Bernhardson (2019) — Tibial Slope and Its Effect on Force in Anterior Cruciate Ligament Grafts: Anterior Cruciate Ligament Force Increases Linearly as Posterior Tibial Slope Increases.

Tibial Slope and Its Effect on Force in Anterior Cruciate Ligament Grafts: Anterior Cruciate Ligament Force Increases Linearly as Posterior Tibial Slope Increases.

·Am J Sports Med·2019·276 citations·Sports Medicine

This controlled cadaveric study quantified how sagittal plane tibial slope affects force on an ACL reconstruction graft. Ten knees were tested across slopes of -2° to 20° at five flexion angles under a 200-N axial load. It asks whether changing tibial slope changes the force the graft must bear.

Study Snapshot

Design

Controlled cadaveric study

Setting: Single biomechanics laboratory

Funding: Industry (Arthrex, others)

Objective

Whether changing sagittal plane tibial slope alters force on an ACL reconstruction graft at varying flexion angles

Outcome(s)

ACL graft force across slopes -2° to 20° under 200-N axial load

Subjects

10 male cadaveric knees

ACL reconstruction with semitendinosus/gracilis allograft, slope varied -2° to 20°

Inclusion

Male fresh-frozen cadaveric knees

Exclusion

Prior surgery
Meniscal, cartilage, or ligament damage
Osteoarthritis

Statistics

Linear mixed-effects modelsBayesian information criterionTukey method

Key Findings

Under axial load, ACL graft force rose linearly with slope, independent of flexion angle (slope coefficient = 0.92, P < .001). Each degree of added slope meant more force on the graft, supporting why steep slope predisposes to graft failure.
Graft force was significantly higher at 0° flexion (full extension) than at every other angle tested (all P < .001). The ACL is the primary restraint to anterior translation near extension, so this is where the graft is most vulnerable.
At 0° flexion under load, graft force climbed from about 59 N at -2° slope to 85 N at 18° slope. The relative increase was even larger at higher flexion angles, showing slope drives loading across the whole arc.
In the unloaded state, increasing slope produced a small linear DECREASE in graft force (coefficient = -0.23, P = .002). The slope-driven loading effect only emerges once the joint is axially compressed.
The authors tie their data to clinical reports that slope-reducing osteotomy from ~13° down to 4°-9° improved re-revision ACL outcomes, recommending a target slope of less than 6°.
A posterior slope greater than 12° carried an 11-times higher ACL graft failure rate at 20 years in prior clinical work the authors cite, giving this biomechanical mechanism real outcome weight.

Board PearlACL graft force rises linearly with posterior tibial slope under axial load — this is why slope-reducing osteotomy protects the graft in revision ACL surgery.

Clinical Relevance

When a patient presents with a failed ACL reconstruction, measure the posterior tibial slope before planning revision. This study explains the mechanism behind a clinical observation: steeper slope means more graft force, which means higher failure rates. Under axial load, graft force rose linearly with slope, and a slope over 12° has been linked to an 11-fold failure rate at 20 years.

The practical decision rule: in a revision (especially second revision) with slope over 12°, consider a slope-reducing anterior closing wedge osteotomy, targeting a slope under 6°. Graft force peaked at full extension, so rehabilitation and return-to-play programs should train control of knee flexion during pivoting and landing in high-slope patients.

Weigh slope reduction carefully against the risk of inducing genu recurvatum, particularly in patients with preexisting hyperextension.

Emerging

Tibial Slope and Its Effect on Force in Anterior Cruciate Ligament Grafts: Anterior Cruciate Ligament Force Increases Linearly as Posterior Tibial Slope Increases.

Bernhardson, LaPrade, et al.·Am J Sports Med·2019·276 citations·Sports Medicine

Tibial Slope and Its Effect on Force in Anterior Cruciate Ligament Grafts: Anterior Cruciate Ligament Force Increases Linearly as Posterior Tibial Slope Increases.

Study Snapshot

Key Findings

Clinical Relevance

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Tibial Slope and Its Effect on Force in Anterior Cruciate Ligament Grafts: Anterior Cruciate Ligament Force Increases Linearly as Posterior Tibial Slope Increases.

Study Snapshot

Key Findings

Clinical Relevance

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Tibial Slope and Its Effect on Force in Anterior Cruciate Ligament Grafts: Anterior Cruciate Ligament Force Increases Linearly as Posterior Tibial Slope Increases.

Study Snapshot

Key Findings

Clinical Relevance

Related Articles

Tibial Slope and Its Effect on Force in Anterior Cruciate Ligament Grafts: Anterior Cruciate Ligament Force Increases Linearly as Posterior Tibial Slope Increases.

Study Snapshot

Key Findings

Clinical Relevance

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