Magnetic Resonance Imaging of the Meniscus

The Value of Ultrasound Diagnostic Imaging of Meniscal Knee Injuries Verified by Experimental and Arthroscopic Investigations

(1) Introduction: Meniscal knee injuries may develop as the result of trauma or overloading. Ultrasound imaging is an observer-dependent modality, meaning that the assessment of structural damage depends on the investigator's experience.. None of the published papers provides a standardized method for ultrasound examination of knee menisci. The main goal of this study is to realize and standardize ultrasound imaging diagnostics of meniscal knee injuries based on individual features of ultrasound presentation and to evaluate the applicability of this modality in clinical practice. (2) Material and methods: This study consisted of two anatomical parts, including a clinical part that started with clinical examination of 50 patients with suspected meniscal knee injuries. After this we performed ultrasound examinations in patients with positive clinical test results, using sonographic confirmation for inclusion in the next stage. Finally, knee arthroscopy by two physicians in an operating room was performed, with procedures documented through photographs and video recordings, and analytic material obtained from patients in the control group documented similarly. (3) Results: In the clinical part of the study, arthroscopic examination revealed 13 longitudinal injuries (corresponding to 36% of all injuries in the group), 14 multidirectional injuries (corresponding to 28% of all injuries), 3 radial injuries (corresponding to 6% of all injuries), and 20 oblique injuries (corresponding to 40% of all injuries). The analysis of the sensitivity and specificity of the diagnostic test in terms of recognizing actual meniscal injuries on the basis of full-thickness or partial-thickness delamination, meniscal cyst oedema, and articular space stenosis revealed that the presence of at least two of these three characteristics was associated with the sensitivity of 88% and the specificity of 86% relative to the number of actual meniscal injuries as seen in arthroscopic examination. (4) Conclusions: Research results confirm that clinical examination combined with ultrasound imaging is a very efficient tool for evaluation of meniscal injuries.

Lateral meniscal body extrusion is associated with MRI-defined knee structural damage progression over 4 years: Data from the osteoarthritis initiative

PURPOSE

To investigate the association of lateral meniscal body extrusion (LMBE) with OA-related knee structural damage progression over 4 years and to obtain thresholds of LMBE in predicting knee structural damage progression.

METHOD

We studied 196 subjects (67 male) with a mean age of 59.5 ± 7.9 (SD) years (range45-78 years) that were randomly selected from the Osteoarthritis Initiative. Radiological assessment was performed using the Osteoarthritis Research Society International grading system. Baseline LMBE was quantified on coronal sections of intermediate-weighted MRI sequences obtained at 3.0 T scanner. Knee structural damages were measured using the whole-organ MRI score. Linear regression analysis and binary logistic regression analysis was used to assess the correlation between LMBE and knee structural damage. ROC analysis and Youden index were used for calculating thresholds.

RESULTS

Cross-sectionally, increased LMBE was significantly associated with more severe lateral meniscal damage, patellofemoral and lateral compartment cartilage damage, and posterior cruciate ligament damage. Longitudinally, LMBE was statistically associated with progression of lateral meniscal damage, lateral compartment cartilage damage and bone marrow edema patterns, posterior cruciate ligament lesions and popliteal cysts. The thresholds of LMBE in suggesting progression of lateral meniscal lesions and lateral compartment cartilage lesions were 1.4 mm and 1.3 mm, respectively.

CONCLUSION

Baseline LMBE was associated with structural damage progression over 4 years in knees with or at risks for OA. Thresholds of 1.4 mm and 1.3 mm could be used in predicting progression over 4 years of lateral meniscal damage and lateral compartment cartilage damage, respectively.

Automatic Detection of Meniscus Tears Using Backbone Convolutional Neural Networks on Knee MRI

BACKGROUND

Timely diagnosis of meniscus injuries is key for preventing knee joint dysfunction and improving patient outcomes because it decreases morbidity and facilitates treatment planning.

PURPOSE

To train and evaluate a deep learning model for automated detection of meniscus tears on knee magnetic resonance imaging (MRI).

STUDY TYPE

Bicentric retrospective study.

SUBJECTS

In total, 584 knee MRI studies, divided among training (n = 234), testing (n = 200), and external validation (n = 150) data sets, were used in this study. The public data set MRNet was used as a second external validation data set to evaluate the performance of the model.

SEQUENCE

A 3 T, coronal, and sagittal images from T1-weighted proton density (PD) fast spin-echo (FSE) with fat saturation and T2-weighted FSE with fat saturation sequences.

ASSESSMENT

The detection system for meniscus tear was based on the improved YOLOv4 model with Darknet-53 as the backbone. The performance of the model was also compared with that of three radiologists of varying levels of experience. The determination of the presence of a meniscus tear from surgery reports was used as the ground truth for the images.

STATISTICAL TESTS

Sensitivity, specificity, prevalence, positive predictive value, negative predictive value, accuracy, and receiver operating characteristic curve were used to evaluate the performance of the detection model. Two-way analysis of variance, Wilcoxon signed-rank test, and Tukey's multiple tests were used to evaluate differences in performance between the model and radiologists.

RESULTS

The overall accuracies for detecting meniscus tears using our model on the internal testing, internal validation, and external validation data sets were 95.4%, 95.8%, and 78.8%, respectively. One radiologist had significantly lower performance than our model in detecting meniscal tears (accuracy: 0.9025 ± 0.093 vs. 0.9580 ± 0.025).

