Anterior cruciate ligament tears: evaluation of multiple signs with MR imaging

Valid and reliable diagnostic performance of dual-energy CT in anterior cruciate ligament rupture

OBJECTIVES

To determine whether dual-energy CT (DECT) can be used to accurately and reliably detect anterior cruciate ligament (ACL) rupture.

MATERIALS AND METHODS

Participants with unilateral ACL rupture were prospectively enrolled, and the bilateral knees were scanned by DECT. A tissue-specific mapping algorithm was applied to improve the visualization of the ACLs. The 80-keV CT value, mixed-keV CT value, electron density (Rho), and effective atomic number (Zeff) were measured to quantitatively differentiate torn ACLs from normal ACLs. MRI and arthroscopy served as the reference standards.

RESULTS

Fifty-one participants (mean age, 27.0 ± 8.7 years; 31 men) were enrolled. Intact and torn ACLs were explicitly differentiated on color-coded DECT images. The 80-keV CT value, mixed-keV CT value, and Rho were significantly lower for the torn ACLs than for the intact ACLs (p < 0.001). The optimal cutoff values were an 80-keV CT value of 61.8 HU, a mixed-keV CT value of 60.9 HU, and a Rho of 51.8 HU, with AUCs of 98.0% (95% CI: 97.0-98.9%), 99.2% (95% CI: 98.6-99.7%), and 99.8% (95% CI: 99.6-100.0%), respectively. Overall, DECT had almost perfect reliability and validity in detecting ACL integrity (sensitivity = 97.1% [95% CI: 88.1-99.8%]; specificity = 98.0% [95% CI: 89.5-99.9%]; PPV = 98.0% [95% CI: 93.0-99.8%]; NPV = 97.1% [95% CI: 91.7-99.4%]; accuracy = 97.5% [95% CI: 94.3-99.2%]). There was no evidence of a difference between MRI and DECT in the diagnostic performance (p > 0.99).

CONCLUSION

DECT has excellent diagnostic accuracy and reliability in qualitatively and quantitatively diagnosing ACL rupture.

CLINICAL RELEVANCE STATEMENT

DECT could validly and reliably diagnose ACL rupture using both qualitative and quantitative methods, which may become a promising substitute for MRI to evaluate the integrity of injured ACLs and the maturity of postoperative ACL autografts.

KEY POINTS

• On color-coded DECT images, an uncolored ACL was a reliable sign for qualitatively diagnosing ACL rupture. • The 80-keV CT value, mixed-keV CT value, and Rho were significantly lower for the torn ACLs than for the intact ACLs, which contributed to the quantitative diagnosis of ACL rupture. • DECT had an almost perfect diagnostic performance for ACL rupture, and diagnostic capability was comparable between MRI and DECT.

Imaging-detected sports injuries and imaging-guided interventions in athletes during the 2022 FIFA football (soccer) World Cup

OBJECTIVE

To describe imaging-detected musculoskeletal injuries and image-guided interventional procedures during the 2022 FIFA football (soccer) World Cup.

MATERIALS AND METHODS

Retrospective analysis of all radiologic examinations performed in a central medical facility for athletes was performed by two board certified musculoskeletal radiologists. Data on muscle, tendon, ligament, cartilage, and bone injuries were collected according to imaging modality and body part.

RESULTS

A total of 143 radiology examinations in 94 athletes were evaluated at the central medical facility. Magnetic resonance imaging (MRI) was the most utilized modality (67%), followed by radiography (12%), ultrasonography (9%), and computed tomography (4%). Image-guided interventions corresponded to 8% of all radiological examinations. There were 112 injuries described, affecting muscles and tendons (42%), ligaments (25%), cartilage (21%), and bone (12%). Most injured body parts were thigh (27%), foot and ankle (23%), knee (23%), and hip/groin (8%). Most injured players were within the age range of 24-35 years old (71%).

CONCLUSION

Imaging was utilized in 11% of players who participated in the 2022 FIFA World Cup in Qatar. MRI was the most utilized modality, and acute muscle tears were the most diagnosed type of injury. Diagnostic imaging played an important role in diagnosing sports-related injuries during the 2022 FIFA World Cup.

Outpatient-based diagnostic criteria for partial ACL injury: clinical outcomes of non-operative treatment and radiographic predictor

INTRODUCTION

This study aimed to (1) evaluate the short-term clinical outcomes of patients who underwent non-operative treatment for partial anterior cruciate ligament (ACL) tears diagnosed using the outpatient-based diagnostic criteria and (2) investigate the radiographic predictors distinguishing patients at risk of non-operative treatment failure.

METHODS

From 2010 to 2019, patients diagnosed with partial ACL tears and treated with non-operative treatment were reviewed retrospectively. Patients were then classified into two groups: those who successfully responded to non-operative treatment (group S) and those who failed to respond to non-operative treatment and required surgical reconstruction within 6 months after injury (group F). ACL laxity, patient-reported outcomes (PROs), and several radiographic parameters were analyzed. To identify radiographic predictors related to clinical outcomes, radiographic parameters were compared between the groups, which were statistically matched for potential confounders (age and activity level) using inverse probability of treatment weighting.

RESULTS

A total of 44 patients were analyzed (mean age, 28.7 ± 8.7 years; 31 men), and classified into two groups (group S, 23 patients; group F, 21 patients). There were no significant differences in ACL laxity and PROs between the groups at 1 year after either non-operative treatment or surgical reconstruction. A comparison of radiographic parameters between the groups revealed significant differences in several parameters related to secondary signs of ACL injury. Subsequent regression analyses revealed that anterior tibial translation and extent of bone bruises were radiographic predictors related to clinical outcomes.

CONCLUSION

Non-operative treatment for partial ACL tears diagnosed using the outpatient-based diagnostic criteria can provide successful short-term clinical outcomes in selective patients. Secondary signs of ACL injuries, particularly the amount of anterior tibial translation and the extent of bone bruises, are radiographic predictors that could differentiate patients at risk of non-operative treatment failure.

LEVEL OF EVIDENCE

Retrospective cohort study, III.

The posterior cruciate ligament-posterior femoral cortex angle: a reliable and accurate MRI method to quantify the buckling phenomenon of the PCL in ACL-deficient knees

PURPOSE

The aim was to validate a new MRI method to measure the buckling phenomenon of the PCL, representative of anterior tibial translation, by comparing its reliability and accuracy to identify anterior cruciate ligament (ACL)-deficient knees with existing methods.

METHODS

Patients were selected retrospectively and separated into a group of primary ACL injuries and ACL-intact knees. Exclusion criteria were: skeletal immaturity, PCL or a concomitant collateral ligament injury, signs of osteoarthritis (> 1 Kellgren and Lawrence score), tibial plateau fracture, previous ACL reconstruction or displaced meniscal bucket handle tear. The assessment of the curvature of the anterolateral bundle of the PCL was performed on T2 sagittal MRI slices according to 3 methods: (1) the PCL angle (PCLA), (2) the PCL inclination angle (PCLIA) and (3) a new method: the PCL-posterior cortex angle (PCL-PCA), representing the angle between the vertical part of the PCL-ALB and the posterior diaphyseal cortex of the femur. For each method, the inter- and intra-observer reliability was measured. The ability to discriminate both ACL-deficient and ACL-intact knees was evaluated using ROC curves.

RESULTS

Twenty-four patients were included in each group. Intra-observer reliability was excellent for all 3 methods (ICCs > 0.90). Inter-observer reliability was excellent for the PCL-PCA (ICC > 0.90) and good for the PCLA and the PCLIA (ICCs between 0.75 and 0.90). The PCL-PCA had the highest precision (lowest standard error of measurement: 2.7°). It yielded an excellent discrimination between the ACL and CTL groups (AUC 0.80 [0.67-0.93]) with the highest sensitivity (71% [52.8-89.2]) and specificity (88% [75-100]) for a positive threshold when the angle was ≤ 22.7°. The PCLA and PCLIA methods led to acceptable discrimination and lower sensitivities and specificities (PCLA: AUC 0.71, sensitivity 63%, specificity 79%, threshold ≤ 117.9°; PCLIA: AUC 0.62, sensitivity 50%, specificity 83%, threshold ≤ 21.4°).

