Bilateral congenital separation of the lateral meniscus. A case report

Reports of congenital abnormalities of the lateral meniscus include discoid meniscus, accessory meniscus, double-layered meniscus and ring-shaped meniscus. We present a rare case of an unusual abnormality of the bilateral lateral meniscus, which was completely separated and duplicated at the midportion, although different from an accessory meniscus, with an anomaly of the anterior horn of the medial meniscus as well as a double-layered medial meniscus. This type of abnormality of the lateral meniscus and double-layered medial meniscus has not previously been described in the literature. We have designated the abnormality of the bilateral lateral meniscus a separated meniscus.     

膝关节内侧半月板突出与后根部损伤相关性的MRI分析

背景：半月板根部损伤是半月板突出的重要原因。近年来,国外有许多关于半月板根部损伤和半月板突出关系的研究报道,而国内暂无相关的报道。 目的：探讨膝关节内侧半月板突出与内侧半月板后根部损伤的相关性。 方法：回顾性分析84例具有膝关节内侧半月板突出征象患者的MRI及关节镜表现,将半月板突出长度≥ 3 mm或半月板突出长度/半月板最大径≥10%定义为严重突出,采用卡方检验分析两种测量方法下的内侧半月板突出与后根部损伤之间的相关性。 结果与结论：MRI显示内侧半月板严重突出(半月板突出长度≥3 mm或半月板突出长度/半月板最大径≥10%)与关节镜检查显示半月板后根部损伤具有显著相关性(P < 0.05),比值比及95%可信区间分别为25.04 (3.07-204.44),6.96(1.38-35.19)。结果可见膝关节内侧半月板严重突出与内侧半月板后根部损伤密切相关,是半月板根部损伤的重要特征。     

The relationship between the medial collateral ligament and the medial meniscus: a topographical and biomechanical study

The functional influence of the medial collateral ligament on the medial meniscus is still discussed controversially. Commonly, a strong fixation of the meniscus by the collateral ligament is described. Injury to the medial meniscus is explained by its reduced mobility due to its strong adherence to the medial collateral ligament. The analysis of 10 plastinated series of the medial femorotibial compartment prove that only few fibres of the ligament radiate into the meniscus. To define the possible contribution of these fibers to the stability of the medial meniscus, experiments on two fresh frozen knee joints were performed. The distal femur was separated by cutting the capsule. The medial collateral ligament was detached carefully from its femoral insertion. The tibial head with both menisci was fixed in a clamping system. A translucent, exact acrylic glass copy of the femoral component to which the medial collateral ligament was reinserted, allowed studying the behaviour of the medial meniscus under axial compression (500 N). Firstly, stress was applied while the collateral ligament was proximally fixed and under tension; then the same experiment was performed after femoral detachment of collateral ligament. All plastinated series revealed only some deep and tender fibrous bundles of the medial collateral ligament radiating into the medial meniscus proximally and posteriorly. The behaviour of medial meniscus was exactly the same in both stress experiment series. The conclusion is that there is no relevant influence of the medial collateral ligament on the stability of the medial meniscus.     

The meniscal flounce: a valuable arthroscopic sign

PURPOSE: The purpose of this study was to characterise the incidence and significance of the meniscal flounce. TYPE OF STUDY: Prospective Cohort Study. METHOD: A prospective study of 1088 consecutive knee arthroscopies. RESULTS: Intact menisci tended to have a flounce of characteristic size and position. The presence of this 'normal' flounce was closely correlated with an intact meniscus (p<0.0001). For the medial meniscus with a small flounce in zone 3 the sensitivity, specificity, and positive predictive value (PPV) for an intact medial meniscus were 68.5%; 92.9%; and 92.1% respectively. Conversely the presence of meniscal pathology correlated closely with either an absent or abnormal flounce (p<0.0001). The absence of a medial flounce had sensitivity, specificity, and PPV for a meniscal tear of 82.8%; 84.9%; and 81.9% respectively. CONCLUSIONS: The findings of this study are useful for arthroscopists especially when there is difficulty visualising all of the posterior half of the meniscus. In this situation the presence of a normal flounce is likely to signify an intact meniscus. However the presence of an abnormal or absent flounce may be the sign of an occult meniscal tear requiring better exposure.     

