Evaluation of knee bone morphology in juvenile patients with complete discoid lateral meniscus using magnetic resonance imaging

The Anteroposterior Diameter of Complete Discoid Lateral Meniscus Versus the Diameter of Normal Lateral Meniscus: An MRI Study in Adults

Background

The abnormal morphology of complete discoid lateral meniscus (CDLM) is associated with a greater propensity for tears. The magnetic resonance imaging (MRI) morphology of CDLM is most often described in the coronal plane, with few morphological studies in the sagittal position.

Hypothesis

The sagittal anteroposterior diameter of CDLM is smaller than that of normal meniscus and is increased after tear in adults.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

The authors searched the radiology records at our institution from June 2018 to December 2023 for patients aged from 18 to 55 years with knee pain. According to inclusion and exclusion criteria, 70 knees (66 patients) with torn CDLM were enrolled as group A, 36 knees (31 patients) with intact CDLM were enrolled as group B, and 48 knees (32 patients) with normal lateral meniscus (LM) were enrolled as group C. The coronal view passing through the middle point of the lateral tibial plateau (LTP) were identified the referrence coronal view, then the sagittal view passing through the middle point of the LTP on the referrence coronal view were selected for the measurements, the anterior distance, posterior distance, and anteroposterior diameter of the LM, sagittal tibial diameter (TD) were measured. The 4 measurements and the ratios were compared among the groups by independent sample t test.

Results

The reliability of all measurements was excellent, except that posterior distance was classified as good in group B. The anteroposterior diameter and TD were smaller in group A than in group C (both P < .001) and smaller in group B than in group C (P < .001 and P = .007). anteroposterior diameter and anteroposterior diameter/TD in group A were larger than in group B (P = .003 and P < .001), while anteroposterior diameter/TD in group A and group C were similar (P > .05). The anterior distance and anterior distance/TD were smaller in group A than in group B (P = .02 and P = .03) and smaller in group A than in group C (P < .001 and P = .008). Posterior distance, posterior distance/anteroposterior diameter, and posterior distance/TD were larger in group A than in group C (P < .001, P < .001, and P < .001) and larger in group B than in group C (P < .001, P < .001, and P < .001).

Conclusion

Our study demonstrates that in adults, the meniscal anteroposterior diameter and the TD are smaller in CDLM than in normal LM, and the anteroposterior diameter of torn CDLM is larger than intact CDLM.

Wrisberg variant of the lateral discoid meniscus in children: review of the literature and presentation of case series

INTRODUCTION

The Wrisberg variant of the discoid lateral meniscus is a very rare disorder and is characterized by the hypermobility and instability of the meniscus caused by the absence of its posterior tibial attachment, with only its meniscofemoral junction (Wrisberg's ligament) maintained, and inserted in the posterior horn of the meniscus. As a result, the posterior horn of the lateral meniscus is mobile; often subluxing into the joint.

MATERIALS AND METHODS

A total of eight skeletally immature patients with symptomatic Wrisberg variant of the discoid lateral meniscus were included in this study. Each knee was evaluated with MRI and arthroscopy. We graded unstable discoid menisci according to their discoid morphology (complete vs. incomplete), meniscal intra-substance degeneration, and the presence or absence of meniscal tears. All eight menisci were evaluated as degenerated with no meniscal tears. Five of them were evaluated as complete. Due to the severely degenerated meniscus, we considered it unnecessary to repair the detached posterior tibial ligament, so we performed a reshaping of the discoid meniscus, restoring a C-shape, excising the hypertrophied central part of the meniscus, and creating a posterior horn with a remaining rim of 6-8 mm. For evaluation of the knee function preoperatively and postoperatively we used the online International Knee Documentation Committee (IKDC) system. The purpose of this study is to emphasize the importance of MRI in identifying and revealing the unstable (Wrisberg variant) type of discoid meniscus in children.

RESULTS

The mean patient age at the time of surgery was 8.25 ± 2.91 years (range 5-13 years). The average follow-up was 3.75 ± 0.46 years (range 3-4) years. The mean preoperative IKDC score was 22.37 ± 1.50 (range 21-25) points. The mean postoperative IKDC score was 80.50 ± 1.77 (range 79-84) points.

CONCLUSIONS

MRI is a valuable tool in the evaluation of the shape, stability, and consistency of symptomatic discoid menisci. It is helpful for the detection of the unstable Wrisberg variant.

Saucerization of complete discoid lateral meniscus is associated with change of morphology of the lateral femoral condyle and tibial plateau

PURPOSE

To determine the effect of saucerization surgery on knee joint morphology associated with a complete discoid lateral meniscus (DLM) using magnetic resonance (MR) imaging.

