Magnetic Resonance Imaging Appearance of a Double Anterior Cruciate Ligament Associated With a Displaced Tear of the Lateral Meniscus

MRI in the Diagnosis of Bucket Handle Tears: What Is the Current Situation?

Introduction The purpose of this study was to determine the utility of current magnetic resonance imaging (MRI) in the diagnosis of bucket-handle meniscal tears. Materials and methods Patients treated for arthroscopic meniscal tears between March 2019 and March 2022 were reviewed. The current study included all patients with bucket handle tears diagnosed arthroscopically and having MRI scans (n=51). A control group of 58 individuals with similar demographic characteristics and meniscal tears apart from bucket handle tears was also formed. The assessment of bucket handle and non-bucket handle tears was performed blindly by a musculoskeletal (MSK) radiologist with 20 years of experience and a trainee radiologist, achieving consensus on group allocation. The MRIs were examined for various findings, including the presence of a bucket handle tear, tear location, presence of anterior cruciate ligament (ACL) rupture, intercondyler notch sign, double anterior horn sign, flipped meniscus sign, double posterior cruciate ligament (PCL) sign, absent bow sign, and the disproportionate posterior horn sign. These well-known signs, detailed in the literature, were evaluated. Additionally, less studied and less commonly known signs such as the V sign and double anterior cruciate ligament sign were assessed. The V sign appears similarly to the letter V, resulting from the displacement of the bucket handle tear and the angle of the intact meniscus on axial images. The double anterior cruciate ligament sign is the appearance formed by the compression of the displaced meniscal part behind the anterior cruciate ligament in bucket handle tears. Results Following the retrospective evaluation of MRI scans, 44 out of 51 tears diagnosed as bucket handle tears by arthroscopy were accurately identified (sensitivity: 86.27%). The same conclusion was reached for MRI scans in 52 out of 58 tears where arthroscopy did not detect a bucket handle tear (specificity: 89.66%). The most prevalent MRI signs in patients with bucket handle tears identified by arthroscopy in the study were the intercondylar notch sign (84.31%), V sign (72.55%), double PCL sign (56.86%), double anterior horn sign (49.02%), absent bow sign (43.14%), flipped meniscus sign (19.61%), disproportionate posterior horn sign (9.80%), and double ACL sign (5.88%). The intercondylar notch sign, V sign, and double PCL sign exhibited the highest sensitivity, while flipped meniscus, disproportionate posterior horn, and double ACL sign demonstrated the highest specificity. Conclusion MRI demonstrates a high level of sensitivity and specificity in identifying meniscal bucket handle tears, particularly when considering the eight MRI signs investigated in this study.

The double ACL sign: An aberrant bucket-handle tear of lateral meniscus

Introduction

Meniscal injuries are one of the most common musculoskeletal injuries around the knee affecting patients of different genders, ages and activity levels. These injuries could be acute or chronic tears that cause pain and mechanical symptoms based on the injury severity and whether it is displaced and entrapped in an abnormal location within the knee or not. Advances in magnetic resonance imaging (MRI) allowed us to have a better understanding of multiple bucket handle meniscal tear patterns with its specific MRI signs which have been reported in the literature.

Case presentation

This report presents a rare case of a 16-year-old boy with atypical bucket-handle tear of lateral meniscus and MRI showed a bucket-handle tear of lateral meniscus with a fragment entrapped behind and parallel to the anterior cruciate ligament (ACL) appearing as another ACL in sagittal views. Meniscus was repaired arthroscopically.

Conclusion

In our case, the unique and infrequent mechanism led to a bucket-handle tear involving lateral meniscus with a meniscal fragment entrapped in an unusual place intra-articularly behind ACL giving the appearance of a rare MRI sign “double ACL sign”. However, double ACL sign secondary to lateral meniscal tear has been reported only once previously up to the authors’ knowledge.

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Radiologically, meniscal tears have multiple pathognomatic signs.

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Double acl sign was reported twice only, one from medial meniscus and the other from lateral meniscus.

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Double acl sign indicates huge bucket handle tear which displaced into the intercondylar notch.

MR imaging-based diagnosis and classification of meniscal tears

Magnetic resonance (MR) imaging is currently the modality of choice for detecting meniscal injuries and planning subsequent treatment. A thorough understanding of the imaging protocols, normal meniscal anatomy, surrounding anatomic structures, and anatomic variants and pitfalls is critical to ensure diagnostic accuracy and prevent unnecessary surgery. High-spatial-resolution imaging of the meniscus can be performed using fast spin-echo and three-dimensional MR imaging sequences. Normal anatomic structures that can mimic a tear include the meniscal ligament, meniscofemoral ligaments, popliteomeniscal fascicles, and meniscomeniscal ligament. Anatomic variants and pitfalls that can mimic a tear include discoid meniscus, meniscal flounce, a meniscal ossicle, and chondrocalcinosis. When a meniscal tear is identified, accurate description and classification of the tear pattern can guide the referring clinician in patient education and surgical planning. For example, longitudinal tears are often amenable to repair, whereas horizontal and radial tears may require partial meniscectomy. Tear patterns include horizontal, longitudinal, radial, root, complex, displaced, and bucket-handle tears. Occasionally, meniscal tears can be difficult to detect at imaging; however, secondary indirect signs, such as a parameniscal cyst, meniscal extrusion, or linear subchondral bone marrow edema, should increase the radiologist's suspicion for an underlying tear. Awareness of common diagnostic errors can ensure accurate diagnosis of meniscal tears. Online supplemental material is available for this article.