Risk Factors Associated With Knee Joint Degeneration After Arthroscopic Reshaping for Juvenile Discoid Lateral Meniscus

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.

Effect of residual volume after surgery of the discoid lateral meniscus on tibiofemoral joint biomechanics: a finite element analysis

BACKGROUND

The purpose of this study was to investigate the influence of different residual meniscus volume on the biomechanics of tibiofemoral joint after discoid lateral meniscus (DLM) surgery by finite element analysis.

METHODS

A knee joint model was established based on CT and MRI imaging data. The DLM model was divided into five regions according to conventional meniscectomy, with volumes of 15%, 15%, 15%, 15%, 15%, and 40% for each region. Additionally, the DLM model was divided into anterior and posterior parts to obtain ten regions. The DLM was resected according to the design scheme, and together with the intact discoid meniscus, a total of 15 models were obtained. Finite element analysis was conducted to assess shear and pressure trends on the knee joint.

RESULTS

The study observed significant changes in peak shear stress and compressive stress in the lateral meniscus and lateral femur cartilage. As the meniscus volume decreased, there was an increase in these stresses. Specifically, when the meniscus volume reduced to 40%, there was a sharp increase in shear stress (302%) and compressive stress (152%) on the meniscus, as well as shear stress (195%) and compressive stress (157%) on the lateral femur cartilage. Furthermore, the model grouping results showed that preserving a higher frontal volume in the meniscus model provided better biomechanical advantages.

CONCLUSION

The use of finite element analysis has demonstrated that preserving more than 55% of the meniscus volume is necessary to prevent a significant increase in joint stress, which can potentially lead to joint degeneration. Additionally, it is crucial to preserve the front volume of the DLM in order to achieve improved knee biomechanical outcomes.

Comparative analysis of discoid lateral meniscus size: a distinction between symptomatic and asymptomatic cases

PURPOSE

This study evaluated the differences in meniscal sizes and occupancy between symptomatic and asymptomatic patients diagnosed with discoid lateral meniscus (DLM) using magnetic resonance imaging (MRI) to understand how these variations relate to the presence of symptoms and the patients' age.

METHODS

A retrospective review of 98 patients with DLM was conducted, excluding those with meniscal displacement. Both the width and extrusion of DLM and the percentage of the meniscus to the tibia were measured using mid-coronal and mid-sagittal MRI and compared between symptomatic and asymptomatic DLM groups. The relationships among each parameter, meniscal size, and patient age were evaluated. Symptomatic cases were divided into those with and without horizontal tears on MRI to compare the differences in meniscal morphology.

RESULTS

A total of 92 knees from 74 patients were included. Sixty-one knees required surgical intervention for symptomatic DLM, while 31 were asymptomatic and included the contralateral side of symptomatic knees. The symptomatic group exhibited larger morphological variations than the asymptomatic group. Moreover, the sagittal meniscal ratio reduced with age in the asymptomatic group (r = - 0.54, p = 0.002) but remained constant in the symptomatic group. The symptomatic cases with horizontal tears demonstrated larger meniscal dimensions and smaller posterior capsule distances than those without tears.

CONCLUSION

Symptomatic patients with DLM had larger knee morphological changes than asymptomatic ones. Age affected the meniscal occupancy in the sagittal plane only in asymptomatic patients.

LEVEL OF EVIDENCE

III.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

Retrospective comparative study; level of evidence, 3.

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.

Arthroscopic treatment of the symptomatic discoid lateral meniscus improves the knee function in the long-term: a ten-year follow-up study

PURPOSE

Discoid lateral meniscus (DLM) is a common meniscal anatomic disorder and can cause irreversible knee consequences. The long-term clinical outcomes of DLM management remain unclear. Moreover, several potential factors would influence the long-term functional outcomes. The factors also remain unclear. This study aims to evaluate the long-term clinical outcomes of the arthroscopic management of the DLM and to identify the patients' factors affecting the long-term results.

METHODS

Medical records were retrospectively examined for patients with symptomatic unilateral DLM who underwent arthroscopic procedures between January 2004 and August 2011. The characteristics of DLM, the preoperative and the long-term postoperative visual analog scale (VAS), the International Knee Documentation Committee (IKDC) score, Lysholm, and Yulish scores were evaluated. Data were collected, processed, and analyzed using SAS software version 9.2. Univariate and multivariate analyses were performed to identify the factors influencing the long-term outcomes of the DLM arthroscopy.

