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

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.

To determine the optimal biomechanical knee alignment for MMPRT treatment during MOWHTO.

Controlled laboratory study.

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.

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.

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.

These findings provide biomechanical evidence to guide optimal knee alignment during MOWHTO for MMPRTs, potentially improving patient outcomes.