Bilateral discoid medial menisci: Incomplete type in one knee and complete type in opposite knee

A discoid medial meniscus is a relatively rare pathology of the knee joint. And bilateral cases are even more rare. In the review of the literature by the authors, Only 13 cases of bilateral medial discoid menisci have been reported. We present one case of bilateral discoid medial menisci. One knee had an incomplete type verified by both magnetic resonance imaging (MRI) and arthroscopy. The other knee showed a complete type of medial discoid meniscus in MRI. Therefore, we suggest that similar pathology in the contralateral knee should be suspected, even if the patient is asymptomatic, if a complete or incomplete discoid medial meniscus is identified.     

膝关节半月板的三维断面解剖学研究

目的    观测膝关节半月板的断面形态特征和变化规律,为诊断膝部病变提供更为详尽的形态学资料。  方法    正常成人尸体膝关节片厚5 mm的连续断面标本27例,其中矢状断面标本9例,冠状断面标本12例,横断面标本6例。通过三维断面标本,观察膝关节半月板的断面形态特征。  结果    内侧半月板矢径（40.36±4.73）mm,横径（33.99±3.77）mm;外侧半月板矢径（34.51±2.18）mm,横径（34.51±　3.25）mm。内、外侧半月板前、后角厚度分别为（4.98±1.83）mm和（4.45±1.44）mm、（3.54±1.24）mm和（6.15±1.43）mm。半月板后角高度外侧大于内侧,外侧半月板后角高度大于前角。内侧半月板后角宽度大于前角。板股韧带出现率为75%。  结论    ①半月板前、后角部在矢状面上,体部在冠状面上显示最好,横断面可见半月板全貌。②由于内侧半月板与关节囊紧密相连,且后角宽度大于前角,致使其易受损伤。③外侧半月板后角高度大于内侧半月板后角及同侧前角,可能是导致外侧半月板后角较易受损的因素之一。     

跳跃运动中不同护膝条件下膝关节半月板应力场的数值研究

目的 采用数值模拟方法,建立人体膝关节肌骨系统生物力学模型,并将人体动力学模型模拟跳跃运动时所获得的运动学和动力学信息作为模型驱动数据,进而分析不同热力耦合护膝条件下膝关节半月板的应力场分布特征。方法 基于受试者CT与MRI断层扫描图像,构建包括骨、关节软骨、半月板、韧带和膝关节外围软组织的较真实人体膝关节模型,依据跳跃运动全周期分析选择蓄力起跳、落地冲击两个半月板损伤风险较大的位姿步态进行模拟,分析4种不同热力耦合护膝条件下膝关节半月板的应力场特征,讨论半月板峰值应力及其应力集中区域的变化,探究半月板损伤以及佩戴护膝的防护功效和力学依据。 结果 膝关节内侧半月板前角是应力集中的易受损区域;在热力场耦合护膝条件下,内侧半月板应力集中区域由其狭长且薄弱的前角转移至其较为宽厚的中部,且峰值应力显著降低;内、外侧半月板的峰值应力接近,表明两者共同承担外载,且半月板应力集中区域面积减小。结论 热力场耦合护膝对于膝关节半月板的损伤具有良好防护作用。数值模拟研究结果可以为热力多功能护膝的设计提供理论支撑和技术指导。     

Meniscal pullout repair following meniscal ossicle resection: A case report

We present this case of a meniscal ossicle of the posterior horn of the medial meniscus that was treated by an arthroscopic ossicle resection followed by a pullout repair of the remaining meniscus. A 49-year-old businessman complained of catching and left knee pain. Radiographic and arthroscopic findings revealed a meniscal ossicle embedded in the posterior horn of the medial meniscus and posterior horn tear. After resection of the posterior horn with the ossicle, a pullout suture repair for the posterior segment of the meniscus was done to minimize the further extrusion of the meniscus. A histologic appearance supported the vestigial development of the meniscal ossicle as the etiology. This is the first report describing a repair of the meniscus after ossicle resection.     