DATA CONCLUSION

The proposed model had high sensitivity, specificity, and accuracy for detecting meniscus tears on knee MRIs.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 2.

Predictive signs of peripheral rim instability with magnetic resonance imaging in no-shift-type complete discoid lateral meniscus

PURPOSE

To investigate the associations between the preoperative MRI findings suggestive of meniscal instability and the intraoperative finding of peripheral rim instability (PRI) in patients with complete discoid lateral meniscus (CDLM) of no-shift-type, which was identified as the peripheral portion was not separated from the capsule.

METHODS

The records of 56 patients diagnosed with no-shift-type CDLM who underwent arthroscopic surgery were reviewed. We evaluated MRI findings of anterior parameniscal soft-tissue edema, linear fluid signal at the anterior meniscal margin, bulging of the meniscal margin, absence of popliteomeniscal fascicles, and hiatus widening on routine MRI. The positive predictive value (PPV), sensitivity, and specificity of these findings in predicting PRI were calculated; PRI was further investigated according to anterior and posterior location.

RESULTS

Linear fluid signal at the anterior meniscal margin and bulging had high PPV and specificity (P = .004 and = .029, respectively) for overall of PRI. The presence of either anterior parameniscal soft-tissue edema or linear fluid signal at the anterior meniscal margin predicted anterior PRI with high PPV, sensitivity, and specificity. Bulging of the meniscal margin had high specificity, and either bulging of the meniscal margin or absence of popliteomeniscal fascicle had high sensitivity in predicting posterior PRI.

CONCLUSIONS

A linear fluid signal at the anterior meniscus and anterior parameniscal soft-tissue edema were important signs of anterior PRI, whereas bulging of the margin had high specificity and either bulging of the meniscal margin or absence of popliteomeniscal fascicle had high sensitivity in detecting posterior PRI on routine MRI of no-shift-type CDLM.

LEVEL OF EVIDENCE

Level IV therapeutic case series.

Magnetic resonance imaging of the knee: An overview and update of conventional and state of the art imaging

Magnetic resonance imaging (MRI) has become the preferred modality for imaging the knee to show pathology and guide patient management and treatment. The knee is one of the most frequently injured joints, and knee pain is a pervasive difficulty that can affect all age groups. Due to the diverse pathology, complex anatomy, and a myriad of injury mechanisms of the knee, the MRI knee protocol and sequences should ensure detection of both soft tissue and osseous structures in detail and with accuracy. The knowledge of knee anatomy and the normal or injured MRI appearance of these key structures are critical for precise diagnosis. Advances in MRI technology provide the imaging necessary to obtain high-resolution images to evaluate menisci, ligaments, and tendons. Furthermore, recent advances in MRI techniques allow for improved imaging in the postoperative knee and metal artifact reduction, tumor imaging, cartilage evaluation, and visualization of nerves. As treatment and operative management techniques evolve, understanding the correct application of these advancements in MRI of the knee will prove to be valuable to clinical practice.

LEVEL OF EVIDENCE

5 J. MAGN. RESON. IMAGING 2017;45:1257-1275.

Reporting knee meniscal tears: technical aspects, typical pitfalls and how to avoid them

Magnetic resonance imaging (MRI) is the most accurate imaging technique in the diagnosis of meniscal lesions and represents a standard tool in knee evaluation. MRI plays a critical role in influencing the treatment decision and enables information that would obviate unnecessary surgery including diagnostic arthroscopy. An accurate interpretation of the knee depends on several factors, starting with technical aspects including radiofrequency coils, imaging protocol and magnetic field strength. The use of dedicated high-resolution orthopaedic coils with a different number of integrated elements is mandatory in order to ensure high homogeneity of the signal and high-resolution images. The clinical imaging protocol of the knee includes different MRI sequences with high-spatial resolution in all orientations: sagittal, coronal, and axial. Usually, the slice thickness is 3 mm or less, even with standard two-dimensional fast spin echo sequences. A common potential reason for pitfalls and errors of interpretation is the unawareness of the normal tibial attachments and capsular attachment of the menisci. Complete description of meniscal tears implies that the radiologist should be aware of the patterns and the complex classification of the lesions.

TEACHING POINTS

• Technical factors may influence MRI interpretation. • Unawareness of the normal meniscal anatomy may lead to errors of interpretation. • Description of meniscal tears implies the knowledge of meniscal tear classification.

ISAKOS classification of meniscal tears-illustration on 2D and 3D isotropic spin echo MR imaging

Magnetic Resonance Imaging is modality of choice for the non-invasive evaluation of meniscal tears. Accurate and uniform documentation of meniscal pathology is necessary for optimal multi-disciplinary communication, to guide treatment options and for validation of patient outcomes studies. The increasingly used ISAKOS arthroscopic meniscus tear classification system has been shown to provide sufficient interobserver reliability among the surgeons. However, the terminology is not in common use in the radiology world. In this article, the authors discuss the MR imaging appearances of meniscal tears based on ISAKOS classification on 2D and multiplanar 3D isotropic spin echo imaging techniques and illustrate the correlations of various meniscal pathologies with relevant arthroscopic images.