MR imaging characteristics and clinical symptoms related to displaced meniscal flap tears

Magnetic Resonance Imaging of Accelerated Bone Remodeling

A regional acceleration of bone remodeling may possibly follow biomechanical insults to the bone. This review assesses the literature and clinical arguments supporting the hypothetical association between accelerated bone remodeling and bone marrow edema (BME)-like signal intensity on magnetic resonance imaging. BME-like signal is defined as a confluent ill-delimited area of bone marrow with a moderate decrease in signal intensity on fat-sensitive sequences and a high signal intensity on fat-suppressed fluid-sensitive sequences. In addition to this confluent pattern, a linear subcortical pattern and a patchy disseminated pattern have also been recognized on fat-suppressed fluid-sensitive sequences. These particular BME-like patterns may remain occult on T1-weighted spin-echo images. We hypothesize that these BME-like patterns, with particular characteristics in terms of distribution and signal, are associated with accelerated bone remodeling. Limitations in recognizing these BME-like patterns are also discussed.

Hidden Unstable Flap Should Be Suspected in Treating Intractable Pain from Medial Meniscus Horizontal Tear

(1) Background: The medial meniscus horizontal tear (MMHT) is known as a lesion that can be treated nonoperatively. However, some patients show persistent pain despite conservative treatments. In arthroscopic surgery for MMHT, surgeons often encounter unexpected unstable flaps, which can explain the intractable pain. This study aimed to determine whether preoperative factors could predict the hidden unstable flaps in MMHT. (2) Materials and Methods: Medical records of 65 patients who underwent arthroscopic partial meniscectomy (APM) for isolated MMHT during 2016–2020 were retrospectively reviewed. APM was indicated when there was no severe chondral degeneration and intractable localized knee pain in the medial compartment did not resolve despite conservative treatments. Unstable flap was confirmed based on arthroscopic images and operation notes. Each of the following preoperative factors were investigated using logistic regression analyses to determine whether they can predict an unstable flap: age, sex, body mass index, lower limb alignment, trauma history, mechanical symptoms, symptom duration, visual analogue scale (VAS), Lysholm score, cartilage wear of the medial compartment, and subchondral bone marrow lesion (BML). (3) Results: Hidden unstable flaps were noted in 45 (69.2%) patients. Based on univariate analyses for each preoperative factor, age, symptom duration, cartilage wear (of the femoral condyle and the tibial plateau), and subchondral BML were included in the multivariate logistic regression analysis. The results showed that symptom duration (p = 0.026, odds ratio = 0.99) and high-grade cartilage wear of the medial femoral condyle (p = 0.017, odds ratio = 0.06) were negatively associated with unstable flaps. A receiver operating characteristic curve was used to calculate the symptom duration at which the prediction of unstable flaps was maximized, and the cutoff point was 14.0 months. (4) Conclusions: More than two thirds of patients suffering intractable pain from MMHT had hidden unstable flaps. However, APM should not be considered when the symptom duration is more than 14 months or high-grade cartilage wear of the medial femoral condyle is noted.

MRI findings of acute anterior instability of the knee in the absence of recent trauma

BACKGROUND

Anterior knee instability is usually encountered in the context of trauma, with the clinical examination and imaging focusing on anterior cruciate ligament (ACL) disruption. Limited data exist on magnetic resonance imaging (MRI) of acute anterior knee instability in the absence of recent trauma.

PURPOSE

To provide the first comprehensive account of MRI findings in acute anterior knee laxity in the absence of acute trauma and to evaluate predictors of ACL integrity and pain.

MATERIAL AND METHODS

A total of 84 consecutive patients with non-traumatic knee instability were prospectively studied. Instability was assessed with Lachman's, pivot shift, and Lelli's tests. MRI findings were recorded, and ACL integrity was surgically confirmed in all 24 cases of MRI suggesting tear and in 21/60 cases of MRI suggesting no tear. Binary logistic regression models were used to identify predictors of ACL tears and pain, and Mann-Whitney U test served for comparisons between continuous variables. The study was approved by the institutional review board.