CONCLUSION

In comparison with previously described methods, the PCL-PCA was the most reliable and accurate method to measure the PCL buckling phenomenon on MRI in anterior cruciate ligament (ACL)-deficient knees. It offers an easy and objective method for the follow-up of ACL-injured patients and can therefore be recommended for routine use.

LEVEL OF EVIDENCE

IV.

How to Report: Knee MRI

The knee is the most commonly examined joint with magnetic resonance imaging (MRI) and, as such, it is the joint that most trainee radiologists start reporting. This article addresses the main pathologies encountered on MRI examination of the knee, outlining the key features to note and report, as well as providing examples of terminology used to describe these findings.

A Deep Learning System for Synthetic Knee Magnetic Resonance Imaging: Is Artificial Intelligence-Based Fat-Suppressed Imaging Feasible?

MATERIALS AND METHODS

This single-center study was approved by the institutional review board. Artificial intelligence-based FS MRI scans were created from non-FS images using a deep learning system with a modified convolutional neural network-based U-Net that used a training set of 25,920 images and validation set of 16,416 images. Three musculoskeletal radiologists reviewed 88 knee MR studies in 2 sessions, the original (proton density [PD] + FSPD) and the synthetic (PD + AFSMRI). Readers recorded AFSMRI quality (diagnostic/nondiagnostic) and the presence or absence of meniscal, ligament, and tendon tears; cartilage defects; and bone marrow abnormalities. Contrast-to-noise rate measurements were made among subcutaneous fat, fluid, bone marrow, cartilage, and muscle. The original MRI sequences were used as the reference standard to determine the diagnostic performance of AFSMRI (combined with the original PD sequence). This is a fully balanced study design, where all readers read all images the same number of times, which allowed the determination of the interchangeability of the original and synthetic protocols. Descriptive statistics, intermethod agreement, interobserver concordance, and interchangeability tests were applied. A P value less than 0.01 was considered statistically significant for the likelihood ratio testing, and P value less than 0.05 for all other statistical analyses.

RESULTS

Artificial intelligence-based FS MRI quality was rated as diagnostic (98.9% [87/88] to 100% [88/88], all readers). Diagnostic performance (sensitivity/specificity) of the synthetic protocol was high, for tears of the menisci (91% [71/78], 86% [84/98]), cruciate ligaments (92% [12/13], 98% [160/163]), collateral ligaments (80% [16/20], 100% [156/156]), and tendons (90% [9/10], 100% [166/166]). For cartilage defects and bone marrow abnormalities, the synthetic protocol offered an overall sensitivity/specificity of 77% (170/221)/93% (287/307) and 76% (95/125)/90% (443/491), respectively. Intermethod agreement ranged from moderate to substantial for almost all evaluated structures (menisci, cruciate ligaments, collateral ligaments, and bone marrow abnormalities). No significant difference was observed between methods for all structural abnormalities by all readers (P > 0.05), except for cartilage assessment. Interobserver agreement ranged from moderate to substantial for almost all evaluated structures. Original and synthetic protocols were interchangeable for the diagnosis of all evaluated structures. There was no significant difference for the common exact match proportions for all combinations (P > 0.01). The conspicuity of all tissues assessed through contrast-to-noise rate was higher on AFSMRI than on original FSPD images (P < 0.05).

CONCLUSIONS

Artificial intelligence-based FS MRI (3D AFSMRI) is feasible and offers a method for fast imaging, with similar detection rates for structural abnormalities of the knee, compared with original 3D MR sequences.

Evolving evidence in the treatment of primary and recurrent posterior cruciate ligament injuries, part 1: anatomy, biomechanics and diagnostics

The posterior cruciate ligament (PCL) represents an intra-articular structure composed of two distinct bundles. Considering the anterior and posterior meniscofemoral ligaments, a total of four ligamentous fibre bundles of the posterior knee complex act synergistically to restrain posterior and rotatory tibial loads. Injury mechanisms associated with high-energy trauma and accompanying injury patterns may complicate the diagnostic evaluation and accuracy. Therefore, a thorough and systematic diagnostic workup is necessary to assess the severity of the PCL injury and to initiate an appropriate treatment approach. Since structural damage to the PCL occurs in more than one third of trauma patients experiencing acute knee injury with hemarthrosis, background knowledge for management of PCL injuries is important. In Part 1 of the evidence-based update on management of primary and recurrent PCL injuries, the anatomical, biomechanical, and diagnostic principles are presented. This paper aims to convey the anatomical and biomechanical knowledge needed for accurate diagnosis to facilitate subsequent decision-making in the treatment of PCL injuries.Level of evidence V.

The influence of a meniscal bucket handle tear on the Posterior Cruciate Ligament Angle in Anterior Cruciate Ligament Rupture - A case report

•

The PCL angle in ACL-deficient knee might be false-negative in the presence of bucket handle tear.

•

There must be always high suspicious of ACL insufficiency in case of medial bucket handle tear.

•

Profound knowledge of clinical examination patient’s history is absolutely mandatory to examine ACL insufficiency.

Introduction

Chronic anterior cruciate ligament (ACL) tear might be difficult to diagnose on MRI. Indirect signs might be a typical meniscal or cartilage lesion, or a spontaneous anterior drawer visualized by a decreased angle of the posterior cruciate ligament (PCL).

Presentation of case

A 27-year-old former ballet dancer was admitted to the emergency department for a locked left knee, without never having experienced previous symptoms of giving way or locking. The MRI performed revealed a medial meniscus bucket handle tear, without traumatic bone marrow oedema or ligament injury. The PCL angle was 130°. A former MRI of her left knee performed 1 year previously to investigate on the recurrent catching of her left knee showed a grade III medial meniscal tear of the posterior horn, and buckling of the PCL angle of 100°, as a sign of chronic ACL rupture. During arthroscopy and medial meniscal repair, the ACL showed complete loss of tension, and was therefore reconstructed simultaneously to enable proper meniscal healing.

Discussion and conclusion

Chronic ACL insuffiency is a major risk factor for subsequent medial meniscus tear, especially bucket handle tear. The locked knee might unable proper pre-operative clinical examination. The preoperative MRI therefore being the only possibility to diagnose concomitant ligamentous injury. This is the first case reported in literature showing, that a positive PCL angle sign might be falsely negative due to a locked medial meniscus bucket handle tear.

A Retrospective Comparison of ACL Tear and Mucoid Degeneration MRI Findings and an Emphasis on Evaluating of ACL, Blumensaat, and PCL Angles

Objective:

To determine MRI findings that can differentiate anterior cruciate ligament (ACL) tears from mucoid degeneration.

Material and Methods:

Thirty-seven patients with complete ACL tears and 43 with ACL mucoid degeneration were included in this study. Discontinuity, the abnormal signal intensity of the ACL on fat-saturated-PD weighted images, contusions, a deep lateral femoral notch, anterior tibial translation, uncovered posterior horn of the lateral meniscus, a celery stalk appearance, thickening, ganglion cysts, intraosseous cysts, the ACL, Blumensaat, and posterior cruciate ligament (PCL) angles were evaluated. Optimum threshold values, sensitivity, specificity, and 95% CIs for the angles were calculated to predict the tear.

