Usefulness of magnetic resonance imaging for detecting intrasubstance tear and/or degeneration of lateral discoid meniscus

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.

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.

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.

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.

Pediatric discoid meniscus: can magnetic resonance imaging features coupled with clinical symptoms predict the need for surgery?

BACKGROUND

Magnetic resonance imaging (MRI) criteria for evaluating discoid meniscus is limited in the pediatric population.

OBJECTIVE

To assess MRI features of intact discoid meniscus and correlate with clinical outcomes.

MATERIALS AND METHODS

In this institutional review board (IRB)-approved retrospective cohort study, knee MRIs at our institution from 2008 to 2019 were reviewed. The inclusion criterion was diagnosis of discoid meniscus on MRI. Exclusion criteria were torn discoid meniscus at presentation, previous meniscal surgery and confounding knee conditions. MRI features of discoid meniscus collected were craniocaudal dimension, transverse dimension, transverse dimension to tibial plateau (TV:TP) ratio and increased intrameniscal signal. The clinical course was reviewed for knee pain, mechanical symptoms and treatment type.

RESULTS

Two hundred and nineteen of 3,277 (6.7%) patients had discoid meniscus. Of the 219 patients, 71 (32.4%) satisfied inclusion criteria. Seven patients had discoid meniscus of both knees resulting in 78 discoid menisci. The average patient age was 11.1 years (min: 2.0, max: 17.0). The average follow-up was 30.6 months. Of the 78 discoid menisci, 14 (17.9%) required surgery. Increased intrameniscal signal was found more in discoid meniscus requiring surgery (surgical: 10/14, nonsurgical: 19/64, P=0.009). Surgically treated discoid meniscus had a statistically significant increase in transverse dimension (surgical: 18.3±5.0 mm, nonsurgical: 15.7±4.3 mm, P=0.045) and TV:TP ratio (surgical: 0.55±0.15, nonsurgical: 0.47±0.12, P=0.036). Mechanical symptoms (surgical: 9/11, nonsurgical: 21/60, P=8.4×10^-6) and pain ≥1 month (surgical: 11/11, nonsurgical: 17/60, P=0.006) were found more often in surgical patients. Clinical and imaging criteria of mechanical symptoms and knee pain ≥1 month and at least one of (1) increased intrameniscal signal or (2) TV:TP ratio greater than 0.47 identified discoid menisci that developed a tear and/or required surgery with a sensitivity of 0.86 and specificity of 0.88.

CONCLUSION

Mechanical symptoms and knee pain ≥1 month, and at least one of (1) increased intrameniscal signal or (2) TV:TP ratio greater than or equal to 0.47, identified discoid menisci that would go on to tear and/or require surgery with a sensitivity and specificity of 0.86 and 0.88, respectively.

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.

Discoid lateral meniscal repair without saucerization for adolescents with peripheral longitudinal tear

Recently, successful clinical outcomes for symptomatic discoid lateral meniscus (DLM) have been reported following partial meniscectomy (saucerization) with repair. In contrast, some studies using radiography and magnetic resonance imaging (MRI) have suggested that function of load transmission might not be appropriately maintained after saucerization with repair. Therefore, in pursuit to uphold load transmission after surgery for DLM, this study tried to preserve the DLM shape to keep the original DLM function. Discoid lateral meniscus repair without saucerization was indicated, with strict criteria, for those who had a painful peripheral longitudinal tear with purely intact body caused after a single traumatic incidence. The repair was performed without saucerization for four adolescents (two males, two females; mean age 16.2 years; three complete types of DLM, and one incomplete type of DLM). Postoperatively, the following were evaluated with radiography and MRI at six, 12, and 24 months after surgery: clinical outcomes, degenerative changes, and morphology of repaired DLM. They all showed good clinical outcomes. Furthermore, no degeneration, deformation, nor extrusion was observed at the two-year follow-up after surgery. For limited cases of DLM, as mentioned above, DLM repair without saucerization can be one treatment option.

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.

Arthroscopic minimum saucerization and inferior-leaf meniscectomy for a horizontal tear of a complete discoid lateral meniscus: Report of two cases

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Arthroscopic minimum saucerization and inferior-leaf meniscectomy at 2-year follow-up.

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Preserving more than 10 mm width could obtain excellent clinical outcomes.

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Leaving more meniscal tissue might prevent meniscal extrusion.

Introduction

Treatment of a horizontal tear of a complete discoid lateral meniscus (DLM) is still controversial. Preserving peripheral rim as a normal shape of the meniscus with single-leaf resection is a conventional treatment, however meniscal function could not be fully restored.

Presentation of case

A 28-year old woman and a 34-year old woman experienced knee pain and had restricted knee extension. MRI showed horizontal tears of complete DLM in both patients. Arthroscopic minimum saucerization preserving more than 10 mm peripheral rim and inferior-leaf meniscectomy was performed. Two years after the surgery, the patient had no pain and no restriction of ROM. MRI showed the remaining superior-leaf maintained about half its width and no progression of coronal/sagittal extrusion.

Discussion and conclusion

As resecting more meniscal tissue has been considered to be a cause of degeneration or extrusion of the meniscus, arthroscopic minimum saucerization, preserving more meniscal tissue than standard saucerization, and inferior-leaf meniscectomy can be an alternative treatment option of horizontal tears of complete DLM with satisfying clinical and radiological results.

