Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI

Three Morphological Risk Factors for Predicting Isolated Meniscal Bucket-handle Tear

Purpose

The study aimed to investigate whether morphometric variables of the knee can predict isolated meniscal bucket-handle tears and identify the risk factors.

Methods

The study included 146 participants with a mean age of 36.547 ± 12.279 years. They included two groups of 73 patients each: one group with isolated meniscal bucket-handle tears and another with no knee injury (control group). Magnetic resonance imaging findings of the participants were retrospectively assessed. A few morphometric variables associated with distal femur, proximal tibia, and cruciate ligaments were measured.

Results

Cruciate ligament tensity (CLT), medial femoral condylar height (MFCH), and lateral meniscal bone angle (LMBA) were found to be 12.7 ± 0.3, 30.1 ± 2.5 mm, and 21.2° ± 3.4°, respectively, in patients with meniscal bucket-handle tear, compared with 11.9 ± 0.2, 28.3 ± 2.7 mm, and 26.5° ± 3.7° in the control group, respectively. Based on multivariate Firth's logistic regression analysis, CLT (Odds ratio [OR]: 456.533; 95% confidence interval [CI]: 27.582 to > 999.999), MFCH (OR: 1.603; 95% CI: 1.023-2.513), and LMBA (OR: 0.780; 95% CI: 0.624-0.975) could distinguish between meniscal bucket-handle tears and knees without meniscus tears (p < 0.05). Based on the multicategorical multinominal regression model, CLT (OR: > 999.999; 95% CI: 49.937 to > 999.999) and MFCH (OR: 1.903; 95% CI: 1.005-3.606) were the determinant variables in differentiating medial meniscal bucket-handle tears from knees without meniscus tears (p < 0.05).

Conclusion

Large CLT, high medial condyle, and small LMBA were revealed as the morphometric risk factors for meniscal bucket-handle tear.

Attachment Type, Thickness, and Volume of the Posterior Meniscofemoral Ligament and Meniscal Pathology

Several studies have investigated the relationship between the thickness of the posterior meniscofemoral ligament (pMFL) and the presence of a discoid meniscus. We investigated the correlation between meniscal pathology and anatomic features of pMFL such as attachment type, thickness, and volume. We retrospectively evaluated 191 patients who underwent knee MRI. MR images were reviewed to assess the attachment type of the pMFL on the medial femoral condyle (high vs. low), the thickness of the pMFL, and the presence of a meniscal tear or a discoid meniscus. The pMFL volume was quantified by using three-dimensional (3D) segmentation software. The relationship between the frequency of medial or lateral meniscal tear and anatomic features of pMFL were analyzed using Chi-square, Fisher's exact, or Mann-Whitney U test. High type pMFLs had significantly greater thickness and volume than low type pMFLs (p < 0.001). Patients with degenerative lateral meniscal tear had significantly higher thickness and volume of the pMFL than patients with intact lateral meniscus (p < 0.05). The pMFL thickness and volume were not significantly related to traumatic lateral meniscal tear, medial meniscal tear, and discoid meniscus. High type pMFLs tended to be thicker and larger than low type pMFLs and higher thickness and volume of the pMFL was significantly related to the degenerative lateral meniscal tear. However, the attachment type of the pMFL itself was not significantly related to the lateral meniscal tear as well as the medial meniscal tear.

Prevalence, Biomechanics, and Pathologies of the Meniscofemoral Ligaments: A Systematic Review

Purpose

To systematically review the literature to examine current understanding of the meniscofemoral ligaments (MFLs), their function, their importance in clinical management, and known anatomical variants.

Methods

A systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines using PubMed, EMBASE, and Cochrane databases. Studies were included if they reported on the biomechanical, radiographic, or arthroscopic evaluation of human MFLs, or if they reported on an anatomical variant. These were then categorized as cadaveric, radiographic, or clinical. Biomechanical, radiographic, patient-reported, and functional outcomes data were recorded.

Results

Forty-seven studies were included in the qualitative analysis, and 26 of them were included in the quantitative analysis. Of these, there were 15 cadaveric, 3 arthroscopic, and 9 radiographic studies that reported on the prevalence of MFLs. Overall, when looking at all modalities, the presence of either the anterior or posterior MFL (aMFL, pMFL) has been noted to be 70.8%, with it being the aMFL 17.4% and the pMFL 40.6%. The presence of both ligaments occurs in approximately 17.6% of individuals. Eleven reported on mean MFL length and thickness. When evaluating mean length in both men and women, the aMFL has been reported between 21.6 and 28.3 mm and the pMFL length in this population is between 23.4 and 31.2 mm. Five reported on cross-sectional area. Nine additional papers report anatomical variants.

