Anatomy, magnetic resonance and arthroscopy of the popliteal hiatus of the knee: normal aspect and pathological conditions

Morphology of the popliteomeniscal fascicles around the popliteal hiatus on three-dimensional images reconstructed from 7 T magnetic resonance imaging: A cadaveric study

BACKGROUND

This study aimed to clarify the characteristic features of the anteroinferior and posterosuperior popliteomeniscal fascicles (aiPMF and psPMF, respectively) and popliteal hiatus using three-dimensional (3D) reconstructions of 7 T magnetic resonance imaging (MRI) arthrography.

METHODS

Six knees from human cadavers fixed using the Thiel embalming method were examined using 7 T MRI arthrography. 3D Images of the structures around the popliteal hiatus were reconstructed. Morphologies of the psPMF, aiPMF, and popliteal hiatus were investigated and their positional relationships analyzed.

RESULTS

The PMFs attached to the periphery of the lateral meniscus (LM) to form the popliteal hiatus. Each coursed in an oblique direction. The mean length of the psPMF and aiPMF attachments to the LM were 6.8 and 21.6 mm, respectively; mean popliteal hiatus length was 12.8 mm. These lengths corresponded to 7.5%, 24.3%, and 14.5% of the total length of the LM, respectively. The aiPMF was thick near the lateral aspect of the articular capsule and became thinner towards the posteromedial aspect of the LM. The psPMF was thick near the posterior aspect of the articular capsule and became thinner towards the posterolateral aspect of the LM.

CONCLUSION

Morphological properties of the aiPMF, psPMF, their attachments to the LM, and the popliteal hiatus were consistent across the cadaver specimens examined. Each PMF was thin near the popliteal hiatus and became thicker towards its attachment to the articular capsule. These findings may be useful for anatomical repair for the LM hypermobility.

Vascular anatomy of the lateral meniscus with special focus on the joint capsule

Previous studies have reported that the lateral meniscus (LM) has two regions, the popliteal hiatus area (PH) with a scarce blood supply and the roots with an abundant one. However, the description of its vascular anatomy remains insufficient. We hypothesized that the difference in the width of the meniscus hilum (MH) affects the scarcity and abundance of blood supply to the LM. The MH is a concept proposed by us and is the only site of entrance or exit of blood vessels and nerves associated with the meniscus. The purpose of this study was to provide a structural explanation for the disparity of blood supply to the LM using the concept of MH. Sixteen knees were examined to investigate the blood supply to LM. In most areas, the femoral joint capsule (FJC) and tibial joint capsule (TJC) continued to the cranial and caudal edges of the LM, respectively. In the roots, the FJC and TJC covered the femoral and the outer-femoral surfaces. In contrast, the FJC in the PH did not attach to the cranial edge and only the TJC there did to the caudal edge of the LM. Histochemical examination showed that the blood vessels enter the LM via the MH. In the PH, the MH at the caudal edge was extremely narrow; and in the roots, the MH on the outer-femoral surfaces was wide. The results suggest that the difference in the width of the MH affected the scarcity and abundance of blood supply to the LM.

Ramp-like lateral meniscus tear. Description of an infrequent lesion

Numerous studies on meniscal tears have been published, a pathology that continues to evolve in terms of treatment and patient outcomes. As our understanding of anatomy and biomechanics improves, new entities have emerged. The lateral meniscus, especially its posterior attachment, tends to be overlooked due to its greater mobility compared to the medial meniscus. Evaluating the instability of the posterior horn poses a challenge, even during arthroscopy, therefore, it is crucial to understand the posterior menisco-synovial detachment lesions, which are indeed real and, to date, haven't received enough attention in the existing literature. The aim is to describe a new entity affecting the posterior synovial attachment of the lateral meniscus, without injury to the posterior horn of the lateral meniscus (PHLM). We also aim to present a case report detailing the intraoperative diagnosis and management of a 20-year-old patient with a sports trauma that led to a combined anterior cruciate ligament (ACL) and lateral meniscus tear managed with arthroscopic ACL reconstruction and all-inside meniscal suture. Through conventional arthroscopic evaluation of the posterior capsule anatomy and dissections, we have identified a distinct lesion of the PHLM at the menisco-synovial junction. Further research is necessary in this field to understand the biomechanical repercussions and determine the ideal surgical management.

