Cadaveric study of 27 knees using direct wire-based fibre measurement. Characterizes how three functional ACL bundles change length during knee flexion-extension and tibial rotation. Determines each bundle's contribution to resisting anterior tibial subluxation via sequential transection under load.
The clinical exam pattern tells you which ACL bundle is torn. An isolated positive Lachman with a negative anterior drawer points to the posterolateral bundle (loaded and at risk in near-extension). An isolated positive anterior drawer with a negative Lachman implicates the anteromedial bundle (loaded in flexion). Comparing side-to-side is essential, since the range of normal anterior drawer laxity is wide enough to obscure even complete tears.
For reconstruction, place your femoral tunnel anterior and superior to the intermediate bundle origin, toward the notch roof — this approximates the most isometric femoral position. But recognize that peripheral graft fibres will still experience strains exceeding the 5–6% damage threshold if knee flexion exceeds roughly 90°.
This paper is the anatomic foundation for modern double-bundle ACL reconstruction: by showing that no single-bundle graft can replicate the reciprocal behaviour of the anteromedial and posterolateral bundles simultaneously, it provided the rationale for separate AM and PL tunnel constructs.
Knowing that tibial rotation does not significantly load the ACL also explains why isolated tibial rotation stress tests are poor for diagnosing ACL tears. The pivot shift works because it combines rotation with axial load, engaging other restraints.
Cadaveric study of 27 knees using direct wire-based fibre measurement. Characterizes how three functional ACL bundles change length during knee flexion-extension and tibial rotation. Determines each bundle's contribution to resisting anterior tibial subluxation via sequential transection under load.
The clinical exam pattern tells you which ACL bundle is torn. An isolated positive Lachman with a negative anterior drawer points to the posterolateral bundle (loaded and at risk in near-extension). An isolated positive anterior drawer with a negative Lachman implicates the anteromedial bundle (loaded in flexion). Comparing side-to-side is essential, since the range of normal anterior drawer laxity is wide enough to obscure even complete tears.
For reconstruction, place your femoral tunnel anterior and superior to the intermediate bundle origin, toward the notch roof — this approximates the most isometric femoral position. But recognize that peripheral graft fibres will still experience strains exceeding the 5–6% damage threshold if knee flexion exceeds roughly 90°.
This paper is the anatomic foundation for modern double-bundle ACL reconstruction: by showing that no single-bundle graft can replicate the reciprocal behaviour of the anteromedial and posterolateral bundles simultaneously, it provided the rationale for separate AM and PL tunnel constructs.
Knowing that tibial rotation does not significantly load the ACL also explains why isolated tibial rotation stress tests are poor for diagnosing ACL tears. The pivot shift works because it combines rotation with axial load, engaging other restraints.