Anterior opening wedge high tibial osteotomy: the effect of increasing posterior tibial slope on ligament strain.

BACKGROUND Although a previous study showed that anterior opening wedge high tibial osteotomy (HTO) for sagittal plane correction induced no increased strain in the anterior cruciate ligament (ACL), we hypothesized that other ligamentous restraints of the knee may be subjected to increased strain. METHODS We mounted 6 cadaveric knees at 15 degrees flexion in a testing apparatus that provided compressive and anterior loading. We measured the strain in the ACL, posterior (PCL), medial (MCL) and lateral (LCL) ligaments for 6 randomized loading combinations and 3 conditions: intact, after anterior opening wedge HTO with a 5-mm plate and with a 10-mm plate. RESULTS The mean ACL strain decreased from 0.84% (standard deviation [SD] 1.50%) at baseline to -6.28% (SD 5.40%) with a 5-mm anterior opening wedge osteotomy and to -6.77% (SD 4.79%) with a 10-mm osteotomy. Stepwise regressions yielded no significant effect of compression, anterior loading or osteotomy on PCL, MCL or LCL strain. CONCLUSION Increasing the posterior slope via HTO did not increase strain in the PCL, MCL or LCL.