The meniscotibial ligament does exist: An anatomic and histological description

Purpose

To describe the anatomical and histological characteristics of the human MTL (meniscotibial ligament) that keeps the meniscus stable and are rarely discussed.

Study design

Descriptive laboratory study.

Methods

In total, six fresh-frozen adult cadaver knees were dissected, and the dissection protocol were designed by two experienced anatomy professors. The anatomical morphology of MTL was observed. The main anatomical specimens included meniscus, tibial plateau, MTL. The osteotome was used to excise the portion of the tibial plateau, which could obtain the complex including partial meniscus, MTL, and a tibial fragment. A histopathologic study was performed by two experienced pathologists.

Results

Macroscopically, the MTL could be divided into two parts: medial meniscotibial ligament (MMTL)and lateral meniscotibial ligament (LMTL). The MMTL is distributed continuously, whereas the LMTL is discontinuous on the tibial plateau. The average length from the tibial attachment of the LMTL to the articular surface was 19 ± 1.0mm (mean ± SD). The average length from the tibial attachment of the MMTL to the articular surface was 10 ± 1.2 mm (mean ± SD). Microscopy of the MTL showed that the MTL is a ligamentous tissue, composed of a network of oriented collagenous fibers.

Conclusions

In all knees, the MTL was inserted on the outer edge of the meniscus, attaching to the tibia below the level of articular cartilage, which was key to maintaining the rotational stability of knee and the meniscus in the physiological position on the tibial plateau. Histological analysis of this ligament demonstrated that the MTL is a veritable ligamentous structure, which is made up of collagen type I-expressing fibroblasts.

Clinical relevance

This article contributes to the understanding of the anatomical and histological characteristics of the MTL. It is beneficial to promote the development of relevant surgical techniques for the MTL lesion.

Anterior Mobility of the Posterior Horn of the Lateral Meniscus Is Associated With Abnormal Magnetic Resonance Imaging Findings of Anteroinferior Popliteomeniscal Fascicle and Posterosuperior Popliteomeniscal Fascicle as Well as a Clinical History of Catching or Locking Symptoms

Purpose

To identify predictors of anterior mobility of the posterior horn of the lateral meniscus (PHLM) among patient demographics (age, sex), clinical characteristics (a history of catching or locking symptoms [CLS], body mass index, alignment of limb), and magnetic resonance imaging (MRI) findings of 4 restraints: anteroinferior popliteomeniscal fascicle (aiPMF), posterosuperior popliteomeniscal fascicle (psPMF), posteroinferior popliteomeniscal fascicle (piPMF), and meniscofibular ligament (MFibL).

Methods

Between October 2010 and December 2014, patients who underwent arthroscopic measurement of mobility of the PHLM were identified. The Sakai classification was used to classify aiPMF and psPMF on MRI into the following 3 types: type A, the fascicle was depicted with obvious continuity and with a low-intensity band; type B, depicted with continuity but with an ambiguous intensity structure; and type C, depicted with discontinuity or not visible. Magnetic resonance images of the piPMF and MFibL were evaluated as presence or absence. The mobility of the PHLM was measured arthroscopically at traction forces of 10 and 20 N.

Results

A total of 73 patients (47 men, mean age 41.8 ± 19.3 years) were included. Multivariate regression analyses revealed aiPMF type C and psPMF types B and C to be independent factors associated with mobility at both traction forces, and CLS was an independent factor at a traction force of 20 N. Compared with that of type A, the increased mobility of aiPMF type C was 5.0 mm (P = .019) and 5.6 mm (P = .011) at 10 and 20 N, respectively; the increased mobility of psPMF type B was 2.5 mm (P = .007) and 3.5 mm (P = .0003), respectively; and the increased mobility of psPMF type C was 3.3 mm (P = .021) and 3.6 mm (P = .014), respectively. The increased mobility associated with CLS was 3.5 mm at 20 N (P = .022).