Releasing the circumferential fixation of the medial meniscus does not affect its kinematics

BackgroundMeniscal functioning depends on the fixation between the meniscal horns and the surrounding tissues. It is unknown, however, whether the integration between the outer circumference of the medial meniscus and the knee capsule/medial collateral ligament also influences the biomechanical behavior of the meniscus. Therefore, we aimed to determine whether detaching and resuturing the circumferential fixation of the medial meniscus influence its kinematic pattern.MethodsHuman cadaveric knee joints were flexed (0°–30°–60°–90°) in a knee loading rig, in neutral orientation and under internal and external tibial torques. Roentgen stereophotogrammetric analysis was used to determine the motion of the meniscus in anteroposterior (AP) and mediolateral (ML) directions. Three fixation conditions were evaluated: (I) intact, (II) detached and (III) resutured.ResultsDetaching and resuturing the circumferential fixation did not alter the meniscal motion pattern in either the AP or ML direction. Applying an additional internal tibial torque caused the medial meniscus to move slightly anteriorly, and an external torque caused a little posterior translation with respect to the neutral situation. These patterns did not change when the circumferential fixation condition was altered.ConclusionsThis study demonstrated that the motion pattern of the medial meniscus is independent of its fixation to the knee capsule and medial collateral ligament.Clinical relevanceThe outcomes of this study can be deployed to design the fixation strategy of a permanent meniscus prosthesis. As peripheral fixation is a complicated step during meniscal replacement, the surgical procedure is considerably simplified when non-resorbable implants do not require circumferential fixation.     

Changes of meniscal interhorn distances: an in vivo magnetic resonance imaging study

The aim of this study was to evaluate the changes of the internal (IID) and external meniscal interhorn distance (EID) of the medial and the lateral meniscus under loading. Sagittal magnetic resonance images of 15 knees were studied. The medial and lateral meniscus were examined with the knee at 0° and 30° of flexion, under no load, with load equal to 50% of body weight and with load equal to 100% of body weight. Under no load, the mean IID was 19.9 mm for the medial meniscus and 12.3 mm for the lateral meniscus and the mean EID was 44.6 mm for the medial meniscus and 34.4 mm for the lateral meniscus. Under load equal to 50% and 100% of patient's body weight, there was a significant increase in both distances (p < 0.05). Under constant loading, flexion of the knee from 0° to 30°, decreased the EID of both menisci. In conclusion, loading increases both IID and EID. Knee position affects only the EID. The quality of magnetic resonance images may affect the reliability of such measurements.     

Relation of discoid lateral meniscus and cord-like anterior intermeniscal ligament: morphological and clinical study

Discoid lateral meniscus is a rare disorder and its association with other variations in the knee joint has been reported. The anterior intermeniscal ligament has also been described as connecting the anterior convex margin of the lateral meniscus to the anterior horn of the medial meniscus. In the normal population, it was observed at 53–94%. Although the functional properties of the anterior intermeniscal ligament are not yet clarified, two distinct types of the ligament have been described according to their morphological characteristics as cord-like and membranous types. The purpose of this study was to evaluate any possible association between morphologic types of anterior intermeniscal ligament and discoid lateral meniscus. A retrospective study was designed; 20 discoid lateral menisci were operated using routine arthroscopic examination. Upon arthroscopic examination the thickness of the ligament and associated morphological changes were recorded systematically. The cord-like anterior intermeniscal ligament was an associated structure in 15 of the 20 knees with discoid lateral meniscus (75%). Patients with discoid lateral meniscus apparently have cord-like type anterior intermeniscal ligament, thus we conclude that cord-like type of anterior intermeniscal ligament is a frequent accompanying structure to discoid lateral meniscus and may have a potential stabilizing effect on its anterior stability.     

