Simulated Biomechanical Analysis of Optimal Knee Alignment for Treating Medial Meniscus Posterior Root Tears

Background: Medial opening-wedge high tibial osteotomy (MOWHTO) is used to correct varus alignment; however, the optimal knee alignment during MOWHTO for medial meniscus posterior root tears (MMPRTs) remains unclear. Purpose: To determine the optimal biomechanical knee alignment for MMPRT treatment during MOWHTO. Study Design: Controlled laboratory study. Methods: This study used 10 fresh-frozen cadaveric legs from human donors (mean age, 61.3 years [range, 33-75 years]). A joint motion simulator assessed the weightbearing line (WBL) from 30% to 70% (0%: medial border; 100%: lateral border), simulating MOWHTO. Tibiofemoral peak contact pressure (PCP) and mean contact pressure (MCP) were measured using a pressure sensor under a 700-N load. MMPRTs were created via a femoral posterior approach and repaired with suture anchors. Measurements were taken in the intact, MMPRT, and repair conditions at alignments of 30% to 70% WBL, with neutral alignment defined as 50% WBL. Statistical analysis was performed using one-way analysis of variance with the Tukey post hoc test. Results: In the medial compartment, PCP was increased by 43% in the MMPRT condition compared with the intact condition at neutral alignment (P = .012). MCP was also significantly increased by 57% in the MMPRT condition compared with the intact condition (P = .006). At varus alignment, PCP and MCP increased in all conditions, with the largest statistically significant differences observed at 30% WBL (P = .002 and P < .001, respectively). PCP and MCP at neutral alignment in the intact condition were comparable with those at 60% to 65% WBL in the MMPRT condition and at 50% to 55% WBL in the repair condition. In the lateral compartment, PCP and MCP increased at valgus alignment, with no significant differences among conditions. Conclusion: MCP at neutral alignment in the intact condition was similar to that at 60% to 65% WBL in the MMPRT condition and at 50% to 55% WBL in the repair condition, indicating optimal biomechanical alignment targets for MOWHTO in patients with MMPRTs. 50-55% WBL corresponds to slight valgus alignment. Neutral alignment was not considered ideal in this context. Clinical Relevance: These findings provide biomechanical evidence to guide optimal knee alignment during MOWHTO for MMPRTs, potentially improving patient outcomes.