The Effect of Lateral Extra-articular Tenodesis on Anterior Cruciate Ligament Graft Forces and Knee Stability Compared With Slope Reduction Osteotomy in the Setting of Increased Posterior Tibial Slope

Abstract

Background:

Anterior cruciate ligament (ACL) reconstruction (ACLR) in the presence of excessive posterior tibial slope (PTS) is a well-established risk factor for increased ACL graft forces and a heightened risk of graft failure.

Purpose/Hypothesis:

The primary aim of this study was to evaluate whether lateral extra-articular tenodesis (LET) could mitigate the adverse effects of increased PTS on knee kinematics and ACL graft forces, achieving results comparable to those of slope-reducing osteotomy (SRO). It was hypothesized that LET would provide similar improvements in knee stability and graft force reduction to SRO in the presence of increased PTS. A secondary aim was to determine if an ALC injury exacerbates the effect of increased PTS on ACL graft forces and overall knee stability. It was hypothesized that ALC injury would amplify the negative effects of increased PTS.

Study Design:

Controlled laboratory study.

Methods:

Eight fresh-frozen cadaveric specimens were prepared, excluding those with previous surgery or significant knee pathology. ACLR was performed using a quadrupled hamstring tendon autograft. The effects of LET and SRO were tested at various degrees of PTS (0°, 10°, and 20°). A simulated pivot-shift maneuver was used to measure ACL graft loads, anterior tibial translation (ATT), and internal rotation (IR). Mixed-effects models were utilized to analyze the data.

Results:

Increasing PTS resulted in significant increases in ACL graft forces (P < .001), ATT (P < .001), and IR (P < .001). LET reduced ACL graft loads by 22.1% at 10° and 36.6% at 20° of PTS. In contrast, a 10° SRO showed only a 2.6% reduction at 10° and 23.9% at 20° of PTS. There were no significant differences in graft forces between the postosteotomy states and LET augmentation states at both 10° and 20° of tibial slope, suggesting equivalent efficacy in reducing graft loads. Additionally, LET significantly decreased graft forces compared with the ALC-sectioned state (P = .019). Finally, ALC sectioning did not significantly increase ACL graft load compared with the ACLR-only condition (P = .320), nor did it exacerbate the effects of increased PTS on ATT and IR.

Conclusion:

LET effectively reduces ACL graft forces and improves knee stability in the presence of increased PTS, performing comparably to or better than SRO under simulated pivot-shift conditions.

Clinical Relevance:

These findings suggest that LET is a viable alternative to SRO, particularly for patients with high PTS undergoing ACLR.