Arthroscopic treatment of symptomatic discoid meniscus in children: classification, technique, and results

Dynamic Magnetic Resonance Imaging Protocol: An Effective and Useful Tool to Assess Discoid Lateral Meniscus Instability in Children

OBJECTIVES

One of the most common symptoms in cases of discoid lateral meniscus (DLM) in children is a "snapping" knee. The clock in extension, followed by a pop in flexion, perceived by the clinician, reflects the meniscal displacement caused by the peripheral meniscocapsular detachment. Standard magnetic resonance imaging (MRI) results in a 40% false-negative rate for detecting this instability. The hypothesis was that a dynamic MRI protocol could reduce the false negative rate and improve the efficiency of the MRI in detecting the direction of instability.

METHODS

Eight DLM knees (8 patients) with snapping knees (grade 2 of Lyon's classification) were included in this monocentric prospective preliminary study in a referral center of pediatric orthopaedic surgery. Every patient underwent a dynamic MRI protocol with both T2-Fat-Sat sagittal and coronal slices, performed "after the clock" and again "after the pop" in a knee with standard 20 degrees of flexion during acquisition. All the MRI data were correlated with an arthroscopic description of the peripheral tear of the DLM according to Ahn's classification to assess for diagnostic accuracy.

RESULTS

The standard MRI protocol resulted in a false-negative rate of 50% for detecting the direction of instability. The dynamic MRI protocol allowed the identification of, and classification of the meniscal instability, meniscal shift, and meniscocapsular tear in 8 of 8 patients (0% false-negative rate), perfectly correlated with arthroscopic findings.

CONCLUSION

This preliminary series, although short, allowed us to understand all the types of movements and lesions associated with the child's discoid meniscus. The detailed case analysis showed a strong benefit of such a protocol for planning the surgical suture procedure. The functionality and reliability of the dynamic MRI protocol is a good and method relatively simple method which does not require specific equipment, minimizing any additional cost compared with standard MRI.

LEVEL OF EVIDENCE

Level IV.

Absorbable Sutures Repair Without Meniscopexy, Results in Superior Outcomes for Discoid Lateral Meniscus With Meniscocapsular Anterior Detachment in Children

BACKGROUND

Despite the fact that meniscocapsular anterior detachment is the most common location of instability in children with a Discoid Lateral Meniscus (DLM), there is a lack of consensus about the type of repair that should be utilized for stabilization. The aim of this study was to determine the best fixation method for anterior detachment of DLM in children. Our hypothesis was that excessive rigidity with fixation would restrict meniscal mobility and increase the rate of failure or prevent full knee flexion.

METHODS

This study was a retrospective single-center study consisting of 51 consecutive knees (45 children) with menico-capsular anterior detachment that underwent stabilization and minimal saucerization of the meniscus between 2007 and 2018. We aimed to compare the need for revision surgery and knee flexion between the different types of fixations utilized; namely we compared meniscopexy using anchors on the tibia (n=30) with outside-in arthroscopic soft tissue fixation (n=21), and absorbable (n=18) and nonabsorbable sutures (n=33) were compared.

RESULTS

The mean age at surgery was 10.4 years (3 to 17) with a mean follow-up of 52 months (18 to 148). The group of knees treated with absorbable sutures had a significantly better rate of full knee flexion (15/18) compared with the nonabsorbable group (17/33) ( P =0.03). Despite the absence of significance ( P =007), there was a lower rate of revision surgery due to suture failure in the soft tissue fixation group (0 revision operations) compared with the meniscopexy group (5 revision operations).

CONCLUSIONS

For anterior meniscocapsular detachment of DLM, it is recommended to perform soft tissue fixation with absorbable sutures, as this technique resulted in better knee flexion and a lower rate of revision surgery when compared with meniscopexy and nonabsorbable suture fixation.

LEVEL OF EVIDENCE

Level III-retrospective case studies.

Age and medial compartmental OA were important predictors of the lateral compartmental OA in the discoid lateral meniscus: Analysis using machine learning approach

PURPOSE

The objective of this study was to develop a machine learning model that would predict lateral compartment osteoarthritis (OA) in the discoid lateral meniscus (DLM), from which to then identify factors contributing to lateral compartment OA, with a key focus on the patient's age.

METHODS

Data were collected from 611 patients with symptomatic DLM diagnosed using magnetic resonance imaging between April 2003 and May 2022. Twenty features, including demographic, clinical and radiological data and six algorithms were used to develop the predictive machine learning models. Shapley additive explanation (SHAP) analysis was performed on the best model, in addition to subgroup analyses according to age.

RESULTS

Extreme gradient boosting classifier was identified as the best prediction model, with an area under the receiver operating characteristic curve (AUROC) of 0.968, the highest among all the models, regardless of age (AUROC of 0.977 in young age and AUROC of 0.937 in old age). In the SHAP analysis, the most predictive feature was age, followed by the presence of medial compartment OA. In the subgroup analysis, the most predictive feature was age in young age, whereas the most predictive feature was the presence of medial compartment OA in old age.

CONCLUSION

The machine learning model developed in this study showed a high predictive performance with regard to predicting lateral compartment OA of the DLM. Age was identified as the most important factor, followed by medial compartment OA. In subgroup analysis, medial compartmental OA was found to be the most important factor in the older age group, whereas age remained the most important factor in the younger age group. These findings provide insights that may prove useful for the establishment of strategies for the treatment of patients with symptomatic DLM.

LEVEL OF EVIDENCE

Level III.

Magnetic Resonance Imaging Indirect Signs for Anterior Instability of the Lateral Meniscus in Pediatric and Adolescent Patients

BACKGROUND

Anterior instability (AI) of the LM is potentially debilitating in young patients. The use of magnetic resonance imaging (MRI) to diagnose AI is limited due to the lack of reliable and accurate MRI findings. The ability to identify AI preoperatively would potentially improve the diagnosis and treatment of this pathology. This study presents a novel MRI finding ("phantom sign") for the detection of AI of the LM and demonstrates its reliability and accuracy.

METHODS

Three independent blinded reviewers performed retrospective review of preoperative MRI for all patients who underwent LM repair between July 1, 2019, and March 31, 2022, at a single center. Positive phantom sign was defined as abnormal signal intensity on MRI of the anterior horn of the LM on the coronal sequence at the anterior tibial insertion of the anterior cruciate ligament (ACL). Preoperative MRI was also evaluated for other signs of LM anterior instability. Intrarater and inter-rater reliability was assessed for rater scoring of presence of pathology on MRI. Predictive ability of each imaging finding with at least good (ICC 0.6 or above) reliability was also evaluated based on documented intraoperative findings.

RESULTS

Fifty-five preoperative MRIs of arthroscopically treated LM tears were reviewed. Median age was 15 years (range 6 to 20), and 21 patients (38.2%) were female. Twenty-seven patients (49.1%) had a discoid meniscus. LM AI was present on arthroscopy for 25 knees (45.45%), and among these, 21 had discoid morphology. Interrater reliability was substantial for phantom sign (ICC 0.71, 97.5% CI: 0.55-0.82), posterior displacement (ICC 0.71, 97.5% CI: 0.55-0.82), and posterior "megahorn" (ICC 0.76, 97.5% CI: 0.62-0.85). On predictive analysis, phantom signs were 98% sensitive and 76.7% specific for LM AI. Posterior displacement and posterior megahorn were specific for AI (both 93.34%), though with limited sensitivity (32% and 28.6%, respectively).

CONCLUSIONS

Phantom sign is a reliable and sensitive MRI finding for anterior instability, even in the absence of frank displacement on preoperative MRI. A positive finding should prompt a thorough arthroscopic evaluation of the anterior horn of the LM.

LEVEL OF EVIDENCE

Level III-case control study.

Patient-Reported Outcomes After Surgically Treated Anterior Horn Tears in the Pediatric Discoid Meniscus

Background

As a subset of symptomatic discoid lateral meniscal (DLM) tears, anterior horn (AH) meniscal tears are not well studied in the pediatric population. There are even fewer studies reporting patient-reported outcomes after surgical treatment of AH tears in DLM.

Purpose

To compare reported outcomes after surgical treatment of DLM tears involving the AH versus other locations in pediatric patients.

Study Design

Cohort study; Level of evidence, 3.

Methods

A retrospective review of prospectively collected patient data between 2013 and 2020 was conducted. Patients aged <18 years who underwent arthroscopic treatment of a symptomatic DLM were included. Pathology was classified as tears of the AH or tears not involving the anterior horn (NAH). Demographic data along with patient-reported outcome scores (Pediatric International Knee Documentation Committee [Pedi-IKDC] and Patient Assessment Questionnaire [PAQ]) were collected preoperatively through 24 months of follow-up.

Results

A total of 41 patients were included (median age, 12.9 years; range, 7-17 years; 32% female, 68% male). The mean follow-up time for was 25 months (range, 8-58 months). There were 17 (41%) patients in the AH group and 24 (59%) patients in the NAH group. Of the AH group, 16 (94%) were treated with meniscal repair (vs menisectomy), while 19 (79%) of the NAH group were treated with meniscal repair. All patients achieved significant pre- to postoperative improvement on both the Pedi-IKDC and the PAQ. At 24-month follow-up, there were no differences between the AH and NAH groups on the Pedi-IKDC (92.51 vs 89.72; P = .18) or the PAQ (2.57 vs 2.61; P = .06).

Conclusion

Patients who underwent meniscal repair for AH DLM reported positive postoperative outcomes.

Knee extension deficit during gait and knee extensor weakness persisting after saucerization and repair of discoid lateral meniscus tears

BACKGROUND

Physical function and knee kinematics recovery after discoid lateral meniscus (DLM) tear surgery are essential for a better prognosis. However, these alterations remain unclear. Therefore, this study aimed to investigate changes in physical function and knee kinematics following saucerization and DLM tear repair.

METHODS

We enrolled 16 patients who underwent saucerization and DLM tear repair. Postoperative changes in knee kinematics during gait, and physical function, were evaluated at 3, 6, and 12 months.