RESULTS

A total of 128 patients were included, most of whom were females (68.7%). The median age of the included participants was 24 (16-31) years old. The median duration of symptoms was 23.3 (10, 31) months, and the median follow-up duration was 126.2 (113, 140) months. The functional scores significantly improved postoperatively compared to the preoperative scores; VAS (1.65 ± 1.17 vs. 6.08 ± 1.31), Lysholm (91.39 ± 5.05 vs. 77.51 ± 10.19), and IKDC (84.63 ± 7.69 vs. 67.89 ± 9.56), respectively; p<0.05. Multivariate analysis revealed that gender, the status of self-reported instability, preoperative VAS, Yulish MR cartilage grade, and Lysholm score had a significant correlation with the worsening of the final follow-up IKDC scores.

CONCLUSIONS

Arthroscopic procedure significantly improved the long-term joint function of the DLM patients, as evidenced by the sustained improvement of the VAS, Lysholm, and IKDC scores. These clinical outcomes were greatly influenced by gender, the status of self-reported instability, preoperative Yulish MR cartilage grade, VAS, and Lysholm score.

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

INTRODUCTION

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

Case-control study, III.

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.

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.

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.

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

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

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.

Update on imaging of the discoid meniscus

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

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.

Radial Width of the Lateral Meniscus at the Popliteal Hiatus: Relevance to Saucerization of Discoid Lateral Menisci

BACKGROUND

A discoid lateral meniscus (DLM) is a congenital anomaly of the knee in which the lateral meniscus has an "O" shape and contains irregular, abnormal collagenous tissue. A DLM can cause mechanical symptoms and pain. Treatment of a symptomatic DLM is arthroscopic saucerization to reshape the meniscus to a more normal contour. Enough tissue must be removed to eliminate mechanical symptoms but not too much to create instability. The residual width of the meniscus is crucial at the popliteus hiatus because here the peripheral rim is unattached at the capsule. Reports in the literature recommend a residual width of 6 to 8 mm.

PURPOSE/HYPOTHESIS

The purpose of this research was to determine the width of the lateral meniscus at the popliteal hiatus in normal specimens. Our null hypothesis was that a residual width of 6 to 8 mm will be sufficient to approximate normal anatomy.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

We made direct measurements of the radial width of the lateral meniscus from the outer rim at the popliteal hiatus to the inner edge in 19 specimens (age, 2-120 months.) We measured one 4-year-old specimen with a bilateral complete DLM. We also measured 39 digital images of specimens (age, 1-132 months) using ImageJ. Finally, we made direct arthroscopic measurements of 8 skeletally mature specimens.

RESULTS

The average width of specimens <3 years old was 5.5 mm. The average width of the 10-year-old specimens was 12 mm. The average width of the skeletally mature specimens was 16 mm. A 4-year-old DLM specimen measured 19 mm.

CONCLUSION

We rejected our null hypothesis. Direct measurements suggest that a residual width of 6 to 8 mm is insufficient for children ≥8 years old. A width of at least a full centimeter approximates the normal for 8-year-olds and at least 15 mm for adolescents.

Surgical Repair of Symptomatic Wrisberg Variant Discoid Lateral Mensicus with Pull-Out Repair and Capsulodesis

Wrisberg variant discoid lateral meniscus (DLM) is a congenital anatomic variation of the meniscus in the knee joint, which is an uncommon type of the DLM. We present a surgical technique in a case of symptomatic Wrisberg variant DLM. To improve the instability due to the lack of the posterior attachment of meniscotibial ligament, the posterior portion of DLM was attached to the insertion site of normal LM posterior root using pull-out repair technique. In addition, a longitudinal tear from the anterior to the middle portion of DLM was repaired with outside-in and inside-out techniques. Finally, a capsulodesis using knotless anchors was performed from outside of the joint to prevent the meniscus extrusion after the surgery. Knee symptoms such as pain, catching, and ROM restriction disappeared at 3 months after the surgery. Postoperative magnetic resonance imaging showed a slightly sharpened shape of the DLM, and the attachment of the posterior portion of the DLM was observed. Longitudinal tear of the DLM was healed without cleavage. This procedure is useful to improve the symptoms of the knee joint with Wrisberg variant DLM and to preserve the function of the meniscus.

