Medial Opening Wedge Tibial Osteotomy and the Sagittal Plane

Abstract

BACKGROUND: Altering the tibial slope in an anterior cruciate ligament-deficient knee has been shown to affect anterior-posterior tibial translation. The effects on articular contact pressure of altering tibial slope during a high tibial osteotomy are unknown. HYPOTHESES: Performing an opening wedge osteotomy anterior to the midaxial line will increase tibial slope. Increasing tibial slope with a high tibial osteotomy in an anterior cruciate ligament-deficient knee redistributes tibiofemoral joint contact pressures onto the posterior tibial plateau. STUDY DESIGN: Controlled laboratory study. METHODS: Medial opening wedge high tibial osteotomies were performed, and a plate fixation with a known diameter inset was placed along the medial tibia in an anterior position and a posterior position on 9 cadaveric knees. Medial and lateral tibiofemoral contact pressures were measured at the resulting 2 different tibial slopes in both ligament-intact and ligament-deficient states using thin electronic sensors. RESULTS: Anterior plate application resulted in an increase in posterior tibial slope by an average of 6.6 degrees (P < .001) compared with posterior plate placement. After medial opening wedge high tibial osteotomy, the mean peak lateral tibiofemoral contact pressure (3.4 MPa) was significantly greater (P = .002) than was the mean peak medial pressure (2.6 MPa). In ligament-intact specimens, altering the tibial slope did not significantly shift peak contact pressures. However, in ligament-deficient knees, increasing tibial slope by an average of 5.5 degrees significantly redistributed the location of peak intra-articular pressure, shifting it posteriorly by 24% (P = .003). CONCLUSION: Increasing tibial slope in anterior cruciate ligament-deficient knees with a high tibial osteotomy redistributes pressure into the posterior tibial plateau. CLINICAL RELEVANCE: In knees with chronic anterior cruciate ligament deficiency, posteromedial compartment degeneration is observed. Inadvertent redistribution of contact pressure into this area may be a cause of pain and premature clinical failure after medial opening wedge tibial osteotomy.