Results:

The prevalence of the significant findings in a tear versus mucoid degeneration, respectively, was as follows: discontinuity (97% vs. 0%, p < 0.001), contusions (65% vs. 2%, p < 0.001), the deep lateral femoral notch (22% vs. 0%, p = 0.001), anterior tibial translation (70% vs. 14%, p < 0.001), uncovered the lateral meniscus (46% vs. 7%, p < 0.001), a celery stalk appearance (0% vs. 66%, p < 0.001), thickening (19% vs. 100%, p < 0.001), ganglion cysts (14% vs. 70%, p < 0.001), and intraosseous cysts (8% vs. 63%, p < 0.001). Threshold values of ACL, Blumensaat, and PCL angles to predict the tear were ≤36° (78% sensitivity, 91% specificity), >11° (84%, 81%), and ≤96° (65%, 91%), respectively.

Conclusion:

A celery stalk appearance in the mucoid degeneration and discontinuity in an ACL tear are important in the differential diagnosis. ACL, Blumensaat, and PCL angles can be helpful in settings of diagnostic uncertainty.

The prevalence of Baker cyst in relation to the arrangement pattern between the medial head of gastrocnemius tendon and the semimembranosus tendon

PURPOSE

The purpose of this study was to investigate whether Baker cyst (BC) was related to the specific arrangement of the medial head of gastrocnemius tendon (MHGT) and the semimembranosus tendon (SMT).

MATERIALS AND METHODS

Patients who underwent knee MRI with "Baker cyst" in PACS from August 2017 to February 2018 were included in this study. Patients who did not have BC in a knee MRI performed during the same period were included in the control group. A total 210 patients were selected for inclusion in this study. For the imaging analysis, the arrangement pattern between MHGT and SMT was classified into three types: type 1, concave; type 2, flat; and type 3, convex. When imaging analysis was performed, the amount of effusion, the presence of osteoarthritis, and major ligament and meniscal tears were also described. Univariate and multivariate logistic regression analyses were performed. Statistical significance was considered at p < 0.05.

RESULTS

The frequency of types 1, 2, and 3 was statistically significant depending on the presence or absence of BC (p < 0.001). The frequency of type 3 was the highest in the presence of BC, while that of type 1 was the highest in the absence of BC. BC was more common in type 2 (OR = 2.54; 95% CI = 1.27-5.07) and type 3 (OR = 4.09; 95% CI = 1.88-8.89).

CONCLUSION

BC is more likely to occur in patients with SMT having a convex shape for MHGT.

KEY POINTS

• Based on axial image of MRI only, one can predict which patients are morphologically more prone to develop a Baker cyst. • On axial images of MRI, Baker cyst is more likely to occur in patients with semimembranosus tendon having a convex shape for medial head of gastrocnemius tendon. • Baker cyst is not associated with the amount of effusion, OA, or internal derangement.

Fully Automated Diagnosis of Anterior Cruciate Ligament Tears on Knee MR Images by Using Deep Learning

Purpose

To investigate the feasibility of using a deep learning-based approach to detect an anterior cruciate ligament (ACL) tear within the knee joint at MRI by using arthroscopy as the reference standard.

Materials and Methods

A fully automated deep learning-based diagnosis system was developed by using two deep convolutional neural networks (CNNs) to isolate the ACL on MR images followed by a classification CNN to detect structural abnormalities within the isolated ligament. With institutional review board approval, sagittal proton density-weighted and fat-suppressed T2-weighted fast spin-echo MR images of the knee in 175 subjects with a full-thickness ACL tear (98 male subjects and 77 female subjects; average age, 27.5 years) and 175 subjects with an intact ACL (100 male subjects and 75 female subjects; average age, 39.4 years) were retrospectively analyzed by using the deep learning approach. Sensitivity and specificity of the ACL tear detection system and five clinical radiologists for detecting an ACL tear were determined by using arthroscopic results as the reference standard. Receiver operating characteristic (ROC) analysis and two-sided exact binomial tests were used to further assess diagnostic performance.

Results

The sensitivity and specificity of the ACL tear detection system at the optimal threshold were 0.96 and 0.96, respectively. In comparison, the sensitivity of the clinical radiologists ranged between 0.96 and 0.98, while the specificity ranged between 0.90 and 0.98. There was no statistically significant difference in diagnostic performance between the ACL tear detection system and clinical radiologists at P < .05. The area under the ROC curve for the ACL tear detection system was 0.98, indicating high overall diagnostic accuracy.

Conclusion

There was no significant difference between the diagnostic performance of the ACL tear detection system and clinical radiologists for determining the presence or absence of an ACL tear at MRI.© RSNA, 2019Supplemental material is available for this article.

The patellar tendon wavy sign as a new secondary sign of ACL tear on MRI

Objective

The purpose of this study was to evaluate the diagnostic value of the patellar tendon wavy (PTW) sign for an anterior cruciate ligament (ACL) tear on MRI.

Methods

One hundred MRI scans were prospectively analyzed, with 50 patients with an ACL tear underwent an ACL reconstruction (group 1) and 50 patients with knee complaints other than ACL tear (group 2). The PTW sign was confirmed on the sagittal MRI. In addition, the patellar tendon length, tibial-femoral angle and tibial anterior translation (TAT) were compared between the groups.

Results

The PTW sign was present in 41/50 (82%) MRI scans in group 1 and 10/50 (20%) in group 2, with significant difference between two groups (p = 0.000). Significant differences were also found, in medial TAT (6.29 ± 3.25 mm versus 3.12 ± 2.85 mm) and in lateral TAT (7.62 ± 3.85 mm versus 1.58 ± 3.93 mm) between two groups (both p = 0.000). Comparison of MRI with and without PTW sign, ACL injury was found to be of significant difference with 41/51 (80.4%) versus 9/49 (18.4%) (p = 0.000), and both medial and lateral TAT were with significant differences, 5.39 ± 3.90 mm versus 3.99 ± 2.71 mm (p = 0.039) and 7.67 ± 3.77 mm versus 1.40 ± 3.81 mm (p = 0.000), respectively. The sensitivity and specificity of PTW sign were 82% and 80%. The positive and negative predictive value were 80.4% and 81.6%. The diagnosis accuracy was 81%.

Conclusion

The PTW sign is a useful secondary MRI sign to establish the diagnosis of an ACL tear. It may be associated with the TAT secondary to an ACL tear.

Level of evidence

Level III, diagnostic study.

Clinical value of pointwise encoding time reduction with radial acquisition (PETRA) MR sequence in assessing internal derangement of knee

PURPOSE

The purpose was to evaluate the clinical value of PETRA sequence for the diagnosis of internal derangement of the knee.

MATERIALS AND METHODS

The major structures of the knee in 34 patients were evaluated and compared among conventional MRI findings, PETRA images, and arthroscopic findings.

RESULTS

The specificities of PETRA with 2D FSE sequence were higher for meniscal lesions than those obtained when using 2D FSE alone.

CONCLUSION

Using PETRA images along with conventional 2D FSE images can increase the accuracy of assessing internal derangements of the knee and, specifically, meniscal lesions.

Comparison of magnetic resonance imaging for patients with acute and chronic anterior cruciate ligament tears

To compare the direct and indirect signs on magnetic resonance imaging (MRI) for patients with acute and chronic anterior cruciate ligament (ACL) tears.Two independent reviewers retrospectively evaluated the MRI images of 377 patients with ACL tear confirmed by arthroscopy. There were 160 cases with acute ACL tear and 217 cases with chronic ACL tear. Direct signs in T1- and T2-wighted images and indirect signs including meniscus injury, the collateral ligament injury, cartilage damage or osteoarthritis, kissing contusion, Notch syndrome and abnormal posterior cruciate ligament (PCL) and other indirect signs were evaluated.For direct signs on MRI, no significant differences were found between the acute and chronic ACL tear in prevalence of focal high signal in substance of T2-wighted images and in that of abnormal orientation, discontinuity, thickening, or focal masses in substance of T1-weighted images. However, higher incidence of diffuse high signal of T2-weighted images for acute ACL tear was found compared to that for chronic ACL tear (55.0% vs 3.2%). For indirect signs on MRI, the collateral ligament tear (20.6% vs 2.3%), cartilage damage or osteoarthritis (14.4% vs 25.8%), kissing contusion (57.4% vs 0%), Notch syndrome (28.1% vs 3.2%), and bowing type of PCL (33.1% vs 47.0%) can differentiate the acute from chronic ACL tear.Some direct and indirect signs on MRI are closely related to the acute and chronic ACL tear.