Discoid lateral meniscus in children and adolescents: a histological study

BACKGROUND

Discoid lateral meniscus is the most frequent variant of the meniscus. Although the histology of normal menisci in children and in adults has been well described, few studies have focused on the histology of discoid menisci. Furthermore, most of the patients in those studies were adults. The aim of the present study was to report the histological findings of discoid lateral meniscus in a group of children and adolescents, aged between 9 and 18, after arthroscopic partial resection, focusing on cellularity, arrangement of collagen fibers, and vascularity of the excised fragments. Furthermore, to report on MRI findings compared to the histological findings in the same region.

METHODS

Six patients (one female and five males) aged 9, 10, 13, 15, 17, and 18, were arthroscopically operated on partial meniscectomy (saucerization) of a discoid lateral meniscus, and the specimens were histologically examined.

RESULTS

The extracellular matrix showed a different distribution and characteristics depending on the different side of the meniscus. Irregularly oriented collagen fibers in discoid lateral meniscus were found. There were no blood vessels in the inner part of discoid lateral meniscus in all patients but the 18-year old (in which we observed also endothelials cells, edematous tissue and leaking of erythrocytes in the extracellular matrix). In the discoid lateral menisci analyzed, irregularly oriented collagen fibers with blood vessels were found only in the presence of degenerating tissue.

CONCLUSIONS

Discoid lateral meniscus is different from a normal meniscus in terms of vascularity and disorganization of collagen fibers.

Predictive factors for osteochondritis dissecans of the lateral femoral condyle concurrent with a discoid lateral meniscus

PURPOSE

Osteochondritis dissecans (OCD) of the lateral femoral condyle is relatively rare, and it is often reported in combination with discoid lateral meniscus. However, little is known about the mechanism underlying this connection. Predictive factors for OCD coinciding with discoid lateral meniscus in Japanese children and adolescents were assessed.

METHODS

During 2000-2015, 152 knees in 133 patients aged 5-15 years were diagnosed with symptomatic complete discoid lateral meniscus. Patients were evaluated using radiography and magnetic resonance imaging (MRI). OCD was radiographically graded using the Brückl classification. Based on Ahn's MRI classifications, discoid lateral meniscus was divided into four types of meniscal shift: no shift (N), anterocentral (AC), posterocentral (PC), or central (C). Relationships between OCD and patient sex, age and Ahn's shift type were analysed.

RESULTS

OCD of the lateral femoral condyle was associated with discoid lateral meniscus in 22 (14.5%) of 152 knees. OCD was classified as Brückl's stage 1 in 5 knees, stage 2 in 12, stage 3 in 3, stage 4 in 1, and stage 5 in 1. OCD was found in 12 of 96 knees (12.5%) with type N meniscal shift, 4 of 24 knees (16.7%) with type AC, 0 of 21 knees (0%) with type PC, and 6 of 11 knees (54.5%) with type C. Multivariate logistic regression analysis showed that males had a significantly increased odds ratio (OR) [14.8; 95% confidence interval (CI) 2.6-83.4]. Those aged 5-11 years had a significantly higher OR (12.5; 95% CI 2.8-55.9) than those aged 12-15 years. The OR for type C coinciding with OCD was significantly elevated (13.4; 95% CI 2.3-78.7).

CONCLUSIONS

Concurrent OCD was found in 22 (14.5%) of 152 knees with discoid lateral meniscus. Male sex, young age (5-11 years), and having a type C meniscal shift of the discoid lateral meniscus as shown by MRI were found to be predictive factors for OCD of the LFC.

LEVEL OF EVIDENCE

III.

Discoid Lateral Meniscus in Children: Diagnosis, Management, and Outcomes

Discoid meniscus is a congenital variant of the knee joint that typically involves abnormal morphology and potential instability of the lateral meniscus. Some discoid menisci have abnormal peripheral attachments and are unstable. Discoid menisci are prone to tearing secondary to increased thickness, poor tissue quality, and instability. Patients may or may not be symptomatic. Torn or unstable discoid menisci cause mechanical symptoms, pain, and swelling. Symptomatic patients in whom nonsurgical management fails most frequently are treated with arthroscopic surgery. Historically, complete meniscectomy has successfully alleviated symptoms but has resulted in poor midterm results, with degenerative changes to the knee joint. Current treatment emphasizes the saucerization of the meniscus, with removal of the central disk and retention of the peripheral crescent. Peripheral meniscal repair is performed when instability is present. Short-term results are good; however, degenerative changes have been reported at intermediate follow-up.

Anatomical Knee Variants in Discoid Lateral Meniscal Tears

Background:

Discoid lateral meniscus was a common meniscal dysplasia and was predisposed to tear. There were some anatomical knee variants in patients with discoid lateral meniscus. The aim of this study was to analyze the relationship between anatomical knee variants and discoid lateral meniscal tears.

Methods:

There were totally 125 cases of discoid lateral meniscus enrolled in this study from February 2008 to December 2013. Eighty-seven patients who underwent arthroscopic surgery for right torn discoid lateral meniscus were enrolled in the torn group. An additional 38 patients who were incidentally identified as having intact discoid lateral menisci on magnetic resonance imaging (MRI) findings were included in the control group. All patients were evaluated for anatomical knee variants on plain radiographs, including lateral joint space distance, height of the lateral tibial spine, height of the fibular head, obliquity of the lateral tibial plateau, squaring of the lateral femoral condyle, cupping of the lateral tibial plateau, lateral femoral condylar notch, and condylar cutoff sign. The relationship between anatomical variants and meniscal tear was evaluated. These anatomical variants in cases with complete discoid meniscus were also compared with those in cases with incomplete discoid meniscus.

