Meniscofemoral Ligament Research Articles

Arthroscopic Centralization of the Medial Meniscus Reduces Load on a Posterior Root Repair Under Dynamic Varus Loading: A Biomechanical Investigation

Background: In addition to the integrity of the meniscal hoop function, both the anterior and posterior meniscus roots as well as the meniscotibial and meniscofemoral ligaments are crucial in restraining meniscal extrusion. However, the interaction and load sharing between the roots and these peripheral attachments (PAs) are not known. Purposes: To investigate the influence of an insufficiency of the PAs on the forces acting on a posterior medial meniscus root repair (PMMRR) in both neutral and varus alignment and to explore whether meniscal centralization reduces these forces. Study Design: Controlled laboratory study. Methods: In 8 fresh-frozen human cadaveric knees, an arthroscopic transosseous root repair (step 1) was performed after sectioning the posterior root of the medial meniscus. The pull-out suture was connected to a load cell to allow measurement of the forces acting on the root repair. A medial closing-wedge distal femoral osteotomy was performed to change the mechanical axis from neutral to 5° of varus alignment. The meniscus was completely released from its PAs (step 2), followed by transosseous arthroscopic centralization (step 3). Each step was tested in both neutral and varus alignment. The specimens were subjected to nondestructive dynamic varus loading under axial compression of 300 N in 0°, 15°, 30°, 45°, and 60° flexion. The changes in force acting on the PMMRR were statistically analyzed using a mixed linear model. Results: Axial loading in neutral alignment led to an increase of the force of root repair of 3.1 ± 3.1 N (in 0° flexion) to 6.3 ± 4.4 N (in 60° flexion). In varus alignment, forces increased significantly from 30° (3.5 N; 95% CI, 1.1-5.8 N; P = .01) to 60° (7.1 N; 95% CI, 2.7-11.5 N; P = .007) flexion, in comparison with neutral alignment. Cutting of the PAs in neutral alignment led to a significant increase of root repair forces in all flexion angles, from 7.0 N (95% CI, 1.0-13.0 N; P = .02) to 9.1 N (95% CI, 4.1-14.1 N; P = .003), in comparison with the intact state. Varus alignment significantly increased the forces in the cut states from 4.8 N (95% CI, 1.0-8.5 N; P = .02) to 11.1 N (95% CI, 4.2-18.0 N; P = .006) from 30° to 60° flexion, in comparison with the neutral alignment. Arthroscopic centralization led to restoration of the native forces in both neutral and varus alignment, with no significant differences between the centralized and intact states. Conclusion: An insufficiency of the PAs of the medial meniscus, as well as varus alignment, led to increased forces acting on a PMMRR. These forces were reduced via an arthroscopic meniscal centralization. Clinical Relevance: Performing arthroscopic meniscal centralization concomitantly with PMMRR may reduce failure of the repair by reducing the load of the root.

Magnetic Resonance Imaging Features of Anterolateral Ligament in Young Adults without Anterior Cruciate Ligament Injury: Preliminary Evaluation.

This study aimed to characterize the Magnetic Resonance Imaging (MRI) features of the Anterolateral Ligament (ALL) in young adults without Anterior Cruciate Ligament (ACL) injury and evaluate its visibility using MRI. In this retrospective analysis, MRI scans of 66 young adults without ACL injuries were assessed by two radiologists. The ALL was examined from its bone-to-bone attachment between the lateral femoral epicondyle and the lateral tibia. The visibility of the ALL was classified as normal, probably normal, abnormal, or non-visualized, based on ligament continuity and thickness relative to the Meniscotibial Ligament (MTL). A continuous structure with thickness equal to or greater than the MTL was considered normal; continuous but wavy and thin features were categorized as probably normal; discontinuity and angulation were deemed abnormal. The proximal attachment of the ALL was categorized as anterior, central, or posterior to the Fibular Collateral Ligament (FCL), while the distal attachment was noted as either at the same location or distal to the MTL. The ALL was identified in 87.9-95.5% of knees and was non-visualized in 4.5-12.1% of cases. Continuous ligamentous structures were observed in 63.7-71.2% of knees (normal in 30.3-37.9%; probably normal in 27.3-40.9%), whereas 19.7-30.3% exhibited abnormal features. Inter-observer agreement was moderate to substantial (κ = 0.66, 0.56), and intra-observer agreement was substantial to excellent (κ = 0.82, 0.66). Among the 58 visible ALLs, proximal attachments were predominantly anterior (63.8%) or central (32.8%) to the FCL, with a minority posterior (1.7%). In total, 4 of the 19 central insertions were incorporated into the FCL mid-substance, and one case was blended into the meniscofemoral ligament. Distal attachments were equally distributed between the same location (50%) and distal to the MTL (50%) (mean 3.7 mm distal). In conclusion, MRI was feasible for detecting the ALL in most young adults without ACL injury, revealing continuous ligament structures in about two-thirds of cases. Approximately 40% of cases exhibited a thickness equal to or greater than the MTL, with the majority of proximal attachments located anterior to the FCL and distal attachments evenly divided between the same insertion and distal to the MTL.