Epidemiology of athletic knee injuries: A 10-year study

The knee is an anatomically and biomechanically complex joint. Few studies have been published reporting the type and frequency of knee injuries. However, this information that may help to prevent, diagnose, and treat knee joint injuries. We have documented 17,397 patients with 19,530 sport injuries over a 10-year period of time. 6434 patients (37%) had 7769 injuries (39.8%) related to the knee joint. 68.1% of those patients were men and 31.6% were women. Almost 50% of the patients were between the ages of 20-29 (43.1%) at the time of injury. The injuries documented were ACL lesion (20.3%), medial meniscus lesion (10.8%), lateral meniscus lesion (3.7%), MCL lesion (7.9%), LCL lesion (1.1%), and PCL lesion (0.65%). The activities leading to most injuries were soccer (35%) and skiing (26%). LCL injury was associated with tennis and gymnastics, MCL with judo and skiing, ACL with handball and volleyball, PCL with handball, lateral meniscus with gymnastics and dancing, and medial meniscus with tennis and jogging.     

Arthroscopic combined medial and lateral meniscus transplantation after double-tunnel,double-bundle anterior cruciate ligament reconstruction in the same knee

Meniscus transplantation in combination with anterior cruciate ligament (ACL) reconstruction has been used in the treatment of patients with meniscus and ACL deficiency. However, there have been no reports of arthroscopic surgery and the outcome of both medial and lateral meniscus allograft transplantation after double-tunnel, double-bundle ACL reconstruction. Herein, we report the case of a young male who received arthroscopic lateral and medial meniscectomy and ACL tibialis allograft reconstruction performed with the double-tunnel and double-bundle technique approximately 8 months after a knee injury. Approximately 4 months postoperatively he began to experience pain and weakness in the operated knee and subsequently underwent arthroscopic lateral and medial meniscus allograft transplantation in the same procedure. Second-look arthroscopy and magnetic resonance imaging revealed the meniscal allografts to have normal shape and the ACL grafts to be relatively intact at 18 and 30 months after surgery. His knee appeared stable and the range of motion was normal. Our hypothesis was that knee stability could reliably be restored with this combined procedure and the meniscal grafts and ACL graft could provide protection for each other. We suggest that medial and lateral meniscus allografts for one patient should be from the same donor. In the operation, attention must be paid to the direction of the bone tunnels used to fix the horns of the meniscal grafts to avoid communication with other tunnels in the tibial plateau.     

Medial meniscus extrusion and stage are related to the size of spontaneous osteonecrosis of the knee in patients who underwent high tibial osteotomy

PurposeSpontaneous osteonecrosis of the knee (SONK) causes acute atraumatic knee pain, and meniscus tears may be associated with the pathogenesis of SONK. The purpose of this study was to investigate the relationship of the type of meniscus tear and medial meniscus extrusion with SONK on the medial femoral condyle in patients who underwent surgical treatment with high tibial osteotomy due to severe knee pain.MethodsWe enrolled 98 patients with 102 knees who underwent medial opening wedge high tibial osteotomy (OWHTO) under the diagnosis of medial femoral condyle osteonecrosis at our hospital from December 2003 to January 2020. Based on the Koshino classification, cases of SONK were classified as stage 1–4. The relationships of demographic data, X-rays and MRI images, including femorotibial angle (FTA), meniscus tear type, and medial meniscus extrusion (MME), with the stage and volume of SONK were investigated.ResultsNinety-eight patients (29 males and 69 females), with an average age at surgery of 69.2 ± 9.6 years and Body mass index(BMI) of 61.0 ± 17.6 kg/m². In 102 cases of SONK, 11 knees, 18 knees, 46 knees, and 27 knees were classified as stage 1–4, respectively. The mean SONK volume was 2161.61 µm (range 95.67–7484.68 µm) on preoperative MRI. The preoperative FTA (mean 180.86°, range 172–187°) was not associated with the stage or volume of SONK. Meniscus tears were found in all cases of SONK and consisted of 2 degenerations, 2 horizontal tears, 0 vertical tears, 40 radial tears, 4 complex tears, and 54 medial meniscus posterior root tears (MMPRTs). In addition, 99% (101/102) of knees showed more than 3 mm of meniscus extrusion. Although the meniscus tear type was not associated with SONK stage, there was a high rate of tears that caused disruption of the hoop strain, such as MMPRTs (52.9%) or radial tears (39.2%). MME was significantly related to SONK volume (r = 0.387, p < 0.001).ConclusionAll patients with SONK had coexisting meniscus tears, most menisci had medial extrusion, and a positive correlation was observed between MME and SONK volume.     

