Summary

Not previously described ligaments stabilising medial meniscus have been found during cadaver dissection and then their presence has been confirmed in MRI scans.

Abstract

Introduction

A new, not previously described pair of ligaments stabilising the medial meniscus (MM) were found during a cadaveric knees’ dissection. Follow-up studies – anatomical (prospective) and radiological (retrospective) were conducted to further investigate and establish their possible clinical and surgical relevance.

Methods

Anatomical study - while dissecting 18 cadaveric knees a previously not reported ligament was observed posterior to the medial collateral ligament (MCL), running from the femur and attaching adjacent to the posterior horn of medial meniscus (Zone 4), tentatively named a medial meniscus meniscofemoral ligament (MMFL). A second ligament running from the inferior border of MM Zone 4, over semimembranosus tendon with a distal insertion at the tibia where it runs posteriorly to MCL was named a medial meniscus meniscotibial ligament (MMTL). The ligaments were photographically documented. Further retrospective radiological analysis of 100 knee 3TMRIs (Coronal PDdixon sequences) was carried out (44 women, 55 males; mean age 41,9 years). The identification of MMFL & MMTL was made through a consensus between MSK radiologist, anatomist, and orthopaedic surgeon based on defined set of criteria: visible/not visible; normal/abnormal structure; torn. Concomitant pathologies were noted: ACL tear/deficiency; MM lesion (acute tear, degeneration, absence); presence/grade of articular cartilage defects in the medial compartment (MCAC). Statistical analysis was done using a Spearman’s p test.

Results

The anatomical dissections so far revealed the ligaments in all specimens. The MRI analysis has confirmed the ligaments’ presence in 95 knees; in 3 cases MMTL and in 4 MMFL 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. Statistically significant correlation was found between the degree of soft tissues pathologies and the extent of MMTFL and MMFL changes – more severe soft tissue damage correlated with higher degree of the ligaments’ abnormalities. Acute MM tears or degeneration correlated highly with abnormal structural changes of MMTL/MMFL.

Conclusions

The ligaments disruption resulting in MM injury or degeneration often coincides with acute ACL tears and soft tissues damage within the knee joint. The injury mechanism in which MM is torn seems likely to be a scenario where the ligaments are pulled away from each other during knee movemnt. Proper stabilisation of the menisci is crucial for the knee biomechanics. Therefore, determining a surgical technique based on the rediscovered medial mensicus anatomy will play a significant role in optimising medial meniscus treatment and improving long-term outcomes. Nevertheless, at the current stage further biomechanical studies and technical analysis of available sutures and treatment solutions are necesary to propose the best approach.