Results:

There were no significant differences between the two groups in lateral joint space distance (P = 0.528), height of the lateral tibial spine (P = 0.927), height of the fibular head (P = 0.684), obliquity of the lateral tibial plateau (P = 0.672), and the positive rates of squaring of the lateral femoral condyle (P = 0.665), cupping of the lateral tibial plateau (P = 0.239), and lateral femoral condylar notch (P = 0.624). The condylar cutoff sign was significantly different between the two groups, with the prominence ratio in the torn group being smaller than that in the control group (0.74 ± 0.11 vs. 0.81 ± 0.04, P = 0.049). With the decision value of the prominence ratio (0.78) in predicting discoid lateral meniscal tear, the sensitivity and specificity of the cutoff sign were 66% and 71%, respectively. There were no significant differences in radiographic variants between the complete and incomplete discoid lateral meniscal groups.

Conclusions:

The condylar cutoff sign observed on the tunnel view of the radiograph is helpful in predicting meniscal tear in adult patients with discoid lateral meniscus. As for these patients, further MRI test is recommended.

Post-operative deformation and extrusion of the discoid lateral meniscus following a partial meniscectomy with repair

PURPOSE

The purpose of this study was to investigate the morphology of the discoid lateral meniscus sequentially following a partial meniscectomy with repair using magnetic resonance imaging (MRI).

METHODS

Nine patients with a symptomatic discoid lateral meniscus with a peripheral tear were enrolled in this study, and a partial meniscectomy with repair was performed arthroscopically. An MRI examination was performed 2 weeks after surgery (before weight bearing was permitted) and again 6 months after surgery (when sporting activities could resume). The width, height and distance of the discoid lateral meniscus were measured. The distance was defined as the distance between the edges of the discoid lateral meniscus and the tibia.

RESULTS

The width of the anterior, middle and posterior segments significantly decreased from 2 weeks to 6 months after surgery. The height of the middle and posterior segments significantly increased from 2 weeks to 6 months after surgery, whereas the height of the anterior segment did not significantly change. The distance of the anterior, middle and posterior segments significantly decreased from 2 weeks to 6 months after surgery.

CONCLUSION

The discoid lateral meniscus exhibited deformation and extrusion from 2 weeks to 6 months after a partial meniscectomy with repair. Therefore, the function of load transmission might not be maintained appropriately after surgery.

LEVEL OF EVIDENCE

IV.

Prevalence of bilateral Discoid Lateral Menisci (DLM) in patients operated for symptomatic DLM with a follow-up study on their asymptomatic contralateral knees: a Magnetic Resonance Imaging (MRI) assessment

Background

The purpose was to investigate prevalence of bilateral discoid lateral menisci (DLM) in Han Chinese patients who received surgery for symptomatic DLM, as well as a follow-up study of their asymptomatic contralateral knees using magnetic resonance imaging (MRI).

Methods

A total of 110 patients [50 males and 60 females; average age: 21.95 ± 12.77 years (range: 6 to 67 years)] admitted to our hospital with symptomatic DLM were treated with arthroscopic surgery. The contralateral asymptomatic knees were evaluated for DLM by MRI. Postoperative clinical evaluation was performed using the Lysholm knee scoring scale and International Knee Documentation Committee subjective knee evaluation.

Results

Eighty (72.73 %) of 110 symptomatic DLM patients had bilateral DLM, of which 68 (85 %) were of homotype (same type). Fourteen of 80 bilateral DLM patients were symptomatic and received operations in both knees. Twelve of remaining 66 bilateral DLM patients with asymptomatic one knee underwent a second arthroscopic surgery as their asymptomatic knees became symptomatic over the five-year interim. Of these 12 cases, seven exhibited no shift and five showed posterocentral meniscal shift. Furthermore, at least two cases showed progression from asymptomatic grade II to symptomatic grade III over the interim. All patients showed significant improvement after surgery.

Conclusions

The bilateral DLM rate of Han Chinese patients with symptomatic DLM was relatively high at 72.7 %, and 85 % of those were of homotype.

Meniscal morphologic changes on magnetic resonance imaging are associated with symptomatic discoid lateral meniscal tear in children

PURPOSE

To determine whether meniscal deformation and displacement on magnetic resonance imaging (MRI) are associated with tears by use of arthroscopic findings as a standard of reference in children with discoid lateral meniscus (DLM).

METHODS

We reviewed MRI scans and intraoperative videos of 69 consecutive patients (79 knees) treated arthroscopically for suspicious DLM tears. The mean age at surgery was 10.9 years (range, 4.3 to 17.6 years). Signal changes and morphologic changes (deformation or displacement) of DLM on magnetic resonance (MR) images were graded by 2 independent observers using our modifications of previously described classification schemes, and then the grades were determined by consensus of the observers. Meniscal tears were assessed by an observer, blinded to the MRI studies, based on arthroscopic findings. Signal changes and morphologic changes of DLM on MR images were correlated with tears.

