Medial Meniscus Rediscovered. Do We Know Everything about Medial Meniscus Stabilization? MRI Evaluation of Newly Discovered Medial Meniscal Ligaments

Purpose or Learning Objective: A new, not previously described pair of ligaments stabilizing the medial meniscus (MM) were found during the dissection of cadaveric knees. The purpose of this retrospective study was to identify these ligaments on magnetic resonance imaging (MRI).

Methods or Background: While dissecting 18 cadaveric knees, a narrow ligament was observed posterior to the medial collateral ligament (MCL), running from the femur and attaching adjacent to the posterior horn of the medial meniscus (phMM), tentatively named a medial meniscus meniscofemoral ligament (MMFL). A second ligament, running from the inferior border of the phMM over the semimembranosus tendon with a distal insertion at the tibia where it runs posteriorly to MCL, was named a medial meniscus meniscotibial ligament (MMTL).

Retrospective analysis of 100 knee 3-T MRIs (proton-density Dixon sequences) was then performed in 44 women and 55 men (mean age: 41.9 years). The identification criteria of the ligaments were defined as visible/not visible, normal/abnormal structure, or torn. The determination was made through a consensus between a musculoskeletal radiologist, anatomist, and orthopaedic surgeon. Concomitant pathologies were noted: anterior cruciate ligament (ACL) tear/deficiency; MM lesion (acute tear, degeneration, or absence); and presence/grade of articular cartilage defects in the medial compartment. Statistical analysis was performed using Spearman's ρ test and presented in tables.

Results or Findings: The MRI analysis confirmed the presence of these ligaments in 95 knees. MMTL in three cases and MMFL in four cases were absent. In 21% the ligaments were normal, in 65% degenerated, and in 10% torn. In 77% of knees, joint effusion and in 34% an ACL injury were recorded. MM in 85% of knees and MCAC in 35% were damaged.

Statistically significant correlation was found between the degree of soft tissue pathologies and the extent of MMTL and MMFL changes. More severe soft tissue damage correlated with a higher degree of the ligaments’ abnormalities. Acute MM tears or degeneration correlated highly with abnormal structural changes of MMTL/MMFL.

Conclusion: The newly discovered ligaments can be identified on MRI. Statistically significant correlation was found, especially with regard to MM pathologies. The findings are significant in terms of MRI evaluation of MM and determination of new treatment approaches, both surgical and conservative. Nevertheless, further prospective anatomical and clinical studies are necessary to establish the actual relevance of the ligaments.

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Artikel online veröffentlicht:
02. Juni 2022