Clinical Feasibility of Synthetic Magnetic Resonance Imaging in the Diagnosis of Internal Derangements of the Knee

Objective

To evaluate the feasibility of synthetic magnetic resonance imaging (MRI) compared to conventional MRI for the diagnosis of internal derangements of the knee at 3T.

Materials and Methods

Following Institutional Review Board approval, image sets of conventional and synthetic MRI in 39 patients were included. Two musculoskeletal radiologists compared the image sets and qualitatively analyzed the images. Subjective image quality was assessed using a four-grade scale. Interobserver agreement and intersequence agreement between conventional and synthetic images for cartilage lesions, tears of the cruciate ligament, and tears of the meniscus were independently assessed using Kappa statistics. In patients who underwent arthroscopy (n = 8), the sensitivity, specificity, and accuracy for evaluated internal structures were calculated using arthroscopic findings as the gold standard.

Results

There was no statistically significant difference in image quality (p = 0.90). Interobserver agreement (κ = 0.649– 0.981) and intersequence agreement (κ = 0.794–0.938) were nearly perfect for all evaluated structures. The sensitivity, specificity, and accuracy for detecting cartilage lesions (sensitivity, 63.6% vs. 54.6–63.6%; specificity, 91.9% vs. 91.9%; accuracy, 83.3–85.4% vs. 83.3–85.4%) and tears of the cruciate ligament (sensitivity, specificity, accuracy, 100% vs. 100%) and meniscus (sensitivity, 50.0–62.5% vs. 62.5%; specificity, 100% vs. 87.5–100%; accuracy, 83.3–85.4% vs. 83.3–85.4%) were similar between the two MRI methods.

Conclusion

Conventional and synthetic MRI showed substantial to almost perfect degree of agreement for the assessment of internal derangement of knee joints. Synthetic MRI may be feasible in the diagnosis of internal derangements of the knee.

Magnetic Resonance Signal Abnormalities within the Pericruciate Fat Pad: A Possible Secondary Sign for Acute Anterior Cruciate Ligament Tears

Purpose

The study sought to investigate the presence of magnetic resonance (MR) signal alterations within the pericruciate fat pad in patients with an acute anterior cruciate ligament (ACL) tear as well as evaluate its diagnostic value in comparison with the main secondary signs of ACL tears.

Methods

Two musculoskeletal radiologists retrospectively reviewed knee MR examinations performed from May to October 2015. The ACL was considered as torn or intact based on either previous arthroscopic findings or unequivocal MR imaging interpretation if arthroscopic correlation was unavailable. Abnormalities of the pericruciate fat pad were evaluated as increased signal on the fluid-sensitive sequences; the main secondary signs of ACL tears were identified. Sensitivity and specificity were calculated for each sign.

Results

A total of 182 patients entered this study: 22 with an acute ACL tear, 160 with intact ACL. Signal hyperintensity of the pericruciate fat pad was demonstrated in all patients with an acutely torn ACL, resulting significantly different between individuals with intact ACL and those with ligament tear ( P < .0001). This sign was much more sensitive (100%) but less specific (72.5%-75%) than other secondary signs.

Conclusions

Signal hyperintensity of the pericruciate fat pad on the fluid-sensitive sequences is associated with acute ACL tears and could be considered as a possible indicator of these injuries.

Diagnostic Efficacy of 3-T MRI for Knee Injuries Using Arthroscopy as a Reference Standard: A Meta-Analysis

OBJECTIVE

The objectives of our study were to assess the evidence for the diagnostic efficacy of 3-T MRI for meniscal and anterior cruciate ligament (ACL) injuries in the knee using arthroscopy as the reference standard and to compare these results with the results of a previous meta-analysis assessing 1.5-T MRI.

MATERIALS AND METHODS

The online Cochrane Library, MEDLINE, and PubMed databases were searched using the following terms: MRI AND ((3 OR three) AND (Tesla OR T)) AND knee AND arthroscopy AND (menisc* OR ligament). Patient demographics, patient characteristics, MRI scanning details, and diagnostic results were investigated. The methodologic quality of the included studies was assessed using the revised Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. A meta-analysis of studies using 3-T MRI was performed, and the results were compared with a previous meta-analysis of studies using 1.5-T MRI.

RESULTS

One hundred one studies were identified by the search strategy, and 13 studies were included in our review. Twelve studies were considered to have level 1b evidence, and one study was considered to have level 2b evidence. All 13 studies had high methodologic integrity and low risk of bias using the QUADAS-2 tool. The studies included 1197 patients with a mean age of 41.9 years. Ten of the 13 studies were eligible for meta-analysis. The mean sensitivity and mean specificity of 3-T MRI for knee injuries by location were as follows: medial meniscus, 0.94 (95% CI, 0.91-0.96) and 0.79 (95% CI, 0.75-0.83), respectively; lateral meniscus, 0.81 (95% CI, 0.75-0.85) and 0.87 (95% CI, 0.84-0.89); and ACL, 0.92 (95% CI, 0.83-0.96) and 0.99 (95% CI, 0.96-1.00). The specificity of 3-T MRI for injuries of the lateral meniscus was significantly lower than that of 1.5-T MRI (p = 0.0013).

CONCLUSION

This study does not provide evidence that 3-T scanners have superior diagnostic efficacy for meniscal damage and ACL integrity when compared with previous studies of 1.5-T machines.

Diagnostic performance of 3D TSE MRI versus 2D TSE MRI of the knee at 1.5 T, with prompt arthroscopic correlation, in the detection of meniscal and cruciate ligament tears

Objective

To compare the diagnostic performance of the three-dimensional turbo spin-echo (3D TSE) magnetic resonance imaging (MRI) technique with the performance of the standard two-dimensional turbo spin-echo (2D TSE) protocol at 1.5 T, in the detection of meniscal and ligament tears.

Materials and Methods

Thirty-eight patients were imaged twice, first with a standard multiplanar 2D TSE MR technique, and then with a 3D TSE technique, both in the same 1.5 T MRI scanner. The patients underwent knee arthroscopy within the first three days after the MRI. Using arthroscopy as the reference standard, we determined the diagnostic performance and agreement.

Results

For detecting anterior cruciate ligament tears, the 3D TSE and routine 2D TSE techniques showed similar values for sensitivity (93% and 93%, respectively) and specificity (80% and 85%, respectively). For detecting medial meniscal tears, the two techniques also had similar sensitivity (85% and 83%, respectively) and specificity (68% and 71%, respectively). In addition, for detecting lateral meniscal tears, the two techniques had similar sensitivity (58% and 54%, respectively) and specificity (82% and 92%, respectively). There was a substantial to almost perfect intraobserver and interobserver agreement when comparing the readings for both techniques.

Conclusion

The 3D TSE technique has a diagnostic performance similar to that of the routine 2D TSE protocol for detecting meniscal and anterior cruciate ligament tears at 1.5 T, with the advantage of faster acquisition.

Rotational Knee Laxity in Anterior Cruciate Ligament Deficiency: An Additional Secondary Sign on MRI

OBJECTIVE

The objective of this study was to evaluate the accuracy of tibial rotation measurement as a secondary sign for diagnosing anterior cruciate ligament (ACL) tears with the use of MRI.