RESULTS

The peak flexion angle of the operated limb during weight acceptance was significantly higher than that of the contralateral limb at 3 (operated limb: 34.6 ± 8.9°, contralateral limb: 23.7 ± 8.3°; P < 0.01) and 6 months (operated limb: 32.1 ± 9.7°, contralateral limb: 24.6 ± 8.2°; P = 0.03) postoperatively, but not at 12 months (operated limb: 27.1 ± 7.1°, contralateral limb: 23.1 ± 9.5°; P = 0.22) postoperatively. The knee extensor strength of the operated limb was significantly lower than that of the contralateral limb at 3 (operated limb: 1.00 ± 0.59 Nm/kg, contralateral limb: 1.37 ± 0.59 Nm/kg; P = 0.01), 6 (operated limb: 1.22 ± 0.55 Nm/kg, contralateral limb: 1.48 ± 0.60 Nm/kg; P < 0.01), and 12 months (operated limb: 1.39 ± 0.57 Nm/kg, contralateral limb: 1.55 ± 0.64 Nm/kg; P = 0.04) postoperatively.

CONCLUSION

Knee extension deficits and extensor weakness persisted at 6 months after saucerization and repair of DLM tears. Postoperative rehabilitation should be focused on knee extension function.

Age-based comparison of meniscal dimensions between an asymptomatic complete discoid lateral meniscus and normal meniscus: MRI evaluation

INTRODUCTION

This study aimed to evaluate the meniscal size of asymptomatic discoid lateral meniscus (DLM) and compare it with that of normal lateral meniscus (LM) and to compare changes in meniscal dimensions with age among patients with asymptomatic DLM and those with normal LM using magnetic resonance imaging (MRI).

MATERIALS AND METHODS

We retrospectively reviewed the medical records, including MRI data, of patients with asymptomatic DLM (DLM group) or normal LM (control group). Width and extrusion of both DLM and normal LM and tibial length were measured and compared using mid-coronal and mid-sagittal MR images. Meniscal size and sagittal and coronal meniscal ratio according to age, as well as differences between DLM and normal menisci, were also evaluated.

RESULTS

Thirty-four knees were included in the DLM group, whereas the control group comprised of 50 patients. The DLM group showed significantly less meniscal extrusion, greater coronal width, posterior capsule distance, sagittal meniscal length, and sagittal meniscal ratio than the control group (DLM: 0.1 ± 0.3 mm, 23.3 ± 2.2 mm, 5.4 ± 2.4 mm, 25.1 ± 2.8 mm, 61 ± 6%, and control: 0.4 ± 0.4 mm, 9.5 ± 2.3 mm, 2.5 ± 1.2 mm, 30.2 ± 2.6 mm, 71 ± 4%, respectively). The coronal meniscal ratio decreased with age in both the control (p = 0.001) and DLM (p = 0.037) groups. The sagittal meniscal ratio (p = 0.001) and minimum height (p = 0.04) decreased and the anterior capsule distance (p = 0.035), posterior capsule distance (p = 0.026), and entire sagittal length (p = 0.005) increased with age in the DLM group, while the distance between the meniscal inner margins (p = 0.019) increased with age in the control group.

CONCLUSIONS

The meniscal ratio in the sagittal plane of the DLM group was significantly lower than that of the control group. The sagittal meniscal ratio of asymptomatic DLM decreased with age, indicating that the size of asymptomatic DLM does not change with age.

LEVEL OF EVIDENCE

III: Retrospective comparative study.

Relationship Between Age and Pathology With Treatment of Pediatric and Adolescent Discoid Lateral Meniscus: A Report From the SCORE Multicenter Database

BACKGROUND

Surgical treatment options of discoid lateral meniscus in pediatric patients consist of saucerization with or without meniscal repair, meniscocapular stabilization, and, less often, subtotal meniscectomy.

PURPOSE

To describe a large, prospectively collected multicenter cohort of discoid menisci undergoing surgical intervention, and further investigate corresponding treatment of discoid menisci.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A multicenter quality improvement registry (16 institutions, 26 surgeons), Sports Cohort Outcomes Registry, was queried. Patient characteristics, discoid type, presence and type of intrasubstance meniscal tear, peripheral rim instability, repair technique, and partial meniscectomy/debridement beyond saucerization were reviewed. Discoid meniscus characteristics were compared between age groups (<14 and >14 years old), based on receiver operating characteristic curve, and discoid morphology (complete and incomplete).

RESULTS

In total, 274 patients were identified (mean age, 12.4 years; range, 3-18 years), of whom 55.6% had complete discoid. Meniscal repairs were performed in 55.1% of patients. Overall, 48.5% of patients had rim instability and 36.8% had >1 location of peripheral rim instability. Of the patients, 21.5% underwent meniscal debridement beyond saucerization, with 8.4% undergoing a subtotal meniscectomy. Patients <14 years of age were more likely to have a complete discoid meniscus (P < .001), peripheral rim instability (P = .005), and longitudinal tears (P = .015) and require a meniscal repair (P < .001). Patients ≥14 years of age were more likely to have a radial/oblique tear (P = .015) and require additional debridement beyond the physiologic rim (P = .003). Overall, 70% of patients <14 years of age were found to have a complete discoid meniscus necessitating saucerization, and >50% in this young age group required peripheral stabilization/repair.

CONCLUSION

To preserve physiological "normal" meniscus, a repair may be indicated in >50% of patients <14 years of age but occurred in <50% of those >14 years. Additional resection beyond the physiological rim may be needed in 15% of younger patients and 30% of those aged >14 years.

Discoid lateral meniscus instability in children: part I. A new grading system of instability to clarify natural history

OBJECTIVE

In young patients, the discoid lateral meniscus (DLM) usually becomes symptomatic at the time of peripheral rim instability of a complete discoid form. However, little is known about the natural history of meniscal instability. The aim was to detect hidden forms of presentation of instability using the history and clinical mechanical symptoms of instability.

METHODS

Retrospective study of 114 paediatric knees treated for DLM. A new clinical grading system for instability (stable, locked, snapping, blocked and unblocked knees) was defined and studied in combination with MRI and arthroscopic findings.

RESULTS

One hundred seven DLMs (94%) showed instability due to edge detachment. Fifteen (13%) knees were stable (grade 0), 2 (2%) were grade 1, 57 (50%) were grade 2, 35 (31%) were grade 3 and 5 (4%) were grade 4. The cause of grade 3 was an extension deficit (26/35) or flexion deficit (9/35). Grade 1 or 2 correlated with limited detachment, unlike grade 3 or 4. The grade of instability never decreased, but rather increased in many knees during the natural history of DLM.

CONCLUSION

A new presentation of DLM is presented: episodic locking phenomenon and blocked knee with flexion deficit. Clinicians should be wary of pseudo-improvement with the recovery of mobility after a period of the blocked knee, which may be due to a progression towards the ultimate degree of instability. Clinical grading of instability has clarified the natural history of DLM-associated tearing.

LEVEL OF EVIDENCE

III.

Discoid lateral meniscus instability in children: part II.: Repair first to minimise the saucerisation

PURPOSE

Despite an improved understanding of discoid lateral meniscus (DLM), the treatment of symptomatic discoid lateral meniscus remains controversial.

METHODS

The aim of this retrospective, single-centred, consecutive-case study was to evaluate the clinical outcome of 60 DLM treated arthroscopically by the "meniscoplasty or saucerisation-suture" technique in children and adolescents [median (range) age 11 (4-17) years], and to investigate surgical failures. The instability was assessed before any saucerisation. The hypotheses were that: (i) the management of instability with suture first was effective and that (ii) a combined classification with clinical and MRI data had a prognostic value.

RESULTS

In 57 knees (95%), the DLM was unstable, and a suture fixation was performed. After a median follow-up of 41.5 months, the median (range) IKDC score was improved from 55 (10-70) preoperatively to 90 (37.5-100) postoperatively. The median (range) Lysholm score at last follow-up was 93.5 (45-100). The procedure was effective in 49 knees (81.6%) after a single procedure. Eleven patients had a failure with a new meniscal tear after a median (range) delay of 42 months (24-60) after the initial procedure. The patterns of discoid lateral meniscus instability were not found to have a prognostic value for surgical failure since they mainly occurred after sport-related injuries. All the patients with initial repair failures but one achieved a good clinical outcome after revision repair without any further meniscectomy.

CONCLUSION

In contrast to adult knees, symptomatic discoid lateral meniscus is rarely stable in children (5%). Meniscal repair is effective to preserve the meniscus tissue, but revision repair became necessary in 18% of the cases and was finally successful. Level of evidence Level III.

Meniscal rim instability has a high prevalence and a variable location

INTRODUCTION

Most classification systems for lateral discoid meniscus do not evaluate instability of the meniscal peripheral rim. Considerable variability in the prevalence of peripheral rim instability has been published, and it appears that instability is underestimated. The purpose of this study was: first, to evaluate the prevalence of peripheral rim instability and its location in the symptomatic lateral discoid meniscus, and second, to investigate if patient age or type of discoid meniscus are possible risk factors for instability.

METHODS

A cohort of 78 knees that underwent operative treatment due to symptomatic discoid lateral meniscus was analyzed retrospectively for the rate and location of peripheral rim instability.

RESULTS

Out of the 78 knees, 57.7% (45) had a complete and 42.3% (33) had an incomplete lateral meniscus. The prevalence of peripheral rim instability in symptomatic lateral discoid menisci was 51.3%, and with 32.5%, the anterior attachment was most commonly affected, followed by the posterior (30%) and central (10%) attachment. 27.5% of the tested menisci were unstable anteriorly and posteriorly. There was no significant difference in the prevalence of rim instability between the type of discoid menisci (complete vs. incomplete), nor was there a significant correlation for age as a risk factor for instability.

