Lateral tibial posterior slope induces anterior tibial translation while lateral-medial slope difference induces internal rotation: a cadaveric biomechanical study
File(s)
Accepted version
Author(s)
Amis, Andrew
Type
Journal Article
Abstract
Background: Posterior tibial slope (PTS) influences tibiofemoral kinematics and anterior cruciate ligament (ACL) function. While previous studies have evaluated symmetrical slope modifications, the isolated influences of the medial or lateral PTS remain unclear. This study investigated the influence of medial and lateral PTS changes on anterior tibial translation (ATT) and internal tibial rotation (ITR) under axial loading, using unicondylar slope-changing osteotomies.
Hypothesis: Increased lateral PTS increases ATT, while a greater delta PTS (lateral minus medial PTS) increases ITR.
Study design: Controlled laboratory study.
Methods: Eight fresh-frozen knee specimens were mounted in a custom-built fixture in a compression/torsion loading machine. Tibiofemoral translation/rotation kinematics were measured under 500 N axial compression load at 0° and 20° knee flexion using optical motion tracking. Unicondylar tibial slope-changing osteotomies were performed on the medial and lateral tibial plateaux with a custom cutting guide, preserving key ligament and meniscal root attachments. Medial and lateral PTS were adjusted independently −5°, 0°, +5°, +10° giving medial -5 to +10 and lateral -5 to +10 using 3D-printed wedges. Repeated-measures ANOVA, post-hoc t-tests and Pearson correlations were used for analysis.
Results: An increase of +10° in lateral PTS significantly increased ATT (P = 0.012), while increasing medial PTS did not (P = 1.0). ITR was most influenced by delta PTS. At 0° flexion, altering lateral or medial PTS alone was insufficient to significantly change rotation, but changing delta PTS +10° produced 7.6° more rotation (P = 0.015). At 20° flexion, changing individual slopes ±10° significantly increased/decreased rotation (P < 0.036). The largest rotational differences correlated with opposing delta PTS values (r = 0.960, P = 0.0006).
Conclusions:
Lateral PTS was the principal determinant of ATT, whereas delta PTS was the principal determinant of ITR under axial loading.
Clinical relevance:
Understanding the independent biomechanical roles of the medial and lateral PTS provides insight into mechanisms of anterior and rotational instability in ACL injury and reconstruction. These findings suggest the potential utility of differential correction of PTS, as a novel surgical approach for optimizing tibiofemoral rotational kinematics.
Hypothesis: Increased lateral PTS increases ATT, while a greater delta PTS (lateral minus medial PTS) increases ITR.
Study design: Controlled laboratory study.
Methods: Eight fresh-frozen knee specimens were mounted in a custom-built fixture in a compression/torsion loading machine. Tibiofemoral translation/rotation kinematics were measured under 500 N axial compression load at 0° and 20° knee flexion using optical motion tracking. Unicondylar tibial slope-changing osteotomies were performed on the medial and lateral tibial plateaux with a custom cutting guide, preserving key ligament and meniscal root attachments. Medial and lateral PTS were adjusted independently −5°, 0°, +5°, +10° giving medial -5 to +10 and lateral -5 to +10 using 3D-printed wedges. Repeated-measures ANOVA, post-hoc t-tests and Pearson correlations were used for analysis.
Results: An increase of +10° in lateral PTS significantly increased ATT (P = 0.012), while increasing medial PTS did not (P = 1.0). ITR was most influenced by delta PTS. At 0° flexion, altering lateral or medial PTS alone was insufficient to significantly change rotation, but changing delta PTS +10° produced 7.6° more rotation (P = 0.015). At 20° flexion, changing individual slopes ±10° significantly increased/decreased rotation (P < 0.036). The largest rotational differences correlated with opposing delta PTS values (r = 0.960, P = 0.0006).
Conclusions:
Lateral PTS was the principal determinant of ATT, whereas delta PTS was the principal determinant of ITR under axial loading.
Clinical relevance:
Understanding the independent biomechanical roles of the medial and lateral PTS provides insight into mechanisms of anterior and rotational instability in ACL injury and reconstruction. These findings suggest the potential utility of differential correction of PTS, as a novel surgical approach for optimizing tibiofemoral rotational kinematics.
Date Acceptance
2026-08-03
Citation
American Journal of Sports Medicine
ISSN
0363-5465
Publisher
SAGE Publications
Journal / Book Title
American Journal of Sports Medicine
Copyright Statement
Copyright This paper is embargoed until publication. Once published the Version of Record (VoR) will be available on immediate open access.
License URL
Publication Status
Accepted