MATERIALS AND METHODS

A total of 893 MRI studies were retrospectively reviewed, and 239 patients were identified as having either an intact ACL (group 1; n = 182), an arthroscopically confirmed acutely torn ACL (group 2; n = 22), or a chronically torn ACL (group 3; n = 35). Tibial rotation was estimated by measuring the femorotibial angle (FTA).

RESULTS

The mean (± SD) FTA was significantly higher in group 2 (10.7° ± 4.8°) and group 3 (11° ± 5.5°) than in group 1 (3.2° ± 3.3°) (p < 0.001, for all cases). An FTA of 4.9° was the optimal threshold (sensitivity, 93%; specificity, 80%) for separating completely torn ACLs from intact ACLs. An FTA ranging from 4.9° to 5.5° (sensitivity, 95%; specificity, 80%) indicated a complete acute ACL tear, whereas an FTA of 5.6° or greater (sensitivity, 91.4%; specificity, 83.5%) suggested a complete chronic ACL tear.

CONCLUSION

An increased FTA indicates alteration in the femorotibial anatomic relationship and could be of value in assessing ACL tears in patients with equivocal signs on MRI.

Bone abnormalities of the knee: MRI features

The knee is one of the most studied anatomical structures by magnetic resonance imaging (MRI). Bone abnormalities are very frequently detected, whether or not related to the symptoms for which imaging was indicated. The aim of this pictorial study is to review the most commonly observed bone abnormalities of the knee, bearing in mind that the interpretation of MR images should always take into consideration both clinical and laboratory data, as well as the results of conventional X-ray imaging.

Interposition of the Posterior Cruciate Ligament into the Medial Compartment of the Knee Joint on Coronal Magnetic Resonance Imaging

Objective

The purpose of our study was to evaluate the overall prevalence and clinical significance of interposition of the posterior cruciate ligament (PCL) into the medial compartment of the knee joint in coronal magnetic resonance imaging (MRI).

Materials and Methods

We retrospectively reviewed 317 consecutive patients referred for knee MRI at our institution between October 2009 and December 2009. Interposition of the PCL into the medial compartment of the knee joint on proton coronal MRI was evaluated dichotomously (i.e., present or absent). We analyzed the interposition according to its prevalence as well as its relationship with right-left sidedness, gender, age, and disease categories (osteoarthritis, anterior cruciate ligament tear, and medial meniscus tear).

Results

Prevalence of interposition of PCL into the medial compartment of the knee joint was 47.0% (149/317). There was no right (50.0%, 83/166) to left (43.7%, 66/151) or male (50.3%, 87/173) to female (43.1%, 62/144) differences in the prevalence. There was no significant association between the prevalence and age, or the disease categories.

Conclusion

Interposition of the PCL into the medial compartment of the knee joint is observed in almost half of patients on proton coronal MRI of the knee. Its presence is not associated with any particular factors including knee pathology and may be regarded as a normal MR finding.

Clinical value of fat-suppressed 3D volume isotropic spin-echo (VISTA) sequence compared to 2D sequence in evaluating internal structures of the knee

BACKGROUND

Although many three-dimensional (3D) magnetic resonance imaging (MRI) sequences have been used in the clinical field, there are no studies on fat-suppressed (FS) 3D sequences for the diagnosis of knee abnormalities.

PURPOSE

To evaluate the usefulness of FS 3D volume isotropic turbo spin echo acquisition (VISTA) imaging for diagnosis of internal structures of knee.

MATERIAL AND METHODS

In 137 patients with 138 knee MRI examinations who had undergone both FS 3D VISTA MRI and two-dimensional (2D) MRI of the knee at 3.0 T, arthroscopic surgery was subsequently performed. Multiplanar reformations (MPR) of FS 3D VISTA images and their MPR sequences were compared with 2D MR images of axial T1-weighted (T1W) images, axial FS T2-weighted (T2W) images, coronal FS T2W images, and sagittal T2W images. Two musculoskeletal radiologists reviewed the images independently.

RESULTS

Arthroscopy revealed 33 anterior cruciate ligament tears, three posterior cruciate ligament tears, 42 lateral meniscus tears, and 68 medial meniscus tears. Five medial collateral ligament tears were clinically confirmed. Image acquisition time was shorter for FS 3D VISTA imaging than 2D imaging. There were no significant differences in diagnostic values between FS 3D VISTA and 2D imaging (P > 0.05). There were excellent inter-observer agreements for both FS 3D VISTA and 2D imaging (κ > 0.84).

CONCLUSION

FS 3D VISTA imaging could replace 2D imaging because of equal diagnostic ability and shorter scan time.

Change in T2* relaxation time of Hoffa fat pad correlates with histologic change in a rat anterior cruciate ligament transection model

The Hoffa fat pad (infrapatellar fat pad) is a source of post-traumatic anterior knee pain, and Hoffa disease is a syndrome leading to chronic inflammation of the fat pad. Herein, change in T2* relaxation time of the fat pad was measured in a rodent anterior cruciate ligament transection (ACLX) model in order to (i) examine the causal relationship of anterior cruciate ligament (ACL) deficiency and Hoffa disease and (ii) demonstrate the feasibility of using T2* as an imaging biomarker to monitor disease progression. Three groups of male Sprague Dawley rats (n = 6 each group), received either (i) no intervention; (ii) sham surgery at the right knee; or (iii) right ACLX. T2* relaxation time was measured and histology was examined in the Hoffa fat pad after surgery. At 13 and 18 weeks after surgery, T2* values were significantly higher in the right fat pad than the left (p < 0.001) and significantly higher in the ACLX group than the control and sham groups (p < 0.001). Histology showed fibrosis and degeneration of adipocytes in the right knees of the ACLX group. We conclude that ACL deficiency and Hoffa disease are causally related and that MRI T2* value can serve as an imaging biomarker of Hoffa disease progression.

MR imaging of cruciate ligaments

Cruciate ligament injuries, and in particular injuries of the anterior cruciate ligament (ACL), are the most commonly reconstructed ligamentous injuries of the knee. As such, accurate preoperative diagnosis is essential in optimal management of patients with cruciate ligament injuries. This article reviews the anatomy and biomechanics of the ACL and posterior cruciate ligament (PCL) and describes the magnetic resonance (MR) imaging appearances of complete and partial tears. Normal postoperative appearances of ACL and PCL reconstructions as well as MR imaging features of postoperative complications will also be reviewed.

Can magnetic resonance imaging findings predict the degree of knee joint laxity in patients undergoing anterior cruciate ligament reconstruction?

Background

The present study was performed to determine whether MRI findings can predict the degree of knee joint laxity in patients undergoing ACL reconstruction and whether the accuracy of the prediction is affected by the MRI acquisition time.

Methods

We assessed prospectively collected data of 154 knees with ACL tears. The presence or absence of four primary findings of ACL tears, i.e., nonvisualization, discontinuity, abnormal signal intensity, and abnormal shape of the ACL, and five secondary findings, i.e., anterior translation of the tibia relative to the femur (≥7 mm), posterior cruciate ligament angle (<105°), bone contusion, Segond fracture, and the deep sulcus sign, were determined. Knee joint laxity was assessed using the Lachman and pivot shift tests. The associations between MRI findings and clinically assessed knee joint laxity were analyzed and compared between subgroups (≤3 months from injury to MRI, 89 knees; >3 months, 65 knees).

Results

Nonvisualization was related to the results of the Lachman test [Odds ratio (OR), 2.6; 95% confidence interval (CI), 1.2–5.5]. Anterior translation of the tibia relative to the femur was related to the results of the pivot shift test (OR, 3.8; 95% CI, 1.6–9.4). In subgroup comparisons of the early and late MRI groups, anterior translation of the tibia relative to the femur was related to the results of the pivot shift test in the early MRI group (OR, 4.5; 95% CI, 1.4–14.4). In contrast, no MRI findings had statistically significant relationships with physical findings in the late MRI group.