Conclusions

Anterior displacement of the PHLM induced by an external traction force at 90° of flexion of the knee joint was associated with abnormal MRI findings of the anteroinferior popliteomeniscal fascicle and posterosuperior popliteomeniscal fascicle, as well as a history of catching or locking symptoms.

Clinical Relevance

Understanding signs and symptoms and associated pathology in patients with symptomatic anterior mobility of the posterior horn of the lateral meniscus may help guide best treatment.

Hypermobile lateral meniscus: A systematic review of current treatment options

PURPOSE

The reliable data on the incidence of hypermobile lateral meniscus (HLM) and its clinical manifestations, diagnostic methods and therapeutic approaches are limited. This systematic study aimed to review available treatment options for HLM and the outcomes of each approach.

METHODS

A systematic search was performed in four electronic databases (PubMed, EMBASE, Scopus, Web of Science) to identify studies in which arthroscopically confirmed cases of HLM were treated surgically or nonsurgically, and the required data comprising study characteristics, patient data, treatment approaches and outcome measures were extracted from eligible studies.

RESULTS

Twenty studies with a total of 212 patients (138 males and 74 females) and 219 knees were included. The most frequently reported symptoms were locking sensations, knee pain, giving way and snapping. Treatments used by the studies were: radiofrequency energy in two studies; arthroscopic partial meniscectomy in one study; open surgery in two studies; and arthroscopic meniscal repair in 17 studies. Eleven studies used an all-inside repair method and an inside-out meniscal repair was reported in eight studies. Three studies reported the usage of posterior arthroscopy for therapeutic or diagnostic approaches. Evaluation of symptom resolution was the main outcome measurement for which almost all of the studies stated relief of symptoms after intervention.

CONCLUSION

Despite the lack of definite consensus about the most appropriate intervention for HLM, therapeutic preference was directed towards arthroscopic all-inside and inside-out repair techniques. Although the surgeon's decision remains the key factor in choosing the most suitable treatment option for each individual, posterior arthroscopic meniscal repair may be considered as a better option for HLM treatment according to the findings of this review.

LEVEL OF EVIDENCE

Level IV.

[Application of anterior region suture of popliteal hiatus in treatment of discoid lateral meniscus injury with instability in popliteal tendon region]

Objective

To discuss the application of anterior region suture of the popliteal hiatus (PH) under arthroscopy in the treatment of discoid lateral meniscus (DLM) injury with instability in the popliteal tendon region.

Methods

The clinical data of 53 patients (56 knees) with DLM injury who met the selection criteria between March 2014 and November 2022 were retrospectively analyzed. There were 15 males and 38 females, aged 8-55 years with an average age of 36.5 years. Fourteen cases had a history of trauma, while the remaining 39 cases had no clear history of trauma. The disease duration ranged from 1 day to 6 years, with an average duration of 15.6 months. According to the Watanabe classification, there were 40 knees of complete type and 16 knees of incomplete type. The preoperative International Knee Documentation Committee (IKDC) knee joint score was 51.2±8.3, the Lysholm score was 59.6±11.2, and the visual analogue scale (VAS) score was 4.7±1.3. After the arthroscopic meniscal plasty, the instability of the popliteal tendon region meniscus was checked by probing traction. Subsequently, the Out-inside technique or a combination of Out-inside and All-inside techniques was used to suture the anterior region of the PH. The stability of the meniscus after suturing was assessed, and if necessary, further suturing using the All-inside technique at the posterior region of the PH, the posterior horn of the meniscus, and using the Out-inside technique at the anterior horn of the meniscus was performed. Postoperative complications were recorded. The effectiveness was evaluated using pre- and post-operative IKDC scores, Lysholm scores, and VAS scores.