RESULTS

Osteoarthritis and notch bony outgrowth (NBO) were present in 44% and 42.9% of all knees, respectively. NBO did not correlate with osteoarthritis (P = 0.606). NBO (odds ratio [OR] = 4.157; P = 0.016) and ACL grafts (OR = 9.277; P = 0.01) predisposed to non-traumatic ACL tears (torn in 28.6% of total cases). Presence of osteoarthritis was predictive of pain (OR = 17.671; P < 0.001).

CONCLUSION

We present a comprehensive analysis of MRI findings in clinically significant non-traumatic anterior instability, showing that NBO and ACL grafts predispose in non-traumatic ACL tears, whereas osteoarthritis is the only predictor of pain.

Illustrative review of knee meniscal tear patterns, repair and replacement options, and imaging evaluation

This review article aims to reinforce anatomical concepts about meniscal tears while linking associated treatment options. The main teaching points start with the basic meniscal anatomy and key differences between the medial and lateral menisci. Subsequently, various meniscal tear patterns along with their associated history and physical exam findings will be discussed with corresponding illustrations and MR images. Additional discussion will involve the different surgical repair techniques (with arthroscopic correlates), their indications with pertinent imaging findings, imaging related to previous meniscal tear repairs, and novel surgical techniques. Lastly, keys to evaluating for retear with an emphasis on MRI arthrogram findings will be reviewed. While each of these topics is not discussed in totality, the key points of the review article will enforce key concepts and help radiologists evaluate the menisci on imaging.

The Meniscal Grammar Signs: Comma and Apostrophe Signs for Characterization of a Displaced Fragment in the Meniscal Recess

Vertical flap tears, or parrot beak flap tears, are oblique tears of the meniscus thought to originate as a central radial tear and propagate longitudinally towards the periphery, generating a partially detached unstable fragment that can subsequently displace into the meniscal recess. Although magnetic resonance imaging (MRI) is frequently used to diagnose and characterize meniscus pathology, imaging findings for displaced flap tears are not well described in the literature. The recently published meniscal comma sign describes inferior displacement of a meniscus flap tear into the meniscotibial recess that, when seen on MRI, resembles a comma. In the present article, we define the meniscal apostrophe sign, characterized by superior displacement of a meniscus flap tear into the meniscofemoral recess found on MRI. Displaced fragments in the meniscal recess are crucial to identify, as they often result in significant pain and mechanical symptoms related to tenting of the deep medial collateral ligament, which responds poorly to nonoperative treatment. Misdiagnosis of these unstable flap tears as degenerative meniscus extrusion or isolated progression of osteoarthritis can lead to a delay in treatment.

Introduction of an MR-based semi-quantitative score for assessing partial meniscectomy and relation to knee joint degenerative disease: data from the Osteoarthritis Initiative

OBJECTIVES

To develop an MR-based semi-quantitative meniscus scoring technique for postoperative assessment of the degree of meniscal resection, to test its reproducibility, and to study the relationship between the amount of resection and degenerative disease burden.

METHODS

We studied the right knee of 135 participants from the Osteoarthritis Initiative that underwent meniscal surgery an average of 14 years previously. The amount of meniscal resection was assessed on baseline 3.0-T MRIs and calculated as meniscus resection score (MenRS) with a range of 0 to 18. Knee abnormalities at baseline and 48 months were graded using a modified Whole-Organ Magnetic Resonance Imaging Score (WORMS). Subjects were also stratified according to meniscal resection performed after injury versus without preceding injury. Statistical analysis included intra-class correlation coefficient (ICC) to determine reproducibility as well as regression models and partial correlations to correlate MenRS with WORMS outcomes.

RESULTS

ICC values for intra- and inter-observer reproducibility of MenRS were 0.980 and 0.977, respectively. Overall, the amount of meniscal resection showed a significant correlation with baseline WORMS grades: higher MenRS was associated with higher total WORMS grades (p = 0.004) and cartilage (p = 0.004) and ligament (p < 0.001) subscores. However, no significant association between MenRS and change in WORMS grades over 48 months was found. The relationship between MenRS and baseline WORMS grades did not change after adjusting for a reported history of knee injury.