RESULTS

Tears were found more frequently in menisci showing morphologic changes on MR images (P = .001). Of the 25 menisci with a grade 3 signal change (linear or band-like signal intensity extending to the superior or inferior meniscal surface), 24 had tears, and a horizontal cleavage was the most commonly associated tear type. Of the 50 menisci with a grade 1 (dot-like intrameniscal signal change), grade 2 (linear or band-like intrameniscal signal change), or diffuse signal change, 34 were morphologically changed on MR images, and 29 of these (85%) were torn, whereas 9 of the 16 menisci (56%) not morphologically changed were torn (P = .036).

CONCLUSIONS

Preoperative MRI evaluations based on signal intensities do not accurately predict the presence of a DLM tear in children, except when a DLM shows a grade 3 signal change. Meniscal deformation or displacement observed on preoperative MR images suggests a higher risk of meniscal tears, even in menisci with signal changes other than grade 3 changes.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

A novel magnetic resonance imaging classification of discoid lateral meniscus based on peripheral attachment

BACKGROUND

In the symptomatic discoid lateral meniscus, the effectiveness of preoperative magnetic resonance imaging (MRI) is not well documented.

HYPOTHESIS

Magnetic resonance imaging classification will provide more information to the surgeon in choosing the appropriate treatment methods with the help of arthroscopic findings.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

Sixty-seven patients (82 knees) were reviewed. The preoperative MRI was checked in 76 of 82 knees. The Lysholm and Ikeuchi grading scales were evaluated. Images were analyzed from MRI, and findings were classified into 4 categories: no shift, anterocentral shift, posterocentral shift, and central shift. Tear pattern classifications were based on arthroscopic findings: horizontal tear, peripheral tear, horizontal and peripheral tear, posterolateral corner loss, and others. The correlations between MRI classification tear patterns and surgical methods were analyzed using the chi-square test or the Fisher exact test. The sensitivity, specificity, and accuracy of shift in preoperative MRI-according to the existence of peripheral tear when corroborated with arthroscopy-were also analyzed with the chi-square test. Inter- and intraobserver reliability was statistically analyzed by producing the inter- and intraclass correlation coefficient.

RESULTS

The mean preoperative Lysholm score was 77.3 (range, 43-97), and the last follow-up Lysholm score had increased to 96.8 (range, 84-100; P < .001). At last follow-up (100% follow-up), the Ikeuchi grading scale scored 48 knees as excellent, 30 as good, and 4 as fair. According to the MRI classification, 43 knees were no shift; 6, anterocentral shift; 15, posterocentral shift; and 12, central shift. Shift-type knees had a significantly larger number of peripheral tears, and repairs were performed in the shift-type knees (55%) more frequently than in the no-shift-type knees (28%). Among 82 knees, 31 were repaired simultaneously after a central partial meniscectomy.

CONCLUSION

Magnetic resonance imaging classification provides more information to surgeons in choosing the appropriate treatment methods, although the final decision regarding procedure is made during arthroscopy after thorough analysis of the tear.

Results of subtotal/total or partial meniscectomy for discoid lateral meniscus in children

PURPOSE

The purpose of this study was to compare the midterm outcomes of subtotal/total meniscectomy with those of partial meniscectomy for symptomatic torn discoid lateral meniscus (DLM) in children and evaluate the correlation of chondral wear in the lateral compartment at index surgery with arthritic changes at final follow-up.

METHODS

We reviewed 43 knees in 36 patients aged less than 15 years who underwent arthroscopic procedures for torn DLMs between 1999 and 2004. The mean patient age at the time of surgery was 9.5 years (range, 5 to 14 years), and the mean follow-up period was 4.3 years (range, 2.1 to 9.4 years). Of the 43 knees, 23 underwent partial meniscectomy and 20 underwent subtotal/total meniscectomy. The status of the articular cartilage at the time of surgery was analyzed with the Outerbridge grading system, and radiologic arthritic changes of the lateral compartment at final follow-up were evaluated by use of the classification of Tapper and Hoover.

RESULTS

Clinically excellent or good results at final follow-up were observed in 36 of 43 knees (83.7%). There was no difference between the partial and subtotal/total meniscectomy groups in terms of the presence of chondromalacia of the lateral compartment at the time of surgery. Radiologic arthritic changes at final follow-up were significantly more severe in the subtotal/total meniscectomy group than in the partial meniscectomy group (P < .001). We observed a positive linear association between the degree of chondral wear of the lateral tibial plateau at the time of surgery and subsequent development of radiologic signs of arthritic change at last follow-up (rho = .628, P = .027). We also found a correlation between symptom duration and chondromalacia of the lateral tibial plateau (rho = .684, P = .021).

CONCLUSIONS

Although there were no differences in clinical results between the partial and subtotal/total meniscectomy groups, partial meniscectomy yielded better radiologic results than subtotal/total meniscectomy for torn DLMs in children. Our findings suggest the need for early diagnosis and greater caution in the treatment of torn DLMs in children.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Central hole tear of the discoid meniscus of the knee in magnetic resonance imaging: mimicking the bucket-handle tear

OBJECTIVE

To analyze the prevalence and describe the magnetic resonance imaging (MRI) features of central hole tear (CHT) of the discoid meniscus.

METHODS

Thirty-six patients with arthroscopically proven CHT who underwent knee MRI were included. We retrospectively reviewed the clinical history and evaluated the MRI findings which have been known as the findings of bucket-handle tear (BHT) and osteoarthritis.