Conclusions

This review shows that there continues to be a variable incidence of MFLs reported in the literature, but our understanding of their function continues to broaden. A growing number of anatomic and biomechanical studies have demonstrated the importance of the MFLs in supporting knee stability. Specifically, the MFLs serve an important role in protecting the lateral meniscus and augmenting the function of the posterior cruciate ligament.

Clinical Relevance

Our findings will aid the clinician in both identifying and treating pathologies of the meniscofemoral ligaments.

Radiological Comparison of Meniscofemoral Ligaments in Patients with Intact and Ruptured Anterior Cruciate Ligament

Background: Evaluating concomitant injury in patients with anterior cruciate ligament (ACL) rupture is important for predicting long-term results. Meniscofemoral ligament (MFL) rupture has been observed in patients with anterior cruciate ligament rupture in arthroscopic evaluation for ruptured ACL. Objectives: The objective of this study was to investigate the concomitant meniscofemoral ligaments injury in patients with anterior cruciate ligament ruptures via magnetic resonance imaging (MRI). Methods: A total of 200 patients (with ruptured ACL, n = 100; with intact ACL, n = 100) were retrospectively evaluated via MRI. In the group with ruptured ACL; the patients who were diagnosed as having noncontact ACL injuries and had undergone primary ACL reconstructions were included. The control group included 100 patients with suspected ACL rupture (from a similar injury mechanism) and whose MRI revealed an intact ACL. In the group with ruptured ACL, the time from injury to MRI was evaluated. A comparison of the presence of anterior MFL (aMFL) and posterior MFL (pMFL) between the two groups was evaluated. Results: In the ACL ruptured group, a significantly lower presence of aMFL or pMFL was observed compared to the control group (P = 0.001). The time from injury to MRI was significantly higher in the patients with absent MFL defined in MRI relative to the other groups (P = 0.001). Conclusions: We observed absence of MFLs (aMFL and pMFL) in a significant majority of patients with ruptured ACLs. Furthermore, we found a significant relationship between the time from injury to MRI and absence of MFL in the ruptured ACL group.

Five Overlooked Injuries on Knee MRI

This article highlights five knee injuries that, in the author's experience, are commonly overlooked by readers inexperienced in knee MRI: ramp lesions, meniscocapsular tears, meniscal root ligament tears, posterior capsular ligament tears, and partial anterior cruciate ligament tear. While these injuries are readily apparent when the images are assessed for the given abnormality, the author's belief is that these may be overlooked because either the injury is not considered, or the affected area is not closely inspected. While these injuries may not alter immediate clinical management or require surgical intervention, they may, nevertheless, result in patient symptoms and may potentially increase the risk of further knee injury. Further, these injuries are difficult to recognize clinically and arthroscopically. In this review, we present these five injuries, emphasising relevant anatomy, normal MRI appearances, common injury patterns, and tips to avoid their being overlooked. Routine review of these areas when interpreting knee MRI, with additional imaging as necessary, will allow these injuries to be recognized more regularly.

The correlation between posterior cruciate ligament buckling sign and meniscofemoral ligaments: A radiological study

Objectives

This study aims to investigate the correlation between posterior cruciate ligament (PCL) buckling phenomena and the presence or absence of the anterior meniscofemoral ligament (aMFL).

Patients and methods

Between January 2012 and January 2019, magnetic resonance imaging of a total of knee joints of 199 patients (163 males, 16 females; mean age: 31.5±5.3 years; range, 18 to 40 years) were reviewed retrospectively. The patients were divided into four groups. The first group included 32 patients with a ruptured anterior cruciate ligament (ACL) and absent aMFL. The second group included 67 patients with a ruptured ACL and apparent aMFL. The third group included 23 patients with an intact ACL and absent aMFL, and the fourth group included 77 patients with an intact ACL and apparent aMFL. The PCL angle was used to measure the buckling degree of the ligament, as calculated as the angle between two lines drawn through the tibial and femoral central portions of the PCL insertions. We assessed the buckling phenomena of the PCL in ACL-ruptured and ACL-intact knees and examined a possible correlation between the PCL buckling angle and the presence or absence of the aMFL of Humphrey.

Results

In the ruptured ACL groups (Groups 1 and 2), the mean PCL buckling angle values were 133.88±6.32 and 104.83±7.34 degrees, respectively. A significant difference was detected between both groups (p=0.026). In the intact ACL groups (Groups 3 and 4), the mean PCL buckling angle values were 143.47±5.96 and 116.77±8.38 degrees, respectively. A significant difference was detected between both groups (p=0.039). No statistically significant difference was observed between Groups 1 and 3 (p=0.13) and between Groups 2 and 4 (p=0.088).