Triple Anterior Horn Insertion of the Medial Meniscus Combined with Posterior Horn Hypertrophy: A Rare Case and Brief Literature Review

Anomalies of the medial meniscus (MM) are uncommon. The most frequently occurring anomaly is found in the anterior horn. This report describes for the first time a case of abnormal multiple insertions of the anterior horn of the MM (AHMM) combined with posterior horn hypertrophy, which was found incidentally during routine dissection of a separate left lower limb from an adult cadaver. The AHMM was found to have a standard attachment to the anterior surface of the tibia in addition to two additional bands. One of these bands was the anteromedial meniscofemoral ligament, which ran parallel and independent of the anterior cruciate ligament and ended at the intercondylar notch of the femur. The other band extended as the transverse ligament that connected the AHMM to the lateral meniscus. The posterior horn of MM was found to be hypertrophied. The clinical implications of these anomalies are discussed below along with a relevant literature review.

Three-Dimensional Imaging Analysis of the Developmental Process of Posterior Meniscofemoral Ligaments in Rat Embryos

Introduction: The posterior meniscofemoral ligament (pMFL) of knee joint is a ligament that runs posterior to the posterior cruciate ligament and it is known that the height of the pMFL attachment site causes meniscus avulsion. Therefore, understanding the three-dimensional (3D) structure of the pMFL attachment site is essential to better understand the pathogenesis of meniscus disorders. However, the developmental process of pMFL has not been well investigated. The purpose of this study was to analyze pMFL development in rat knee joints using 3D reconstructed images produced from episcopic fluorescence image capture (EFIC) images and examine its relationship with other knee joint components. Methods: Knee joints of Wistar rat embryos between embryonic day (E) 16 and E21 were observed with HE-stained tissues. Serial EFIC images of the hind limbs of E17–E21 were, respectively, captured from which 3D images were reconstructed and the features of pMFL structure: length and angle were measured. Besides, the chronological volume changes and the volume ratio of the knee joint components compared to E17 were calculated to identify the differences in growth by components. Results: pMFL was observed from E17 and was attached to the medial femoral condyle and lateral meniscus at all developmental stages, as in mature rats. The lack of marked variation in the attachment site and angle of the pMFL with the developmental stage indicates that the pMFL and surrounding knee joint components developed while maintaining their positional relationship from the onset of development. Conclusion: Current results may support to congenital etiology of meniscus disorder.

MENISCAL ANOMALIES IN CONGENITAL CRUCIATE LIGAMENT DEFICIENCY: EXPERIENCE IN A TERTIARY CHILDREN'S KNEE UNIT

ObjectivesCongenital cruciate ligament deficiency is a rare condition that may occur in isolation or in association with longitudinal limb deficiencies such as fibular hemimelia or proximal femoral focal deficiency. Often anomalies of the menisci and their attachments can be very abnormal and impact on surgical management by standard techniques. Arthroscopic surgical knee reconstruction is undertaken to improve symptomatic instability and/or to stabilise and protect the knee for future planned limb lengthening surgery.The aim of this study is to evaluate the arthroscopic findings of patients undergoing surgery for congenital cruciate ligament deficiency, and specifically to determine the frequency and types of meniscal anatomical variations seen in these cases.MethodsPatients undergoing surgery for congenital cruciate ligament deficiency were identified from a prospectively collated database. Diagnosis was confirmed through review of the clinical notes and imaging. Operative notes and 4K saved arthroscopic images and video recordings for these cases were reviewed.ResultsOver a six-year period (July 2017 – September 2023), 42 patients underwent surgery for congenital ligament deficiency and tibiofemoral instability (45 surgical episodes). Median age of patients at time of surgery was 10 years (range 4 – 17 years). The most frequent diagnosis was congenital longitudinal limb deficiency syndromes in 27 cases, with the most frequent being fibular hemimelia. Isolated congenital ligament deficiency without any other associated extra-articular manifestations occurred in 11 cases. Absence of meniscal root attachments or hypertrophy of meniscofemoral ligaments acting as ‘pseudo-cruciates’ were seen in over 25% of patients. In isolated ACL deficiency these were injured causing onset of instability symptoms and pain following trauma. Often these abnormal structures required addressing to allow surgical reconstruction.ConclusionsOur findings demonstrate that there are often meniscal variations seen in association with congenital absence or hypoplasia of the cruciate ligaments. In these patients hypertrophied meniscofemoral ligaments may act as cruciate-like structures and play a role in providing a degree of sagittal plane stability to the knee. However, when the knee becomes unstable to the point that cruciate ligament reconstruction is indicated, these meniscal variants may often require stabilisation using complex meniscal root repair techniques or variations to standard cruciate ligament reconstruction techniques to accommodate the variant anatomy.

