An anatomical examination of iatrogenic nerve injury during inside out meniscus repair with flexion and extension of the knee.

BACKGROUND

In this study, we aim to assess the safe, risky and high-risky zones by measuring the proximity of the needles to the peroneal and saphenous nerves in millimeters for the repair of tears of the anterior, middle and posterior horns of the medial and lateral menisci at flexion and extension position during inside-out repair technique.

METHODS

First, a cadaveric study was conducted on 10 cadaver knees in which both (lateral and medial) menisci were divided into anterior, corpus and posterior with the longitudinal tear simulating in each section. The next phase involved the suture of the simulated tears of the menisci while the knee was at 90° of flexion and full extension. Finally, the distance from the exit points of the K-wire being inserted through meniscal anterior, corpus and posterior tears to the aforementioned nerves was measured with a digital caliper.

RESULTS

The distance between K-wire exit points and neurovascular structures concerning corpus and anterior horn tear repair of both menisci were considered far away and not included. However, closer posterior menisci measurements were taken to avoid the risk of iatrogenic nerve injury. The measured distances for lateral meniscus posterior tears were recorded 11±5.2 mm at 90° of flexion and 8±4.5 mm at extension, whereas those recorded 17.3±5.7 mm at 90° of flexion and 13.7±4.7 mm at extension for medial meniscus. These variables were evaluated statistically using a paired t-test; the mean of t value was not considered statistically significant.

CONCLUSION

Our results show that the inside-out technique at knee flexion is safe even in the posterior meniscus tears. However, safety distance can be increased with the higher flexion degrees of the knee. Lastly, in posterior meniscal tear repair, we recommend either retractor assisted mini-open technique at knee flexion, or all-inside suture technique, to avoid nerve injury risk in this zone. Although many surgeons do not prefer inside-out techniques for posterior menisci tears, inside-out posterior meniscal repair of both menisci is as safe as an all-inside technique using retractor assisted mini-open technique with the knee at higher than 90° flexion.