Conclusions

Our study indicates that MRI findings may have some usefulness for predicting the grade of knee laxity in patients with symptomatic ACL injury, but its value is limited, especially in patients with a longer time interval between injury and the performance of MRI.

Case-control study to estimate the performance of dual-energy computed tomography for anterior cruciate ligament tears in patients with history of knee trauma

OBJECTIVE

Computed tomography (CT) is used to assess for fracture after knee trauma, but identification of ligamentous injuries may also be beneficial. Our purpose is to assess the potential of dual-energy computed tomography (DECT) for the detection of complete anterior cruciate ligament (ACL) disruption.

METHODS

Sixteen patients with unilateral traumatic ACL disruption (average of 58 days following trauma) confirmed by MRI, and 11 control patients without trauma, underwent DECT of both knees. For each knee, axial, sagittal, and oblique sagittal images (with DECT bone removal, single-energy (SE) bone removal, and DECT tendon-specific color mapping) were reconstructed. Four musculoskeletal radiologists randomly evaluated the 324 DECT reconstructed series (54 knees with 6 displays) separately, to assess for ACL disruption using a five-point scale (1 = definitely not torn, to 5 = definitely torn). ROC analysis was used to compare performance across readers and displays.

RESULTS

Sagittal oblique displays (mixed kV soft tissue, SE bone removal, and DECT bone removal) demonstrated higher areas under the curve for ACL disruption (AUC = 0.95, 0.93 and 0.95 respectively) without significant differences in performance between readers (p > 0.23). Inter-reader agreement was also better for these display methods (ICC range 0.62-0.69) compared with other techniques (ICC range 0.41-0.57). Mean sensitivity for ACL disruption was worst for DECT tendon-specific color map and axial images (24 % and 63 % respectively).

CONCLUSION

DECT knee images with oblique sagittal reconstructions using either mixed  kV or bone removal displays (either DECT or SE) depict ACL disruption in the subacute or chronic setting with reliable identification by musculoskeletal radiologists.

Manual khalifa therapy improves functional and morphological outcome of patients with anterior cruciate ligament rupture in the knee: a randomized controlled trial

Rupture of the anterior cruciate ligament (ACL) is a high incidence injury usually treated surgically. According to common knowledge, it does not heal spontaneously, although some claim the opposite. Regeneration therapy by Khalifa was developed for injuries of the musculoskeletal system by using specific pressure to the skin. This randomized, controlled, observer-blinded, multicentre study was performed to validate this assumption. Thirty patients with complete ACL rupture, magnetic resonance imaging (MRI) verified, were included. Study examinations (e.g., international knee documentation committee (IKDC) score) were performed at inclusion (t 0). Patients were randomized to receive either standardised physiotherapy (ST) or additionally 1 hour of Khalifa therapy at the first session (STK). Twenty-four hours later, study examinations were performed again (t 1). Three months later control MRI and follow-up examinations were performed (t 2). Initial status was comparable between both groups. There was a highly significant difference of mean IKDC score results at t 1 and t 2. After 3 months, 47% of the STK patients, but no ST patient, demonstrated an end-to-end homogeneous ACL in MRI. Clinical and physical examinations were significantly different in t 1 and t 2. ACL healing can be improved with manual therapy. Physical activity can be performed without pain and nearly normal range of motion after one treatment of specific pressure.

Oblique coronal and oblique sagittal MRI for diagnosis of anterior cruciate ligament tears and evaluation of anterior cruciate ligament remnant tissue

BACKGROUND

The purpose of this study was to investigate the efficacy of additional oblique magnetic resonance imaging (MRI) for the diagnosis of anterior cruciate ligament (ACL) tear and evaluation of ACL remnant tissue.

METHODS

We retrospectively reviewed the records of 54 knees. Three independent readers evaluated the MR images by the use of three methods: orthogonal sagittal images only (method A); orthogonal sagittal and additional oblique sagittal images (method B); and orthogonal sagittal and oblique coronal images (method C). The sensitivity, specificity, and accuracy for the diagnosis of an ACL tear and the detection of the condition of the ACL remnant tissue by the use of each method were calculated in comparison with arthroscopic findings as the reference standard.

RESULTS

The arthroscopic records revealed 27 knees with intact ACLs and 27 with torn ACLs. Among the 27 knees with torn ACLs, 9 did not have continuous remnant tissue and 18 had certain remnant tissue attached to the femur or the posterior cruciate ligament. The specificities and accuracies of methods B and C for diagnosing an ACL tear were higher than those for method A. The sensitivity, specificity, and accuracy of method C for the detection of ACL remnant tissue were higher than those for method A and B.

CONCLUSIONS

Additional use of oblique MRI improved the accuracy of diagnosis of ACL tear and showed a reasonable level of efficacy in detecting ACL remnant tissue.

LEVEL OF EVIDENCE

Level IV (case series).

MRI of the knee with arthroscopic correlation

Major advances in MRI and arthroscopy have allowed for enhanced diagnosis and subsequent management of ligamentous and soft tissue injuries of the knee. Recognition of the appearance of acute ACL and PCL injuries on MRI can enhance arthroscopic reconstruction. PCL injuries are often more subtle and can present with indirect signs. T2-weighted MRI imaging can examine which structures have been damaged in the posterolateral corner which may manifest arthroscopically as a drive-through sign. Characterization of PLC, meniscus, MCL injuries and OCD lesions on MRI have remarkable correlation with arthroscopic findings. This article focuses on current understanding of how MRI and athroscopy can enhance treatment of ligamentous and soft tissue injuries of the knee.

Diagnosis of ACL and meniscal injuries: MR imaging of knee flexion versus extension compared to arthroscopy

The aim of the study was to evaluate whether MR Imaging of the knee at 30° and 55° of flexion can improve the diagnosis of anterior cruciate ligament and menisci injuries compared to arthroscopy and imaging during extension of the knee joint. Knee joints from 40 patients with clinical suspicion of an anterior cruciate ligament (ACL) rupture were examined using MRI while the knee joint was either extended or flexed at 30° and 55° of knee flexion. A standard MR knee coil was used at extension, whereas at 30° and 55° of flexion a non-metallic positioning device and a flexible surface coil was placed ventral to the patella. Sagittal T2-weighted TSE sequences were acquired. In 29 of 40 patients, arthroscopy results were compared to the MRI examinations. Image quality of MRI examinations was evaluated using a three-point rating scale in a blinded fashion. Images were compared between groups and rated as better quality, same quality, or worse quality. Additionally, each angle MRI was compared to arthroscopy results. Partial ACL ruptures were diagnosed with 63% accuracy using MR imaging at 30° and 55° of knee flexion compared to 50% accuracy during knee extension. MRI imaging of complete ACL ruptures resulted in 83% accuracy of diagnosis when imaged at 30° flexion, 93% accuracy at 55° flexion, and 83% accuracy at extension. The accuracy of diagnosing medial meniscus lesions was 73% at extension, 64% at 30° flexion and 73% at 55° of flexion. MR imaging was only able to diagnose lateral meniscus tears with 55% accuracy in all three knee positions. The diagnosis of meniscal tears was more difficult due to small peripheral tears. The improved results in the diagnosis of ACL tears in response to 30° flexion and in particular in response to 55° flexion were based on the fact that the anterior cruciate ligament moved further away from the intercondylar roof with increased knee flexion. During flexion the ligament tension decreased, which causes the anterior cruciate ligament to have cylindrical shape and therefore made visualization of the injury easier. In conclusion, MR Imaging of the knee at 55° of flexion and less at 30° of flexion allows an improved diagnosis of injuries to the anterior cruciate ligament as compared to MRI examinations at extension. The diagnosis of meniscal injuries, however, was not superior at both flexion positions compared to commonly performed examinations at knee extension.