Relationship between medial meniscus extrusion and damage to medial stabilizers: Should extrusion be considered significant only when more than 3 mm?

BackgroundThis study was conducted with patients with anterior and medial extrusion of the medial meniscus (MM-AE, MM-ME) to investigate the relationship of the amount of extrusion with damage to the meniscus, meniscofemoral ligament (MFL), meniscotibial ligament (MTL), presence of effusion, osteoarthritis (OA) grade and other medial stablizers. A cut-off value for significant MM-ME was also suggested. MethodsAll patients aged 18 and above who had measurable MM extrusion on knee MRI were included. Patients with acute injury detected on knee MRI and any disease that could disrupt the anatomy were not included. The relationship between the amount of MM-AE, MM-ME and the investigated comorbidities were evaluated. The patients were divided into two: those with and without positive findings for each comorbidities. The amount of MM-AE, MM-ME were evaluated. ROC analysis was undertaken for significant differences, and cut-off values were determined. ResultsThere was a correlation between MM-ME and age, weight, and BMI (p < 0.001, p = 0.027, p = 0.025, respectively). The amount of MM-ME was higher in the groups with OA (p = 0.007), MTL damage (p < 0.001), MFL damage (p < 0.001), meniscus damage (p < 0.001), effusion (p < 0.001), and the amount of MM-AE was higher in the groups with OA (p = 0.042), effusion (p = 0.002). The cut-off values of MM-ME were determined to be 2.69 mm (MTL), 2.65 mm (MFL), 2.49 mm (meniscus), and 2.85 mm (OA). ConclusionOA grade, effusion, and meniscus, MTL, and MFL damage were all found to be related to the amount of MM-ME. MM-ME values 2.49–2.85 mm may indicate meniscus, MFL, MTL damage and OA.

Poster 127: The Posteromedial Knee: An Anatomic, Biomechanical, and Radiographic Analysis of the Posterior Oblique Ligament

Objectives: The structures of the posteromedial knee are important for coronal and rotational stability. These can be injured along with the medial collateral ligament (MCL) during traumatic or sporting activities. The posterior oblique ligament (POL) is largest and best-known structure at the posteromedial knee at risk of injury. When surgical reconstruction is needed, the location and positioning of this reconstruction is often grouped together with the medial collateral ligament, despite the specific biomechanical role of and the much larger anatomic area covered by the various structures of the posteromedial knee. The POL provides a complex load sharing interplay with the MCL, such that these ligaments both contribute to resist the combination of valgus and rotational strains. As such, the POL is an important structure that contributes to the stability of the medial knee, and severe injuries may benefit from a separate procedure to directly address the ligament. The purpose of this study was to evaluate the anatomy of the posteromedial knee as well as the radiographic locations and biomechanical strengths of the POL. Methods: 10 nonpaired fresh cadaveric knees were dissected and the medial structures were elevated off bone, except for the POL. The anatomic locations were noted and recorded with a robotic coordinate measuring device to establish structure location, distances, and attachment areas for the superficial MCL, adductor tubercle, medial epicondyle, meniscofemoral ligament, tibiofemoral ligament, semimembranosus and the POL. For the radiographic analysis, radiopaque T-pins were placed in the POL attachment sites, as well as other clinically relevant and bony landmarks. True anteroposterior (AP) and lateral radiographs were taken with fluoroscopy. Digital software was utilized to measure the distances from these anatomic points to the center of the attachment of the POL. Biomechanically, the specimens were loaded onto a computerized actuator, and all soft tissues connecting the tibia and the femur were resected except for the POL. A pull-to-failure test was completed and the ultimate tensile strength and location of the failure was recorded. Results: On average, the POL attachment on the femur is 15.4mm posterior and 6.6mm superior to the medial epicondyle. On the tibia, the POL attachment center is 21.4mm posterior and 2.2mm inferior to the center of the meniscotibial ligament, and 28.6mm posterior and 41.9mm superior to the center of the superficial MCL tibial attachment. On radiographic exam, the femoral POL was 17.6mm distal to the adductor tubercle, and 17.3mm posterosuperior to the medial epicondyle on the lateral radiograph. On the tibial side, the center of the POL attachment is 5.0mm distal to the joint line on the AP radiograph and 6.3mm distal to the tibial joint line on the lateral, at the far posterior aspect of the tibia. The biomechanical pull-to-failure demonstrated an average ultimate tensile strength of 225.2N ± 71.0N. Conclusions: This study successfully localized the medial and posteromedial knee structures, establishing their anatomic location, the radiographic location of the POL relative to clinically relevant structures, and established the pull-to-failure ultimate tensile strength. This provides good clinical information for location and type of graft that can help anatomically reconstruct the central arm of the POL. [Table: see text] [Table: see text]

