Poster 304: Isolating The Medial Meniscal Artery with Ultrasonography: Anatomical Characterization of the Novel Vascular Structure and a Technical Note on Imaging Technique

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Objectives: The vascularity of the human meniscus was first famously described by Arnoczky and Warren, who used histological analysis to map out vessel contributions to the medial and lateral menisci. This study determined that the medial and lateral superior and inferior genicular arteries branches give rise to a perimeniscal capillary plexus within the capsular and synovial tissues of the knee. However, since this study, there have been limited investigations into the macro- and microvascularity of the menisci. This includes anatomical, biomechanical, and imaging studies. Doppler ultrasound is an easily accessible, safe, and non-invasive modality that gives clinicians real-time visualization of vascular anatomy. To date, there have been no ultrasound studies that have highlighted vascular deviations from the popliteal artery to the medical meniscus, including the newly discovered medial meniscal artery (MMA), as described in Part 1 of this study (Figure 1, from Part 1 of this investigation). The purpose of this study was to use find a reproducible ultrasound technique to identify the MMA and provide a detailed characterization of the vessel’s precise anatomy. We hypothesized that the MMA would be consistently identifiable in vivo using ultrasound imaging and that multiple anatomic variants of the MMA would exist. Methods: Fifty-six patients underwent ultrasound examination of the left knee. Patient demographics were collected. The MMA was isolated by one of two techniques. In the first approach, the inferior medial genicular artery (IMGA) was isolated and followed back to the popliteal artery, where the examiner then coursed the artery proximally to find medial-sided vasculature branching to the medial meniscus. In the second approach, the probe was started on the medial meniscus and once an arterial supply was found, it was traced back to the popliteal artery. Once the MMA was isolated by either technique, the following variables were measured: presence or absence of MMA, artery diameter, presence of arterial calcifications or atheromatous plaques, and any vascular variations. Once the MMA was found and isolated in the left knee, its presence was investigated in the right knee. Results: The MMA was identified in 50/56 patients (89.2%). The average vessel diameter was 0.89 mm (SD ± 0.39). All 50 patients with a MMA present on the left knee also had the presence of the artery on the right knee. None of the MMA isolated in this study were noted to have any plaques or calcifications. 45 patients were noted to have a Type 1 MMA, whereas five patients were noted to have a Type 2 MMA where the vessel shares an origin with the IMGA (Figure 2). Conclusions: This is the first study to utilize ultrasound to isolate and characterize the MMA in a in vivo human model. The MMA can be consistently seen on ultrasonography in the majority of patients and ultrasound examination demonstrated that the artery perforates into the meniscal tissue to contribute to the meniscal microplexus. The key methods to ensure reproducible identification of the artery and patient characteristics that produce lesser quality images are discussed in detail. Ultrasound identification in clinic may serve as a point-of-care diagnostic modality to determine the likelihood of success of procedures such as medial meniscal repair, given the artery provides a direct blood supply to the meniscus. The MMA may play a pivotal role in meniscal injury, repair, healing, and preservation. Future studies are necessary to determine the extent to which this vessel contributes to said mechanisms.