Highly crosslinked polyethylene stopped wearing after five years in uncemented knees

Design

Double-blinded randomised trial with radiostereometric analysis, 10-year follow-up

Population

96 uncemented cruciate-retaining total knee replacements

Primary outcome

Insert wear and tibial and femoral component migration

Effect

Wear 0.13 mm (crosslinked) vs 0.46 mm (conventional) at 10 years; migration similar

A double-blinded randomised trial allocated 96 uncemented cruciate-retaining total knee replacements to a highly crosslinked or conventional polyethylene insert, and tracked insert wear and component migration with model-based radiostereometric analysis for ten years.

Medial wear with crosslinked polyethylene did not progress after five years (0.15 mm at five, 0.13 mm at ten), whereas conventional polyethylene wear doubled over the same period (0.22 mm to 0.46 mm). Tibial component migration at ten years was similar (about 1.0 mm in both groups), as was femoral migration (1.16 vs 1.04 mm), and patient-reported outcomes did not differ.

Radiostereometric analysis is a precise surrogate for long-term survival, and this is one of the longest blinded comparisons available for uncemented knees. It supports crosslinked inserts on wear grounds, without signs of the fixation problems once feared. The trial was not powered for revision, which remains the outcome that matters to patients.

• Crosslinked polyethylene is a reasonable default insert in uncemented knees on ten-year wear data.
• Uncemented components in this trial migrated early and then stayed stable to ten years.
• Patients will not notice a difference in function at ten years — the benefit is in long-term wear.
• Revision rates were not the trial's endpoint; registry data remain the guide there.

Why it matters

It answers whether crosslinking helps knees as it did hips, with ten years of blinded, precise measurement.

Don't overread it

Wear and migration are surrogate measures; the trial was too small to show a difference in revision.

The statistics, in plain English

The migration intervals for the two groups overlap almost completely (tibial 0.83–1.18 vs 0.87–1.24 mm), so there is no meaningful difference in fixation. Wear figures are means measured in fractions of a millimetre — small numbers, but wear accumulates and drives late loosening.

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