RESULTS

A CHT accounts for 15% of discoid meniscus tears. In all patients, CHT involved the lateral meniscus. Of 36 patients, 28 (78%) had not any history of trauma to the knee. Intercondylar notch sign, coronal truncation sign, absent bow tie sign, and flipped meniscus sign were seen in 36 (100%), 35 (97%), 34 (94%), and 10 patients (28%), respectively. In addition, 26 (72%), 21 (58%), and 17 (47%) of 36 patients showed osteophytes formation, chondral lesion, and subchondral bone change, respectively. Of these 36 patients, 23 (64%) and 22 (61%) demonstrated increased signal intensity in the meniscus on proton density-weighted image and irregularities of the margin of the residual menisci, respectively.

CONCLUSIONS

Although a CHT had many of the MRI features of BHT, it was usually accompanied by changes of osteoarthritis. Presence of degenerative change, absence of trauma, and presence in the lateral meniscus are features that favor a CHT over a BHT of the meniscus.

Histomorphologic study of discoid meniscus

PURPOSE

The purpose of this study was to investigate the matrix collagen network of the discoid lateral meniscus in comparison with normal lateral meniscus.

METHODS

Discoid meniscus samples obtained arthroscopically from 10 patients with a diagnosis of intact complete-type discoid lateral meniscus by a technique of excision in 1 piece were examined histomorphologically regarding the integrity of both main collagen fiber systems, radial and circular, because they have been described in the structure of normal knee meniscus. As a control group, intact lateral menisci excised during knee arthroplasty procedures were used.

RESULTS

Histomorphologic scoring showed statistically significant disorganization of the circular collagen network in the discoid meniscus group compared with the normal meniscus group, especially along the posterior third of the specimen (P < .001). In addition, a heterogeneous course of the circumferentially arranged collagen fibers was shown in the discoid meniscus structure.

CONCLUSIONS

Findings of discontinuity and inhomogeneity of the circumferential collagen network in the discoid meniscus in comparison with normal meniscus indicate that the discoid lesion represents a structural lesion rather than a morphologic variant.

CLINICAL RELEVANCE

Disorganization of the circular collagen fiber system in the discoid meniscus matrix may contribute to the pathogenesis of the high tear and degenerative lesion rate observed among menisci with discoid configuration.

Discoid lateral meniscus in children: limited knee extension and meniscal instability in the posterior segment

BACKGROUND

Limited knee extension is a well-known sign in children with discoid meniscus, but its causative mechanism is controversial. The purpose of this study was to characterize discoid meniscus with this clinical manifestation with a focus on instability of the posterior segment and its morphologic features.

METHODS

The authors retrospectively reviewed magnetic resonance imaging and intraoperative arthroscopic videos of 34 knees in 32 consecutive patients (age range, 4.5-15.0 years) who underwent arthroscopic treatment for symptomatic discoid lateral meniscus. Knees were classified into 2 groups, depending on the presence (n = 19) or absence (n = 15) of an extension block, which was defined as a limitation of knee extension by 10 degrees or more under general anesthesia. Meniscal instability in the posterior segment was determined based on arthroscopic findings, and its correlation with knee extension block was analyzed. Using magnetic resonance imaging, the thicknesses of anterior and posterior segments were measured to assess significance of the thickness differences by a presence of knee extension block and by the posterior segment instability.

RESULTS

There were 13 knees with a stable posterior segment and 21 knees with an unstable posterior segment. Meniscal instability in the posterior segment was observed in the knees with a surface tear (n = 12), in a hypermobile posterior rim despite the absence of a surface tear (n = 5), and in knees with a freely movable posterior rim without posterior tibial attachment (n = 4). Knee extension block occurred exclusively in complete type menisci and was significantly correlated with meniscal instability in the posterior segment. Magnetic resonance imaging observations suggested that morphologic features characteristic of thick anterior and thin posterior segments were significantly associated with meniscal instability in the posterior segment. Clinically, knee extension block disappeared in all cases within 4 months of arthroscopic treatment.

CONCLUSIONS

A redundant anterior segment associated with meniscal instability in the posterior segment is likely to cause limited knee extension in children with discoid lateral meniscus. This correlation mandates that discoid menisci be thoroughly evaluated during arthroscopic treatment to identify any instability that might require stabilization.

Arthroscopic partial meniscectomy with repair of the peripheral tear for symptomatic discoid lateral meniscus in children: results of minimum 2 years of follow-up

PURPOSE

This study was undertaken to document the clinical results and technical aspects of arthroscopic partial meniscectomy in conjunction with peripheral tear repair for the treatment of symptomatic discoid lateral meniscus in children.

METHODS

From June 1998 to May 2005, the senior author (J.H.A.) performed arthroscopic surgery on 77 children (89 knees) with symptomatic discoid lateral meniscus. Of these patients, we retrospectively studied 23 patients (28 knees) with a peripheral tear that was treated by partial central meniscectomy in conjunction with peripheral suture repair. Mean age at operation was 9.0 years (range, 4 to 15 years), and the mean follow-up period was 50.9 months (range, 24 to 94 months). Arthroscopic findings were categorized into 3 types in terms of peripheral rim stability and tear site: (1) meniscocapsular junction (MC), anterior horn type (MC-A type); (2) MC, posterior horn type (MC-P type); and (3) posterolateral corner (PLC) loss type. These 3 types needed different arthroscopic techniques for saucerization with repair. Clinical results were evaluated using Lysholm knee scores and Hospital for Special Surgery (HSS) scores preoperatively and at final follow-up.

