MR imaging of the anatomy of the anterior horn of the medial meniscus

Clinical, imaging, arthroscopic, and histologic features of bilateral anteromedial meniscofemoral ligament: A case report

BACKGROUND

The anteromedial meniscofemoral ligament (AMMFL) is a very rare entity, commonly unrecognized and underreported. Although it was not proved to be a cause of anterior knee pain, concerns have been raised on the relationship between the presence of this structure and medial meniscus injury secondary to its abnormal motion. Regarding histologic examination, some studies have shown meniscus-like fibrocartilage, while others have identified it as ligament-like collagenous fibrous connective tissue.

CASE SUMMARY

We report the case of a 34-year-old ballerina with an AMMFL associated with a torn medial meniscus of both knees. Surgery was performed to treat the meniscal injury and two biopsies of each AMMFL were taken in different locations to define the histopathological composition. Histologic examination revealed fibrocartilaginous tissue compatible with meniscus. Follow-up evaluation one year after surgery evidenced full remission of symptoms and the patient had resumed her athletic activities.

CONCLUSION

Clinical, magnetic resonance imaging, arthroscopic, and histological features have been carefully described to better characterize the AMMFL.

Personalized statistical modeling of soft tissue structures in the knee

Background and Objective: As in vivo measurements of knee joint contact forces remain challenging, computational musculoskeletal modeling has been popularized as an encouraging solution for non-invasive estimation of joint mechanical loading. Computational musculoskeletal modeling typically relies on laborious manual segmentation as it requires reliable osseous and soft tissue geometry. To improve on feasibility and accuracy of patient-specific geometry predictions, a generic computational approach that can easily be scaled, morphed and fitted to patient-specific knee joint anatomy is presented.

Methods: A personalized prediction algorithm was established to derive soft tissue geometry of the knee, originating solely from skeletal anatomy. Based on a MRI dataset (n = 53), manual identification of soft-tissue anatomy and landmarks served as input for our model by use of geometric morphometrics. Topographic distance maps were generated for cartilage thickness predictions. Meniscal modeling relied on wrapping a triangular geometry with varying height and width from the anterior to the posterior root. Elastic mesh wrapping was applied for ligamentous and patellar tendon path modeling. Leave-one-out validation experiments were conducted for accuracy assessment.

Results: The Root Mean Square Error (RMSE) for the cartilage layers of the medial tibial plateau, the lateral tibial plateau, the femur and the patella equaled respectively 0.32 mm (range 0.14–0.48), 0.35 mm (range 0.16–0.53), 0.39 mm (range 0.15–0.80) and 0.75 mm (range 0.16–1.11). Similarly, the RMSE equaled respectively 1.16 mm (range 0.99–1.59), 0.91 mm (0.75–1.33), 2.93 mm (range 1.85–4.66) and 2.04 mm (1.88–3.29), calculated over the course of the anterior cruciate ligament, posterior cruciate ligament, the medial and the lateral meniscus.

Conclusion: A methodological workflow is presented for patient-specific, morphological knee joint modeling that avoids laborious segmentation. By allowing to accurately predict personalized geometry this method has the potential for generating large (virtual) sample sizes applicable for biomechanical research and improving personalized, computer-assisted medicine.

Periodical assessment of four horns of knee meniscus using MR T2 mapping imaging in volunteers before and after amateur marathons

To observe the changes and recovery of T2 values of menisci in amateur marathon participants at different times, and to examine the effect of marathon exercise on meniscal microstructure. Twelve healthy marathon volunteers were recruited continuously, including 5 males and 7 females, with mean (± SD) age of 27.5 ± 5.2 years. The body mass indices (BMIs) ranged from 17.6 to 27.2 kg/m², with a mean of 21.9 ± 2.5 kg/m². The 24 knee joints were scanned using a 3 T MR scanner at 1 week before the event, and at 12 h and 2 months after the event. T2 values of the anterior horn of the medial meniscus (MMAH), posterior horn of the medial meniscus (MMPH), anterior horn of the lateral meniscus (LMAH), and posterior horn of the lateral meniscus (LMPH) were measured by drawing the regions of interest (ROIs) on the T2 map images. Wilcoxon sign rank test was used to compare the T2 values between 1 week before and 12 h after the event, and between 1 week before and 2 months after the event in each anatomical region, respectively. The T2 values of the menisci at 12 h after the event were significantly higher (P < 0.05) than those at 1 week before the event. No statistically significant differences in the T2 values of the menisci were found between 2 months after and 1 week before the event (P > 0.05). The T2 values of MMAH, MMPH, LMAH, and LMPH showed a trend of "increasing first and then decreasing" over time, suggesting that the T2 values may reflect meniscal microstructure in amateur marathon runner.

