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°(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° 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.