RESULTS

All patients were able to return to their previous life activities with little or no limitation, and no reoperation was required after an average follow-up of 51 months. Mean Lysholm knee scores improved from 78.5 (range, 69 to 89) preoperatively to 95.5 (range, 85 to 100) at the final follow-up (P < .0001), and the mean HSS score improved from 80.3 (range, 69 to 89) preoperatively to 95.9 (range, 90 to 100) at the final follow-up (P < .0001).

CONCLUSIONS

We believe that the described arthroscopic partial meniscectomy in conjunction with the meniscal repair of the peripheral tear are effective for treating children with a symptomatic discoid lateral meniscus.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Effects of arthroscopic meniscectomy on the long-term prognosis for the discoid lateral meniscus

This study compared the long-term clinical and radiological outcomes, according to the extent of arthroscopic meniscectomy, of complete and incomplete types of the discoid lateral meniscus. A total of 125 discoid menisci (74 complete and 51 incomplete types) without significant cartilage erosion at the time of surgery were included. The extent of meniscectomy was decided along with tear patterns and the stability of the discoid meniscus. Both clinical and radiological results were evaluated after total or partial meniscectomy. In the complete type of discoid meniscus with less than 5 years of follow-up, the total meniscectomy group showed better clinical results than the partial meniscectomy group. However, with over 5 years of follow-up, there were no differences between the two groups. In the radiological results, there was no significant difference between the two groups during the first 5 years after operation. However, with more than 5 years of follow-up, the partial meniscectomy group showed better results than the total meniscectomy group. In the incomplete-type discoid meniscus, clinical results were better in the partial meniscectomy group regardless of the follow-up periods. In the radiological results, the partial meniscectomy group showed better results for only more than 5 years of follow-up. The long-term prognosis after arthroscopic meniscectomy for the torn discoid lateral meniscus was related to the volume of the meniscus removed.

Les ménisques discoïdes chez l’enfant : manifestations cliniques et indications thérapeutiques

PURPOSE OF THE STUDY

Surgery is indicated when discoid menisci become symptomatic. The purpose of the surgical procedure is to resect any damaged tissue and restore the physiological shape of the meniscus. As a rule, as much meniscal tissue as possible must be spared because of the long-term deleterious effects on the cartilage of total meniscectomy. We analyzed a consecutive series of 18 cases of discoid menisci in children to search for secondary lesions and factors favoring their development in order to determine the optimal surgical procedure.

MATERIAL AND METHODS

This retrospective series included 17 children (18 menisci) aged 7.5 years on average at diagnosis between 1985 and 2003. We noted the clinical manifestations, the imaging findings, time to treatment, and operative observations. The Watanabe classification was used to describe the discoid menisci. We also noted meniscal and cartilage damage and their consequences, as well as the consequences of late surgery on the type of procedure used.

RESULTS

The main complaint was pain. Physical examination usually revealed a positive pivot test. Signs of osteochondral lesions of the lateral condyle were also observed in three children, and the MRI revealed degenerative menisci in four. Mean time from diagnosis to surgical treatment was 20 +/- 17 months. The Watanabe classification was type I (n=9), type II (n=5), type III (n=4). Arthroscopy revealed nine meniscal lesions and three cartilage lesions, one associated with osteochondritis. Meniscectomy was performed in eleven cases, meniscoplasty in seven. Meniscectomy was significantly more frequent (p<0.05) when there was a meniscal lesion (9/11 of the meniscectomies) and when the time from diagnosis to treatment was long (28 months versus 8 months for meniscoplasty, p<0.01). Time to surgery was associated significantly (p<0.05) with the proportion of meniscal, chondral, or osteochondral lesions. Inversely, the type of meniscus did not affect age at diagnosis, initial manifestations, or presence of a positive pivot test.

DISCUSSION

While therapeutic abstention is warranted for asymptomatic menisci, surgical treatment should be undertaken if symptoms develop, irrespective of the type. If possible, surgery should be performed less than six months after diagnosis. The risk of secondary meniscal or cartilage injury increases with longer delay before surgery. Similarly, the chances of performing meniscoplasty are reduced with longer time from diagnosis to surgery. It must be recalled that the objective of conservative mensical surgery is to prevent secondary cartilage lesions after extensive meniscectomy and consequently the risk of osteoarthritis.