Conclusion

The PCL buckling sign is not specific for ACL ruptures, and can be seen frequently in normal knee joints which it is strongly associated with the presence of aMFL of Humphrey.

Posterior cruciate ligament: Anatomy, femoral insertion and relationships with the anterior menisco-femoral ligament in 23 cadaver knees

BACKGROUND

Abundant anatomic descriptions exist of the posterior cruciate ligament (PCL) and menisco-femoral ligaments (MFLs). There is broad agreement that the PCL is composed of two bundles and inserts on the femur near the distal cartilage. However, a different configuration with a single bundle and a complex femoral insertion has been reported. The main objective of our cadaver study was to determine the number of anatomical bundles forming the PCL. We also described the insertion of the PCL and its relationships with the anterior menisco-femoral ligament (AMFL).

HYPOTHESIS

The PCL consists of a single ribbon-like bundle and inserts on the femur separately from the AMFL.

MATERIAL AND METHODS

We used 23 knees of fresh unembalmed cadavers, which we dissected under a microsurgery loupe. Inclusion criteria for the knees were freedom from trauma and scars. No age limits were set. The features of the PCL were studied using the clock method. Measurements were taken using callipers with a precision of 0.01mm.

RESULTS

No knees were excluded from the final analysis. Macroscopically, the PCL appeared as a single bundle forming a slender flat ribbon. With the knee flexed at 90°, the ligament footprint extended from 58min to 25min on the right and from 48min to 2min on the left. The femoral insertion of the AMFL started 2.07mm from the distal cartilage and masked the distal insertion of the PCL. After removal of the AMFL, the middle of the femoral insertion of the PCL started on average 5.99mm from the distal cartilaginous rim when the knee was flexed at 90°.

DISCUSSION

Our study confirms descriptions of the PCL as a single bundle shaped as a flat ribbon. The presence of the AMFL gives the appearance of a double bundle and partially masks the femoral insertion of the PCL, which is located further back relative to the distal joint cartilage.

LEVEL OF EVIDENCE IV

Experimental cadaver study.

Clinical Anatomy of the Anterior Meniscofemoral Ligament of Humphrey: An Original MRI Study, Meta-analysis, and Systematic Review

Background:

The anterior meniscofemoral ligament (aMFL) of Humphrey is an anatomically variable fibrous band of connective tissue that attaches between the lateral aspect of the medial femoral condyle and posterior horn of the lateral meniscus, running posterior to the anterior cruciate ligament and anterior to the posterior cruciate ligament (PCL). The presence of an intact aMFL may contribute to stabilization of the lateral compartment of the knee joint.

Purpose:

The original magnetic resonance imaging (MRI) arm of this study aimed to assess the aMFL incidence among Polish patients. The goal of the systematic review and meta-analysis was to review the literature discussing the clinical anatomy of the aMFL and provide data on its prevalence. It was hypothesized that significant heterogeneity exists within the published literature.

Study Design:

Cross-sectional study and systematic review; Level of evidence, 3.

Methods:

A retrospective investigation was performed on the MRI scans of 100 knees (52 right, 48 left) of Polish patients. Scans were randomly selected from a database of MRI examinations performed in 2019. For the meta-analysis, major online databases were queried for data on the aMFL, and 2 authors independently assessed and extracted data from all included studies. A quality assessment of the included articles was performed using the Anatomical Quality Assessment tool.

Results:

In the MRI arm of this study, the aMFL was found in 62 of the 100 lower limbs. The meta-analysis included 41 studies with a total of 4220 limbs. The aMFL was present in 55.5% (95% CI, 45.5%-65.3%) of cases. Arthroscopic studies yielded the highest prevalence (82.3% [95% CI, 36.6%-100.0%]); of MRI studies, the highest prevalence was at 3.0-T strength (51.0% [95% CI, 13.3%-88.2%]).

Conclusion:

Significant variability in the prevalence of the aMFL was found in the literature. More emphasis should be placed on the clinical relevance of injuries to the aMFL because of its significant role in the function of the knee. It is important to be aware that, because of the anatomy of the aMFL, the ligament can also function to support a torn PCL.

Clinical Anatomy of the Posterior Meniscofemoral Ligament of Wrisberg: An Original MRI Study, Meta-analysis, and Systematic Review

Background

The posterior meniscofemoral ligament (pMFL) of Wrisberg attaches to the posterior horn of the lateral meniscus and the lateral intercondylar aspect of the medial femoral condyle and passes posteriorly to the posterior cruciate ligament (PCL). The pMFL plays a role in recovery after PCL injuries and offers stability to the lateral meniscus, promoting normal knee function.