CONCLUSION

The discoid lateral meniscus has a high prevalence and variable location of peripheral rim instability. Meniscal rim stability must be tested and addressed cautiously in all parts and in all types of discoid lateral menisci during operative treatment.

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).

Efficacy of short-term splint immobilization in the treatment of pediatric discoid lateral meniscus after saucerization management

There are no universal guidelines for rehabilitation after saucerization for children with discoid lateral meniscus. This study determined if short-term knee splint immobilization and delayed rehabilitation produces the same benefit as early rehabilitation after saucerization in children, in terms of knee function and pain intensity. A retrospective review was performed by categorizing patients into 2 groups depending on whether a splint immobilization was adopted postoperatively: for group A, rehabilitation began early without splint immobilization after surgery, and for group B, a knee splint was immobilized for 2 weeks. Numerical rating scale scores were collected in patients 1, 3, and 7 days, Lysholm scores were measured at 4 and 8 weeks postoperatively, and the gradual return to normal activities was documented. Forty-eight patients and 53 knees were included: group A had 30 patients with 31 knees, and group B had 18 patients with 22 knees. There was no improvement in numerical rating scale scores on the 1st (P=.519), 3rd (P=.421), and 7th (P=.295) postoperative days in group B. The Lysholm scores of group A (62.94 ± 8.68) was higher than that of group B (46.68 ± 9.82) measured 4 weeks following surgery, but there was no difference at 8 weeks (P=.237), and both groups had similar time to return to normal activities (P=.363). For discoid lateral meniscus patients who underwent isolated saucerization, short-term splint immobilization did not significantly help relieve postoperative pain. There was a comparable time-course for return to normal activities in both study groups.

Effect of the volume of resected discoid lateral meniscus on the contact stress of the tibiofemoral joint: A finite element analysis

BACKGROUND

Partial meniscectomy is commonly performed for symptomatic patients with discoid lateral meniscus (DLM) if conservative treatment fails. However, the development of knee osteoarthritis and osteochondral lesion are detrimental postoperative complications. This study aimed to evaluate the effect of the volume of resected DLM on the contact stress of the tibiofemoral joint using a finite element analysis.

METHODS

Subject-specific finite-element models of the knee joint of a patient with DLM were developed from computed tomographic and magnetic resonance images. To evaluate the effect of partial meniscectomy on the contact stress in the lateral tibiofemoral joint, six knee models were created in the study (the native DLM, and five partially meniscectomized DLMs (according to the preserved width of the meniscus: 12 mm, 10 mm, 8 mm, 6 mm, and 4 mm)).

RESULTS

As the volume of resected DLM increased, higher contact stress was applied to the lateral tibiofemoral joint. Greater contact stress was applied to the preserved lateral meniscus than to the native DLM.

CONCLUSIONS

From a biomechanical viewpoint, the native DLM was the most protective against lateral tibiofemoral contact stress in comparison to partially meniscectomized DLMs.

Medial Discoid Meniscus in Children: A Multicenter Case Series of Clinical Features and Operative Results

BACKGROUND

The discoid medial meniscus is a rare congenital anomaly of the knee. The literature is limited to small case series.

PURPOSE/HYPOTHESIS

Our purpose is to report the clinical manifestations and operative treatments of discoid medial menisci in children from multiple centers in North America. We hypothesized that symptoms and signs, arthroscopic findings, surgical treatments, and outcomes are similar to those for symptomatic discoid lateral menisci.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A retrospective review identified patients with a diagnosed discoid medial meniscus confirmed at surgery across 8 children's hospitals between January 2000 and June 2021. The literature on discoid lateral menisci was reviewed and summarized for comparison.

RESULTS

A total of 21 patients (9 female, 12 male) with 22 discoid medial menisci were identified. The mean ± SD age at the time of diagnosis was 12.8 ± 3.8 years. The most common symptoms and signs were locking and/or clunking, present in 12 of 22 knees (55%), similar to that reported in patients with discoid lateral menisci. Twelve discoid medial menisci were complete (55%); 8, incomplete (36%); and 2, indeterminate (9%). Tears were present in 13 knees, most commonly horizontal cleavage (54%). Five discoid medial menisci were unstable (23%): 3 for posterior tears and 2 for rim insufficiency. All 22 knees underwent arthroscopic saucerization, and of the 13 torn menisci, 7 (54%) were repaired. The median follow-up was 24 months (range, 2-82 months). Four knees underwent reoperation. All knees that required reoperation had undergone repair for a posteriorly located tear. There was a significant association between operative repair and need for reoperation (P = .0048). High rates of peripheral instability were also noted in case series of patients with discoid lateral menisci.

CONCLUSION

Patient presentations and treatments for those with discoid medial menisci were similar to those reported for patients with discoid lateral menisci. Knees with discoid medial menisci also demonstrated instability attributed to peripheral insufficiency and posterior tears. Tears were present in over half of knees with discoid medial menisci, and reoperation was more common in knees that underwent repair of tears than those without repair.

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.

Posterior subtotal meniscectomy revealed the worst scenario for the progression of osteocartilaginous damage in cases of juvenile discoid lateral meniscus with peripheral tear

INTRODUCTION

We compared subtotal meniscectomy and saucerization with stabilization for osteocartilaginous damage based on injured location and further examined the factors related to osteocartilaginous damage in juvenile discoid lateral meniscus (DLM) with peripheral tear after a follow-up period of at least 5 years.

MATERIALS AND METHODS

We retrospectively reviewed juvenile DLM patients with peripheral tear who underwent arthroscopic surgery with more than 5 years of follow-up. Osteocartilaginous damage, which was identified by osteochondritis dissecans (OCD) development and the whole-organ magnetic resonance imaging score (WORMS) of cartilage grade ≥ 3, was compared between subtotal meniscectomy and saucerization with stabilization. A subgroup analysis examining the location of the tear site was performed. Factors for osteocartilaginous damage were analyzed between the damaged and non-damaged groups.

RESULTS

Forty-one patients, including 29 who underwent saucerization with stabilization and 12 who underwent subtotal meniscectomy, were included in this study. Seven patients developed OCD lesions; six patients showed cartilage WORMS of more than grade 3. Overall, there was a significant difference in the total cartilage and meniscus WORMS between the two groups at the final follow-up. The subgroup analysis demonstrated more severe osteocartilaginous damage developed in posterior subtotal meniscectomy than in posterior stabilization following saucerization. The damaged group showed significant difference compared to the non-damaged group in terms of age (p = 0.003), sex (p = 0.036), and posterior subtotal meniscectomy (p < 0.001).

CONCLUSIONS

Posterior subtotal meniscectomy revealed the worst scenario for the progression of osteocartilaginous damage in cases of juvenile DLM with peripheral tear over a minimum follow-up period of 5 years.

Mid-term study on the effects of arthroscopic discoid lateral meniscus plasty on patellofemoral joint: An observational study

In the present study, we aimed to investigate the clinical outcomes of arthroscopic discoid lateral meniscus (DLM) plasty and the adaptive changes in the patellofemoral joint after surgery. From September 2010 to March 2012, 25 patients with DLM injuries who underwent arthroscopic meniscus plasty were enrolled in the prospective study. All patients underwent clinical evaluation before the operation and at the last follow-up, and imaging evaluation was performed by upright magnetic resonance imaging before and 1 month after the operation as well as at the last follow-up. Clinical evaluation included Lysholm score, Kujala score, McMurray's sign, patellar mobility, patella grind test, and quadriceps atrophy. Imaging evaluation included bisect offset index, patella tilt angle (PTA), and cartilage damage. Lysholm score, Kujala score, McMurray's sign, and quadriceps atrophy at the last follow-up were significantly improved compared with the preoperative levels (P < .05). At the last follow-up, there were no statistical differences in patella mobility and patella grind test compared with the preoperative levels. In addition, bisect offset index and PTA showed a dynamic trend of rising and then falling over time (P < .05). At 1 month after the operation, bisect offset index and PTA were significantly increased compared with the preoperative levels or the values at the last follow-up (P < .05), while there were no differences between the preoperation and the last follow-up. Cartilage damage became worse with time (P < 0.05), and the 2 were positively correlated (Spearman = 0.368). At the last follow-up, the degree of cartilage damage was significantly increased compared with the preoperative level (P < .017), while there was no significant difference between the 1-month postoperative grade and the preoperational grade or the last follow-up grade. The effect of arthroscopic DLM plasty on the patellofemoral joint was dynamic, with the position of the patella deviating in the early stages and recovering in the mid-term, especially when the knee was in the biomechanical standing position. In addition, the patellofemoral joint cartilage might undergo accelerated degeneration after the operation, while the mid-term effect of the operation was positive, and the patellofemoral joint function was acceptable.

Young Children with a Bucket-Handle Tear to the Discoid Lateral Meniscus Successfully Treated Using Arthroscopic Saucerization and Repair: Two Case Reports

Observations of a symptomatic discoid lateral meniscus in young children are infrequent. The objective of this report was to demonstrate the use of arthroscopic saucerization and repair for treating a bucket-handle tear of a lateral discoid meniscus in two young children. Two young children (a 28-month-old girl and a 5-year-old boy) presented with a bucket-handle tear of the complete type lateral discoid meniscus. Both patients received arthroscopic saucerization and repair. A full knee extension under a long leg cast was applied for one month after surgery. The two patients were able to achieve a full range of motion of their operated knees without limping or presenting an antalgic gait at the third month after surgery. Both patients and their parents felt satisfied with the treatment at the 2- and 3-year follow-ups, respectively. Our results demonstrated that arthroscopic saucerization and repair seems to be an effective treatment for bucket-handle tears of the lateral discoid meniscus in young children—even those younger than 3 years old. We reported the youngest case (a 28-month-old girl) in comparison with the findings from a literature review.

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

INTRODUCTION

We evaluated the efficacy of two positioned magnetic resonance imaging (MRI) for visualizing the snapping phenomenon and detecting peripheral rim instability (PRI) in no-shift-type complete discoid lateral meniscus (CDLM).