Anterior menisco-femoral ligaments combined with agenesis of the anterior cruciate ligament

Introduction. The given article describes a rare case of congenital anomaly in the knee joint. It also analyzes the current state of art on such malformations and options for their treatment. The authors present their rationale on selecting a curative modality. The described developmental anomaly included the following: no tibial attachment of anterior horns of both meniscus, agenesis of the anterior cruciate ligament as well as of anterolateral and anteromedial meniscofemoral ligaments which were joined into a structure mimicking the track of native anterior cruciate ligament and attaching the femur lateral condyle in the projection of intercondylar ridge.Material and methods. Based on examination findings as well as on known curative options for similar anomalies, the researchers decided to perform the anchor stabilization of anterior horns of both menisci. Since there are no data on this type of knee surgery, the surgeons decided to make anchor stabilization similar to that which is used for the capsulolabral complex in case of instability of the shoulder joint. Surgical stages: stitching the anterior horns of both menisci, formation of bone channels in the projection of the proper anatomical attachment of the anterior horns to tibia condyles , their installation and fixation to the system of suture anchors.Results. The chosen curative modality has shown good clinical results during 12-month clinical observation.Conclusions. For the first time, the authors have described such combination of anomalies and variants of its correction. As it has been noted, MRI and clinical findings may contradict each other and create a false picture of the presence of anterior cruciate ligament and meniscus injury. For better differentiation of such anomalies, it is recommended to perform additional axial MRI protocols with the increased number of images.

Posterior Root Tears of the Lateral Meniscus Only Affect Tibiofemoral Contact Forces when the Meniscofemoral Ligament Is Involved: A Cadaveric Study

The objective of this study was to examine the impact of progressive radial tears in the lateral meniscal root on the lateral compartment contact forces and joint surface area through a range of motion of knee and evaluate the role of the meniscofemoral ligament (MFL) in preventing adverse tibiofemoral joint forces. Ten fresh frozen cadaveric knees were tested using 6 experimental conditions (0% lateral meniscal posterior root tear, 25% tear, 50% tear, 75% tear, 100% tear, 100% tear and resection of MFL) at five flexion angles (0°, 30°, 45°, 60°, and 90°) under 100-1,000-N axial load. Contact joint pressure and lateral compartment surface area were measured using Tekscan sensors. Statistical analysis, including descriptive, ANOVA, and post hoc Tukey analysis, was performed. Progressive radial tears of the lateral meniscal root were not associated with an increase in tibiofemoral contact pressure or decrease in lateral compartment surface area. Complete lateral root tear and resection of MFL were associated with increased joint contact pressure (P < .001) at knee flexion angles of 30, 45, 60, and 90° and decreased lateral compartment surface (P < .001) at all knee flexion angles area compared to complete lateral meniscectomy alone. Isolated complete tears of lateral meniscus root and progressive radial tears of the lateral meniscus posterior root were not associated with any change to tibiofemoral contact forces. However, additional resection of the MFL increased contact pressure and decreased lateral compartment surface area.

Isolated Posterior Lateral Meniscofemoral Ligament Tears Show Greater Meniscal Extrusion in Knee Extension, and Isolated Posterior Lateral Meniscal Root Tears Show Greater Meniscal Extrusion at 30° Using Ultrasound: A Cadaveric Study

To quantify the effects that posterior meniscofemoral ligament (pMFL) lesions have on lateral meniscal extrusion (ME) both with and without concomitant posterior lateral meniscal root (PLMR) tears and describe how lateral ME varied along the length of the lateral meniscus. Ultrasonography was used to measure ME of human cadaveric knees (n= 10) under the following conditions: control, isolated pMFL sectioning, isolated PLMR sectioning, pMFL+PLMR sectioning, and PLMR repair. ME was measured anterior to the fibular collateral ligament (FCL), at the FCL, and posterior to the FCL in both unloaded and axially loaded states at 0° and 30° of flexion. Isolated and combined pMFL and PLMR sectioning consistently demonstrated significantly greater ME when measured posterior to the FCL compared with other image locations. Isolated pMFL tears demonstrated greater ME at 0° compared with 30° of flexion (P < .05), whereas isolated PLMR tears demonstrated greater ME at 30° compared with 0° of flexion (P < .001). All specimens with isolated PLMR deficiencies demonstrated greater than 2 mm of ME at 30° flexion, whereas only 20% of specimens did so at 0°. When the pMFL was sectioned following an isolated PLMR tear, there was a significant increase in ME at 0° (P < .001). PLMR repair after combined sectioning restored ME to levels similar to that of controls in all specimens when measured at and posterior to the FCL (P < .001). The pMFL protects against ME primarily in full extension, whereas the presence of ME in the setting of PLMR injuries may be better appreciated in knee flexion. With combined tears, isolated repair of the PLMR can restore near-native meniscus position. The stabilizing properties of intact pMFL may mask the presentation of PLMR tears and delay appropriate management. Additionally, the MFL is not routinely assessed during arthroscopy due to difficult visualization and access. Understanding the ME pattern of these pathologies in isolation and combination may improve detection rates so that the source of patients' symptoms can be addressed to satisfaction.