Meniscus Allograft Transplantation Obtained From Adult Patients Undergoing Total Knee Arthroplasty May be Used for Younger Patients After Lateral Discoid Meniscus Meniscectomy

Purpose

To investigate the clinical outcomes following meniscus allograft transplantation (MAT) to replace removed discoid lateral meniscus using intact lateral meniscus obtained from patients undergoing total knee arthroplasty for medial compartment osteoarthritis.

Methods

Pediatric patients who underwent MAT secondary to partial or total meniscectomy due to discoid lateral meniscus between August 2010 and November 2018 were identified. Lateral menisci with bone blocks were transplanted arthroscopically. The demographic data, range of motion, meniscal allograft failure, which was defined as removal of an implanted meniscus, and complications were recorded. The Lysholm score and the Kellgren-Lawrence (KL) grade on radiographs were evaluated preoperatively and at final follow-up. The Knee injury and Osteoarthritis Outcome Score was evaluated in the final follow-up.

Results

Eight patients who were symptomatic after discoid lateral meniscectomy were included. Donated allografts were harvested from adult patients aged between 64 and 78 years (mean 70.5 years). The mean age at previous meniscectomy and MAT were 10.5 and 18.1 years, respectively. All patients were followed up for a mean time of 5.2 years, and there were no cases of meniscus failure and complication. The Lysholm score significantly improved from preoperative to the final follow-up. Preoperatively, 6 and 2 knees were of KL grades II and III, respectively. At final follow-up, no increased KL grade was observed in 5 patients; however, an increase by 1 grade was observed in 2 patients and an increase by 2 grades was observed in 1 patient. The Knee injury and Osteoarthritis Outcome Scores at the final follow-up were 87.2 for pain, 87.9 for symptoms, 95.4 for activities of daily living, 79.4 for sports, and 65.6 for quality of life.

Conclusions

Older lateral meniscus allografts obtained from knees of adult patients undergoing total knee arthroplasty and transplanted into younger patients with defects from discoid lateral meniscectomy resulted in improved Lysholm scores but no improvement in Tegner scores or knee motion. KL grades were unchanged in 5 of the 8 patients at the final follow-up.

Level of Evidence

IV, therapeutic case series.

Arthroscopic Saucerization With Inside-Out Repair and Anterocentral Shift of a Discoid Lateral Meniscus With Retention of Adequate Volume of Residual Meniscus

ABSTRACT

Preservation of the meniscus has been shown to influence the progression of osteoarthritic changes in the knee. Discoid lateral meniscus (DLM) is classified on the basis of the presence and location of instability resulting from deficient capsular attachments. Recently, meniscal stabilization after saucerization was recommended in cases of DLM to preserve the meniscus shape and avoid the progression of osteoarthritis. However, it is difficult to identify the accurate resection volume and residual meniscal width during surgery, especially when there is an anterocentral shift of the DLM. This Technical Note describes an arthroscopic technique for an anterocentral shift of the DLM in which we highlight the resection point and confirm the methods of retaining an adequate volume of residual meniscus to restore and maintain the shape and function of the meniscus.

LEVEL OF EVIDENCE

Level 1, Knee; Level 2, Meniscus.

Examination of refractory discoid lateral meniscus injury

BACKGROUND

Lateral discoid meniscus (LDM) should be treated and preserved with saucerization and/or suture repair. However, repair of the meniscal hoop structure is sometimes difficult due to displacement or large defects. In this study, we aimed to examine tear patterns based on the Ahn classification in those requiring meniscal repair and those undergoing subtotal meniscectomy.

METHODS

Twenty-three patients were evaluated (mean age, 27.4 years; mean follow-up period, 2.5 years). The following were evaluated: displacement morphology based on the Ahn classification, site of tear under arthroscopy, morphology, surgical procedure, Lysholm score at final postoperative follow-up, and clinical outcome of meniscus using Barrett's criteria.