Results

After operation, knee joint pain, crepitus, and locking disappeared, with McMurray and grinding tests turning negative. All patients were followed up 12-93 months with an average of 57.5 months. There was no complication such as common peroneal nerve injury, deep vein thrombosis of the lower limbs, joint infection, or joint stiffness. At last follow-up, the IKDC knee joint score was 76.7±5.5, the Lysholm score was 94.0±4.1, and the VAS score was 1.1±0.8. The differences compared with preoperative scores were significant ( t=-22.090, P<0.001; t=-23.704, P<0.001; t=19.767, P<0.001).

Conclusion

Suturing of the anterior region of the PH is crucial in the treatment of DLM injury with instability in the popliteal tendon region.

Retrospective evaluation of MRI findings in arthroscopically confirmed cases of hypermobile lateral meniscus

OBJECTIVE

To identify preoperative MRI findings in patients with arthroscopically confirmed hypermobile lateral meniscus utilizing a standard MRI knee protocol, with comparison to normal control and lateral meniscal tear groups.

SUBJECTS AND METHODS

All patients with arthroscopically confirmed hypermobile lateral meniscus diagnosed at our institution were retrospectively identified. The following structures were evaluated on preoperative knee MRIs: superior and inferior popliteomeniscal fascicles, lateral meniscus and meniscocapsular junction, popliteal hiatus, and soft tissue edema around the popliteal hiatus. The same MRI features were evaluated in the normal control and lateral meniscal tear groups.

RESULTS

Study, normal control, and lateral meniscal tear patients (18 each) were included. In the study group, 94.4% had superior popliteomeniscal fascicle abnormality, 89.0% had inferior popliteomeniscal fascicle abnormality, and 72.2% had lateral meniscal abnormality. Incidence of these abnormalities was significantly higher than in the normal control group. Meniscal abnormalities in the study group all involved the posterior horn meniscocapsular junction, 12/13 of which had vertical signal abnormality at the junction and 1/13 with anterior subluxation of the entire posterior horn. Popliteus hiatus measurements were largest in the lateral meniscal tear group.

CONCLUSION

In patients with hypermobile lateral meniscus, the combination of popliteomeniscal fascicle abnormality and vertical signal abnormality at the meniscocapsular junction was seen in the majority of patients. Popliteomeniscal fascicle signal abnormality without identifiable lateral meniscal injury was the next most common imaging appearance. Radiologists may provide valuable information by suggesting the diagnosis of hypermobile lateral meniscus in such cases.

Surgical treatment of popliteomeniscal fascicles tears is associated with better patient-reported outcome measures. A systematic review and meta-analysis

PURPOSE

Popliteomeniscal fascicles (PMFs) are a component of the popliteal hiatus complex in the knee, and their injury primarily affects young athletes participating in sports activities involving twisting movements. The identification of PMFs tears presents a challenge, often accompanied by lateral pain and a locking sensation. The objective of this systematic review (SR) and meta-analysis is to enhance the suspicion and recognition of PMFs tears, aiming to facilitate the treatment of this condition, particularly in symptomatic young patients.

METHODS

A comprehensive search, focused on studies examining PMFs injuries and their treatment, was conducted in four databases, PubMed, Scopus, Embase, and Web of Science. The ROBINS-I tool was used to evaluate the risks of bias. The PRISMA flow diagram was used to conduct the research and select the included studies. A meta-analysis was conducted for the Lysholm score, the Tegner Activity Scale, and the subjective IKDC score. The present SR and meta-analysis was registered on PROSPERO.

RESULTS

Five clinical studies were included in the final analysis, comprising 96 patients. All the patients underwent a preoperative MRI assessment and a diagnostic arthroscopy to detect the PMFs tears, with a subsequent surgical procedure either open or arthroscopically performed. Surgery was associated with the resolution of symptoms. A statistically significant improvement in the Lysholm score (p: 0.0005) and the subjective IKDC score (p: 0.003) after the surgical procedure with respect to the preoperative evaluation was found.

CONCLUSION

This SR and meta-analysis showed a significant improvement in the Lysholm score and subjective IKDC score following surgery for PMFs tears. However, controversy persists regarding the optimal surgical approach, with current literature favoring arthroscopic procedures.