In situ repair of segmental loss posterior lateral meniscal root tears outperforms meniscofemoral ligament imbrication in the ACL reconstructed knee

PurposeThe purpose of this study was to compare the biomechanical effect of in-situ repair of posterior lateral meniscal root (PLMR) tear with segmental meniscal loss, with and without meniscofemoral ligament (MFL) imbrication, on anterior cruciate ligament (ACL) graft force and knee joint kinematics.MethodsTen fresh-frozen cadaveric knee specimens underwent kinematic evaluation in five states: 1) Native, 2) ACLR, 3) Segmental PLMR loss, 4) In-situ PLMR repair, and 5) MFL augmentation. Kinematic evaluation consisted of five tests, each performed at full extension and at 30° of flexion: 1) Anterior drawer, 2) Internal Rotation, 3) External Rotation, 4) Varus, and 5) Valgus. Additionally, a simulated pivot shift test was performed. Knee kinematics and ACL graft force were measured.ResultsPLMR tear did not significantly increase ACL graft force in any test. However, PLMR repair significantly reduced ACL graft force compared to the ACLR alone (over constraint -26.6 N, p = 0.001). PLMR tear significantly increased ATT during the pivot shift test (+ 2.7 mm, p = 0.0001), and PLMR repair restored native laxity. MFL augmentation did not improve the mechanics.ConclusionsIn-situ PLMR repair eliminated pivot shift laxity through ATT and reduced force on the ACL graft, indicating that this procedure may be ACL graft-protective. MFL augmentation was not shown to have any effect on graft force or knee kinematics and untreated PLMR tears may place an ACL graft at higher risk. This study suggests concomitant repair to minimize additional forces on the ACL graft.

Anatomical and topographic features of the quadriceps femoris muscle in the Amur tiger

The article presents the specific features of the anatomical design of the quad- riceps femoral muscle in the Amur tiger. The aim of the study is to establish anatomical and topographic features and skeletotopic landmarks of the quadriceps femoral muscle in the Amur tiger, as well as to assess the functional significance of the studied structures. It was found that its straight head in its distal part has a muscle-tendon method of attachment to the kneecap. It is shown that the terminal tendons of the lateral and medial heads of the quadriceps femoris fuse with the plate-shaped tendons of the lateral and medial parts of its intermediate head. A more extensive area of fixation is characterized, in comparison with other heads, by the lateral head extending to the top of the cranial tubercle of the kneecap. The intermediate head with its distal end, together with the joint capsule, is fixed in the area of the articular surface of the kneecap. The study was performed at the Department of Anatomy and Histology of Animals named after Professor A.F. Klimova, Moscow State Academy of Veterinary Medicine and Biotechnology – MBA named after K.I. Scriabin. The object of study was the Amur tiger. The material for the study was pelvic limbs, without external signs of pathologies. We used methods of conventional and fine anatomical dissec- tion of muscles under the control of a binocular magnifier “Micromed HR 350 S”, as well as biomechanical modeling of a static-locomotor act. Based on the conducted studies, we have identified additional collateral lateral and medial menisco-femoral ligaments in the tiger, which stabilize the menisci and strengthen the knee joint. The revealed features of the mac- roarchitecture of the kneecap in a tiger can provide optimal conditions for the functioning of the quadriceps femoral muscle and biomechanical perfection of the knee joint

Intrameniscal degeneration and meniscotibial ligament loosening are associated factors with meniscal extrusion of symptomatic discoid lateral meniscus.

