- Design
- Retrospective cohort, minimum 6-year follow-up
- Population
- 581 patients after primary hamstring ACL reconstruction
- Primary outcome
- ACL graft rerupture
- Effect
- OR 1.28 per degree of slope (95% CI 1.10 to 1.47); age OR 0.91 per year (0.87 to 0.95)
A French retrospective cohort followed 581 patients for at least six years after primary hamstring ACL reconstruction, with or without lateral extra-articular tenodesis. There were 38 reruptures.
Each degree of posterior tibial slope was associated with 28% higher odds of rerupture (OR 1.28 per degree, 95% CI 1.10 to 1.47), and each year of age with 9% lower odds (OR 0.91). The relative effect of slope did not change with age, but the absolute risk did: with a 15° slope, predicted rerupture was 36.6% at 18 and 3.9% at 45. Predicted risk fell below 10% at about 27 years for a 12° slope and about 35 years for 15°.
The practical point is that a slope worth correcting in a 19-year-old may not be worth correcting in a 40-year-old. The absolute probabilities come from a model, and this was hamstring grafts only.
- Measure posterior tibial slope on a lateral radiograph before every ACL reconstruction.
- Discuss slope and age together when counselling on rerupture risk.
- Reserve discussion of slope-reducing osteotomy for young patients with steep slopes.
- Consider lateral extra-articular tenodesis in young, high-slope patients having primary reconstruction.
Why it matters
It turns slope from a yes-or-no threshold into a risk that depends on who the patient is.
Don't overread it
The absolute risks are modelled from a single cohort with 38 reruptures; they have not been validated elsewhere.
The statistics, in plain English
An odds ratio of 1.28 per degree means each extra degree multiplies the odds by about 1.28, so three extra degrees roughly doubles them. The age thresholds and the 36.6% figure are model predictions from 38 events and should be treated as estimates, not measured rates.
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