Summary

Floating medial meniscus lesions are rare and exclusively noted in KD3M multiple ligament injured knees and can be successfully repaired with a systematic surgical approach, resulting in satisfactory functional outcomes.

Abstract

Introduction

High energy knee dislocations have the potential not only to disrupt multiple ligaments but also to cause complex meniscal tears not commonly encountered in non-dislocated knees. A particularly devastating injury pattern involves avulsion of both the anterior and posterior roots of the medial meniscus associated with disruption of the medial ligament complex and extra-articular displacement of the medial meniscus in the medial soft-tissues. We have termed this tear pattern as a ‘floating medial meniscus lesion’. This study aims to define this lesion, report its incidence, assess its impact on surgical timing, describe the repair technique, and evaluate healing rates and outcomes.

Materials And Methods

We retrospectively analysed a database of multiple ligament knee injury surgeries performed between 2008 and 2022 at a referral centre for complex knee injuries and identified cases with a floating medial meniscus lesion. The surgical procedure involved a combined arthroscopic and medial open approach that addressed the meniscus tear and ligament tears in one stage. We first performed open medial exploration which allowed for meniscus reduction. This was especially useful for everted menisci. The medial arthrotomy prior to arthroscopy allowed accurate delineation of torn layers devoid of fluid extravasation, and also ensured that subsequent arthroscopy did not cause fluid accumulation in the soft-tissues. The arthrotomy did hamper joint distention and clear visualisation during arthroscopy but was not significant enough to affect accurate ACL and PCL tunnel creation, or medial meniscus anterior and posterior root repair using a transtibial pull-out suture technique. Injury characteristics using the Schenk classification, preoperative imaging, and operative reports were reviewed. Clinical, functional and radiological outcome measures were determined at a minimum two-year follow-up. Chronicity was evaluated to determine whether the time interval from injury to surgery contributed to surgical challenges. Early intervention was defined as surgery within three weeks of injury.

Results

From a database comprising 341 knees operated for multiple ligament knee injuries (119 KD3M type), we identified 7 patients (all KD3M type) who had a floating medial meniscus lesion. Five patients underwent early surgery, two had delayed intervention. Preoperative MRI effectively identified the lesions. Early surgery facilitated easier meniscus identification, reduction, and repair, whereas delayed surgery posed challenges. At follow-up, all patients had regained a minimum 0-130 degrees knee range of motion, with no residual instability or pain. Bilateral weight bearing radiographs revealed no significant difference in medial joint space between the affected and normal knees, with no evidence of degenerative changes. MRI revealed healed medial menisci roots, though some extrusion was noted in 4 patients. The mean IKDC score two years following surgery was 89.5 (range 76 to 93). There were two competitive elite athletes in this series and both returned to their previous level of sports.

Conclusion

Although floating medial meniscus lesions are daunting at presentation, they can be successfully repaired with a systematic surgical approach, resulting in satisfactory functional outcomes. Early surgery enables easier meniscus dissection, reduction and repair.