Bicruciate-retaining knees: no gain in fixation or function at ten years, and two revisions

Design

Randomised trial with radiostereometric analysis, 10-year follow-up

Population

50 patients undergoing total knee arthroplasty

Primary outcome

Maximum total point motion of the tibial component

Effect

0.88 vs 0.64 mm at 10 years; difference −0.23 mm (95% CI −0.57 to 0.10)

This is the ten-year follow-up of a Danish randomised trial of 50 patients, comparing bicruciate-retaining with cruciate-retaining total knee replacement using radiostereometric analysis of tibial migration.

Mean tibial migration at ten years was 0.88 mm with bicruciate-retaining and 0.64 mm with cruciate-retaining implants (difference −0.23 mm, 95% CI −0.57 to 0.10). Oxford Knee and Forgotten Joint Scores followed similar paths. Two bicruciate knees were revised; no cruciate-retaining knee was.

The theoretical advantage of keeping both cruciates — more natural kinematics and higher satisfaction — did not appear. The technique is more demanding, and in this trial it came with more complications.

• Do not offer bicruciate-retaining replacement on the promise of better function.
• If you use it, audit your own revisions and complications.
• Cruciate-retaining implants remain a sound default where the PCL is competent.

Why it matters

It answers the long-term question for a design that was marketed on better function.

Don't overread it

The trial was powered for implant migration, not revision; 50 patients cannot measure revision risk.

The statistics, in plain English

The difference in migration was small and its interval crossed zero, so the two implants fixed similarly. With 25 per group, two revisions against none is a signal, not a reliable estimate of revision rate.

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