Effect of meniscus repair on pivot-shift during anterior cruciate ligament reconstruction: Objective evaluation using triaxial accelerometer

Background

Some types of meniscus tear, especially lateral meniscus tear, have been reported to be associated with rotatory knee laxity. However, precise information regarding the effect of meniscus repair on rotatory laxity is limited. The purpose of this study was to investigate the effects of lateral and medial meniscus repair on rotatory laxity in anterior cruciate ligament (ACL) injured knees.

Meniscal ossicle: a case report

Meniscal ossicle is a cortical or cancellous tissue with central viable marrow surrounded by meniscal cartilage. We present a case of medial meniscal ossicle at its posterior horn. A 21-year-old male military recruit visited our clinic due to left knee discomfort. He had not undergone any notable injury on the knee, but complained of intermittent catching or giving way without locking. Simple radiographs showed a small round bony fragment at posteromedial side of knee joint. The magnetic resonance imaging revealed an intra-substance lesion of meniscus, whose signal is identical to bone. On arthroscopy, the articular cartilage of medial femoral condyle and tibial plateau appeared degenerative with a groove-like scar. The medial meniscus seemed swollen at the posterior horn, but there was no discernible tear in the adjacent meniscus. After piecemeal removal of meniscal substance, a small osseous fragment was identified, which was evacuated via posteromedial portal. The resection of meniscus amounted to a subtotal meniscectomy. The activities of daily living were possible without any trouble even after 9 months of follow-up. This entity should be distinguished from intra-articular loose body, and included in the differential diagnosis of the incidental findings of small ossified density around knee joint.     

膝关节半月板根部MRI影像解剖

目的 总结半月板根部的MRI解剖特点,确定半月板主体部分与根部的分界。方法 收集2012年10月—2014年2月保定市第一中心医院骨科24例经关节镜证实正常半月板根部的膝关节MRI资料和1例男性成人患者因下肢动脉硬化而截肢的新鲜膝关节标本,对半月板根部的MRI解剖行前瞻性研究,总结半月板根部MRI的形态、走行及附着点的位置,分析信号特点,并测量根部的长度、宽度、高度以及各根部走行角度。另在新鲜膝关节标本上确定半月板主体部分与根部的分界并用铜丝标示之,对标本行MRI扫描。结果 24例患者膝关节MRI显示:内侧半月板后根部呈梳状斜向下走行,信号较半月板主体部分稍高,附着于髁间后区;外侧半月板后根部较内侧半月板后根部明显长,走行于髁间隆起,附着于内侧髁间隆起的外侧面,信号与半月板主体部分类似;内侧半月板前根部较细,附着于髁间前区最前缘,为低或较低信号;外侧半月板前根部呈梳状稍向下向后走行,信号稍高,附着于髁间前区并稍向外下方倾斜的骨表面。各根部测量数据显示:横断面外侧半月板后根部最长,为(15.74±2.03)mm;冠状面内侧半月板后根部最短,为(7.88±1.57)mm;外侧半月板后根部走行与标准冠状面扫描线的夹角角度最大,为34.00°±9.24°。1例新鲜标本MR扫描图片清晰,半月板主体部分与根部分界标记显示清晰。结论 内外侧半月板前后根部各有其特点,MRI能够清晰显示半月板根部的形态、走行、信号特点及附着点位置。     

