferred imaging modality for evaluating meniscal pathology, with high accuracy reported in most studies. It allows accurate characterization of various tear patterns, such as the previously discussed, which can be instrumental for patient counseling and surgical planning. Page 13 of 14

14 References Nguyen JC, De Smet AA, Graf BK, Rosas HG. MR Imaging-based Diagnosis and Classification of Meniscal Tears. RadioGraphics 2014; 34: Rosas, HG. Magnetic Resonance Imaging of the Meniscus.Magn Reson Imaging Clin N Am 22 (2014) De Smet AA. How I Diagnose Meniscal Tears on Knee MRI. AJR 2012; 199: Fox MG. MR Imaging of the Meniscus: Review, Current Trends, and Clinical Implications. Magn Reson Imaging Clin N Am 2007 Feb;1(1): Page 14 of 14