This study aimed to compare the amount of extrusion of the discoid lateral meniscus (DLM), which was symptomatic and required surgery, with normal meniscuses and asymptomatic DLMs and examine factors associated with the extrusion of symptomatic DLM. Medical records of participants with DLM or normal lateral meniscus (LM) were retrospectively reviewed using magnetic resonance imaging (MRI). DLM cases were divided into symptomatic and asymptomatic groups. The midbody meniscal extrusion was measured using mid-coronal MRI. The association between meniscal extrusion and MRI findings, including the meniscofemoral ligament, meniscotibial ligament (MTL), intrameniscal signal intensity of the peripheral rim, meniscal shift, and skeletal maturity, was evaluated. Eighty-six knees with DLM (63 symptomatic) were included. The control group included 31 patients. The symptomatic group showed significantly greater meniscal extrusion (mean ± standard deviation symptomatic DLM: 1.0 ± 1.1mm, asymptomatic DLM: 0.1 ± 0.4mm, and normal LM: 0.3 ± 0.6mm, P < 0.001) and had a significantly higher incidence of MTL loosening (P = 0.02) and intrameniscal signal (P < 0.001) than the other two groups. In the symptomatic group, multivariable linear regression analysis showed that MTL loosening [β = 1.45, 95% confidence interval (CI) 1.03-1.86, P < 0.001] and intrameniscal signal (β = 0.49, 95% CI 0.09-0.90, P = 0.002) were independent associated factors. LM extrusion was significantly more common in patients with symptomatic DLM than in those with asymptomatic DLM or a normal LM. MTL loosening and intrameniscal high-signal intensity on MRI were independently associated with meniscal extrusion. These findings help explain the pathogenesis and diagnosis of symptomatic DLM. III.

MRI study of the cruciate ligaments and menisco-femoral ligaments of the knee.

It has been argued that the meniscus-femoral ligaments disappear with age. We therefore analyzed the presence of the meniscus-femoral ligaments, in MRI. We measured the PCL, ACL and MFL, noting their presence or absence in 120 Knee MRIs, 51 in women and 69 in men. All knees underwent MRI in the coronal, sagittal and axial planes. T1 and T2 weighted sequences were obtained. A descriptive statistical study of all the variables was carried out, and a comparative study was performed between sexes, sides and age groups. The MFLp was more frequent, found in 67 (55.8%) cases, than the MFLa, in 36 (30%) cases, and both together were present in 27 (22.5%) knees. We found a strong correlation between ACL length and PCL length (p = 0.001), we found no correlation between the presence of the posterior MFL either with age (p = 0.307) or with sex (p = 0.779) or side (p = 0.733). We also found no relationship between the presence of the anterior MFL and age (p = 0.553), or sex (p = 0.913), or laterality (p = 0.082). We found a strong correlation between ACL length and PCL length. In our study, the presence of the posterior MFL was more frequent, being present in 55.68%, while the anterior MFL was found in 30% of the knees. We did not observe that the presence of LMF decreases with age.

Poster 218: Biomechanical Function of the Lateral Meniscus Posterior Root and Meniscofemoral Ligaments: A Computational Study

Objectives:Tear of the posterior root of the lateral meniscus (LMPR[ICP1] ) is commonly associated with ACL rupture. Surgical repair of the LMPR is indicated to stabilize the knee and protect the knee from progressive osteoarthritis. However, this surgery may be technically challenging or the location of the tear may not support anatomic repair to the tibial footprint. Even in the setting of a torn LMPR, a common intraoperative observation is that the anterior (Humphrey) meniscofemoral ligament (aMFL) remains intact. We denote this constellation as the HIRO lesion (Humphrey Intact, Root Out). This studied utilized a computational model of the knee to understand load sharing between the ACL, LMPR, and the MFLs in response to pivoting maneuvers. We hypothesized that (1) lateral compartment ATT would be greater in the knee with a combined deficiency of the LMPR and MFLs compared to intact MFLs (i.e. HIRO lesion, Figure 1) and that (2) the ACL force would be lower in the presence of a HIRO lesion as compared to combined LMPR and MFL injury.Methods:A previously developed computational model of the native tibiofemoral joint was utilized. The model including geometries of the tibia, femur, cartilage and menisci incorporating average properties for ligaments, capsule, meniscal attachments, and MFLs. Multiplanar torques simulating a pivoting maneuver were applied to the computational model at 30° of flexion, consisting of valgus (8 Nm), and internal rotation (4 Nm) to assess the impact of simulated sectioning of the ACL, LMPR, and MFLs. Lateral compartment anterior tibial translation and force carried by the ACL, LMPR, and each MFL were assessed at the peak applied pivoting loads.Results:With all structures intact, peak applied pivoting loads resulted in lateral compartment anterior tibial translation of 10.4 mm. With sequential ligament sectioning, lateral compartment anterior translation increased by 0.5 mm with LMPR deficiency; 5.8 mm with ACL deficiency; 8.5 mm with combined LMPR and ACL deficiency; and 8.9 mm with combined LMPR, ACL, and aMFL deficiency. Force carried by the ACL was 100 N at baseline; this increased by 12 N with LMPR deficiency and by an additional 1 N with combined sectioning of the LMPR and both MFLs. The intact LMPR saw an increase in force by 18 N with ACL deficiency from baseline. The aMFL force increased by 12 N with LMPR sectioning and by an additional 4 N with combined LMPR and ACL deficiency. The posterior MFL did not see force with simulated pivot shift testing at 30° knee flexion.Conclusions:A HIRO lesion results in a 14% increase in lateral compartment ATT (versus ACL deficiency alone) compared to a 16% increase when both the LMPR and MFLs are sectioned. While the ACL saw 12% increased force with a HIRO lesion, there was a 1 N increase in ACL force with combined LMPR and MFL sectioning. The load-bearing role of the aMFL was more pronounced with combined ACL and LMPR tear compared to LMPR tear with intact ACL. The biomechanical model confirms that, during a pivot shift, the LMPR has a primary role in lateral compartment ATT and load-sharing with the ACL compared to the aMFL. Surgeons should attempt to repair the LMPR with ACL reconstruction.Figure 1.Arthroscopic image demonstrating Humphrey Intact Root Out (HIRO) lesion in a 34-year-old male patient with combined anterior cruciate ligament/ lateral meniscus posterior root (LMPR) injury. The lateral meniscus (LM) body is disrupted from the LMPR footprint as a consequence of a radial tear (note the gap in the tissue continuity from LM body to LMPR). The anterior meniscofemoral ligament of Humphrey is visible with robust attachment to LM body connecting to the medial femoral condyle. LFC = Lateral femoral condyle (visualized in figure 1B).Table 1.Lateral compartment ATT and forces subjected to ACL, LMPR, aMFL and pMFL as outputs of a computational cadaveric knee model subjected to peak applied pivoting loads at 30° of flexion, consisting of valgus (8 Nm) and internal rotation (4 Nm).

