Comparison of Tibiofemoral Contact Mechanics After Various Transtibial and All-Inside Fixation Techniques for Medial Meniscus Posterior Root Radial Tears in a Porcine Model

Purpose: To compare tibiofemoral contact mechanics after fixation for medial meniscus posterior root radial tears (MMPRTs). Methods: Seven fresh knees from mature pigs were used. Each knee was tested under 5 conditions: normal knee, MMPRT, pullout fixation with simple sutures, fixation with modified Mason-Allen sutures, and all-inside fixation using Fastfix 360. The peak contact pressure and contact surface area were evaluated using a capacitive sensor positioned between the meniscus and tibial plateau, under a 1,000-N compression force, at different flexion angles (0°, 30°, 60°, and 90°). Results: The peak contact pressure was significantly higher in MMPRTs than in normal knees (P =.018). Although the peak contact pressure decreased significantly after fixation at all flexion angles (P =.031), it never recovered to the values noted in the normal meniscus. No difference was observed among fixation groups (P =.054). The contact surface area was significantly lower in MMPRTs than in the normal meniscus (P =.018) and increased significantly after fixation at all flexion angles (P =.018) but did not recover to within normal limits. For all flexion angles except 60°, the contact surface area was significantly higher for fixation with Mason-Allen sutures than for fixation with simple sutures or all-inside fixation (P =.027). At 90° of flexion, the contact surface area was significantly better for fixation with simple sutures than for all-inside fixation (P =.031). Conclusions: The peak contact pressure and contact surface area improved significantly after fixation, regardless of the fixation method, but did not recover to the levels noted in the normal meniscus after any type of fixation. Among the fixation methods evaluated in this time 0 study, fixation using modified Mason-Allen sutures provided a superior contact surface area compared with that noted after fixation using simple sutures or all-inside fixation, except at 60° of flexion. However, this study had insufficient power to accurately detect the differences between the outcomes of various fixation methods. Clinical Relevance: Our results in a porcine model suggest that fixation can restore tibiofemoral contact mechanics in MMPRT and that fixation with a locking mechanism leads to superior biomechanical properties.