RESULT

There were 16 knees without displacement (saucerization with suture repair, 13 knees; subtotal meniscectomy, 3 knees) and 10 knees with displacement (reduction with suture repair, 3 knees; subtotal meniscectomy, 7 knees). Subtotal meniscectomy was performed more often in cases with dislocation, especially in the central shift type as defined by the Ahn classification. The mean Lysholm score was 65.0 points preoperatively and 95.3 points postoperatively. Twenty-three knees (88%) were postoperatively categorized under the Barrett's criteria as healing and 3 knees (12%) were categorized as non-healing. The number of non-healing cases that underwent subtotal meniscectomy was relatively small (1 of 10 knees), and the short-term results were not poor.

CONCLUSION

Localized peripheral longitudinal tears tended to be repairable even with displacement, while peripheral tears covering the entire meniscus or with severe defects/tears in the body of the meniscus tended to be difficult to repair, leading to subtotal meniscectomy.

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.

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.

The postoperative shorter meniscal width was the risk factor of lateral meniscal extrusion in the middle portion for juvenile and adolescent knees with discoid lateral meniscus

PURPOSE

The study aim was to clarify the risk factors for postoperative meniscal extrusion in a middle portion in juvenile and adolescent knees with DLM.

METHODS

Forty-six patients with symptomatic DLM who underwent surgery were retrospectively assessed. Inclusion criteria were set as follows: (1) aged ≤ 17 years with an open growth plate, (2) preoperative and postoperative follow-up MRI, and 3) reshaping surgeries comprising of saucerization alone or with meniscal repair. Average (95%CI) age during surgery, body mass index (BMI), and follow-up duration were 12 years (11-13), 19.9 kg/m² (18.7-21.0), and 26.4 months (19.5-33.3), respectively. Age, sex, sports activities, BMI, postoperative rehabilitation, preoperative shift of DLM by Ahn's classification, surgical procedures, postoperative meniscal width of all portions, and meniscal healing were analyzed.

RESULTS

Postoperatively, eight knees in the no-extrusion group and 38 knees in the extrusion group were observed. In the univariate logistic regression analysis, shorter meniscal width in a middle portion (OR = 1.580, p = 0.006), shorter minimum width of all portions (OR = 1.674, p = 0.024), and meniscal healing (OR = 0.160, p = 0.028) were the risk factors for meniscal extrusion in a middle portion. Multiple logistic regression analysis demonstrated that shorter meniscal width in a middle portion was the risk factor.

CONCLUSIONS

As the clinical relevance, to prevent postoperative meniscal extrusion of the middle portion with DLM, surgeons are necessary to pay attention to maintain the adequate meniscal width for juvenile and adolescent knees.

LEVEL OF EVIDENCE

III.

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.

Editorial Commentary: Saucerization Is Superior to Total Meniscectomy in Patients With Symptomatic Discoid Lateral Meniscus

Current treatment recommendations favor meniscal rim preservation through partial meniscectomy with repair when indicated in patients with symptomatic discoid lateral menisci. Although many studies have shown the importance of meniscal rim preservation, some have shown that suture repair does not yield improved outcomes over partial meniscectomy without repair, considering the cost of repair and lack of available data. However, partial meniscectomy with repair is essential when peripheral instability is seen in patients with symptomatic discoid lateral menisci. Arthroscopic reshaping in young patients can be challenging for an inexperienced surgeon because visualization within the lateral joint space may be limited by a thickened meniscus and the small size of the pediatric knee. To preserve a stable peripheral rim, various meniscal repair methods should be used for stabilizing the reshaped meniscus on the capsule based on repair location, tear type, and surgeon preference.

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.

Predictive factors for developing osteochondritis dissecans after surgery for discoid lateral meniscus are younger age and shorter meniscal width

PURPOSE

This study aimed to identify the predictive factors for postoperative osteochondritis dissecans (OCD) in juvenile and adolescent knees with discoid lateral meniscus (DLM).

METHODS

In total, 242 patients with symptomatic DLM who underwent surgery were identified. Inclusion criteria were set as follows: (1) age ≤ 17 years with an open growth plate, (2) follow-up magnetic resonance imaging, and (3) absence of preoperative OCD. Consequently, 52 patients were retrospectively investigated. Average age during surgery, body mass index (BMI), and follow-up duration were 12 years [95% confidence interval (CI) 11-13], 19.2 kg/m² (95% CI 18.4-20.1), and 27.3 months (95% CI 20.9-33.7), respectively. Age, sex, sports activities, BMI, symptomatic OCD in other joints, postoperative rehabilitation, preoperative shift of DLM by Ahn's classification, surgical procedures (saucerization alone or with stabilization, and subtotal meniscectomy), and postoperative meniscal width were analyzed as possible predictive factors.

