High tibial osteotomy achieves unloading of the medial tibiofemoral compartment irrespective of arthritic status or medial collateral ligament release: A biomechanical assessment.

Purpose: The purpose of this study was to determine the impact of (1) healthy versus arthritic knees and (2) partial versus complete release of the superficial medial collateral ligament (sMCL) on tibiofemoral compartment pressures at varying mechanical axis alignments following medial open-wedge high tibial osteotomy (MOW-HTO). Methods: Contact pressure (CP) was measured in seven cadaver knees (four healthy; three arthritic) under 1000 N axial load. Tests were conducted at constitutional alignment and MOW-HTO alignment corrections to 50%, 55%, 60% and 65% of the tibial plateau width (TPW) with the sMCL intact and repeated at each alignment following a partial and complete sMCL release. Linear mixed-effects models assessed differences in tibiofemoral CP with factors (1) arthritic status and alignment and (2) alignment and sMCL condition. Main effects were assessed for each factor followed by pairwise comparisons when significant. Results: Medial CP in healthy and arthritic knees did not differ in response to varying alignment corrections ( Conclusion: The presence of medial compartment arthritis may not be a significant factor in the loading biomechanics of cadaver knees secondary to MOW-HTO corrections. MOW-HTO correction to 55% of TPW was most effective in decreasing medial CP. sMCL release did not impact medial CP; however, it significantly increased lateral CP when the sMCL was completely released. Level of Evidence: NA, cadaveric study.