Minimum five-year wear rate of metal-on-highly cross-linked polyethylene in primary total hip arthroplasty.

PURPOSE: Highly cross-linked polyethylenes (PE) have been developed with encouraging results in terms of wear. Another body of the literature has indicated potential catastrophic failures related to reduced fatigue properties and oxidation. Each PE available on the market has its own processing characteristics. The aim of this retrospective study was to evaluate the minimum five-year wear properties of an original highly cross-linked PE in a consecutive series of primary THAs.

METHODS

Between August 2005 and December 2007, 80 patients with a mean age of 62.7 years were included. All patients had a 28-mm CoCr femoral head articulating with a highly cross-linked insert (Highcross®, Medacta SA) that was 100 Mrads gamma radiated, remelted at 150 °C, and ethylene oxide sterilized. The primary criterion for evaluation was the femoral head penetration, as measured by Hip Analysis Suite software. The steady state wear was also calculated. Functional results were evaluated according to the WOMAC score.

RESULTS

Complete data were available for analysis in 67 patients at a mean follow-up of 5.5 years. The mean femoral head penetration was 0.128 ± 0.62 mm and the steady state wear was-0.025 ± 0.22 mm/year. The WOMAC score significantly decreased from 16.5 ± 5.93 pre-operatively to 4.12 ± 5.5 at the latest follow-up (p <0.001).

CONCLUSIONS

The minimal five-year results of this retrospective study indicate that this particular highly cross-linked and remelted polyethylene had a low wear rate. Longer-term results are needed to warrant that these mid-term data will generate less osteolysis and resultant aseptic loosening.