RESULTS

Postoperatively, 42 patients without OCD and 10 with OCD were observed. In univariate analysis, younger age [odds ratio (OR) 1.5; p = 0.003], subtotal meniscectomy (OR 6.3; p = 0.027), and shorter meniscal width (OR 2.7; p = 0.005) were predictive factors for postoperative OCD. Multivariate analysis demonstrated that younger age (OR 1.6; p = 0.009) and shorter meniscal width (OR 1.5; p = 0.003) were predictive factors.

CONCLUSIONS

To prevent postoperative OCD after DLM surgeries, achieving stabilization with adequate meniscal width is necessary for juvenile knees.

LEVEL OF EVIDENCE

III.

Can an injured discoid lateral meniscus be returned to the correct anatomic position and size of the native lateral meniscus after surgery?

BACKGROUND

No previous studies have compared the position and size of the remaining discoid lateral meniscus (DLM) with that of a normal lateral meniscus. This study aimed to evaluate the postoperative position and size of DLM compared with that of normal controls using magnetic resonance imaging (MRI).

METHODS

This retrospective study involved 52 symptomatic complete type DLMs (discoid group) who underwent arthroscopic surgery and 50 normal controls (control group). Pre- and postoperative MRI evaluations, height, width, and relative percentage of extrusion (RPE) were assessed. Sagittal position parameters, including distances from articular cartilage center to anterior meniscus (CAMD) and from anterior articular cartilage margin to anterior horn (ACMD), were also assessed. Logistic regression analysis was performed to find factors with extrusion of remaining DLM.

RESULTS

The height of the discoid group was significantly lower than that of the control group (P = 0.000). RPE in the discoid group was significantly larger than in the control group (P = 0.005). Only CAMD and ACMD in the discoid group were different (positioned more anteriorly) from the control group (P = 0.000). Preoperative meniscal shift (odds ratio (OR): 12.448; P = 0.003) and operative technique, especially partial meniscectomy with repair (OR: 19.125; P = 0.000), were the major factors associated with extrusion.

CONCLUSION

The width of remaining DLM was comparable to that of normal controls, but the position was found to be more anterior and lateral than that of normal controls. Preoperative meniscal shift and combined meniscus repair were the major factors for smaller width and greater extrusion; thus, surgeons should address and counsel these factors before surgery.

Saucerization and Repair of Discoid Lateral Menisci With Peripheral Rim Instability: Intermediate-term Outcomes in Children and Adolescents

BACKGROUND

Historically, total meniscectomy was recommended as the treatment for a symptomatic discoid meniscus. Improved meniscal repair techniques and inferior long-term outcomes associated with meniscectomy have resulted in a trend toward meniscal preservation, with saucerization and repair of meniscocapsular tears. Reoperation rates after treatment of torn discoid menisci vary, with some series reporting high rates of reinjury and reoperation. The purpose of this study is to describe the intermediate-term outcomes of pediatric patients treated with saucerization and meniscocapsular repair of discoid lateral menisci with peripheral rim instability.

METHODS

A single-institution retrospective review was performed of consecutive patients less than 18 years of age treated with saucerization and repair for a meniscocapsular tear of a discoid lateral meniscus from 2013 to 2017. All patients had a minimum 24-month follow-up. A chart review was performed to describe tear location and repair type. The primary outcomes were revision meniscus surgery and Pedi-International Knee Documentation Committee and Tegner activity scores obtained at the final follow-up.

RESULTS

In total, 32 knees in 30 patients, including 15 males and 15 females with a mean age of 12 years (range, 5 to 17 y), were included. Tear patterns included anterior meniscocapsular (14 knees), posterior meniscocapsular (16 knees), and both anterior and posterior meniscocapsular (2 knees). Arthroscopic saucerization and meniscocapsular repair were performed in all knees. Repair types were outside-in (10 knees), inside-out (8 knees), all-inside (8 knees), and hybrid (6 knees). The mean follow-up was 54 months (range, 30 to 86 mo). Three knees (9%) underwent revision meniscus surgery, including 2 all-inside repairs and 1 partial meniscectomy. At the final follow-up, mean International Knee Documentation Committee score was 96 (range, 82 to 100). A total of 89% of patients reported returning to the same or higher level of activity following surgery.