LEVEL OF EVIDENCE

IV.

Clinical presentation and arthroscopic treatment of hypermobile Type III Wrisberg variant of lateral discoid meniscus: Report of nine cases

BACKGROUND

The aim of the present study was to document a series of patients with meniscal hypermobility due to a Type III Wrisberg variant lateral discoid meniscus, describing their clinical presentation, analyzing their magnetic resonance imaging (MRI) and arthroscopic characteristics, and reporting the outcomes of an all-inside stabilization.

METHOD

Nine cases of Wrisberg variant Type III discoid lateral menisci were identified based on patient's history and clinical examination. Knee MRIs were reviewed to exclude the presence of Type I-II discoid meniscus (complete or incomplete) or bucket handle tears and general arthroscopic criteria. For the Wrisberg variant discoid lateral meniscus were applied for the final diagnosis.

RESULTS

All nine cases presented similar peculiar clinical, radiological, and arthroscopic features, which led to the diagnosis of hypermobile Wrisberg variant of lateral discoid meniscus. This rareclinical entity is responsible for suggestive symptoms such as pain, popping and knee locking; moreover, subtle but peculiar MRI and arthroscopic characteristics can be observed.

CONCLUSION

Considering the possibility of repeated dislocation and relocation, diagnosis can be challenging, and a high degree of suspicion should be used, especially in young patients, bilateral symptoms, and absence of trauma.

[A study on repair method of type c injury in lateral meniscus popliteal tendon area of porcine knee]

Objective

To investigate the repair method of type Ⅱc injury in the lateral meniscus popliteal tendon area based on the porcine knee joint.

Methods

Eighteen commercially available fresh porcine knee joints were randomly divided into 3 groups ( n=6). After preparing a type Ⅱc injury in the lateral meniscus popliteal tendon area, and the anterior (group A), posterior (group B), or anterior and posterior (group C) of the popliteal hiatus (PH) was sutured by vertical mattress. The tension meter was used to apply gradient tensions of 2, 4, 6, 8, and 10 N along the tibial plateau horizontally, respectively, to pull the midpoint of the lateral meniscus popliteal tendon area. The displacement values before modeling, after modeling, and after suture were recorded. The reduction value of lateral meniscus displacement and reduction rate after suture were calculated and compared between groups.

Results

There was no significant difference between groups ( P>0.05) in the displacement values before modeling, after modeling, and after suture under different tensions. There was no significant difference between groups A and C ( P>0.05) in the reduction value of lateral meniscus displacement and reduction rate after suture under different tensions. The reduction value of lateral meniscus displacement and reduction rate after suture in group B were lower than those in groups A and C. The reduction value of lateral meniscus displacement under tension of 2 N and the reduction rates under tensions of 2, 4, and 6 N between groups A and B showed significant differences ( P<0.05). The reduction value of lateral meniscus displacement and the reduction rate under tensions of 2, 4, and 6 N between groups B and C showed significant differences ( P<0.05).

Conclusion

Suturing the anterior area of PH is the key to repairing type Ⅱc injury of lateral meniscus popliteal tendon area.

Meniscus tears treatment: The good, the bad and the ugly-patterns classification and practical guide

Over the years, several studies demonstrated the crucial role of knee menisci in joint biomechanics. As a result, save the meniscus has become the new imperative nowadays, and more and more studies addressed this topic. The huge amount of data on this topic may create confusion in those who want to approach this surgery. The aim of this review is to provide a practical guide for treatment of meniscus tears, including an overview of technical aspects, outcomes in the literature and personal tips. Taking inspiration from a famous movie directed by Sergio Leone in 1966, the authors classified meniscus tears in three categories: The good, the bad and the ugly lesions. The inclusion in each group was determined by the lesion pattern, its biomechanical effects on knee joint, the technical challenge, and prognosis. This classification is not intended to substitute the currently proposed classifications on meniscus tears but aims at offering a reader-friendly narrative review of an otherwise difficult topic. Furthermore, the authors provide a concise premise to deal with some aspects of menisci phylogeny, anatomy and biomechanics.

