low wear of a secondgeneration highly crosslinked polyethylene liner a 5year radiostereometric analysis study background a sequentially irradiated and annealed secondgeneration highly crosslinked polyethylene xlpe liner was introduced clinically in 2005 to reduce in vivo oxidation this liner design has also been shown to reduce wear in vitro when compared with conventional and firstgeneration crosslinked liners to date there is only one study reporting an in vivo wear rate of this liner at 5 years followup however that study used measurements made from plain radiographs which have limited sensitivity particularly when monitoring very low amounts of wearquestionspurposes what is the amount and direction of wear at 5 years using radiostereometric analysis rsa in patients who had thas that included secondgeneration xlpemethods we prospectively reviewed 21 patients who underwent primary cementless tha with the same design of xlpe acetabular liner and 32mm articulation tantalum markers were inserted during surgery and all patients had rsa radiographs at 1 week 6 months and 1 2 and 5 years postoperatively femoral head penetration within the acetabular component was measured with umrsa software one patient died and two had incomplete radiographs leaving 18 radiographic series for analysisresults the mean amounts of proximal twodimensional and threedimensional head penetration between 1 week and 5 years were 0018 0071 and 0149 mm respectively the mean proximal twodimensional and threedimensional wear rates calculated between 1 year and 5 years were all less than 0001 mmyear with no patient recording a wear rate of more than 0040 mmyearconclusions the head penetration of a secondgeneration xlpe liner remained low at 5 years and the wear rate calculated after the first year was low in all directions this low level of wear remains encouraging for the future clinical performance of this material