MATERIALS AND METHODS

The records of 39 patients diagnosed with no-shift-type CDLM under routine MRI who underwent arthroscopic surgery were reviewed. The snapping phenomenon and meniscal shift on two positioned MRI in full extension and deep flexion were evaluated and calculated the agreement between these findings. The positive predictive value (PPV), sensitivity, and specificity of meniscal shift on two positioned MRI for predicting PRI were calculated; PRI was further investigated according to anterior and posterior location. The hypotheses of this study were asfollows: (1) Two positioned MRI can visualize the snapping phenomenon and (2) Meniscal shift on two positioned MRI is an important predictive sign of detecting the instability site in no-shift-type CDLM.

RESULTS

The κ values between the snapping phenomenon and meniscal shift on two positioned MRI were 0.84. The snapping and two positioned MRI findings had high PPV (1.0, 0.96), sensitivity (0.82, 0.85), and specificity (1.0, 0.91) for predicting overall PRI. For anterior PRI, the snapping and posterior shift on two positioned MRI had moderate and high PPV (0.78, 0.9), high sensitivity (0.9, 0.9), and specificity (0.8, 0.89). The anterior shift on two positioned MRI findings predicted posterior PRI with high PPV (1.0) and specificity (1.0).

CONCLUSIONS

Two positioned MRI visualized the snapping phenomenon. Meniscal shift on two positioned MRI was an important predictive sign of overall PRI, anterior PRI, and posterior PRI in no-shift-type CDLM.

Partial resection of lateral discoid meniscus changes lower limb axial alignment - A retrospective cohort study

AIM

This study aimed to explore the changes in lower limb axial alignment and knee joint function after arthroscopic partial resection of the discoid lateral meniscus.

METHODS

Preoperative and postoperative full-length weight-bearing radiographs of the lower limb were obtained from a total of 161 patients with lateral menisci tears from September 2018 to September 2020 who underwent partial meniscal resection. The patients were divided into discoid meniscus group (DMG) and ordinary meniscus group (OMG). The measured mechanical axis deviation (MAD), proximal tibia angle (PTA), and distal femoral angle (DFA) in the axial alignment of the lower limb were determined before and after surgery. Knee joint function on the affected side was determined using the International Knee Documentation Committee (IKDC) subjective scale and the Lysholm knee scoring scale before surgery and at one, six, 12, and 24 months after surgery.

RESULTS

For MAD and DFA, there were statistically significant differences between the preoperative and postoperative findings within each group (P < 0.01); the MAD and DFA were smaller after surgery. The difference in preoperative and postoperative PTA of the DMG was statistically significant (P < 0.01), meaning that the PTA becomes larger after surgery. The differences in preoperative and postoperative PTA of the OMG, preoperative PTA between the two groups, and postoperative PTA between the two groups were not statistically significant (P > 0.05). Intragroup comparisons of the IKDC subjective scale and the Lysholm knee scoring scale before and after surgery revealed significant differences (P < 0.05).

CONCLUSION

Arthroscopic partial resection of the discoid lateral meniscus is a safe and effective surgical method that can significantly improve knee joint function. Although the axial arrangement of the lower limbs will be slightly changed in the early stage, it will still be within the normal range after surgery in patients with normal lower limb axial alignment. For patients with varus or valgus before surgery, this procedure should be applied with caution.

Association of Postoperative Lateral Meniscal Extrusion With Cartilage Degeneration on Magnetic Resonance Imaging After Discoid Lateral Meniscus Reshaping Surgery

Background:

Although arthroscopic reshaping surgery for a discoid lateral meniscus (DLM) has good clinical results, it cannot completely prevent degeneration. The degree of DLM extrusion associated with degenerative changes is unclear.

Purpose/Hypothesis:

To measure meniscal extrusion preoperatively and postoperatively in patients who underwent DLM-reshaping surgery and examine factors associated with knee articular cartilage degeneration. It was hypothesized that meniscal extrusion existed preoperatively, progressed postoperatively, and was related to knee joint degeneration.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

We retrospectively reviewed the medical records of patients who underwent DLM-reshaping surgery and attended ≥2 years of follow-up. Magnetic resonance imaging (MRI) was performed preoperatively and at 24 months postoperatively, and residual midbody meniscal extrusion was measured. Cartilage degeneration was detected when the Whole-Organ Magnetic Resonance Imaging Score (WORMS) of the lateral compartment was grade ≥3 at 2 years postoperatively. Factors associated with MRI cartilage degeneration were evaluated.

Results:

Included in this study were 48 knees in 39 patients; the mean patient age at the time of surgery was 12.0 years. The mean midbody meniscal extrusion significantly increased from 0.8 mm preoperatively to 1.6 mm at 24 months postoperatively ( P < .001). According to the WORMS cartilage score, 16 patients were categorized as having MRI cartilage degeneration. Multivariate logistic analysis showed that an inferior preoperative Lysholm score (odds ratio, 0.89; P = .024) and postoperative extrusion (odds ratio, 6.18; P = .010) significantly increased the risk of cartilage degeneration. The receiver operating characteristic curve showed that a residual meniscal extrusion of 2.0 mm was the cutoff value indicating cartilage degeneration (sensitivity, 87.5%; specificity, 78.1%).

Conclusion:

DLM extrusion significantly increased from 0.8 mm preoperatively to 1.6 mm at 2 years postoperatively. Postoperative extrusion and a lower preoperative Lysholm score were factors related to MRI cartilage degeneration postoperatively. A postoperative extrusion of 2.0 mm was the cutoff value for MRI cartilage degeneration.

Symptomatic discoid lateral meniscus shows a relationship between types and tear patterns, and between causes of clinical symptom onset and the age distribution

PURPOSE

Discoid meniscus is a congenital abnormality of the lateral meniscus and is seen more frequently in East Asia. The purpose of this study was to retrospectively assess the relationship between discoid lateral meniscus (DLM) types and tear patterns and causes of age-specific clinical symptom onset.

METHODS

Of 1650 arthroscopic surgeries over a 20-year period, 138 (105 patients) were performed for DLM and were evaluated in this study. The mean age at surgery was 21.5 ± 15.8 years. The DLM type was classified by Watanabe's classification, and tear patterns were classified by the modified Bin's classification as simple horizontal, complicated horizontal, longitudinal, radial, complex, and no tear. Additionally, patients were divided by age group (< 10, 10-19, 20-39, 40-59, and ≥ 60 years) and classified according to the causes of clinical symptom onset as follows: sports activities, minor trauma in daily living, and no traumatic episode.

RESULTS

The DLM was complete in 78 (56.5%) knees and incomplete in 60 (43.5%); no Wrisberg type DLM was observed. Simple horizontal and complicated horizontal tears were significantly more frequent in complete DLM, whereas radial tears and no tears were significantly more frequent in incomplete DLM (p < 0.0001). When classified by age group, 74 (53.6%) knees with DLMs were found in teenagers. Sports activities caused symptom onset significantly more often in teenagers, no traumatic episode caused symptom onset in patients aged < 10 years, and minor trauma in daily living caused symptom onset in patients aged 40-59 years and ≥ 60 years (p < 0.0001). No relationship was found between the age distribution and tear patterns; however, the absence of tears tended to be more common in teenaged patients, and complicated horizontal tears were more common in patients over 20 years of age.

CONCLUSION

Symptomatic DLM occurred most often in teenagers. A relationship was identified between the DLM types and tear patterns, which could be helpful in preoperative planning. Causes of clinical symptom onset in patients with DLM were characterised by age group, which might help clinicians to suspect the presence of DLM.

LEVEL OF EVIDENCE

Level IV.

Reliability of a New Arthroscopic Discoid Lateral Meniscus Classification System: A Multicenter Video Analysis

BACKGROUND

The discoid lateral meniscus (DLM) is one of the most common congenital anomalies of the knee. The pathomorphology of DLM varies. Current classification systems are inadequate to describe the spectrum of abnormality.

PURPOSE

A study group of pediatric orthopaedic surgeons from 20 academic North American institutions developed and tested the reliability of a new DLM classification system.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 3.

METHODS

After reviewing existing classifications, we developed a comprehensive DLM classification system. Four DLM features were evaluated: meniscal width, meniscal height, peripheral stability, and meniscal tear. Stepwise arthroscopic examination using anteromedial and anterolateral viewing portals was established for evaluating these features. Three senior authors who were not observers selected 50 of 119 submitted videos with the best clarity and stepwise examination for reading. Five observers performed assessments using the new classification system to assess interobserver reliability, and a second reading was performed by 3 of the 5 observers to assess intraobserver reliability using the Fleiss κ coefficient (fair, 0.21-0.40; moderate, 0.41-0.60; substantial, 0.61-0.80; excellent, 0.81-1.00).

RESULTS

Interobserver reliability was substantial for most rating factors: meniscal width, meniscal height, peripheral stability, tear presence, and tear type. Interobserver reliability was moderate for tear location. Intraobserver reliability was substantial for meniscal width and meniscal height and excellent for peripheral stability. Intraobserver agreement was moderate for tear presence, type, and location.

CONCLUSION

This new arthroscopic DLM classification system demonstrated moderate to substantial agreement in most diagnostic categories analyzed.

Utility of Stability and Tear Location in a Classification System for Discoid Meniscus Surgical Planning

BACKGROUND

Despite the presence of multiple classification systems for discoid meniscus, no system has yet to demonstrate utility in predicting the need for meniscal repair. The purpose of this study was to correlate characteristics associated with meniscal repair and propose a model that can inform preoperative planning and initial counseling of surgical plans and expectations.

METHODS

Medical and operative records of 434 knees with lateral discoid meniscus in children and adolescents treated between 1991 and 2016 were reviewed retrospectively to determine the surgical procedure performed (saucerization with or without meniscal repair), discoid meniscal morphology and stability, and location and type of any associated tear. Univariate associations between discoid meniscal characteristics and surgery type were calculated and a logistic regression model of surgery type was generated.

