Placement of an anatomic tibial tunnel significantly improves the medial meniscus posterior extrusion at 90° of knee flexion following medial meniscus posterior root pullout repair

Purpose The purpose of this study was to evaluate the influence of tibial tunnel position in pullout repair for a medial meniscus (MM) posterior root tear (MMPRT) on postoperative MM extrusion. Methods Thirty patients (median age 63 years, range 35-72 years) who underwent transtibial pullout repairs for MMPRTs were included. Three-dimensional computed tomography images of the tibial surface were evaluated using a rectangular measurement grid for assessment of tibial tunnel position and MM posterior root attachment. Preoperative and postoperative MM medial extrusion (MMME) and posterior extrusion (MMPE) at 10 degrees and 90 degrees knee flexion were measured using open magnetic resonance imaging. Results Tibial tunnel centers were located more anteriorly and more medially than the anatomic center (median distance 5.8 mm, range 0-9.3 mm). The postoperative MMPE at 90 degrees knee flexion was significantly reduced after pullout repair, although there was no significant reduction in MMME or MMPE at 10 degrees knee flexion after surgery. In the correlation analysis of the displacement between the anatomic center to the tibial tunnel center and improvements in MMME, and MMPE at 10 degrees and 90 degrees knee flexion, there was a significant positive correlation between percentage distance and improvement of MMPE at 90 degrees knee flexion. Conclusion This study demonstrated that the nearer the tibial tunnel position to the anatomic attachment of the MM posterior root, the more effective the reduction in MMPE at 90 degrees knee flexion. Our results emphasize that an anatomic tibial tunnel should be created in the MM posterior root to improve the postoperative MMPE and protect the articular cartilage in a knee flexion position. Placement of an anatomic tibial tunnel significantly improves the MMPE at 90 degrees of knee flexion after MM posterior root pullout repair.