METHODS

This retrospective study included cases had undergone saucerization surgery for symptomatic DLM between 2007 and 2022. All cases were divided into two by age group: < 12 (U13) and > 13 (O13). The cases in the match group were randomly selected from preoperative cases in the O13 group matched with the age at the final follow-up (F/U) of cases in the U13 group. The following morphological parameters were evaluated using MR images preoperatively and at the final postoperative F/U in each group: anterior obliquity of the lateral tibial plateau (AOLTP), posterior obliquity of the lateral tibial plateau (POLTP), and the lowest point of the lateral femoral condyle (LPLFC). Each parameter was compared between the U13 preoperative (pre-OP) group and the O13 pre-OP group, the preoperative and final follow-up in the U13, and the U13 group at the final F/U and the match group preoperatively.

RESULTS

A total of 77 cases were evaluated. 31 cases were in the U13 pre-OP group and 46 were in the O13 pre-OP group. With a minimal F/U of 2 years, 27 cases in the U13 group and 36 in the O13 group were included. The mean F/U period was 4.6 years in the U13 group and 3.2 years in the O13 group. 32 cases were included in the match group. In the match group, the inclination of the POLTP was significantly larger (P = 0.042) and the LPLFC was more lateral (P = 0.0034) than at the final F/U in the U13 group.

CONCLUSIONS

Saucerization surgery for DLM in juvenile patients can prevent progression to the characteristic bone morphology DLM. These results could help the surgeon making the decision when the surgery would be performed for symptomatic DLM patients.

LEVEL OF EVIDENCE

Retrospective comparative study; level of evidence, 3.

MRI Analysis of Knee Bony Morphology Variations in Children and Adolescents With Lateral Discoid Meniscus Compared With Asymptomatic Healthy Controls

BACKGROUND

Lateral discoid meniscus accounts for most meniscal tears in children 10 years of age and younger. The role of bony morphology in discoid meniscus has been previously studied in a limited capacity using radiographs.

PURPOSE

To use magnetic resonance imaging to measure features of the femoral condyles and tibial plateaus in patients with discoid meniscus to assess potential determinants of symptoms and subsequent surgery and to compare with matched controls to investigate age-related changes in bony features.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

After institutional review board approval, detailed morphology of the femoral condyles and tibial plateau was measured in 177 patients (3-18 years of age; 56% female) with confirmed lateral discoid meniscus. Measurements from 269 participants (3-18 years of age; 55% female) with asymptomatic knees were used as controls. Two-way analysis of variance with Holm-Šídák post hoc was used to compare measurements between discoid menisci and matched controls. Independent t tests were used to compare aspects of bony morphology within the discoid meniscus cohort.

RESULTS

Compared with controls, patients with a lateral discoid meniscus had a larger bicondylar width and notch width (7- to 10-year-old and 15- to 18-year-old age groups; P < .05), larger tibial plateau width (11- to 14-year-old and 15- to 18-year-old age groups; P < .001), and smaller lateral (P < .02) and coronal (P < .02) tibial slopes across all age groups. Among patients with a discoid meniscus, larger bicondylar width, larger tibial plateau width, larger notch width, and a flatter lateral femoral condyle were associated with pain (P < .005) and lateral meniscal tears (P < .02). Larger notch width and notch width index were also associated with subsequent surgery (P < .05).

CONCLUSION

There are clinically significant abnormalities in bony morphology in patients with a discoid meniscus, including larger femoral condyles and tibial plateaus and a flatter tibial plateau. Additionally, femoral size, femoral curvature, and tibial plateau size may influence the likelihood of knee pain, meniscal tear, and need for surgery. These findings highlight the importance of bony morphology in discoid meniscus pathophysiology in children and adolescents. Such measurements may also aid radiographic detection of discoid meniscus and guide decisions regarding the timing of potential surgical intervention.

Evaluation of the knee joint morphology associated with a complete discoid lateral meniscus, as a function of skeletal maturity, using magnetic resonance imaging

INTRODUCTION

A discoid lateral meniscus (DLM) is associated with increased risk for meniscal tears and progression of knee joint osteoarthritis. Our aim was to differentiate knee joint morphology between patients with and without a DLM, as a function of skeletal maturity, using magnetic (MR) imaging.

MATERIALS AND METHODS

This was a retrospective analysis of MR images of the knee for 110 patients, 6-49 years of age. Of these, 62 were in the open physis group (38 with a DLM) and 48 in the closed physis group (23 with a DLM). The following morphological parameters were measured: anterior obliquity of the lateral tibial plateau (AOLTP), posterior obliquity of the lateral tibial plateau (POLTP), the lowest point of the lateral femoral condyle (LPLFC), and the posterior lateral condylar angle (PLCA).

RESULTS

Regardless of skeletal maturity, a DLM was associated with a greater inclination of the POLTP, lateralization of the LPLFC, and smaller PLCA (p < 0.001 for all compared to that of the control group). In the DLM group, the inclination of the AOLTP and the POLTP were significantly smaller (p < 0.001) and the LPLFC was more lateral (p < 0.001) in the closed physis group than in the open physis group. In the control group, the inclination of the POLTP was larger (p < 0.001) and the PLCA smaller (p = 0.019) in the open than in the closed physis group.