An all-arthroscopic surgery technique for snapping popliteal tendon syndrome: A case report and literature review

RATIONALE

The incidence of snapping popliteus tendon syndrome, a type of lateral knee snapping, is not high, so making an accurate diagnosis is difficult. A proper treatment following an accurate diagnosis is essential for improvement. Very few cases have been reported of its treatment.

PATIENT CONCERNS

An 18-year-old male patient had experienced painful popping in the lateral part of the knee during knee flexion for 3 years before his hospital visit.

DIAGNOSES

Snapping popliteus tendon syndrome.

INTERVENTIONS

The patient underwent an all-arthroscopic surgery. Tendon debulking and tissue debridement around the popliteus tendon was conducted, but the snapping did not resolve. The enlarged tubercle was excised through an arthroscopic procedure using a burr, and the surgery was finished after confirming that snapping was resolved.

OUTCOMES

Full range of motion (ROM) was recovered 6 weeks after surgery and the snapping did not recur.

LESSONS

Snapping popliteus tendon syndrome is a disease that is hardly recognized due to its low prevalence and difficulty in diagnosis, and it requires close observation of the patient before surgery. The location of the tenderness and the snapping occurrence must also be carefully identified. Our procedure is an entirely arthroscopic technique; as it has the prominent advantage of a speedy recovery and easy rehabilitation, it could also be helpful to set treatment standards for this disease in the future.

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.

MRI evaluation of the peripheral attachments of the lateral meniscal body: the menisco-tibio-popliteus-fibular complex

PURPOSE

To determine, identify and measure the structures of the menisco-tibio-popliteus-fibular complex (MTPFC) with magnetic resonance imaging (MRI) in knees without structural abnormalities or a history of knee surgery.

METHODS

One-hundred-and-five knees without prior injury or antecedent surgery were analyzed by means of MRI. The average age was 50.1 years ± 14.8. All the measurements were performed by three observers. The peripherical structures of the lateral meniscus body were identified to determine the location, size, and thickness of the entire MTPFC. The distance to other "key areas" in the lateral compartment was also studied and compared by gender and age.

RESULTS

The lateral meniscotibial ligament (LMTL) was found in 97.1% of the MRIs, the popliteofibular ligament (PFL) in 93.3%, the popliteomeniscal ligaments (PML) in 90.4% and the meniscofibular ligament (MFL) in 39%. The anteroposterior distance of the LMTL in an axial view was 20.7 mm ± 3.9, the anterior thickness of the LMTL was 1.1 mm ± 0.3, and the posterior thickness of the LMTL 1.2 mm ± 0.1 and the height in a coronal view was 10.8 mm ± 1.9. The length of the PFL in a coronal view was 8.7 mm ± 2.5, the thickness was 1.4 mm ± 0.4 and the width in an axial view was 7.8 mm ± 2.2.

CONCLUSIONS

The MTPFC has a constant morphological and anatomical pattern for three of its main ligaments and can be easily identified and measured in an MRI; the MFL has a lower prevalence, considering a structure difficult to identify by 1.5 T MRI.

Five Overlooked Injuries on Knee MRI

This article highlights five knee injuries that, in the author's experience, are commonly overlooked by readers inexperienced in knee MRI: ramp lesions, meniscocapsular tears, meniscal root ligament tears, posterior capsular ligament tears, and partial anterior cruciate ligament tear. While these injuries are readily apparent when the images are assessed for the given abnormality, the author's belief is that these may be overlooked because either the injury is not considered, or the affected area is not closely inspected. While these injuries may not alter immediate clinical management or require surgical intervention, they may, nevertheless, result in patient symptoms and may potentially increase the risk of further knee injury. Further, these injuries are difficult to recognize clinically and arthroscopically. In this review, we present these five injuries, emphasising relevant anatomy, normal MRI appearances, common injury patterns, and tips to avoid their being overlooked. Routine review of these areas when interpreting knee MRI, with additional imaging as necessary, will allow these injuries to be recognized more regularly.