RESULTS

In univariate models, unstable menisci (93%, or 179/204, P<0.001) and menisci with tears extending peripherally (75%, or 85/204, P<0.001) were more likely to receive surgery with repair. In isolation, instability demonstrated 89% sensitivity and 94% specificity in predicting surgery with repair. A logistic regression model including stability, tear, and their interaction (stability×tear) showed that that the odds of unstable lateral discoid menisci receiving surgery with repair was 114 times higher than stable menisci (P<0.001) while lateral discoid menisci with peripherally extending tears had 6.4 times higher odds of receiving repair than those that had an isolated central tear (P<0.001).

CONCLUSION

Stability and tear location of lateral discoid menisci were associated with surgical treatment in univariate and logistic regression models. The proposed classification system, in which menisci are classified by stability [Stable (S0), Unstable (S1), morphology (Incomplete (M0), Complete (M1))], and tear [No tear (T0), Central tear, isolated (T1), or Central tear, peripheral extension (T2)], is easily remembered and predicts surgical repair for discoid menisci. This scheme can serve to inform preoperative planning and initial counseling of primary surgical management and postoperative expectations. Subsequent research should develop a system that predicts meniscal survival and patient outcomes following the index operation.

LEVEL OF EVIDENCE

Level III.

Long-term Minimum 15-Year Follow-up After Lateral Discoid Meniscus Rim Preservation Surgery in Children and Adolescents

BACKGROUND

Discoid meniscus is a congenital variant typically affecting the lateral meniscus of the knee. Historically, surgical intervention when symptomatic consisted of total meniscectomy; however, after degenerative changes were observed, current treatments now focus on rim preservation with arthroscopic saucerization and meniscal repair for instability, when indicated. The purpose of our study was to examine long-term patient-reported outcomes of lateral discoid meniscus (LDM) treated with meniscal-preserving techniques.

METHODS

Ninety-eight patients treated arthroscopically for LDM at a single institution at a minimum of 15 years ago were retrospectively identified and contacted by mailers and telephone to participate. Subjective functional outcomes and patient satisfaction data were collected using a questionnaire that included the validated International Knee Documentation Committee Subjective Knee Evaluation Form, Lysholm Score, Marx Activity Rating Scale, Tegner Activity Score, and Western Ontario and McMaster University Osteoarthritis Index Osteoarthritis Index. Patient and surgical characteristics and patient-reported outcomes were summarized by mean and SD, median and interquartile range (interquartile range), or frequency and percent, as appropriate.

RESULTS

Of the 46 patients contacted (response rate of 46/98 eligible), 25 (54%) completed the questionnaires. The mean (±SD) age at initial surgery was 10.8 (±3.4) and 30.3 (±3.7) years at final follow-up. The mean (±SD) follow-up time from initial surgery was 19.5 (±2.8) years (range, 16 to 27). Patient-reported outcomes included: International Knee Documentation Committee 77.4±17.2, Lysholm 78.6±21, Western Ontario and McMaster University Osteoarthritis Index 7.6±11.3, Tegner Activity 7 (of 10), and Marx Activity Rating Scale 8 (of 10). Eleven (44%) cases underwent subsequent LDM-related surgery on the ipsilateral knee(s). There were no cases of total knee replacement.

CONCLUSIONS

Overall, patient-reported outcomes were favorable at a minimum of 15-year follow-up after rim-preserving saucerization of LDM. While two thirds of patients were satisfied with their surgical outcomes, nearly half of patients underwent revision saucerization with or without meniscal repair. Subsequent long-term follow-up studies with objective outcome measures are important to further elucidate the natural history of LDM and understand how rim-preserving procedures may prevent the development of degenerative processes.

LEVEL OF EVIDENCE

Level IV-case series, prognostic study.

Morphological Changes in the Residual Meniscus After Reshaping Surgery for a Discoid Lateral Meniscus

BACKGROUND

Arthroscopic reshaping surgery is the first treatment option for a symptomatic discoid lateral meniscus (DLM) to preserve the peripheral rim. However, the degree of postoperative morphological change in the residual meniscus is unclear.

PURPOSE/HYPOTHESIS

The purpose of this study was to measure the meniscus after reshaping surgery for a DLM, to verify when the morphological change occurred, and to examine the related risk factors. The hypothesis was that the residual meniscal width would decrease throughout the postoperative course.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

We retrospectively reviewed the medical records of patients who underwent reshaping surgery for a symptomatic DLM and had undergone follow-up for ≥2 years. Magnetic resonance imaging (MRI) was routinely performed preoperatively and at 3, 6, 12, and 24 months postoperatively, and the width, height, and extrusion of the residual meniscus were measured. According to the width of the midbody on final MRI scans, we compared the preoperative and postoperative data for the preserved group (≥5 mm) and decreased group (<5 mm). The associated risk factors for a decreased meniscal width (<5 mm) of the midbody were analyzed on final MRI scans.

RESULTS

We included 61 knees of 54 patients in this study. The mean age at the time of surgery was 11.7 years. The intraobserver and interobserver reliabilities of the midbody width were 0.937 and 0.921, respectively. The width of the anterior horn, midbody, and posterior horn decreased significantly from 3 to 24 months after surgery (from 9.1 to 8.6 mm [P < .001], from 7.5 to 6.1 mm [P < .001], and from 9.5 to 8.9 mm [P = .001], respectively). Meniscal extrusion of the midbody did not change significantly (from 1.2 to 1.5 mm; P = .062). Overall, 46 knees (n = 20/32 in the preserved group and n = 26/29 in the decreased group) had longitudinal tears that required meniscal repair. Clinical outcomes did not differ significantly between the 2 groups. Multivariate logistic analysis showed that intrameniscal degeneration (odds ratio, 4.36; P = .023) significantly increased the risk of a decreased meniscal width.

CONCLUSION

The width of the anterior horn, midbody, and posterior horn decreased significantly from 3 to 24 months after surgery. In particular, the average decrease rate of the midbody was 19%. No clinical difference was seen in patients with a decreased width and height or with peripheral extrusion. Increased intrameniscal signals on preoperative MRI scans were associated with an increased risk of a decreased meniscal width. Surgeons should consider this result to determine the amount of resection.

A Useful MRI Classification for Symptomatic Discoid Lateral Meniscus

Purpose

The purpose of this study is to classify the discoid lateral meniscus (DLM) according to the signal and shape in magnetic resonance imaging (MRI), and to provide information not only in diagnosis but also in treatment.

Materials and Methods

We reviewed 162 cases who diagnosed with DLM by MRI and underwent arthroscopic procedures from April 2010 to March 2018. Three observers reviewed MRI findings of all cases and predicted arthroscopic tear using three MRI criteria (criterion 1,2 and 3). Among three criteria, the criterion that most accurately predicts arthroscopic tear was selected. Using this criterion, the cases of predicted tear were named group 1. In addition, group 1 was divided into three subgroups (group 1a, 1b and 1c) by deformation or displacement on MRI and arthroscopic type of tear and procedures were analyzed according to these subgroups.

Results

The intra-meniscal signal change itself (criterion 3) on MRI showed the highest agreement with the arthroscopic tear. No meniscal deformation and displacement on MRI (group 1a) showed no specific type of tear and more cases of meniscal saucerization. The meniscal deformation on MRI (group 1b) showed more simple horizontal tears and more cases of meniscal saucerization. The meniscal displacement on MRI (group 1c) showed more peripheral tears and more cases of meniscal repair and subtotal meniscectomy. Comparing arthroscopic type of tear and type of arthroscopic procedure between three subgroups, there were significant differences in three groups (P < .05).

Conclusions

Intra-meniscal signal change itself on MRI is the most accurate finding to predict arthroscopic tear in symptomatic DLM. In addition, subgroup analysis by deformation or displacement on MRI is helpful to predict the type of arthroscopic tear and procedures.

Symptomatic Discoid Meniscus in Children and Adolescents: A Review of 470 Cases

BACKGROUND

Discoid meniscus is a congenital variant, typically involving the lateral meniscus, that comprises a spectrum of meniscal shapes and degrees of instability in an estimated 1% to 15% of the population. The purpose of this study was to describe the clinical and operative course of a large cohort of children and adolescents patients with symptomatic lateral discoid meniscus.

METHODS

Medical records of 470 knees with symptomatic lateral discoid meniscus in 401 patients ages 18 years or younger diagnosed at a single institution between 1991 and 2016 were reviewed retrospectively for patient characteristics, treatment course (nonoperative and/or operative), and complications. Surgical reports were reviewed in the operative group.

RESULTS

The series included 401 patients of mean age 11.6 years (range: 1 mo-18.9 y), of which 222 (55%) were female, and 69 (17%) had bilateral involvement. Of 470 knees, 83 (18%) were initially managed nonoperatively. Of these, 32 knees (39%) failed nonoperative management and were converted to surgical treatment at a median of 7.9 months (interquartile range: 4.0-15.1). In total, 419 knees were managed surgically with saucerization (partial meniscectomy) with or without meniscal repair/stabilization; 84 knees (20%) required at least one concurrent nonmeniscal procedure. Discoid meniscus tears were reported in 264/419 knees (63%) intraoperatively; horizontal cleavage tears were most common. Reoperation was required for 66/379 cases (17%) with clinical follow-up, at a median of 19.6 months (range: 9.2-34.9) after index saucerization; 60/379 cases (16%) had ongoing pain and/or mechanical symptoms at final follow-up.

CONCLUSION

With a failure rate of 39% (32/83 knees), nonoperative management for discoid lateral meniscus frequently convert to surgical treatment. During surgery, meniscus tearing and instability are common and should be anticipated. Postoperatively, 33% (126/379) of knees with clinical follow-up underwent either reoperation, or had ongoing symptoms of the knee at final follow-up. Discoid mensical retear is the most common complication (94%, 62/66) prompting repeat surgery, and should be discussed with families before the index operation.

LEVEL OF EVIDENCE

Level IV-descriptive case series.