Clinical and arthroscopic features of meniscal tears and a search for the role of infection in histologically confirmed meniscal mucoid degeneration

Mucoid degeneration (MD) of the meniscus has received little attention. The pathology deserves special interest as it may lead to loss of the meniscus even in very young individuals. The cause of MD and the clinical features of meniscal tears due to that pathology have not been understood. This study analyzed the age profile and the role of trauma in patients with torn menisci with MD, examined meniscal tear patterns and clinical features, and investigated the role of bacterial infection in causing MD. Meniscal samples obtained from 27 consecutive patients during arthroscopic resection of torn menisci considered to be due to MD (typical yellow color) underwent pathological investigation. The samples were scored according to the light microscopic criteria of Copenhaver; 24 menisci (23 patients) with stage 2-3 MD comprised the study group. Magnetic resonance imaging obtained in 11 patients typically revealed increased intrasubstance signal intensity that extended to at least one of the meniscal surfaces. Pieces of resected meniscal tissue were also subject to PCR investigation to search for presence of bacteria. Of the 24 knees 21 (87%) had no history of trauma. Mean Tegner activity level was 4 (1 and 7). Mean duration of symptoms was 11.6 months (1-36). Pain was the most frequent symptom ( n=22). Joint line tenderness and McMurray's test (pain and/or clicking) were present in 22 and 16 knees, respectively. Medial meniscus was affected in 16 and lateral meniscus in 8. Meniscal cyst and incomplete discoid meniscus was present in 5 and 2 of the lateral menisci. All of the torn menisci were degenerated and yellow in color. The most common tear patterns were radial and/or flap, and longitudinal-horizontal tears. PCR study revealed no bacteria. Mucoid degeneration of the meniscus does not seem to be related to the aging process. Clinical findings of torn such menisci are insidious compared to traumatic tears. Lack of history of trauma may delay the diagnosis. Bacterial infection has no role in the cause.

Arthroscopic meniscectomy for discoid lateral meniscus in children and adolescents: 4.5 year follow-up

We retrospectively reviewed the 4.5 year (range, 21-88 months) follow-up results of arthroscopic partial meniscectomies performed in 11 knees between 1994 and 2000 to treat a symptomatic discoid lateral meniscus. The average age at surgery was 11.5 years (range, 5-17 years). All except one of the discoid menisci were of a complete type, and all except three were torn menisci. At the latest follow-up examination, the result was excellent for nine knees, and good for two; no degenerative changes were evident on the roentgenograms. Arthroscopic partial meniscectomy should be the treatment of choice for the complete type symptomatic lateral discoid meniscus, even if it is intact. Preoperative lack of the knee extension requires a gentle rehabilitation program postoperatively.

Management of discoid lateral meniscus tears: observations in 34 knees

PURPOSE

The goal of this study was to evaluate arthroscopic partial resection of discoid lateral meniscus tears with an emphasis on radiographic evidence of degenerative changes after this procedure.

TYPE OF STUDY

Retrospective clinical study.

METHODS

Of 41 patients with an arthroscopic diagnosis of discoid meniscus over an 8-year period, 34 symptomatic lateral discoid meniscus tears in 33 patients were analyzed at an average follow-up of 5.6 years. The average age at operation was 19.8 years and most patients had vague and intermittent symptoms that caused delay in clinical diagnosis.

RESULTS

Eight patients were lost to follow-up and were excluded from the study. Magnetic resonance imaging, performed in 12 cases, and arthroscopy in all of these patients provided the precise diagnosis. All of the knees with symptomatic torn discoid menisci underwent arthroscopic partial meniscectomy. Only 1 Watanabe Wrisberg ligament type of discoid meniscus with posterior instability was totally meniscected. Based on Ikeuchi's grading, 39% of the knees had an excellent result, 46% had a good result, and 15% had a fair result; none of the results was poor.

CONCLUSIONS

At an average 5-year follow-up, partial meniscectomy in patients with a Watanabe complete or incomplete discoid meniscus showed 85% good or excellent clinical results. However, a significant percentage of patients show femoral condyle flattening on radiography.

Magnetic resonance imaging of the pediatric knee

Magnetic resonance imaging (MRI) is an excellent modality for imaging the pediatric knee because of its superb soft-tissue contrast, multiplanar capability, and lack of ionizing radiation. The knee is the most common joint imaged by MRI in the pediatric population. The majority of studies are performed on older children or adolescents with pain and/or known trauma. There are variations of injury and patterns of injury that are unique to children. The knee of a child also may be studied by MRI for other indications, including tumor, inflammatory disease, and developmental abnormalities. It is important to have a systematic approach to analysis of the knee MR images. Analysis should include individual attention to bones, articular cartilage, muscles and tendons, soft tissues, neurovascular bundle, joint space, fluid collections, ligaments, and menisci.

Discoid lateral meniscus in children

The discoid meniscus is the most common abnormal meniscal variant in children. It is most likely a congenital deviation and usually occurs laterally. The discoid shape results in greater coverage of the tibia and usually is associated with increased thickness of the meniscus that may lead to abnormal shearing forces across the knee joint. The Watanabe classification divides this anomaly into three distinct types: complete, incomplete, and Wrisberg ligament. The complete and incomplete types are often asymptomatic; unless symptomatic, they generally should be left alone. Tears should be treated with resection back to a stable rim. The Wrisberg ligament type is a hypermobile meniscus secondary to a lack of posterior tibial attachment. This type may or may not be associated with an abnormal shape and may appear in childhood as a classic snapping knee syndrome. These children complain of intermittent popping and snapping within the knee that clinically manifests as a dramatic audible and visible adjustment of the knee with each flexion and extension. Treatment of a symptomatic Wrisberg ligament type requires surgical repair of the posterior disruption. Saucerization of the remaining meniscus may be required to protect the repair from abnormal shear forces.

Symptomatic ring-shaped lateral meniscus

Abnormalities of the lateral meniscus in humans are a long-known fact. Three different types of discoid menisci are described in Watanabe's atlas, being considered as congenital malformations. For the second time in the literature, a fourth ring-shaped type of discoid lateral meniscus was described as an incidental finding in this Journal by Monllau et al. in 1998. The present case is the first description of a symptomatic, ring-shaped lateral meniscus with a concomitant, recurrent cyst at the lateral aspect of a child's knee.