Attachment Type, Thickness, and Volume of the Posterior Meniscofemoral Ligament and Meniscal Pathology.

Several studies have investigated the relationship between the thickness of the posterior meniscofemoral ligament (pMFL) and the presence of a discoid meniscus. We investigated the correlation between meniscal pathology and anatomic features of pMFL such as attachment type, thickness, and volume. We retrospectively evaluated 191 patients who underwent knee MRI. MR images were reviewed to assess the attachment type of the pMFL on the medial femoral condyle (high vs. low), the thickness of the pMFL, and the presence of a meniscal tear or a discoid meniscus. The pMFL volume was quantified by using three-dimensional (3D) segmentation software. The relationship between the frequency of medial or lateral meniscal tear and anatomic features of pMFL were analyzed using Chi-square, Fisher's exact, or Mann-Whitney U test. High type pMFLs had significantly greater thickness and volume than low type pMFLs (p < 0.001). Patients with degenerative lateral meniscal tear had significantly higher thickness and volume of the pMFL than patients with intact lateral meniscus (p < 0.05). The pMFL thickness and volume were not significantly related to traumatic lateral meniscal tear, medial meniscal tear, and discoid meniscus. High type pMFLs tended to be thicker and larger than low type pMFLs and higher thickness and volume of the pMFL was significantly related to the degenerative lateral meniscal tear. However, the attachment type of the pMFL itself was not significantly related to the lateral meniscal tear as well as the medial meniscal tear.

The hypermobile and unstable lateral meniscus: a narrative review of the anatomy, biomechanics, diagnosis and treatment options.

The purpose of this review is to improve the awareness of lateral meniscal hypermobility by describing its relevant anatomy, biomechanics, pathophysiology, imaging and arthroscopic findings as well as the treatment options. The lateral meniscus is less stable than the medial meniscus. Its important posterior stabilizers are the popliteomeniscal fascicles, the posterior capsule, the meniscofemoral ligaments and the posterior meniscotibial ligament, which are divided by a bare area, the popliteal hiatus. Atraumatic insufficiency or rupture of one of these key structures may impact the mobility of the lateral meniscus and can lead to an unstable, hypermobile lateral meniscus. Lateral meniscus hypermobility can cause lateral knee pain and mechanical symptoms as locking. Ruptures of the popliteomeniscal fascicles are frequently associated with anterior cruciate ligament and posterolateral corner injuries. Their repair may be important to fully restore knee stability. This is a narrative overview of the literature synthesizing current knowledge about the hypermobile lateral meniscus. Anatomy, biomechanics, diagnosis and treatment of this entity was of particular interest for this review. Literature was retrieved from PubMed database, hand searches and cross-reference checking. Diagnosing lateral meniscus hypermobility is challenging since the magnetic resonance imaging are often unspecific and may show no structural alterations of the meniscus and its attachments. The only hint can be the patient's history and clinical symptoms (e.g., locking). Ultimately, the diagnosis is confirmed during knee arthroscopy, when the lateral meniscus can be mobilized over 50% of the lateral tibial plateau or lateral femoral condyle while anterior probing or by using the aspiration function during arthroscopy. Treatment includes stabilizing the posterior lateral meniscus by repairing the injured structures. Therefore, a systematic arthroscopic evaluation of the lateral compartment is important to fully recognize the problem. Repair can be achieved arthroscopically with various suturing techniques used for meniscal repair with satisfactory results and low recurrence rates.

