Introduction: Aseptic implant loosening caused by wear debris is a common reason for early implant failure after total hip replacement (THR).
Materials and methods: We prospectively studied 96 patients (110 hips), 48 men and 48 women (mean age 46.8 years, mean body mass index 26.1) who had undergone cementless THR (titanium stem, press-fit cup, Al(2)O(3) ball, XLPE liner) at a mean of 17.4 months (SD 13.4).
Results: The semi-computerized evaluation of wear rate showed wear of 0.25 mm (SD 0.3) corresponding to a volume of 97.6 mm(3) (SD 121.1) during the first year. It was remarkable that the annual rate of wear was significantly lower in the second year: 0.14 mm (SD 0.1), 60.0 mm(3) (SD 78.7). The implant survival rate was 100%. However, two patients underwent revision surgery.
Interpretation: Good, early functionality can be achieved by a cementless THR including a modular stem and a XLPE-Al(2)O(3) bearing system. The rate of wear debris for XLPE-Al(3)O(2) was much higher than expected within the first year after THR. However, after the initial running-in period a significant decrease of wear was documented, suggesting a biphasic abrasion [0.38 mm (SD 0.2) within the first year vs. 0.14 mm (SD 0.1)] after the running-in-period 1 year following surgery.