MR imaging of tears of discoid lateral menisci

OBJECTIVE

The purpose of this study was to determine the positive predictive value (PPV) for diagnosis of discoid lateral meniscal tear using MR imaging and to describe various patterns of such tears in the knee.

SUBJECTS AND METHODS

MR reports of 77 patients (10-67 years old) who underwent prospective MR imaging that led to a diagnosis of discoid lateral meniscal tear were correlated with arthroscopic results. MR images obtained in 71 patients confirmed to have discoid lateral meniscial tear were retrospectively reviewed for the presence, site, and pattern of discoid lateral meniscal tear, including type of displacement of the torn segment. MR abnormalities were correlated with arthroscopic findings.

RESULTS

For the prospective MR interpretations, the PPV for discoid meniscus was 92%. PPV for discoid meniscal tear was 57%. PPVs for individual types of discoid meniscal tears were 46% (peripheral tear, 19/41), 76% (peripheral tear with horizontal tears, 16/21), 56% (horizontal tear, 5/9), 50% (transverse tear, 1/2), 67% (horizontal tear combined with transverse tear, 2/3), and 100% (longitudinal tear, 1/1). Peripheral tear alone and peripheral tear with horizontal tear were the most common types of tears (n = 20, 28%). Multiple tears (n = 34, 48%) were common. Displacement of the torn segments was seen in 51 patients (72%).

CONCLUSION

MR imaging has a low PPV for diagnosing discoid lateral meniscal tear. Peripheral tear alone and peripheral tear with horizontal tear were the most common types of tears, and displacement of the torn segment was frequent.

Arthroscopic technique: two-piece excision of discoid meniscus

This article describes a new arthroscopic technique of excision of complete discoid meniscus with a tear in which the discoid is divided into anterior and posterior pieces for removal. It is easy to perform because an excellent visualization of the posterior segment is obtained after removal of the anterior piece. The extent of intrasubstance pathology can be evaluated with a transverse cut to the mid portion of the discoid, and therefore, it is easy to determine the width of the rim to be retained. Because the meniscus is divided into two pieces, a large portal is not required for removal.

Accuracy of imaging the menisci on an in-office, dedicated, magnetic resonance imaging extremity system

Magnetic resonance imaging effectively defines and characterizes musculoskeletal pathologic lesions, particularly meniscal tears. Most studies comparing the efficacy of magnetic resonance imaging and arthroscopic evaluation have been performed on high-field (1.5-T) systems. The effectiveness of a low-field (0.2-T), dedicated, extremity magnetic resonance imaging device in diagnosing meniscal tears was studied prospectively on 35 patients with knee symptoms who subsequently had arthroscopic evaluation. Magnetic resonance imaging examinations were performed before surgery and were read by an experienced radiologist who was blinded to the results of the arthroscopic evaluations. Specificity was 100% for both the medial and lateral menisci. Sensitivity was 86% for the medial menisci, 89% for the lateral menisci, and 87% for both. Accuracy was 91% for the medial menisci, 97% for the lateral menisci, and 94% overall. The positive predictive values were 100% for the medial menisci, 100% for the lateral menisci, and 100% for both. The negative predictive values were 81% for the medial menisci, 96% for the lateral menisci, and 91% for both. The low-field magnetic resonance imaging system provided specificity and sensitivity that were equal to or better than previous reports with high-field systems. In particular, this low-field system eliminated the problem of false-positive results that has been found in some studies using high-field systems.

The impact of magnetic resonance imaging of the knee on surgical decision making

Although magnetic resonance imaging (MRI) of the knee is known to be an accurate technique for diagnosing soft tissue disorders of the knee, the value of MRI in improving patient outcome is controversial. The purpose of this project was to study the value of MRI in a subgroup of patients with knee pain and disability whose diagnosis was uncertain after standard orthopaedic evaluation. An extensive database was recorded prospectively for each of 208 patients providing clinical data as well as diagnoses from clinical, MRI, and surgical observations. These data were analyzed to determine the effect of MRI on diagnosis and patient outcome regarding surgical decision making. The overall diagnostic accuracy of MRI was determined to be 97% in patients undergoing arthroscopy. MRI differed from the clinical diagnosis in 33% of cases, the most common variance being diagnosis of meniscal tear. After combining the MRI and clinical information, surgical decision making was altered in 27% of cases. In a group of patients with acute knee symptoms, the decision not to proceed with surgery was made in 64% of cases. The study shows that MRI of the knee is a valuable tool for augmenting the diagnostic process. The data further show that MRI is a cost-effective technique for avoiding unnecessary surgery and affects patient outcome by improving surgical decision making.

Lateral Meniscal Variants: Evaluation and Treatment

The normal lateral meniscus is morphologically more variable than the medial meniscus. The abnormal lateral meniscus also varies with respect to size, shape, and stability. Variations can occur in patients of all ages. The underlying causes of lateral meniscal abnormalities are multifactorial. The spectrum of abnormalities includes the most common variant, discoid lateral meniscus, as well as less common conditions, such as a lateral meniscal variant with absence of the posterior coronary ligament. Treatment should be based on the severity of symptoms and the type of pathologic lesion.