Clinical significance of meniscal abnormalities on magnetic resonance imaging in an older population

This study examined the prevalence of degenerative changes of knee menisci in aging and evaluated the diagnostic values of magnetic resonance (MR) imaging for assessing meniscal pathology in an older population. Eighty-five knees of asymptomatic volunteers over the age of 40 were scanned using MR imaging. Meniscal abnormalities were graded from 0 to 3 according to intrameniscal MR signals. The subjects were divided into two groups based on the presence or absence of radiographic osteoarthritis. Group I included 43 knees that had normal radiographs and group II consisted of 42 knees that had radiographic evidence of osteoarthritis. Degenerative changes in the menisci involved primarily the posterior segment of the medial meniscus in both groups. Signal changes in the other segments were of a significantly lesser grade than that in the posterior segment of the medial meniscus. The meniscal grade in each segment was significantly higher in group II than in group I. In group I, only two menisci (4.6% ) showed grade 3 signals, even in the posterior portion of the medial meniscus, compared to 21 (50.0%) in group II. Frequency of asymptomatic grade 3 was relatively low even in older subjects if there was no evidence of radiographic osteoarthritic changes. Abnormal MR signals are more likely to have clinical significance, in patients with radiographic changes on plain X-ray.     

The potential effect of anatomic relationship between the femur and the tibia on medial meniscus tears

Background

The anatomic and the kinematical relationships between the femur and the tibia have been previously examined in both normal and diseased knees. However, less attention has been directed to the effect of these relationships on the meniscal diseases. Therefore, we aimed to investigate the impact of femorotibial incongruence on both lateral and medial meniscal tears.

Materials and methods

A total of 100 images obtained from MRI of 100 patients (39 males and 61 females) were included in the study. Diameters of the medial and the lateral femoral condyles, thicknesses of the menisci, and diameters of the medial and the lateral tibial articular surfaces were measured.

Results

The medial meniscus tear was detected in 40 (40 %) patients. However, no lateral meniscus tear was found. Significant relationships were found between the diameters of the posterior medial femoral condyle and the medial tibial superior articular surface and between the diameters of the posterior lateral femoral condyle and the lateral tibial superior articular surface. The mean values for the diameter of the medial condyle of the femur, the lateral condyle of the femur, the medial superior articular surface of the tibia, and the lateral superior articular surface of the tibia were found to be significantly higher in cases with meniscus tear compared to cases without meniscus tear. However, no significant difference was present regarding the thicknesses of the medial and the lateral menisci. A positive relationship between the diameter of the posterior medial femoral condyle and the tibial medial superior articular surface was found in cases with (n = 40) (r ² = 0.208, p = 0.003) and without tear (n = 60) (r ² = 0.182, p = 0.001). In addition, a significant positive relationship was found between the diameter of the posterior medial femoral condyle and the medial tibial superior articular surface in cases with and without tear.

Conclusion

The impact of femorotibial incongruence on the medial meniscus tear is important for the understanding of the lesions.     

Repair of the posterior root of the medial meniscus

Tears of the posterior root of the medial meniscus are becoming increasingly recognized. Early identification and treatment of these tears help halt the progression of cartilage degeneration and osteoarthritis of the knee. Repair of these tears is essential for recreating the hoop stress of the medial meniscus. In this note, we describe a successful arthroscopic technique to repair this lesion. A posteromedial portal is established by which two 2-0 PDS sutures are placed through the meniscus root and pulled down through a trans-tibial tunnel and fixed using an EndoButton distally along the anterolateral cortex of the tibia. This has been performed successfully in five patients with no complications.