Knee derangements: comparison of isotropic 3D fast spin-echo, isotropic 3D balanced fast field-echo, and conventional 2D fast spin-echo MR imaging

PURPOSE

To compare diagnostic performance, subjective image quality, and artifacts of isotropic three-dimensional (3D) intermediate-weighted (IW) fast spin-echo (SE), isotropic 3D balanced fast field-echo (FFE), and conventional two-dimensional (2D) fast SE 3.0-T MR sequences in evaluation of cartilage, ligaments, menisci, and osseous knee structures in symptomatic patients.

MATERIALS AND METHODS

Institutional review board approval and waiver of informed consent were obtained for this HIPAA-compliant study. One hundred MR studies, each with three data sets (3D IW fast SE, 3D balanced FFE, 2D fast SE), were reviewed retrospectively. Two radiologists independently evaluated images for cartilaginous defects, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial meniscus (MM), lateral meniscus (LM) tears, subchondral bone marrow signal abnormalities, subjective image quality, and image artifacts. Arthroscopic results were the reference standard. Statistical analysis was performed to calculate interobserver agreement and compare diagnostic performance of sequences.

RESULTS

Sensitivity and specificity were greater than 85% for all lesions. For cartilaginous defects, sensitivity of 3D IW fast SE was significantly greater than that of 3D balanced FFE (95.5% vs 89.7%). Sensitivity of 3D IW fast SE and 2D fast SE for MM, LM, and ACL tears tended to be greater than that of 3D balanced FFE. IW fast SE had a higher detection rate for subchondral bone marrow signal abnormality than did 3D balanced FFE (34% vs 21%); it also had the best image quality and fewest artifacts, followed by 2D fast SE and 3D balanced FFE. Interobserver agreement was excellent for evaluation of all intraarticular structures (κ = 0.85-1) and good to excellent for detection of subchondral bone marrow signal abnormality (κ = 0.76-0.91).

CONCLUSION

The performance of IW fast SE is superior to that of balanced FFE in evaluation of cartilaginous defects, with no significant difference in performance between 2D fast SE, 3D IW fast SE, and 3D balanced FFE in evaluation of meniscal and ligament tears. Subchondral bone marrow signal abnormality is more easily seen on 3D IW fast SE images, with better subjective image quality and fewer artifacts, than on images obtained with other techniques.

Prediction of chronicity of anterior cruciate ligament tear using MRI findings

Background

The estimation of anterior cruciate ligament (ACL) tear is required in certain cases involving legal and financial administration, such as the worker's compensation and/or insurance. The aim of this study is to propose and evaluate a quantitative evaluation instrument to estimate the chronicity of the ACL tear, based on the four magnetic resonance imaging (MRI) findings.

Methods

One hundred and fifty one cases of complete ACL tear confirmed by arthroscopy were divided into 4 groups according to the time from ACL injury to MRI acquisition: acute (< 6 weeks), subacute (6 weeks to 3 months), intermediate (3 months to 1 year), and chronic (> 1 year). The four MRI findings including ACL morphology, joint effusion, posterior cruciate ligament angle, and bone bruise were analyzed for temporal changes among the 4 groups. Binary logistic regression equations were formulated using the MRI findings to estimate the chronicity of ACL tear in a quantitative manner, and the accuracy of the formulated regression equations was evaluated.

Results

The four MRI findings showed substantial temporal correlation with the time-limits of ACL injury to be included in the estimation model. Three predictive binary logistic equations estimated the probability of the ACL injury for the three cutoff time-limits of 6 weeks, 3 months, and 1 year with accuracies of 82.1%, 89.4%, and 89.4%, respectively.

Conclusions

A series of predictive logistic equations were formulated to estimate the chronicity of ACL tear using 4 MRI findings with chronological significance.

The value of the sagittal-oblique MRI technique for injuries of the anterior cruciate ligament in the knee

BACKGROUND

Complete rupture of the anterior cruciate ligament (ACL) does not represent a diagnostic problem for the standard magnetic resonance (MR) protocol of the knee. Lower accuracy of the standard MR protocol for partial rupture of the ACL can be improved by using additional, dedicated MR techniques. The study goal was to draw a comparison between sagittal-oblique MR technique of ACL imaging versus flexion MR technique of ACL imaging and, versus ACL imaging obtained with standard MR protocol of the knee.

PATIENTS AND METHODS

In this prospective study we included 149 patients who were referred to magnetic resonance imaging (MRI) examination due to knee soft tissues trauma during 12 months period. MRI signs of ACL trauma, especially detection of partial tears, number of slices per technique showing the whole ACL, duration of applied additional protocols, and reproducibility of examination were analysed.

RESULTS

Accuracy of standard MRI protocol of the knee comparing to both additional techniques is identical in detection of a complete ACL rupture. Presentations of the partial ruptures of ACL using flexion technique and sagittal-oblique technique were more sensitive (p<0.001) than presentation using standard MR protocol. There was no statistically significant difference between MRI detection of the ruptured ACL between additional techniques (p> 0.65). Sagittal-oblique technique provides a higher number of MRI slices showing the whole course of the ACL and requires a shorter scan time compared to flexion technique (p<0.001).

CONCLUSIONS

Both additional techniques (flexion and sagittal-oblique) are just as precise as the standard MR protocol for the evaluation of a complete rupture of the ACL, so they should be used in cases of suspicion of partial rupture of the ACL. Our study showed sagittal-oblique technique was superior, because it did not depend on patient's ability to exactly repeat the same external rotation if standard MR protocol was used or to repeat exactly the same flexion in flexion MR technique in further MR examinations. Sagittal-oblique technique does not require the patient's knee to be repositioned, which makes this technique faster. We propose this technique in addition to the standard MR protocol for detection of partial ACL tears.

Diagnostic performance of 3D SPACE for comprehensive knee joint assessment at 3 T

Objective

To assess the diagnostic performance of 3D sampling perfection with application-optimised contrasts using variable flip-angle evolution (SPACE) turbo spin-echo (TSE) sequences compared to 2D TSE for comprehensive knee assessment at 3 T.

Methods

From January to July 2011, isotropic 3D SPACE was added to a 2D knee protocol at 3 T. Forty patients underwent subsequent arthroscopy. Three readers independently assessed MR images for meniscus, anterior cruciate ligament (ACL) and cartilage lesions. Readers 1 and 2 evaluated 3D and 2D data at separate sittings; reader 3 interpreted the complete exam including 3D and 2D sequences. Accuracies were calculated using arthroscopy as reference standard. McNemar’s test (p < 0.05) was used to compare 3D and 2D techniques.

Results

The highest diagnostic yield was obtained by reader 3 (accuracies ≥88 %). For the medial meniscus, readers performed better with the 2D technique than with 3D SPACE (accuracies 85–88 % vs. 78–80 %, respectively) (p > 0.05). For the lateral meniscus and ACL, 3D and 2D techniques had similar performance (accuracies ≥93 %). For cartilage lesions, 3D SPACE had significantly lower specificity (p = 0.0156) than the 2D protocol for one reader.

Conclusion

The conventional 2D TSE acquisition is more reliable than 3D SPACE for comprehensive assessment of the knee at 3.0 T.

Main Messages

• 3D SPACE is a valuable component of a knee MR protocol at 3 T.

• 3D SPACE cannot be used as a single sequence in the MR evaluation of the knee at 3 T.

• Knee MR protocols at 3 T should include both 2D and 3D TSE sequences.

Knee joint examinations by magnetic resonance imaging: The correlation of pathology, age, and sex

Aims:

The aim of our study was to investigate the incidence and coexistence of multiple knee joint pathologies and the distribution of knee joint pathologies according to age and sex.