CONCLUSIONS

Postoperative assessment of the knee following partial meniscectomy using the newly developed MenRS showed excellent reproducibility and significant cross-sectional correlation with WORMS gradings.

KEY POINTS

• The newly developed semi-quantitative MR-based meniscal resection score demonstrated excellent reproducibility. • A significant correlation between the amount of meniscal resection measured using the newly developed score and the degree of overall knee joint degenerative disease and cartilage defects was found.

Magnetic resonance imaging and clinical features of glenoid labral flap tears

OBJECTIVE

Displaced flaps of glenoid labral tissue are an uncommonly encountered finding on MRI of the shoulder, and are of unclear clinical significance. The purpose of this study is to describe the imaging characteristics of displaced glenoid labral flaps, evaluate for any common concomitant injuries, and identify the typical clinical presentation and management of patients with this lesion.

MATERIALS AND METHODS

This retrospective, observational study was approved by the institutional review board. Nineteen patients with flap-type tears of the labrum on preoperative MRI were identified. Each examination was retrospectively reviewed by two radiologists for size, location, and signal intensity of the displaced flap of tissue, in addition to any co-existing labrum or cartilage pathological conditions and clinical information.

RESULTS

All displaced flaps extended from the inferior margin of the glenoid into the axillary recess. The average size of the visualized flap was 10.9 by 6.0 by 2.6 mm. Seventy percent of the flaps had signal intensity isointense to labrum and hypointense to hyaline cartilage on T2-weighted images. All 19 patients had concomitant labral pathological conditions and 63% had cartilage defects, visualized on MRI. Clinical evidence of shoulder instability was seen in 83% of patients, and 67% were managed surgically.

CONCLUSION

Glenoid labral flap tears have distinct imaging characteristics that may aid in their identification. Their presence should prompt careful evaluation of the glenoid articular cartilage. Recognition of a labral flap tear may have clinical importance, as 83% of patients with this finding demonstrated clinical evidence of shoulder instability, often requiring surgical intervention.

Imaging of Athletic Injuries of Knee Ligaments and Menisci: Sports Imaging Series

Acute knee injuries are a common source of morbidity in athletes and if overlooked may result in chronic functional impairment. Magnetic resonance (MR) imaging of the knee has become the most commonly performed musculoskeletal MR examination and is an indispensable tool in the appropriate management of the injured athlete. Meniscal and ligamentous tearing are the most frequent indications for surgical intervention in sports injuries and an understanding of the anatomy, biomechanics, mechanisms of injury, and patterns of injury are all critical to accurate diagnosis and appropriate management. These will be discussed in reference to meniscal tears and injuries of the cruciate ligaments as well as injuries of the posterolateral and posteromedial corners of the knee. (©) RSNA, 2016.

Arthroscopic Meniscectomy for Medial Meniscus Horizontal Cleavage Tears in Patients under Age 45

Purpose

The purpose of this study was to evaluate the demographics, clinical features, and outcomes of arthroscopic partial meniscectomy (APM) for isolated medial meniscus horizontal cleavage tears (MMHCTs) in patients under 45 years of age.

Materials and Methods

We retrospectively reviewed 98 patients (100 knees) under 45 years who underwent APM for MMHCTs. Clinical outcomes were assessed using International Knee Document Committee (IKDC) subjective core, Tegner activity scale, visual analog scale (VAS) pain score, and a question on the symptom relief.

Results

79% were male and 70% had no trauma. The mean symptom duration was 10 months. At arthroscopy, a flap tear was identified in 75%. At a mean of 19-month follow-up, the IKDC subjective score, Tegner activity scale, and VAS pain score were significantly improved compared to the preoperative values (p=0.025, p=0.043, and p=0.032, respectively). While 85% were free of symptoms, 15% had persistent pain. No significant differences in outcomes were observed based on the tear type and the presence of flap tears. No progression or development of radiographic degenerative changes was observed in all knees.

Conclusions

Demographics of MMHCTs under age 45 showed a male dominance and higher frequency of non-traumatic tears. APM was beneficial to symptomatic HCTs in this cohort during the short-term follow-up. Type of HCTs and combined flap tears did not affect clinical outcomes.