gms | German Medical Science

Objectives: Wear debris may cause implant loosening in total hip arthroplasties (THA). Bearings including highly crosslinked (XLPE) inlays and ceramic femoral heads may lead to lower wear rates and thus promote the longevity of hip arthroplasties. However, long-term-results are missing.

Methods: With a mean follow-up of 9,8 ± 1,5 years (range: 7-12 years), the x-rays of 32 patients (40 hips, 17 men, 15 women, 22right, 18 left hips, age 43.5 ±17,3 years, mean body mass index 26,5 ± 5,8 kg/m²) were assessed, who had undergone cementless THA (Press-fit Duraloc^® cup, Marathon^® XLPE liner, S-ROM^® modular titanium stem, DePuy, Warsaw, IN; Biolox^® ceramic head) for symptomatic hip osteoarthritis (OA) in our department. The amount of polyethylene wear and the linear penetration of the femoral head were calculated using a two-dimensional vector wear analysis system via the semiautomatic, computer-assisted, edge-detection Martell method (Hip-Analysis-Suite Version 8.0.4.1). Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney-U Test with SPSS 23.0.0.2 Software (IBM).

Results and Conclusion: Results: The semi-computerized evaluation of wear rate showed 2D wear of 0,055± 0,033 mm corresponding to a volume of 35,27 ± 24,87 mm³ in average per year and a total of 0,53 ± 0,30mm 2D wear and 344,78 ± 236,86 mm³ overall. Cup Inclination did not affect wear rate. Besides, patient characteristics (sex, age at implantation and BMI) as well as implantational aspects (surgeon, cup positioning) did not affect wear rate per year or absolute wear. A significant difference (p<0.05) was noted in volumetric wear regarding the head size (32 mm head (n=26), 28 mm Head (n=14)), with higher volumetric wear rates for the bigger heads (total wear 406,05 ± 266,59mm³ vs 230,97 ± 100,92 mm³; volumetric wear per year 41,49 ± 27,94 mm³ vs 23,73 ± 11,58 mm³).

Interpretation: After 9.8 years of follow up, the combination of a XLPE-Al2O3 bearing system has low wear rates irrespective of patient characteristics (sex, weight, age). As expected, bigger heads cause significantly more debris than smaller heads. A longer follow-up and larger sample-size is necessary to draw valid conclusions.