Patients and Methods:

A retrospective analysis was performed using the clinical data of patients evaluated with magnetic resonance imaging (MRI) of the knee joint. Data from 308 patients examined between August 2002 and July 2003 were included into this study. A Pearson correlation analysis was performed to examine the relationship between the pathological findings and the age and sex of the patients.

Results:

The ages of the patients ranged between 1 and 74 years (mean: 43.3 years). Age was significantly correlated with meniscal degeneration and tears, medial collateral ligament degeneration, parameniscal cyst, and chondromalacia patellae. There was a significant correlation between male gender and anterior cruciate ligament injury. Meniscal injury was significantly correlated with bursitis, as well as medial collateral ligament injury. Bone bruise was significantly correlated with medial collateral ligament injury, lateral collateral ligament injury, Baker's cyst, and anterior cruciate ligament injury. Chondromalacia patellae was significantly correlated with anterior cruciate ligament injury, patellae alta, and osteochondral lesion. Bursitis (in 53.2% of the patients) followed by grade-II meniscal degeneration (in 43% of the patients) were the most common knee pathologies observed by MRI.

Conclusions:

MRI findings of select knee pathologies are significantly correlated with each other and the age and sex of the patient.

MRI appearance of the distal insertion of the anterior cruciate ligament of the knee: an additional criterion for ligament ruptures

OBJECTIVE

Anterior cruciate ligament tears are frequent and if not diagnosed may lead to relevant patient disability. Magnetic resonance imaging is the method of choice for the non-invasive diagnosis of these tears. Despite the high performance of this method some cases are challenging and the criteria described in the literature are not sufficient to reach a diagnosis. We propose a systematic method for the evaluation of anterior cruciate ligament tears based on the aspect of its distal portion.

MATERIALS AND METHODS

Magnetic resonance studies of 132 knees were evaluated in correlation with arthroscopy. The performance of the proposed method was compared with that of classic imaging signs of anterior cruciate ligament tear. The impact of image quality and reader expertise on the proposed method and the classic signs of tear were taken into account.

RESULTS

This method had a sensitivity and specificity of 91.1% and 82.9% for the detection of abnormal ACLs. The interobserver agreement (kappa) of the proposed method was significantly higher than that of the classic signs at all levels of expertise (0.89 vs 0.76). This method was not influenced by image quality. Distal ACL analysis identified more partial tears and synovialization (granulation scar tissue)than the conventional method (71% vs 58.5% for partial tears and 83.5% vs 58.5% for synovialization).

CONCLUSION

The proposed classification has a high performance and reproducibility for the identification of abnormal anterior cruciate ligament. The results were influenced neither by the level of expertise of the readers nor by the image quality.

The contribution of MRI to the diagnosis of traumatic tears of the anterior cruciate ligament

When faced with a clinical suspicion of knee ligament injury, MRI nowadays has a central role in the diagnostic strategy. In particular, it is essential for assessing the cruciate ligaments and any associated meniscal tears. The objective of this review is to present the various direct and indirect MRI signs of tearing of the anterior cruciate ligament (ACL) and then describe the lesions associated with it. The anatomical and clinical aspects are also discussed so that the contribution of MRI to the diagnosis and therapeutic management of an ACL tear can be better understood.

Spontaneous healing in complete ACL ruptures: a clinical and MRI study

BACKGROUND

Most authors believe the ACL does not spontaneously heal after a complete rupture. Although several studies have reported spontaneous healing of torn ACLs, it is difficult to determine its healing potential and whether patients will be able to return to sports activities.

QUESTIONS/PURPOSES

We therefore asked whether (1) a complete ACL rupture in patients can spontaneously heal without the use of a specific rehabilitation program or bracing and (2) patients are able to return to their athletic activity after spontaneous ACL healing.

PATIENTS AND METHODS

We retrospectively reviewed 14 patients with acute ACL injury established by physical examination and MRI (proximal third in eight patients and the midligament in six). Average age at injury was 31 years (range, 23-41 years). All patients were athletically active before injury. Surgery was indicated in all patients but for various reasons postponed. We obtained International Knee Documentation Committee scores, Lysholm-Gillquist scores, and MRI. The minimum followup was 25 months (mean, 30 months; range, 25-36 months).

RESULTS

At last followup, the mean Lysholm-Gillquist score was 97. According to the International Knee Documentation Committee evaluation, 10 knees were normal and four nearly normal. All knees regained end point with a negative pivot shift test; MRI at followup showed an end-to-end continuous ACL with homogeneous signal. All patients returned to their former activity level. However, after the study period, two patients had a rerupture of the ACL (2.5 years after the first lesion).

CONCLUSIONS

Our observations indicate an acutely injured ACL may eventually spontaneously heal without using an extension brace, allowing return to athletic activity.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Anterior cruciate ligament reconstruction: MR imaging signs of anterior knee laxity in the presence of an intact graft

PURPOSE

To determine the accuracy of secondary magnetic resonance (MR) imaging signs of anterior cruciate ligament (ACL) insufficiency in predicting clinical anterior translational knee laxity, in the presence of an intact graft, after ACL reconstruction.

MATERIALS AND METHODS

Institutional review board approval was obtained, and the requirement to obtain informed consent was waived. Fifty-two patients with ACL reconstruction and no injury to the contralateral knee were included. Three patients with visible ACL graft tears at MR imaging were excluded. All patients underwent MR imaging of the affected knee, functional assessment with use of the International Knee Documentation Committee (IKDC) score, and arthrometric testing of both the affected and uninjured knee. A side-to-side difference of more than 3 mm at 133 N was considered to be indicative of knee laxity. Two radiologists independently evaluated all MR images for seven signs of anterior knee laxity. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were calculated for each MR imaging sign.

RESULTS

Ten patients demonstrated knee laxity at arthrometric testing. Patients with knee laxity at arthrometric testing had significantly lower IKDC scores (P < .03). Sensitivities for all signs were low (0%-50%). Anterior translation of the tibia of more than 7 mm, a posterior cruciate ligament (PCL) angle of less than 100°, and a PCL curvature ratio of more than 0.39 demonstrated high specificity (range, 82%-90%). Uncovering of the posterior horn of the lateral meniscus and the posterior femoral line had a specificity of 97%-100% and a sensitivity of 0%. All signs had a low PPV and high NPV for laxity. All MR imaging signs demonstrated near-perfect interobserver agreement.

CONCLUSION

Although MR imaging signs of knee laxity in the presence of an intact ACL graft have a high specificity, the low PPV means that MR imaging is of little value in predicting anterior knee laxity as demonstrated with mechanical testing.

A case of anterior cruciate ligament tear accompanied by avulsion fractures of tibial tuberosity and Gerdy's tubercle

A 54-year-old man visited our clinic due to a painful swelling of his right knee. He had attempted a forceful kick by his right leg during a Sepak Takraw-like sports activity, only to fail to hit the ball. He felt a popping sense on the knee and collapsed, even without direct trauma. Imaging studies revealed a disruption of the anterior cruciate ligament (ACL), and separate avulsion fractures of the tibial tuberosity and Gerdy's tubercle. The fractures were stabilized by two cancellous screws, respectively. The intra-operative fluoroscopy demonstrated a manifest ACL insufficiency. A simultaneous reconstruction of the ligament was not performed. At 6 months after surgery, he had no difficulty in his activities of daily living. The involved knee joint was believed to have undergone a forceful pivot shift mechanism. Injuries to the ACL can be suspected from indirect signs on the radiologic images by a careful reconstitution of the injury mechanism and the associated lesions. Manifest osseous lesions on the plain radiographs can herald a major ligamentous injury and may be interpreted as an indirect sign of the ACL injury, which helps to establish a relevant management plan.