The influence of the morphometric parameters of the intercondylar notch on occurrence of meniscofemoral ligaments.

The purpose of this study was to examine the existence of correlation between the morphometric parameters of the intercondylar notch of the femur and the occurrence of meniscofemoral ligaments (MFLs) and if there is any relationship in the running angle (RA) value between narrowed and normal sized intercondylar notch. Coronal, sagittal and horizontal magnetic resonance (MR) images of 90 patients with specified exclusion criteria were included in this study. The c2 test was used for statistical analysis. In our research either one or both MFLs were identified in 70 (77.8%) of the 90 coronal MR images. In normal sized intercondylar notch, MFLs was seen in 39 (43.3%) cases and on 31 (34.4%) MR images with narrowed intercondylar notch. A significant correlation was established between the occurrence of the MFL and morphometric parameters of the intercondylar notch (p < 0.05). In normal sized intercondylar notch, 12 posterior meniscofemoral ligaments (pMFLs) of type I were detected (RA value 42°), 8 of type II (RA value 33°), 5 of type III (RA value 23°) and two were of indeterminate type, whilst 10 anterior meniscofemoral ligaments (aMFLs) were of type I (RA value 39°), 7 of type II (RA value 31°), 2 of type III (RA value 25°) and the remaining 6 were indeterminate. In narrowed intercondylar notch, 10 ligaments of pMFLs were of type I (RA value 30°), 8 of type II (RA value 25°), 5 of type III (RA value 20°), 10 ligaments of aMFLs were of type I (RA value 35°) and 9 were indeterminate. Statistically significant differences in the value of the running angle of pMFL type I and of type II were evaluated between two groups with different shaped intercondylar notch (p < 0.05). The results shown in our study may be useful in medical clinical practice, reconstructive surgery, interpretation of knee MR images as well as genetic research.

Magnetic Resonance Imaging of the Dromedary Camel Stifle

The objective of the present investigation was to develop a high-field magnetic resonance imaging (MRI) protocol for assessment of the dromedary camel stifle region and to describe normal MRI appearance of the stifle by comparing MRI images with their corresponding anatomic slices. Twelve cadaveric hind limbs were obtained from 6 clinically sound adult dromedary camels without hind limb lameness. Cadaveric stifles were scanned by 1.5 Tesla MRI system using T1-weighted, T2-weighted, proton density gradient echo and short Tau inversion recovery sequences in 3 planes. After imaging, stifles were frozen at – 18°C for 2 weeks, then sectioned in sagittal, dorsal or transverse planes. Optimal MRI images from different sequences and planes were evaluated and correlated to their corresponding gross anatomic slices. Descriptive findings of the articular cartilage, subchondral bone, cruciate ligaments, menisci, menisco-tibial and menisco-femoral ligaments, long digital extensor tendon, and patellar ligament were reported. The high-field MRI protocol described in this study provided high spatial and contrast resolution of the osseous and soft tissue structures of the dromedary camel stifle joint. Data obtained in this study could be used as normal reference standards for evaluation of the dromedary camel stifle in clinical situations.

Medial collateral ligament injury of the knee: correlations between MRI features and clinical gradings.

To evaluate the degree of correlation between MRI and clinical gradings of medial collateral ligament (MCL) injuries and assess for associated structures on MRI which may influence the clinical perception of MCL laxity. All knee MRIs with acute MCL injuries between 2016 and 2020 at our centre were retrospectively reviewed by two blinded musculoskeletal radiologists. The clinic notes were reviewed for clinical gradings. One hundred and nineteen MRIs included. Forty-eight percent (57/119) agreement between MRI and clinical gradings (κ = 0.21, standard error (SE) 0.07). MRI grades: I 29% (34/119), II 50% (60/119), III 21% (25/119). Clinical grades: I 67% (80/119), II 26% (31/119), III 7% (8/119). In patients with clinical grade III MCL injury, there was waviness of the superficial MCL on MRI in 100% (8/8), deep meniscofemoral ligament tear in 75% (6/8), anterior cruciate ligament (ACL) partial or complete tear in 75% (6/8) and posteromedial corner (PMC) injury in 100% (8/8); compared with 0% (0/111), 34% (38/111), 44% (49/111) and 41% (46/111) respectively in clinical grade I or II injuries (p < 0.05). Agreement between MRI and clinical gradings of MCL injuries was only 'fair', with MRI almost always overestimating the grade of the injury when there was a mismatch. Waviness of the superficial MCL and injuries to the deep MCL, ACL and PMC correlate with clinical instability.