Two positioned MRI can visualize and detect the location of peripheral rim instability with snapping knee in the no-shift-type of complete discoid lateral meniscus

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.

Feasibility and efficacy of ultrasound in the diagnosis of discoid lateral meniscus and its classification in children: protocol for a prospective, multicentre, diagnostic test study

INTRODUCTION

Although ultrasound can reportedly diagnose discoid lateral meniscus (DLM) in children, its widespread application is challenging because the diagnostic criteria are based on qualitative descriptions of DLM morphology rather than quantitative parameters. Additionally, no studies have applied ultrasound in classifying DLM. Therefore, this study aims to establish the quantitative ultrasound parameters that reflect DLM morphology, evaluate the feasibility and validity of these parameters for identifying DLM and their classification, and develop the quantitative ultrasound diagnostic criteria for DLM and their classification in children.

METHODS AND ANALYSIS

Patients will be recruited from the outpatient clinics of the orthopaedics department at West China Hospital, Sichuan University, the Fourth Medical Center of the Chinese People's Liberation Army General Hospital, Xinhua Hospital affiliated with Shanghai Jiao Tong University School of Medicine, Yibin Hospital affiliated with West China Hospital Sichuan University, Suining Central Hospital and the Third Hospital of Mianyang from August 2022 to July 2024. Eligible patients are those aged ≤14 years, with knee symptoms such as pain, locking and limited extension, and who planned to undergo arthroscopic surgery. Exclusion criteria are patients with contraindications to ultrasound examination, such as severe skin damage or fracture around the knee. The sample size is estimated to be 576 cases with a power of 0.9 for hypothesis testing, a two-sided α of 0.05, and an expected sensitivity and specificity of 95%. Three days before surgery, ultrasound will be used to observe the morphology of the lateral meniscus and measure its width, angle α formed by the chord of upper and lower arc-shaped articular surface at the free edge, and the movement distance of the peripheral rim. Participants will be categorised according to the arthroscopy results for the DLM and its classification. The diagnostic performance of each parameter will be assessed and compared in terms of the area under the curve, sensitivity, specificity, and positive and negative predictive values.

ETHICS AND DISSEMINATION

This study was approved by the Ethics Committee of West China Hospital, Sichuan University (approval no. 2022-923), and this approval covers all study hospitals. Written informed consent is required from all participants before enrolment in the study. The study's findings will be disseminated through peer-reviewed publications and conference presentations.

TRIAL REGISTRATION NUMBER

Chinese Clinical Trial Registry (ChiCTR2200062000).

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.

Surgical Management of Discoid Lateral Meniscus With Anterior Peripheral Instability: Retaining an Adequate Residual Meniscus Volume

Discoid lateral meniscus (DLM) presents with differing pathoanatomy and may exhibit various types of tears. The treatment strategy is based on the presence and location of instability as a result of deficient capsular attachment. Recently, meniscal stabilization after saucerization has been recommended for DLM to preserve the meniscus shape, prevent extrusion, and mitigate against the progression of osteoarthritis. In addition to stabilization, the resection volume is important to prevent osteoarthritic changes. Although there was no tear and no displacement of the lateral meniscus on magnetic resonance imaging, some DLMs were found to have tears and peripheral instability during arthroscopy. Therefore, the assessment of peripheral instability during surgery is very important to achieve a desirable clinical outcome. This Technical Note describes an arthroscopic technique for anterior peripheral stabilization of the DLM, in which we highlight the surgical procedure for repair of the anterior horn, reassess the instability around the popliteal hiatus after the anterior horn is repaired, and the stabilization of the posterior horn, if necessary.