CONCLUSIONS

Saucerization of discoid lateral menisci with repair of meniscocapsular tears is associated with low rates of revision surgery and good intermediate-term outcomes.

LEVEL OF EVIDENCE

Level IV.

Discoid lateral meniscus: importance, diagnosis, and treatment

Discoid lateral meniscus (DLM) is a common anatomic variant in the knee typically presented in young populations, with a greater incidence in the Asian population than in other populations. As DLM is a congenital anomaly, the ultrastructural features and morphology differ from those of the normal meniscus, potentially leading to meniscal tears. Snapping and pain are common symptoms, with occasional limitations of extension, in patients with DLM. Examination of the contralateral knee is necessary as DLM affects both knees. While simple radiographs may provide indirect signs of a DLM, magnetic resonance imaging (MRI) is essential for diagnosis and treatment planning. Although DLM was traditionally classified into three categories, namely, complete, incomplete, and Wrisberg DLM, a recent MRI classification provides useful information for surgical planning because the MRI classification was based on the peripheral detachment in patients with DLM, as follows: no shift, anterocentral shift, posterocentral shift, and central shift. Asymptomatic patients require close follow-up without surgical treatment, while patients with symptoms often require surgery. Total or subtotal meniscectomy, which has been traditionally performed, leads to an increased risk of degenerative arthritis; thus, partial meniscectomy is currently considered the treatment of choice for DLM. In addition to partial meniscectomy, meniscal repair of peripheral detachment is recommended for stabilization in patients with DLM to preserve the function of the meniscus. Previous studies have reported that partial meniscectomy with or without meniscal repair is effective and shows superior clinical and radiological outcomes to those of total or subtotal meniscectomy during the short- to long-term follow-up. Our preferred principle for DLM treatment is reduction, followed by reshaping with reference to the midbody of the medial meniscus and repair as firm as possible.

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.

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.

Ring-shaped meniscus formation may arise from the regenerative response to meniscectomy during growth spurts: A case report

•

We presented a case of newly formed ring-shaped meniscus-like tissue after partial resection of discoid lateral meniscus.

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The newly formed interhorn bridge could have represented a meniscus-like tissue that appeared secondary to tissue repair.

•

Intra-patient findings indicate that growth spurts may promote the tissue repair.

Introduction

Ring-shaped meniscus is very rare and generally considered to be a congenital malformation. Here, we report a case of newly formed ring-shaped meniscus-like tissue following arthroscopic partial meniscectomy for a complete discoid lateral meniscus.

Presentation of case

A 14-year-old boy underwent arthroscopic partial meniscectomy for complete discoid lateral meniscus of the left knee. The growth plates were present at the surgery. Although pain improved immediately after surgery, he reported left knee pain at the 7-month follow-up. Magnetic resonance imaging revealed a bucket-handle tear of the lateral meniscus and a second arthroscopic surgery was performed. During arthroscopy, we found that the anterior and posterior horns of the lateral meniscus were connected by meniscus-like tissue forming a ring-shaped meniscus and the newly formed interhorn meniscal bridge was resected. Histological evaluation indicated that the newly formed tissue was meniscus-like tissue that had appeared secondary to tissue repair. He visited our hospital at 16 years old, after the growth plates had closed, complaining of right knee pain. Arthroscopic partial meniscectomy was performed for complete discoid lateral meniscus of the right knee. As of two years after this surgery, no morphological changes have been observed.

Discussion

Although the exact mechanisms of meniscus-like tissue formation remain unclear, the growth spurt may promote the mechanisms of tissue repair, forming ring-shaped meniscus-like tissue.

Conclusion

This is the first case of ring-shaped meniscus-like tissue forming after partial resection of a complete discoid lateral meniscus. Ring-shaped meniscus-like tissue can develop in growing patients.

Midbody of the medial meniscus as a reference of preservation in partial meniscectomy for complete discoid lateral meniscus

PURPOSE

To evaluate the postoperative size of discoid lateral meniscus using magnetic resonance imaging (MRI) after partial meniscectomy relative to the size of medial meniscus midbody.

