- Design
- Retrospective cohort, minimum 6-year follow-up, penalised logistic regression
- Population
- 581 patients after primary hamstring ACL reconstruction, France
- Primary outcome
- ACL graft rerupture
- Effect
- OR 1.28 per degree of slope (95% CI 1.10–1.47); modelled risk at 15° slope 36.6% at age 18 vs 3.9% at 45
A French cohort followed 581 patients for at least six years after primary hamstring ACL reconstruction, some isolated and some with lateral extra-articular tenodesis. There were 38 reruptures.
Each degree of posterior tibial slope raised rerupture odds by 28% (OR 1.28, 95% CI 1.10–1.47) and each year of age lowered them by 9% (OR 0.91). The effect of slope was the same at every age, but absolute risk was not. A patient with a 15° slope had a modelled rerupture risk of 36.6% at 18 and 3.9% at 45. Risk fell below 10% at about 27 years for a 12° slope and about 35 for a 15° slope.
This turns a relative risk factor into a bedside number. A steep slope in a teenager is a high-risk combination that deserves a conversation about added procedures; the same slope in a patient in their forties may not need one.
The estimates are modelled from a modest number of events, in hamstring grafts only, from one group. They support individualised counselling rather than a fixed slope cut-off.
- Measure posterior tibial slope on a true lateral radiograph before ACL reconstruction.
- Interpret a steep slope in light of age; risk is far higher in teenagers and young adults.
- Consider discussing additional procedures with young patients who have a steep slope.
- Avoid applying a single slope threshold to every patient regardless of age.
Why it matters
It tells you in whom a steep slope is worth acting on.
Don't overread it
Absolute risks are model-based from 38 reruptures and apply to hamstring grafts.
The statistics, in plain English
No significant interaction means slope multiplies risk by about the same factor at every age. Because young patients start from a higher baseline, the same multiplier adds far more absolute risk for them.
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