CONCLUSIONS

We identified a characteristic knee morphology among patients with a complete DLM using MR imaging, which was observed before physeal closure and persisted after skeletal maturity was attained. We also noted lateralization of the LPLFC in the presence of a DLM, with an increase in lateralization with skeletal maturation.

LEVEL OF EVIDENCE

Case-control study, III.

Arthroscopic surgery for symptomatic discoid lateral meniscus improves meniscal status assessed by magnetic resonance imaging T2 mapping

INTRODUCTION

Discoid lateral meniscus (DLM) is an anatomic knee variant associated with increased tears and degeneration. This study aimed to quantify meniscal status with magnetic resonance imaging (MRI) T2 mapping before and after arthroscopic reshaping surgery for DLM.

MATERIALS AND METHODS

We retrospectively reviewed the records of patients undergoing arthroscopic reshaping surgery for symptomatic DLM with ≥ 2-year follow-up. MRI T2 mapping was performed preoperatively and at 12 and 24 months postoperatively. T2 relaxation times of the anterior and posterior horns of both menisci and of the adjacent cartilage were assessed.

RESULTS

Thirty-six knees from 32 patients were included. The mean age at surgery was 13.7 years (range 7-24), and the mean follow-up duration was 31.0 months. Saucerization alone was performed on five knees and saucerization with repair on 31 knees. Preoperatively, the T2 relaxation time of the anterior horn of the lateral meniscus was significantly longer than that of the medial meniscus (P < 0.01). T2 relaxation time significantly decreased at 12 and 24 months postoperatively (P < 0.01). Assessments of the posterior horn were comparable. The T2 relaxation time was significantly longer in the tear versus non-tear side at each time point (P < 0.01). There were significant correlations between the T2 relaxation time of the meniscus and that of the corresponding area of the lateral femoral condyle cartilage (anterior horn: r = 0.504, P = 0.002; posterior horn: r = 0.365, P = 0.029).

CONCLUSIONS

The T2 relaxation time of symptomatic DLM was significantly longer than that of the medial meniscus preoperatively, and it decreased 24 months after arthroscopic reshaping surgery. The meniscal T2 relaxation time of the tear side was significantly longer than that of the non-tear side. There were significant correlations between the cartilage and meniscal T2 relaxation times at 24 months after surgery.

Evaluation of tibial eminence morphology using magnetic resonance imaging (MRI) in juvenile patients with complete discoid lateral meniscus

Background

Many studies have shown that hypoplasia of knee bone morphology is related to the morphological features of the discoid lateral meniscus (DLM). However, few studies have focused on hypoplasia of tibial eminence morphology in juvenile patients with complete DLM. The purpose of this study was to determine the relationship between tibial eminence morphology characteristics and complete DLM in juvenile patients.

Methods

The DLM group comprised 34 juvenile patients with complete DLM, and the control group comprised 34 juvenile individuals, each with a normal lateral meniscus based on magnetic resonance imaging (MRI) findings. All parameters, including tibial width (TW), tibial eminence width (TEW), the height of the lateral tibial spine (HLTS), the height of the medial tibial spine (HMTS), lateral slope angle of the lateral tibial eminence (LSALTE), lateral slope angle of the medial tibial eminence (LSAMTE), tibial eminence width ratio (TEWR), height of the lateral tibial spine ratio (HLTSR), and the height of the medial tibial spine ratio (HMTSR), were recorded using coronal MR images. Statistical analyses were used to determine the differences between the two groups and whether differences were significant.

Results

The TEW and TEWR were significantly greater (P < 0.05), and LSALTE and LSAMTE were significantly smaller (P < 0.05) in patients in the DLM group than in participants in the control group. Receiver operating characteristic (ROC) analysis revealed that a larger TEW, above 13.4 mm, was associated with complete DLM, with a sensitivity of 77.0% and specificity of 88.2%, and a larger TEWR, above 19.7%, was associated with complete DLM, with a sensitivity of 76.5% and specificity of 91.2%.

Conclusions

MR imaging can be used to diagnose tibial eminence hypoplasia in juvenile patients with complete DLM. Additionally, TEW and TEWR could help clinicians screen for complete DLM in juvenile patients.

Update on imaging of the discoid meniscus

Discoid menisci represent a range of morphological meniscal variants, most commonly involving the lateral meniscus. Clinical presentation ranges from an asymptomatic incidental finding to snapping, pain, swelling and reduced range of knee movement. Symptomatic presentation of discoid menisci is usually due to meniscal tears and instability resulting from abnormal meniscal morphology and ultrastructure, with absent peri-meniscal ligamentous and meniscocapsular attachments characteristic of the Wrisberg sub-type. This article reviews the current classification systems of discoid menisci, gross morphological characteristics of each sub-type and ultrastructure. Clinical presentation, arthroscopic findings and indirect radiological diagnostic criteria are described, as are the MRI findings of normal and pathological discoid menisci. Current concepts of surgical management and outcomes of the discoid meniscus are also briefly discussed.