Predictive signs of peripheral rim instability with magnetic resonance imaging in no-shift-type complete discoid lateral meniscus

PURPOSE

To investigate the associations between the preoperative MRI findings suggestive of meniscal instability and the intraoperative finding of peripheral rim instability (PRI) in patients with complete discoid lateral meniscus (CDLM) of no-shift-type, which was identified as the peripheral portion was not separated from the capsule.

METHODS

The records of 56 patients diagnosed with no-shift-type CDLM who underwent arthroscopic surgery were reviewed. We evaluated MRI findings of anterior parameniscal soft-tissue edema, linear fluid signal at the anterior meniscal margin, bulging of the meniscal margin, absence of popliteomeniscal fascicles, and hiatus widening on routine MRI. The positive predictive value (PPV), sensitivity, and specificity of these findings in predicting PRI were calculated; PRI was further investigated according to anterior and posterior location.

RESULTS

Linear fluid signal at the anterior meniscal margin and bulging had high PPV and specificity (P = .004 and = .029, respectively) for overall of PRI. The presence of either anterior parameniscal soft-tissue edema or linear fluid signal at the anterior meniscal margin predicted anterior PRI with high PPV, sensitivity, and specificity. Bulging of the meniscal margin had high specificity, and either bulging of the meniscal margin or absence of popliteomeniscal fascicle had high sensitivity in predicting posterior PRI.

CONCLUSIONS

A linear fluid signal at the anterior meniscus and anterior parameniscal soft-tissue edema were important signs of anterior PRI, whereas bulging of the margin had high specificity and either bulging of the meniscal margin or absence of popliteomeniscal fascicle had high sensitivity in detecting posterior PRI on routine MRI of no-shift-type CDLM.

LEVEL OF EVIDENCE

Level IV therapeutic case series.

Nationwide Ethnic/Racial Differences in Surgical Treatment of Discoid Meniscus in Children: A PHIS Database Study

BACKGROUND

Discoid meniscus, a congenital meniscus variant, may have greater incidence in Asian populations. No US population-based studies have examined the discoid meniscus ethnic/racial distribution. In pediatric patients undergoing meniscus surgery, it is hypothesized that ethnic/racial variability exists in patients with discoid meniscus and this variability is different than in patients with medial meniscus tears.

METHODS

The Pediatric Health Information System was queried from 48 hospitals to examine patients 18 years of age and younger between 2015 and 2019, using International Classification of Diseases, 10th Revision, Clinical Modification codes. A cohort of patients treated surgically for discoid meniscus was compared with a cohort of patients treated surgically for medial meniscal tear. These 2 populations were compared based on age, sex, ethnicity/race, Current Procedural Terminology code, insurance, urban versus rural, and region of country. Univariate testing and multivariable logistic modeling were used to test for associations.

RESULTS

A discoid meniscus cohort of 399 children (median age, 13.0 y) was compared with a medial meniscus tear cohort of 3157 children (median age, 16.0 y) (P<0.001). Hispanic/Latino children accounted for 36.8% of the discoid lateral meniscus and 22.7% of the medial meniscus populations (P<0.001). Among pediatric patients that had surgery for discoid lateral meniscus or medial meniscus, Hispanic/Latino children had 2.36 times the odds of surgery for discoid meniscus compared with White patients after adjusting for age and insurance (P<0.001). Asian children also had 2.41 times the odds of surgery for discoid meniscus compared with White patients (P=0.017).

CONCLUSIONS

This study shows a significant association of ethnicity/race with discoid versus medial meniscus surgical treatment in children. Among pediatric patients undergoing surgery for discoid meniscus, Hispanic/Latino and Asian patients were a significantly larger percentage of the population than White patients. Hispanic/Latino children made up a greater percentage of the population having surgery for a torn discoid meniscus versus a torn medial mensicus. When evaluating pediatric patients, younger age and Asian or Hispanic/Latino ethnicity should increase attention to the possibility of a discoid meniscus.

LEVEL OF EVIDENCE

Level IV.

Discoid Lateral Meniscus Saucerization and Treatment of Intrasubstance Degeneration Through an Accessory Medial Portal Using a Small Arthroscope

Discoid lateral meniscus (DLM) is a rare meniscal variant characterized by an increased amount of meniscal tissue that resembles the shape of a disc as opposed to the typical crescent shape of the lateral meniscus. Surgical intervention is recommended for symptomatic DLM with persistent pain, mechanical symptoms, or motion impairment. The technique described is a reliable and reproducible method to identify and treat intrasubstance degeneration (ID) in the setting of DLM. A small arthroscope is used that allows more room for a meniscal repair device, as well as improved visualization and access of the lateral compartment. An accessory medial portal is used that allows perpendicular access to the anterior half of the body, as well as the posterior aspect of the anterior horn for repair. Successful surgery with this technique preserves meniscus and produces a strong reliable all-meniscal based repair of ID that allows early weight bearing and range of motion postoperatively.

Evaluation of the Peripheral Rim Instability of the Discoid Meniscus in Children by Using Weight-Bearing Magnetic Resonance Imaging

OBJECTIVE

The aim of the study was to assess the peripheral rim instability and the clinical value of discoid meniscus.

METHODS

We retrospectively studied 79 magnetic resonance imaging (MRI) examinations of discoid meniscus from May 2017 to September 2019. The patient symptoms and physical findings were documented. The patients underwent "dedicated" 0.25 T supine and weight-bearing MRI examination. Finally, all patients underwent arthroscopy.

RESULTS

Sound/clicking during motion (P = 0.009) and limited extension (P = 0.044) of subjective symptoms, clunk during motion (P = 0.035), and flexion contracture (P = 0.012) of physical findings were significant predictors of peripheral rim instability. The comparison of the weight-bearing MRI with the supine position MRI demonstrated that the disformed discoid meniscus was shifted significantly and that no shift was displaced centrally (P = 0.001). A correlation between discoid meniscal displacement and the presence of peripheral rim instability in arthroscopy was noted (P < 0.001) using weight-bearing MRI.

CONCLUSIONS

The clinical symptoms of the patients combined with weight-bearing MRI can determine peripheral rim instability optimally.

The aspiration test: an arthroscopic sign of lateral meniscus posterior horn instability

The suspensory mechanism of the posterior horn of the lateral meniscus (PHLM) is an anatomically complex structure including the popliteomeniscal fascicles, the meniscotibial posterior root attachment and the meniscofemoral ligaments. Damage to one or several of these structures – either through knee trauma or congenital abnormalities—can result in an instability of the PHLM that may lead to lateral knee pain, locking sensations or lack of rotational control of the knee (e.g. after anterior cruciate ligament injuries). The diagnosis of PHLM instability is complex due to the lack of reliable clinical tests and imaging signs. Direct visual dynamic inspection via arthroscopy thus remains the gold standard. However, arthroscopic probing of the PHLM is not always reliable and the precise quantification of the amount of subluxation of the PHLM can be difficult. Therefore, the main objective of this report was to describe a quick and easy arthroscopic screening test called “the aspiration test” in order to help surgeons to detect PHLM instability. During the exploration of the lateral tibiofemoral compartment with the knee kept in the figure of 4 position, the arthroscope is placed in the antero-lateral portal and directed towards the lateral tibiofemoral compartment. The aspiration test is then performed by activating the aspiration of the 4-mm shaver when located in the intercondylar notch. In case of a PHLM instability, an excessive displacement of the PHLM is observed. After repair, a second aspiration test allows to verify that the PHLM has been stabilized.

Meniscoplasty leads to good mid-term to long-term outcomes for children and adolescents with discoid lateral meniscus

PURPOSE

To date, there have been limited studies reporting the mid- to long-term outcomes of meniscoplasties for discoid lateral meniscus. The current study aims to evaluate the mid- to long-term outcomes of arthroscopic meniscoplasty for discoid lateral meniscus in children and adolescents.

METHODS

In the study, all patients under the age of 21 years who had undergone arthroscopic meniscoplasty with or without meniscal repair or partial meniscectomy for symptomatic lateral discoid meniscus were included. All patients were then followed up for a minimum of 5 years (median 84 months; range 68-110 months). The Lysholm scores and Ikeuchi scores were collected pre-operatively and at final follow-up and were compared.

RESULTS

A total of 24 knees were included in the study. The median duration of follow-up was 84.0 months (range 68-110 months). The Lysholm score improved from 53 (range 11-95) pre-operatively to 100.0 (range 60-100) at final follow-up (p < 0.001). Based on the Ikeuchi score pre-operatively, 15 knees were rated as poor (62.5%), 7 knees were rated as fair (29.2%), and 2 knees were rated as good (8.4%). The Ikeuchi score improved significantly at the final follow-up, such that 1 knee was rated as good (4.2%) and 23 knees were rated as excellent (95.8%) (p < 0.001). When analysing the effect of concomitant meniscal repair or partial meniscectomy on the outcomes at final follow-up, there was no apparent difference in the improvement in Lysholm score or Ikeuchi score when comparing between patients who had meniscoplasty alone and patients who had concomitant meniscal repair, as well as when comparing between patients who had meniscoplasty alone and patients who had concomitant partial meniscectomy.

CONCLUSION

Meniscoplasty leads to good mid-term to long-term outcomes for children and adolescents with discoid lateral meniscus. Concomitant procedures such as meniscal repair or partial meniscectomy do not improve or worsen the mid- to long-term outcomes in these patients.

LEVEL OF EVIDENCE

IV.

Magnetic Resonance Imaging T2 Relaxation Times of Articular Cartilage Before and After Arthroscopic Surgery for Discoid Lateral Meniscus

PURPOSE

To quantitatively evaluate degeneration of articular cartilage using magnetic resonance imaging (MRI) T2 mapping before and after arthroscopic surgery for discoid lateral meniscus (DLM).

