The popliteal region: an anatomical study and a new approach to the tibial attachment of the posterior cruciate ligament

Inverted deltoid posterior cruciate ligament femoral insertion accompanied with medial synovial fold: a case of a complex posterior cruciate ligament anatomical variation recalcitrant to conservative treatment

PURPOSE

The present study aims to report a symptomatic rare anatomical variation of the posterior cruciate ligament (PCL) that was encountered during arthroscopy.

CASE PRESENTATION

A 34-year-old female suffered from dull anterior pain in the right knee, along with stiffness and the presence of an audible click and occasionally locking during deep knee flexion. Physical examination revealed only slight pain during single-leg squatting and mild knee effusion with painful limitation of the last degrees of flexion. Following unsuccessful conservative treatment, knee arthroscopy was performed in which the PCL was found to be hypertrophic, having a broad femoral insertion that almost completely occupied the intercondylar notch and impinged the anterior cruciate ligament. Moreover, the PCL presented a large medial synovial fold that formed a plica inserting to the medial meniscus's posterior horn. Ligamentoplasty was performed by excising one-third of the PCL lateral portion. The PCL medial synovial fold and the plica attaching to the medial meniscus were resected. The patient was allowed to return to full activity when her symptoms resolved, and the knee function was restored, at 5 weeks post-operatively.

CONCLUSION

The current study presented a rare and complex anatomical variation of the PCL that was symptomatic and recalcitrant to conservative treatment. Magnetic resonance imaging (MRI) can reveal the variant morphology of the PCL, and arthroscopy provides the definite treatment. This case report may be useful for orthopaedic surgeons and radiologists to consider anatomical PCL variations during differential diagnosis in patients with non-specific clinical presentation and findings.

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.

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.

Successful reconstruction of the posterior cruciate ligament: assessment of posterior cruciate ligament footprints using an objective coordinate system

Introduction

Anatomic cruciate ligament reconstruction is known to be correlated with better clinical results. The aim of the study was to provide a simple method to enable anatomic results in the setting of PCL reconstruction. We, therefore, assessed the tibial and femoral insertion site of the posterior cruciate ligament (PCL) by the use of an objective coordinate system in an anatomical study. We also sought to show reproducibility of these measurements using intra- and inter-observer coefficients.

Materials and methods

We studied 64 knees, previously preserved according to Thiel’s technique. After proper preparation of the articular surfaces of both the tibiae and femora, photographs were taken according to a standardized protocol. PCL footprints were measured by the use of a coordinate system twice by two examiners. We evaluated these measurements by use of the Cohen’s kappa inter- and intra-observer coefficient for two observers.

Results

Tibial and femoral measurements of PCL footprints were generated with highly comparable inter- (k = 0.970) and intra-observer (k = 0.992) coefficients and may, therefore, be considered as highly reproducible.

Conclusion

Our findings confirmed the reproducibility of defining PCL footprints using a coordinate system and may contribute to planning intraoperative graft-placement to ensure optimal conditions in the upcoming techniques for PCL reconstruction.

Anatomical evaluation of the tibial nerve within the popliteal fossa

The purpose of this study was to evaluate the inter-hamstring position (medial to lateral intertendinous position) of the tibial nerve within the popliteal fossa. A descriptive cadaver model study was performed to permit controlled and direct measures of the tibial nerve. Fourteen embalmed lower extremities (8 left, 6 right) from nine cadavers (4 males, 5 females; 84.3 +/- 10.7 years of age) were examined. Nine anatomical variables were measured. All measurements, except the diameter of the tibial nerve at the apex of the popliteal fossa, were performed at the level of the femoral condyles, at their widest medial-to-lateral point. The tibial nerve's diameter increased as it descended from the apex (3.95 +/- 0.50 mm; CI = 2.94-4.96 mm) to the condyles (4.46 +/- 0.92 mm; CI = 2.62-6.31 mm). The distance between the semimembranosus tendon and the biceps femoris tendon in the popliteal fossa (the mid-intertendinous distance) was 48.50 +/- 11.50 mm. The location of the tibial nerve between these two tendons was highly variable: 21.45 +/- 8.40 mm lateral of the semimembranosus tendon and 22.60 +/- 4.90 mm medial of the biceps femoris tendon. Therefore, in 95% of the patients the tibial N could be located within 48.2% of midpoint of the inter-hamstring distance.

Establishing a popliteal portal using the METRx system under ultrasound guidance

This report describes a special technique for safe establishment of a popliteal portal with the METRx system (Medtronic Sofamor Danek, Memphis, TN) under ultrasound guidance with the patient in the awake state. Herbert screws located at the posterior tibial plateau were removed via this portal in a minimally invasive way. Before surgery, we performed surface mapping of the screw tract with an image intensifier and target needling under ultrasound guidance. The METRx system was used to establish the soft-tissue corridor along the guide pin. Screw removal and tibial plateau resurfacing were performed with the Acufex Mosaicplasty system (Smith & Nephew Endoscopy, Andover, MA). In our review of the literature, no similar method establishing the knee popliteal portal was found. The method is recommended especially for minimally invasive surgery in regions rich with neurovascular structures.

An inconstant ligament in the popliteal region associated to the superior genicular arteries: surgical importance

MATERIALS AND METHODS

In the dissection of 60 knees of 30 cadavers (13 women and 17 men), a ligament was located in the posterior femur face above the lateral or medial condyle.

RESULTS

This ligamentous structure was found in 12 (20%) out of 60 knees studied (38% of the women and 35% of the men). It had a vertical arrangement and a constant direct relation to the superior (lateral or medial) genicular artery, and in no case it appeared as a posterior reinforcement of the capsule. The superior vessels were fixed by this ligament.

DISCUSSION

This fixation may provide stability to the vascular tree but it could be a cause of post-surgical hemarthrosis in arthroscopy of the posterior knee area or in posterior or lateral knee approaches or it could be even implicated in vascular injury of the popliteal artery during knee dislocation.

CONCLUSION

The objective was to describe this inconstant ligament and to study its clinical relevance for surgical procedures, and particularly for those using the posterior approach to the knee joint.

Surgical approaches to the posteromedial and posterolateral aspects of the knee

Surgical approaches to the posterior aspect of the knee are not commonly needed, and their use has become even rarer with the increasing sophistication of arthroscopic technology. As a result, physicians in orthopaedic surgical training are not often exposed to the practical use of surgical dissection around the posterior corners of the knee. For certain procedures, however, greater clinical utility and decreased surgical morbidity render focused posterior exposure the preferred alternative to the classic popliteal dissection with its wide exposure of the popliteal anatomy. Surgical indications include ligament repair or reconstruction around the posteromedial or posterolateral aspect of the knee, inside-out meniscal repair, posterior cruciate ligament tibial inlay reconstruction, and Baker's cyst excision. To minimize complications, these focused approaches require adeptness with the complex anatomy of the posterior, posteromedial, and posterolateral aspects.