Meniscal allograft transplants and new scaffolding techniques

Clinical management of meniscal injuries has changed radically in recent years. We have moved from the model of systematic tissue removal (meniscectomy) to understanding the need to preserve the tissue.Based on the increased knowledge of the basic science of meniscal functions and their role in joint homeostasis, meniscus preservation and/or repair, whenever indicated and possible, are currently the guidelines for management.However, when repair is no longer possible or when facing the fact of the previous partial, subtotal or total loss of the meniscus, meniscus replacement has proved its clinical value. Nevertheless, meniscectomy remains amongst the most frequent orthopaedic procedures.Meniscus replacement is currently possible by means of meniscal allograft transplantation (MAT) which provides replacement of the whole meniscus with or without bone plugs/slots. Partial replacement has been achieved by means of meniscal scaffolds (mainly collagen or polyurethane-based). Despite the favourable clinical outcomes, it is still debatable whether MAT is capable of preventing progression to osteoarthritis. Moreover, current scaffolds have shown some fundamental limitations, such as the fact that the newly formed tissue may be different from the native fibrocartilage of the meniscus.Regenerative tissue engineering strategies have been used in an attempt to provide a new generation of meniscal implants, either for partial or total replacement. The goal is to provide biomaterials (acellular or cell-seeded constructs) which provide the biomechanical properties but also the biological features to replace the loss of native tissue. Moreover, these approaches include possibilities for patient-specific implants of correct size and shape, as well as advanced strategies combining cells, bioactive agents, hydrogels or gene therapy.Herein, the clinical evidence and tips concerning MAT, currently available meniscus scaffolds and future perspectives are discussed. Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180103.

Anteromedial Meniscofemoral Ligament of the Anterior Horn of the Medial Meniscus: Clinical, Magnetic Resonance Imaging, and Arthroscopic Features

PURPOSE

To describe the clinical, arthroscopic, and magnetic resonance imaging (MRI) findings of knees with anomalous insertion of the anterior horn of the medial meniscus (AHMM) into the intercondylar notch via an anteromedial meniscofemoral ligament (AMMFL).

METHODS

A total of 2,503 arthroscopic knee surgeries performed from July 2003 to October 2016 were reviewed retrospectively to identify knees with an AMMFL. Medical records, arthroscopic photographs, and MRI of identified cases were analyzed. Meniscus width and extrusion were measured on MRI. Fifty patients with a normal meniscus were selected as a control group.

RESULTS

A total of 13 (0.52%) patients had an AMMFL with insertion at the intercondylar notch. All cases were diagnosed incidentally during arthroscopy. The characteristics of knee pain were related to surgical pathology. Arthroscopic examination revealed the AMMFL as a band-like structure covering the anterior cruciate ligament. In all cases, the AHMM had no bony attachment to the tibia, and increased mobility was observed on probing of the AHMM. The medial meniscus (MM) was significantly larger than the general size in 8 cases (61.5%). Twelve knees (92.3%) had meniscus tears. On MRI, the AMMFL appeared as a low-signal linear structure arising at the AHMM and coursing superiorly along the anterior cruciate ligament. The mean MM width was greater than that in the control group at the mid-body (P = .030), anterior horn (P = .002), and posterior horn (P = .001).

CONCLUSIONS

All cases of AMMFL were found incidentally during arthroscopic surgery, and the AMMFL was a silent lesion. There was no significant meniscal extrusion, although the AHMM had no bony attachment. This is because the AMMFL may act as an anchor for the AHMM. Therefore, the AMMFL should not always be removed. The MM with an AMMFL tended to be larger than the typical MM and may be related to some degree of hypermobility, which raises the risk of meniscal tears.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Protruding anterior medial meniscus-An indirect sign of posterior cruciate ligament deficiency

BACKGROUND

to examine if PROTruding of the Anterior Medial Meniscus (PROTAMM) could be an indirect sign of PCL deficiency by comparing PROTAMM to passive posterior tibial sagging (PSS) for chronic PCL rupture on routine MRI.

METHODS

Patients with PCL reconstruction between 2011 and 2016 were included in a case control study. Primarily cases with combined ACL/PCL injury were excluded. Secondary exclusion criteria were bony fractures, medial meniscus pathology and poor quality MRIs. Three (blinded) observers reviewed the pre-operative MRIs according to a pre-defined protocol.

RESULTS

After applying the inclusion and primary exclusion criteria 16 patients were identified in the PCL rupture group. The control group consisted of 15 patients. After reviewing the MRIs, 6 were excluded due to secondary exclusion criteria. Mean PPS measured 4.8 mm (± 4.4 mm) in the PCL rupture group and 1.8 mm (±2.9 mm) in the control group, p = 0.05. Mean PROTAMM was 3.6 mm (±0.6 mm) in the PCL rupture group and 0.7 mm (±0.9 mm) in the control group, p = 0.004.

CONCLUSION

We found a mean PROTAMM of 3.6 mm in patients with PCL rupture. We suggest that this sign, after knee injury in an otherwise normal medial meniscus, is a promising indirect sign of PCL deficiency compared to PPS. Implementation of this sign in clinical practice may improve the sensitivity of routine non-weight bearing MRI in identifying PCL deficient knees.

Meniscal transplantation: state of the art

Meniscal resection is the most common surgical procedure in orthopaedics. When a large meniscal loss becomes clinically relevant, meniscal allograft transplantation (MAT) is a feasible option. However, although this technique has evolved since the ‘80s, there are still several controversial issues related to MAT. Most importantly, its chondroprotective effect is still not completely proven. Its relatively high complication and reoperation rate is another reason for this procedure not yet being universally accepted. Despite its controversial chondroprotective effect, nevertheless, MAT has become a successful treatment for pain localised in a previously meniscectomised knee, in terms of pain relief and knee function. We conducted a careful review of the literature, highlighting the most relevant studies in various aspects of this procedure. Precise indications, how it behaves biomechanically, surgical techniques, return to sport and future perspectives are among the most relevant topics that have been included in this state-of-the-art review.