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

## TL;DR

This study shows that high tibial osteotomy effectively reduces pressure on the inner knee joint regardless of arthritis or ligament release.

## Contribution

The study demonstrates that medial tibiofemoral compartment unloading via high tibial osteotomy is consistent across arthritic and healthy knees and is not affected by medial collateral ligament release.

## Key findings

- Medial compartment pressure decreased significantly at 55% and 60% tibial plateau width corrections.
- Complete medial collateral ligament release increased lateral compartment pressure by 10.8%.
- Arthritis status did not significantly affect compartment pressure changes after osteotomy.

## Abstract

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).

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.

Medial CP in healthy and arthritic knees did not differ in response to varying alignment corrections (p = 0.103). The interaction of alignment and sMCL condition was not significant (p = 0.61). With the sMCL intact, altering alignment was found to significantly impact medial CP (p = 0.01). Medial CP significantly decreased from constitutional alignment to 55% and 60% of TPW by 19.0% and 13.9%, respectively (p = 0.02; p = 0.02). Additionally, medial CP at 55% of TPW was found to be 6.6% lower than at 50% of TPW (p = 0.046) and 10.4% lower than at 65% TPW (p = 0.03). sMCL release did not impact medial CP (p = 0.24) but significantly increased lateral CP by 10.8% when completely released (p < 0.001).

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.

NA, cadaveric study.

Optimal unloading of the medial compartment with high tibial osteotomy corrections of mechanical axis to 55% of tibial width and overloading of the lateral compartment with complete MCL release.