Purpose/Hypothesis

The aim of the magnetic resonance imaging (MRI) arm of this study was to evaluate the prevalence of the pMFL in Polish patients. The purpose of the systematic review and meta-analysis was to evaluate the clinical relevance of the pMFL in knee surgery. It was hypothesized that extensive variability exists in reports on the prevalence, function, and clinical significance of the pMFL.

Study Design

Cross-sectional study and systematic review; Level of evidence, 3.

Methods

A retrospective MRI investigation was conducted on 100 randomly selected lower limbs of Polish patients (56 male, 44 female) performed in 2019 to determine the prevalence of the pMFL. Additionally, an extensive literature search of major online databases was performed to evaluate all reported data on the pMFL. Assessments of article eligibility and data extraction were completed independently by 2 reviewers, and all disagreements were resolved via a consensus. A quality assessment of the included articles was performed using the Anatomical Quality Assessment tool.

Results

In the MRI arm of this study, the pMFL was observed in 73 of the 100 limbs. In the meta-analysis, 47 studies were included, totaling 4940 lower limbs. The pooled prevalence of the pMFL was found to be 70.4% (95% CI, 63.4%-76.9%); the mean length was 27.7 mm (95% CI, 24.8-30.5 mm) and the mean widths were 4.5, 6.1, and 4.1 mm for the meniscal and femoral attachments and midportion, respectively. The mean pMFL thickness was 2.3 mm (95% CI, 1.8-2.7 mm).

Conclusion

Despite the variability in the literature, the pMFL was found to be a prevalent and large anatomic structure in the knee joint. The shared features of this ligament with the PCL necessitate the consideration of its value in planning and performing arthroscopic procedures of the knee.

Magnetic resonance imaging of the meniscal roots

The meniscal roots and supporting structures anchor the menisci to the tibial plateau and resist hoop stress, thereby preventing radial displacement of the menisci and secondary degenerative tibiofemoral compartment changes that may occur if this is compromised. The anatomy of the four meniscal roots and their supporting structures on magnetic resonance imaging (MRI) will be outlined in this review article, as well as the imaging appearances of meniscal root-related pathology, namely meniscal root degeneration and tears, meniscal extrusion and tibial plateau cystic lesions.

Lateral Meniscus Posterior Root Lesion Influences Anterior Tibial Subluxation of the Lateral Compartment in Extension After Anterior Cruciate Ligament Injury

BACKGROUND

The lateral meniscus posterior root (LMPR) lesion further decreases dynamic knee stability after anterior cruciate ligament (ACL) injury owing to the loss of the "wedge effect" maintained by the posterior horn of the lateral meniscus. However, the effect of LMPR lesions on the static tibiofemoral relationship in extension after ACL injuries is not determined.

PURPOSE

To (1) determine the effect of LMPR lesions on anterior tibial subluxation of the lateral compartment (ATSLC) in extension in patients with ACL injuries and to (2) identify the LMPR-related factors associated with excessive ATSLC in extension.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Between January 2015 and December 2017, 405 consecutive patients with diagnosed ACL injuries who underwent primary ACL reconstructions were retrospectively reviewed. Among them, 45 patients with combined ACL injuries and LMPR lesions (ACL+LMPR group) and 51 patients with isolated ACL injuries (ACL group) were identified. Values of ATSLC in extension were measured on preoperative supine magnetic resonance imaging and classified into high grade (≥6 mm) and low grade (<6 mm). The mean ATSLC in extension and the proportion of patients with high-grade ATSLC in extension were compared between the groups by univariate analysis. In the ACL+LMPR group, predictors of high-grade ATSLC in extension-including age, sex, body mass index, affected side, cause of injury, period from injury (<12 or ≥12 weeks), LMPR lesion pattern (radial tear or root avulsion), and meniscofemoral ligament integrity (intact or impaired)-were assessed by univariate analysis and multivariate logistic regression analysis.

RESULTS

The mean ATSLC in extension in the ACL+LMPR group was significantly greater than that in the ACL group (5.6 mm vs 3.1 mm; P = .001). The proportion of patients with high-grade ATSLC in extension in the ACL+LMPR group was also significantly larger than that in the ACL group (44.4% vs 15.7%; P = .002). In addition, the root avulsion (instead of radial tear) (odds ratio, 28.750; 95% CI, 2.344-352.549; P = .009) and the period from injury ≥12 weeks (odds ratio, 17.095; 95% CI, 1.207-242.101; P = .036) were determined to be the 2 independent predictors of high-grade ATSLC in extension. However, age, sex, body mass index, affected side, cause of injury, and meniscofemoral ligament integrity were not.

CONCLUSION

After ACL injuries, concomitant LMPR lesion further increased ATSLC in extension. Chronic LMPR avulsion was associated with high-grade ATSLC in extension.