Crosslinked polyethylene in uncemented knees: wear stopped after five years

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 component migration

Effect

Medial wear 5→10 years: crosslinked 0.15→0.13 mm; conventional 0.22→0.46 mm

This double-blinded randomised trial allocated 96 uncemented cruciate-retaining total knee replacements to a sequentially annealed highly crosslinked polyethylene insert or a conventional one, and followed wear and component migration by model-based radiostereometric analysis to ten years.

In the crosslinked group, medial wear did not progress after five years (0.15 mm at five years, 0.13 mm at ten). In the conventional group it continued, from 0.22 mm to 0.46 mm. Tibial and femoral migration were stable after the early settling period and did not differ between groups (tibial maximal total point motion about 1.0 mm in both). Patient-reported outcomes did not differ.

Radiostereometric analysis is a precise surrogate: early migration and wear predict later loosening. Ten-year data in a small trial cannot show a revision difference, but they support crosslinked inserts in uncemented knees on the measure most likely to matter at twenty years. The trial used a single implant design.

• Consider highly crosslinked polyethylene inserts in uncemented knees, particularly in younger, active patients.
• Expect early component settling; stable migration after that is reassuring.
• Note that the findings apply to one uncemented cruciate-retaining design.
• Do not expect better patient-reported outcomes at ten years from the insert choice.

Why it matters

It addresses the long-standing worry that crosslinking benefits seen in hips might not hold in knees.

Don't overread it

This is a surrogate-outcome trial in one implant; it does not show fewer revisions.

The statistics, in plain English

Wear and migration are measured in fractions of a millimetre, and are surrogates for later loosening and revision. With 96 knees the trial is powered for these precise measurements, not for revision rates.

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