METHODS

We retrospectively reviewed the medical records of patients who underwent arthroscopic reshaping surgery for symptomatic DLM from September 2013 to October 2017 and who had undergone follow-up for ≥2 years. MRI T2 relaxation examinations had been performed preoperatively and at 3, 6, 12, and 24 months postoperatively. The T2 relaxation times of the whole lateral femoral condyle and the tibial plateau were assessed. In addition, the lateral femoral condyle was divided into 3 subcompartmental areas: anterior, middle, and posterior.

RESULTS

In total, 30 knees of 27 patients were included in this study. The patients' mean age at operation was 13.3 years (range 6-23 years), and the mean follow-up period was 31.6 months. Saucerization alone was performed in 3 knees and saucerization with repair in 27 knees. The T2 relaxation time of the whole lateral femoral condyle was significantly increased at 3 and 6 months postoperatively and significantly decreased at 12 and 24 months. The T2 relaxation time of the whole lateral tibial plateau was significantly increased at 3 months postoperatively and significantly decreased at 24 months. The T2 relaxation time of the posterior subcompartment of the lateral femoral condyle was significantly increased at 3 months and significantly decreased at 12 and 24 months.

CONCLUSIONS

The T2 relaxation time of the lateral femorotibial joint cartilage increased at 3 and 6 months postoperatively and then had decreased at 12 and 24 months. Quantitative MRI allowed us to monitor the substantial changes in the cartilage during the early postoperative period and the recovery at the distant time point after reshaping surgery for DLM.

LEVEL OF EVIDENCE

Level IV, case series.

A predictive model with radiographic signs can be a useful supplementary diagnostic tool for complete discoid lateral meniscus in adults

PURPOSE

To investigate the diagnostic accuracy of radiographic signs for complete discoid lateral meniscus and whether a predictive model combining the radiographic signs can improve its diagnostic accuracy in adults.

METHODS

A total of adult 119 knees with complete discoid lateral meniscus confirmed by arthroscopy and 119 age- and sex-matched knees with normal meniscus were included. The radiographic signs of lateral joint space, fibular head height, lateral tibial spine height, lateral tibial plateau obliquity, lateral femoral condyle squaring, lateral tibial plateau cupping, lateral femoral condyle notching, and the condylar cut-off sign were evaluated. The receiver-operating characteristic (ROC) curves and area under the curve (AUC) were evaluated for best accuracy. A prediction model was developed by multivariable regression with generalized estimating models, and was validated using data from 111 knees of children with complete discoid lateral meniscus and 111 normal controls.

RESULTS

The fibular head height, lateral joint space, lateral tibial plateau obliquity, and the condylar cut-off sign were significantly different between the complete discoid lateral meniscus and the normal groups (p < 0.05). Among the four radiographic signs, the fibular head height showed the highest accuracy with 78.9% sensitivity and 57.3% specificity. The prediction models developed by logistic regression showed significantly improved accuracy for complete discoid lateral meniscus compared to the fibular head height (sensitivity: 69.8%, specificity: 82.9%, p = 0.001). For validation, the AUC of children seemed to be larger than that of adults, which indicated that the prediction models could be applied for children to detect complete discoid lateral meniscus.

CONCLUSION

Among several radiographic signs, the fibular head height can be used as a screening tool for complete discoid lateral meniscus. The prediction models combined with lateral joint space, fibular head height, lateral tibial plateau obliquity, and/or the condylar cut-off sign yielded a much higher diagnostic value than each radiographic sign. Therefore, fibular head height and prediction models combined with radiographic signs can provide improved diagnostic value for complete discoid lateral meniscus.

LEVEL OF EVIDENCE

III.

Demographics and Epidemiology of Discoid Menisci of the Knee: Analysis of a Large Regional Insurance Database

Background:

A discoid meniscus is a morphological variant of normal knee joint meniscus shape and ultrastructure that can lead to traumatic tearing of this tissue and early joint osteoarthritis.

Purpose/Hypothesis:

The purpose of this study was to determine the prevalence of discoid menisci in a large, ethnically diverse regional cohort and to evaluate possible risk factors. The hypothesis was that there would be no difference in the epidemiological distribution of discoid menisci based on ethnicity or sex.

Study Design:

Descriptive epidemiology study.

Methods:

The study population was from a regional, integrated health care system cohort from Kaiser Permanente of Southern California that, as of 2016, included more than 4.5 million patients. Patient demographics included age, sex, and ethnicity within this cohort. Potential risk factors analyzed included age, sex, ethnicity, and body mass index (BMI). Unique characteristics of a discoid meniscus were analyzed, including a symptomatic versus asymptomatic meniscus, location of meniscal tear and type of meniscus, and frequency of meniscal surgical treatment.

Results:

A total of 223 patients with a confirmed discoid meniscus were identified, yielding an overall prevalence rate of 4.88 per 100,000 patients. Those identifying as Black had the lowest prevalence (2.68/100,000), while Hispanic ethnicity had the highest (6.01/100,000). However, there was no significant difference with regard to ethnicity (P = .283), nor any significant difference between sexes. BMI did not significantly influence the rate of discoid menisci (P = .504). A majority (77.5%) of patients were symptomatic, while 22.5% of patients with discoid menisci were asymptomatic and discovered incidentally. Symptomatic discoid menisci were more likely to be operated on compared with asymptomatic discoid menisci (71% vs 14%, respectively; P = .001; odds ratio, 14.8 [95% CI, 5.8-37.2]). Horizontal and bucket-handle tears were the more common tear types. Of the discoid menisci in this cohort, 55.6% underwent surgery, with 95.2% undergoing reported saucerization.

Conclusion:

In this very diverse population-based cohort of patients, there did not seem to be a significant predilection of discoid menisci with regard to ethnicity. Neither sex nor BMI significantly influenced the rate of discoid menisci. More than three-quarters of those with a diagnosed discoid meniscus were symptomatic. Of the tears that occurred with discoid menisci, horizontal and bucket-handle tears made up the largest proportion.

Factors Related to Postoperative Osteochondritis Dissecans of the Lateral Femoral Condyle After Meniscal Surgery in Juvenile Patients With a Discoid Lateral Meniscus

PURPOSE

The purpose was to assess the incidence of postoperative osteochondritis dissecans (OCD) and the related epidemiologic factors following meniscal surgery for juvenile discoid lateral meniscus (DLM).

METHODS

The study was a retrospective review of 103 knees in 89 patients with a mean age of 12.1 years who underwent arthroscopic meniscal surgery for DLM. Mean follow-up was 4.2 years. The surgical procedures were either saucerization, saucerization with repair or subtotal meniscectomy, depending on the type of DLM tear. Postoperative OCD lesions were identified radiographically. Age, sex, weight, Lysholm score, Tegner activity scale, exercise frequency, and surgical procedure were compared between the postoperative OCD diagnosis group and non-OCD control group.

RESULTS

Postoperative OCD was diagnosed in 8/103 (7.8%) knees following DLM surgery. The incidence of postoperative OCD was significantly greater for patients age less than 10 years old, and male sex, low weight, Lysholm score, Tegner activity scale preinjury and after returning to sports, and exercise frequency per week on univariate analyses. On multivariate analyses, postoperative OCD occurred more commonly with subtotal meniscectomy than with saucerization or saucerization with repair, and in patients less than 11 years of age. Receiver operating characteristic curve analysis revealed a cutoff value of age at surgery of 10 years.

CONCLUSIONS

Subtotal meniscectomy and patients younger than 10 years at the time of surgery are at greater risk for postoperative OCD. To decrease this risk, if possible, we recommend performing saucerization or saucerization with repair in patients undergoing surgery for DLM.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Discoid lateral meniscus: current concepts

The discoid meniscus is a congenital morphological abnormality encountered far more commonly on the lateral than the medial side. The discoid lateral meniscus (DLM) is more prevalent in Asia with an incidence of 10%-13%, than in the Western world with an incidence of 3%-5%. DLM can be bilateral in more than 80% cases. Due to its abnormal shape and size, the discoid meniscus is prone to tearing and has an impact on gait mechanics. The discoid meniscus has deranged collagen arrangement and vascularity which can have implications for healing after a repair. Patients with a DLM may or may not be symptomatic with mechanical complaints of locking, clicking, snapping or pain. Symptoms often arise due to a tear in the body of the meniscus or a peripheral detachment. Asymptomatic patients usually do not require any treatment, while symptomatic patients who do not have locking are managed conservatively. When a peripheral detachment is present, it must be stabilised while preserving the meniscus rim to allow transmission of hoop stresses. Rehabilitation after surgery is highly individualised and return to sports is possible after more than 4 months in those undergoing a repair. The functional outcomes and onset of radiographic arthritis after saucerisation and repairing a discoid meniscus are better in the long term, compared with a subtotal meniscectomy. However, there is no compelling evidence currently favouring a repair as results deteriorate with increasing follow-up. Poor prognosis is reported in patients undergoing a total meniscectomy, a higher age at presentation and valgus malalignment.

Discoid meniscus: current concepts

Discoid meniscus is the most frequent congenital malformation of the menisci, and primarily affects the lateral meniscus; it is highly prevalent in the Asian population.The anatomic, vascular, and ultrastructural features of the discoid meniscus make it susceptible to complex tears.Discoid meniscus anomalies are described according to their shape; however, there is consensus that peripheral stability of the meniscus should also be defined.Initial workup includes plain X-rays and magnetic resonance imaging, while arthroscopic evaluation confirms shape and stability of the meniscus.Clinical presentation is highly variable, depending on shape, associated hypermobility, and concomitant meniscal tears.Treatment seeks to re-establish typical anatomy using saucerization, tear reparation, and stable fixation of the meniscus. Cite this article: EFORT Open Rev 2020;5:371-379. DOI: 10.1302/2058-5241.5.190023.

