Clinical Anatomy of the Posterior Meniscofemoral Ligament of Wrisberg: An Original MRI Study, Meta-analysis, and Systematic Review

Background: The posterior meniscofemoral ligament (pMFL) of Wrisberg attaches to the posterior horn of the lateral meniscus and the lateral intercondylar aspect of the medial femoral condyle and passes posteriorly to the posterior cruciate ligament (PCL). The pMFL plays a role in recovery after PCL injuries and offers stability to the lateral meniscus, promoting normal knee function. Purpose/Hypothesis: The aim of the magnetic resonance imaging (MRI) arm of this study was to evaluate the prevalence of the pMFL in Polish patients. The purpose of the systematic review and meta-analysis was to evaluate the clinical relevance of the pMFL in knee surgery. It was hypothesized that extensive variability exists in reports on the prevalence, function, and clinical significance of the pMFL. Study Design: Cross-sectional study and systematic review; Level of evidence, 3. Methods: A retrospective MRI investigation was conducted on 100 randomly selected lower limbs of Polish patients (56 male, 44 female) performed in 2019 to determine the prevalence of the pMFL. Additionally, an extensive literature search of major online databases was performed to evaluate all reported data on the pMFL. Assessments of article eligibility and data extraction were completed independently by 2 reviewers, and all disagreements were resolved via a consensus. A quality assessment of the included articles was performed using the Anatomical Quality Assessment tool. Results: In the MRI arm of this study, the pMFL was observed in 73 of the 100 limbs. In the meta-analysis, 47 studies were included, totaling 4940 lower limbs. The pooled prevalence of the pMFL was found to be 70.4% (95% CI, 63.4%-76.9%); the mean length was 27.7 mm (95% CI, 24.8-30.5 mm) and the mean widths were 4.5, 6.1, and 4.1 mm for the meniscal and femoral attachments and midportion, respectively. The mean pMFL thickness was 2.3 mm (95% CI, 1.8-2.7 mm). Conclusion: Despite the variability in the literature, the pMFL was found to be a prevalent and large anatomic structure in the knee joint. The shared features of this ligament with the PCL necessitate the consideration of its value in planning and performing arthroscopic procedures of the knee.

Clinical Anatomy of the Anterior Meniscofemoral Ligament of Humphrey: An Original MRI Study, Meta-analysis, and Systematic Review

Background: The anterior meniscofemoral ligament (aMFL) of Humphrey is an anatomically variable fibrous band of connective tissue that attaches between the lateral aspect of the medial femoral condyle and posterior horn of the lateral meniscus, running posterior to the anterior cruciate ligament and anterior to the posterior cruciate ligament (PCL). The presence of an intact aMFL may contribute to stabilization of the lateral compartment of the knee joint. Purpose: The original magnetic resonance imaging (MRI) arm of this study aimed to assess the aMFL incidence among Polish patients. The goal of the systematic review and meta-analysis was to review the literature discussing the clinical anatomy of the aMFL and provide data on its prevalence. It was hypothesized that significant heterogeneity exists within the published literature. Study Design: Cross-sectional study and systematic review; Level of evidence, 3. Methods: A retrospective investigation was performed on the MRI scans of 100 knees (52 right, 48 left) of Polish patients. Scans were randomly selected from a database of MRI examinations performed in 2019. For the meta-analysis, major online databases were queried for data on the aMFL, and 2 authors independently assessed and extracted data from all included studies. A quality assessment of the included articles was performed using the Anatomical Quality Assessment tool. Results: In the MRI arm of this study, the aMFL was found in 62 of the 100 lower limbs. The meta-analysis included 41 studies with a total of 4220 limbs. The aMFL was present in 55.5% (95% CI, 45.5%-65.3%) of cases. Arthroscopic studies yielded the highest prevalence (82.3% [95% CI, 36.6%-100.0%]); of MRI studies, the highest prevalence was at 3.0-T strength (51.0% [95% CI, 13.3%-88.2%]). Conclusion: Significant variability in the prevalence of the aMFL was found in the literature. More emphasis should be placed on the clinical relevance of injuries to the aMFL because of its significant role in the function of the knee. It is important to be aware that, because of the anatomy of the aMFL, the ligament can also function to support a torn PCL.

Comparative Morphological Studies of the Stifle Menisci in Donkeys, Goats and Dogs

The present work aims to provide more anatomical information on the stifle joint of the investigated species using computed tomography with gross anatomical cross-sections. The current work analyzed the stifle joint of the pelvic limbs of 12 adult donkeys, goats and dogs of both genders. The medial condyle of the femur was larger than the lateral one in the donkey, while it was smaller and lower than the lateral one in the goat and in the dog. The unsuitable femoral and tibial condyles were adapted by the presence of menisci. In the donkey, the medial meniscus was crescentic in shape, but it was semicircular in the goat, while in the dog, the medial and lateral menisci were C-shaped. In the donkey, the medial meniscus was larger than the lateral one, but in the goat and in the dog, the lateral meniscus was the largest, and more concave and thicker. The lateral meniscus was semicircular in the donkey, but it was shaped like an elongated kidney in the goat. In the goat and in the dog, the central border of two menisci was thin, concave and notched centrally. The meniscal ligaments included cranial and caudal ligaments of the medial and lateral menisci, and meniscofemoral ligament of the lateral meniscus. In the dog, the cranial ligament of the medial meniscus was absent, and the medial meniscus had no bony attachment to the tibia but it attached to the transverse intermeniscal ligament, which connected the cranial horn of the medial meniscus with the cranial ligament of the lateral meniscus. The meniscofemoral ligament connected the caudal pole of the lateral meniscus with the intercondyloid fossa of the femur.

Complementary Function of the Meniscofemoral Ligament and Lateral Meniscus Posterior Root to Stabilize the Lateral Meniscus Posterior Horn: A Biomechanical Study in a Porcine Knee Model

Background: It has been demonstrated that the load distribution function of the lateral meniscus (LM) is compromised by resecting both the meniscofemoral ligament (MFL) and LM posterior root (LMPR). However, the effect of resecting these fibers on load transmission through the LM needs to be investigated. Purpose: To evaluate using a porcine knee model (1) the in situ forces of the MFL and LMPR and (2) the effect of resecting these fibers on the in situ force of the LM under a compressive load and valgus torque to the lateral knee compartment. Study Design: Controlled laboratory study. Methods: Twenty fresh-frozen porcine knees and a 6 degrees of freedom robotic system were utilized. An axial compressive load of 250 N and 5 N·m of valgus torque were applied to intact, MFL-deficient, LMPR-deficient, and MFL/LMPR-deficient knees at 30°, 60°, and 90° of flexion. The valgus angles under the applied loads were compared among the 4 states. The in situ forces of the MFL and LMPR under the applied loads were calculated under the principle of superposition. The in situ forces of the LM under the applied loads were also calculated and compared among the 4 conditions (intact, without the MFL, without LMPR, and without the MFL/LMPR). Results: The valgus angles significantly increased after resecting both the MFL and LMPR at all the flexion angles. The in situ forces of the MFL and LMPR changed reciprocally as the knee flexed. The in situ forces of the LM significantly decreased after resecting both the MFL and LMPR, although resecting only the MFL or LMPR represented no significant effect. Conclusion: The MFL and LMPR functioned complementarily as the posterior attachments of the LM against a compressive load and valgus torque to the lateral knee compartment in porcine knee joints. Clinical Relevance: If the LMPR is completely detached and needs to be repaired, the MFL should be preserved because it may provide some stability to the LM posterior horn and protect the repaired LMPR.