METHODS

This study included 48 patients who underwent arthroscopic partial meniscectomy with or without repair for symptomatic complete discoid meniscus. The intraoperative size of midbody of medial meniscus was used as a reference for partial meniscectomy. MRIs were performed pre- and postoperatively. Quantitative evaluations of the height, width, extrusion of the meniscus, and relative percentage of extrusion in the coronal and sagittal planes were completed. Demographic data, preoperative shift, type of shift, and operative technique were analyzed while considering the remaining meniscus. Logistic regression analyses were used.

RESULTS

The mean remaining discoid meniscal width in the coronal plane of MRI was not significantly different from the width of midbody of medial meniscus (9.1 ± 4.2 mm vs. 9.4 ± 1.4 mm, n.s.) Absolute meniscal extrusion and relative percentage of extrusion in the coronal plane and the ratio of t meniscus in sagittal plane of the final MRI were significantly increased as compared with the preoperative MRI. Preoperative shift was a risk factor for the reduction of remaining meniscal width (odds ratio 11.997, p = 0.016, 95% CI 1.586-90.737).

CONCLUSION

The size of midbody of medial meniscus could be a reference for partial meniscectomy in symptomatic complete discoid meniscus. Preoperative shift represents a risk factor for decreased remaining meniscal width. These findings could be helpful in ensuring appropriate surgical planning and explaining poor prognostic factors.

LEVEL OF EVIDENCE

Prospective cohort study, Level II.

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.

Management of Long-Term Complications in the Setting of Lateral Meniscal Deficiency After Saucerization of a Discoid Lateral Meniscus in an Adolescent Patient: A Case Report and Review of the Literature

CASE

A 14-year-old adolescent with bilateral discoid menisci who had previously undergone discoid meniscal saucerization presented with pain and mechanical knee symptoms bilaterally. She had a torn left discoid lateral meniscus, a right lateral meniscal deficiency with an associated osteochondral defect, and valgus collapse of the right femur. She underwent successful repair of the left discoid meniscus as well as a femoral osteotomy, a meniscal transplant, and an osteochondral allograft transplantation in the right knee.

CONCLUSION

New treatment paradigms following initial interventions for discoid menisci are discussed. Patients may benefit from longer follow-up after discoid meniscal surgery, and providers should consider joint-preserving techniques early in the setting of meniscal deficiency.

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.

•

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.

Arthroscopic partial meniscectomy in young patients with symptomatic discoid lateral meniscus: an average 10-year follow-up study

INTRODUCTION

The aim of this study is to evaluate mid-to-long-term clinical and radiological outcomes after an arthroscopic partial meniscectomy for symptomatic discoid lateral meniscus (DLM) in young patients and to determine whether degeneration of the residual meniscus and articular cartilage progresses during the follow-up period using magnetic resonance imaging (MRI).

MATERIALS AND METHODS

We retrospectively reviewed patients aged ≤ 40 years at surgery who underwent arthroscopic partial meniscectomy for symptomatic DLM and were followed up for ≥ 5 years. Lysholm knee scores and reoperation rates were assessed as clinical outcomes. Factors that affect clinical outcomes were evaluated. Tapper-Hoover classification and femorotibial angle were used for radiological assessment. The degree of degeneration of articular cartilages and residual meniscus was evaluated using preoperative and follow-up MRIs.

RESULTS

A total of 73 knees (66 patients) were enrolled. The mean follow-up period was 10.0 years. The mean follow-up Lysholm knee score was 84.2 ± 14.5, and the reoperation rate was 32.9%. Follow-up Lysholm knee scores were related to duration of symptoms prior to surgery (β = - 0.129, P = 0.003) and femorotibial angle at the last follow-up (β = 1.362, P = 0.045). On simple radiographs, progression of arthritis of the lateral compartment was observed in 68.5% (49 knees). In MRI analyses, degeneration of the residual meniscus progressed in 52.9% (34 knees) (P < 0.001), and significant changes in modified Yulish scores were observed in both lateral femoral and tibial condyles (P < 0.001, both condyles).

CONCLUSIONS

After an arthroscopic partial meniscectomy for symptomatic DLM, unfavorable clinical outcomes were shown in > 30% of the patients during a mean follow-up of 10.0 years. Clinical outcomes based on the patient-reported outcome measures were related to durations of symptoms prior to surgery and alignment at the last follow-up. In radiological and MRI assessments, progression of degeneration of articular cartilages in the lateral compartments of the knees and residual menisci was observed.