Abnormal displacement of discoid lateral meniscus with snapping knee detected by full extension and deep flexion MRI: Report of two cases

We evaluated the abnormal displacement of a complete discoid lateral meniscus in two patients with symptoms of a large popping sound during knee flexion and extension, so-called "snapping", and no displacement of the discoid meniscus on routine Magnetic Resonance Imaging (MRI) analysis. MRI images indicated an anterocentral shift of the lateral discoid meniscus on knee deep flexion in one case and a posterocentral shift of the meniscus on knee full extension in the other case. Abnormal meniscal instability was confirmed under arthroscopy in both knees. After arthroscopic partial meniscectomy, one case of posterior horn instability was treated with an inside-out arthroscopic technique, whereas the other case of anterior horn instability was treated with an all-inside repair technique. We conclude that the symptom of a large popping sound during knee motion may indicate abnormal displacement of a complete discoid lateral meniscus and that further MRI analyses on knee full extension and deep flexion may reveal discernible meniscal displacement.

Prediction of the Peripheral Rim Instability of the Discoid Lateral Meniscus in Children by Using Preoperative Clinicoradiological Factors

BACKGROUND

The discoid lateral meniscus (DLM) in children often presents peripheral rim instability (PRI) and is susceptible to tear or subluxation, which manifests symptoms and leads to a poor prognosis. We aimed to investigate the association between preoperative clinical and MRI findings and the intraoperative findings of PRI.

METHODS

Children and adolescents aged younger than 16 years who underwent surgical treatment for DLM were retrospectively reviewed. Cases of bucket-handle tear were not included because they would confound the stability of the peripheral rim. Total 60 knees from 47 children were included. PRI was additionally subdivided based on the location, such as anterior, middle, and posterior, during the investigation.

RESULTS

In multivariate analyses, both central (inward) (P=0.004) and external (outward) (P=0.029) displacement of lateral meniscal margin, and peripheral tear of the anterior body (P=0.022) were significant predictors of PRI, regardless of the location. The predictive factors for PRI based on each location were female gender (P=0.004), subjective symptom of clicking sound (P=0.023), and central displacement of the anterior meniscal margin (P=0.034) for anterior PRI; flexion contracture >10 degrees (P=0.017) and peripheral tear of the middle body (P<0.001) for middle PRI; and central displacement of the posterior meniscal margin (P=0.036) and peripheral tears of the anterior (P=0.029) and middle bodies (P=0.047) for posterior PRI.

CONCLUSIONS

We evaluated the preoperative clinical and MRI findings that predict PRI of pediatric DLM. Displacements of the DLM, not only centrally (inward) but also externally (outward), seem to be significant predictive factors for PRI. Furthermore, some clinical findings were associated with PRI, even predicting the locations. Although the actual surgical procedure should be determined by meticulous probing during arthroscopy, preoperative prediction of the presence and location of PRI would help decrease the risk of oversight during surgery.

LEVEL OF EVIDENCE

Level III-Diagnostic Study.

Discoid lateral meniscus: a simple horizontal tear was associated with less articular cartilage degeneration compared to other types of tear

PURPOSE

The relationship between the tear type of discoid lateral meniscus (DLM) and articular cartilage degeneration has not been well studied.

METHODS

Data from patients with DLM tears who underwent arthroscopic surgery, between 2008 and 2016, were reviewed retrospectively. Demographic variables were obtained from medical records. The types of DLM and meniscal tear and status of cartilage were assessed using operation records and arthroscopic images. Patients were assigned to horizontal or non-horizontal tear groups according to the types of the tear. Factors affecting cartilage degeneration of the lateral femoral condyle (LFC) and lateral tibial plateau (LTP) were identified using logistic regression analysis. The horizontal tear group was divided into two subgroups on the basis of the median value of duration of symptoms and difference in cartilage degeneration between the two subgroups was evaluated.

RESULTS

Overall, 355 knees were enrolled and assigned to the horizontal (n = 53) or the non-horizontal (n = 302) tear groups. The incidence of International Cartilage Repair Society grades 2-4 cartilage lesions of the LFC (0%, P < 0.001) and LTP (24.5%, P < 0.001) was significantly lower in the horizontal tear group than in the non-horizontal tear group. Horizontal tear [LFC, odds ratio (OR) = 0.02, P < 0.001; LTP, OR = 0.27, P < 0.001] and age (LFC, OR = 1.04, P < 0.001; LTP, OR = 1.03, P < 0.001) were significantly related to cartilage status. There was no difference in cartilage degeneration between the two subgroups in the horizontal tear group.

CONCLUSIONS

A simple horizontal tear was associated with less articular cartilage degeneration compared to other types of tear in the DLM. In the case of simple horizontal tear, there was no difference in the degree of cartilage degeneration according to the duration of symptoms. Therefore, it is not necessary to perform surgical treatment promptly in cases of simple horizontal tears unless the patient's symptoms are severe.

LEVEL OF EVIDENCE

III, Case-Control Study.

High Rate of Recurrent Meniscal Tear and Lateral Compartment Osteoarthritis in Patients Treated for Symptomatic Lateral Discoid Meniscus: A Population-Based Study

Background:

Little is known about the natural history of a surgically treated symptomatic lateral discoid meniscus. The goals of this study were to describe the rate and factors associated with recurrent lateral meniscal tears and progression to symptomatic lateral compartment osteoarthritis (OA) in patients surgically treated for a symptomatic lateral discoid meniscus.

Hypothesis:

Patients with surgically treated lateral discoid meniscus have a high incidence of meniscal retear and progression to lateral compartment OA.

Study Design:

Case series; Level of evidence, 4.

Methods:

A large geographic database was reviewed to identify and confirm patients presenting with symptomatic lateral discoid meniscus between 1998 and 2015. Charts were reviewed to document treatment and outcomes at a minimum clinical follow-up of 2 years.

Results:

A total of 59 patients (27 females, 32 males) with a mean age of 25.7 years (range, 4.0-66.0 years) underwent surgical management of a discoid lateral meniscus and were evaluated for a mean of 5.6 years (range, 2.0-23.7 years). Of these, 48 (82%) patients underwent partial lateral meniscectomy, with 24 patients undergoing concurrent saucerization. Eleven (18%) underwent meniscal repair. Tear-free survival following surgery was 41% at 8 years. Progression to symptomatic lateral compartment OA was 50% at 8 years. Young age (hazard ratio, 0.96; 95% CI, 0.93-0.99; P = .01) and open growth plates (hazard ratio, 3.19; 95% CI, 1.15-8.88; P = .03) were associated with increased incidence of postoperative retear. Older age at diagnosis and body mass index ≥30 kg/m² were associated with increased risk of progression to lateral compartment OA on final radiographs.

Conclusion:

Patients with a surgically treated lateral discoid meniscal tear had a high rate of recurrent meniscal tear (59% at 8 years). Approximately 50% of surgically treated patients developed symptomatic lateral compartment OA at 8 years from diagnosis.

The Fate of the Contralateral Knee in Patients With a Lateral Discoid Meniscus

PURPOSE

To analyze the survivorship of the lateral meniscus (LM) in the contralateral knee after surgery for symptomatic torn discoid lateral meniscus (DLM) and to determine its associated factors.

METHODS

Two hundred ninety-six patients who underwent arthroscopic meniscectomy for torn symptomatic DLM were reviewed retrospectively. Patients were classified into subgroups based on demographic, clinical, and radiologic variables. The survivorship analysis of the LM on the contralateral knee was calculated using the Kaplan-Meier method, and comparison among the subgroups was conducted using the log-rank test. The predicted prognostic factors associated with survivorship were determined using Cox proportional hazard regression analysis.

RESULTS

Of the 296 patients, 51 (17%) had arthroscopic surgery in the contralateral knee during the study period. The group ≥40 years old had significantly worse survival than the group <40 (log-rank test, P < .001). In terms of radiologic variables, the group with Kellgren-Lawrence grade 3 or 4 had significantly poorer survivorship than that with grade 1 or 2 (log-rank test, P = .045). Age ≥40 years was associated with poorer survivorship (hazard ratio, 3.235; 95% confidence interval, 1.782-5.875; P < .001). Kellgren-Lawrence grades 3 and 4 in the contralateral knee were associated with poorer survival (hazard ratio, 2.071; 95% confidence interval, 1.061-4.043; P = .033). The cumulative survival rate at 10 years of the LM in the contralateral knee after surgery for symptomatic torn DLM was 81%.

CONCLUSIONS

Patients with a lateral discoid meniscus have a risk of a similar condition in the contralateral knee. Increased risks of symptomatology are associated with age and degenerative changes.

LEVEL OF EVIDENCE

Level IV, retrospective uncontrolled case series.

Does discoid lateral meniscus have inborn peripheral rim instability? Comparison between intact discoid lateral meniscus and normal lateral meniscus

INTRODUCTION

Little is known about peripheral rim instability (PRI) of adult discoid lateral meniscus (DLM). We compared PRI of the intact DLM (iDLM) to those of intact normal lateral meniscus (LM) in adult patients and also investigated whether there was any association between PRI and DLM tears.

MATERIALS AND METHODS

We investigated PRI in 17 DLMs and 60 normal LMs without tears during arthroscopic surgery for medial compartmental pathologies between June 2012 and October 2015. We also investigate PRI of torn DLM (tDLM) excluding peripheral tear to compare the PRI between intact and torn DLM. Stability parameters were measured using a probing hook and arthroscopic ruler at the anterior, middle, and posterior parts of the peripheral rim of the menisci: translating the anterior horn (AH) and mid-body (MB) and lifting the posterior horn (PH).

RESULTS

AH and PH instabilities were greater in the iDLM group than in the iLM group (2.2 ± 1.4 vs. 0.9 ± 1.4 mm, p = 0.006 and 3.4 ± 1.7 vs. 1.7 ± 1.2 mm, p = 0.004, respectively). However, there was no significant difference in MB instability between two groups. In addition, no significant difference was observed in all the parameters between the iDLM and tDLM groups.

CONCLUSION

Both iDLM and tDLM had greater PRI of the AH and PH than the iLM in adult patients. Thus, the DLM is prone to tear and careful inspection is needed not to overlook PRI of a DLM even if the peripheral attachment is intact.

LEVEL OF EVIDENCE

Level 3, comparative study of anatomical instability of living subjects.