Poster 265: The Risk of Iatrogenic Posterior Neurovascular Injury in Lateral Meniscal Repair Based on Real Arthroscopic Position: An MRI Study

OBJECTIVES: Posterior horn of lateral meniscal repair using an all-inside meniscal repair device involves a risk of iatrogenic posterior neurovascular injury. Some studies have evaluating the injury risk in this area but most were based on preoperative MRIs and landmarks which are difficult to clearly see under actual arthroscopic surgery. To our knowledge, there have been no studies to date evaluating the risk of injury based on MRIs with the knee in the standard operational figure-of-4 position with joint dilatation in arthroscopic lateral meniscal repair related to the lateral border of the lateral meniscal root which is easy to identify during surgery. The objective of this study was to evaluate and compare the risk of posterior neurovascular injury and establish the safe and danger zones in repairing the lateral meniscus through the anterolateral and anteromedial portals in relation to the medial and lateral borders of the lateral meniscal root (LMR) using standard operational figure-of-4 position with joint dilatation MRIs. METHODS: This study was descriptive laboratory study. Using 29 axial magnetic resonance imaging (MRI) studies of knees in the figure-of-4 position with joint fluid dilatation at the level of the lateral meniscus, direct lines were drawn to simulate a straight all-inside meniscal repair device deployed from the anteromedial and anterolateral portals to the medial and lateral borders of the LMR extending 14 mm beyond the joint capsule. If the line passed through or touched the posterior neurovascular structure, a risk of iatrogenic injury was noted, and measurements were made to determine the safe zones in relation to the medial or lateral border of the LMR. RESULTS: Repairing the lateral meniscus through the anterolateral portal in relation to the lateral border of the LMR had a significantly greater risk of posterior neurovascular injury than repairing through the anteromedial portal, of which the incidences were 68.97% and 10.35%, respectively (p-value = 0.001). The “safe zones” of lateral meniscal repair in relation to the lateral border of the LMR through the anterolateral and anteromedial portals were 4.15 ± 1.87 mm and 6.57 ± 0.98 mm lateral to the lateral border of the LMR, respectively. CONCLUSIONS: Our study found a risk of iatrogenic posterior neurovascular injury when repairing the posterior lateral meniscus tissue through both the anterolateral and anteromedial portals in relation to both the lateral and medial borders of the LMR, with repairs through the anterolateral portal having greater risk than through the anteromedial portal. To reduce this risk, the surgeon can use the “safe zones” as described in this study to decrease the potential risk of iatrogenic posterior neurovascular injury during arthroscopic lateral meniscal repair. CLINICAL RELEVANCE: Iatrogenic injury is always a concern in any surgery, and the results of this study can be a guide to reducing iatrogenic posterior neurovascular injury during posterior horn of lateral meniscal repair.