Wear of polyethylene according to polyethylene type and femoral head material in hip arthroplasty

Objective: Total hip arthroplasty is a highly efficient surgical. The major long term complication is aseptic loosening related to wear of the polyethylene (PE) socket leading to wear debris induced osteolysis. At Cochin hospital, we have been using for more than 40 years, the metal on polyethylene combination and cement fixation. Since 2000, we have performed three prospective randomized studies for which the only variable was polyethylene type and/or material of the femoral head.Methods: Study (1) conducted between 2000 and 2002 included 100 patients with a mean age of 66 years randomized to receive metal on conventional PE versus metal on highly cross-linked PE (HXLPE). Study (2) conducted in 2006 included 100 patients with a mean age of 65 years randomized into 4 groups: metal-PE, oxinium (oxidized zirconium)-PE, metal-XLPE, oxinium-XLPE. Study (3) conducted between 2007 and 2008 included 110 patients with a mean age of 60 years randomized to receive metal-PE versus Delta ceramic-PE. In each of these studies, the main criterion for evaluation was linear femoral head penetration.Results: In study (1), 30 patients could be analyzed after a median follow-up of 8.7 years in the conventional PE group and 38 patients in the HXLPE group after 9.1 years. The mean steady state wear was 0.14 mm/year in the conventional PE group versus 0.0002 mm/year in the HXLPE group (p < 0.0001). In study (2), 86 patients could be analyzed after a median follow-up of 6.5 years. The steady state wear was 0.11 mm/year in the metal-PE group, 0.03 mm/year in the oxinium-PE group, 0.05 mm/year in the metal-XLPE group, 0.02 mm/year in the oxinium-HXLPE group (p< 0.01). In study (3), 38 patients could be analyzed after a median follow-up of 4.4 years in the metal group and 42 patients after a median follow-up of 4.0 years in the Delta group. The mean steady state wear was 0.07 mm/year in the metal group versus 0.06 mm/year in the Delta group (p = 0.48).Conclusion: Our results demonstrated that use of HXLPE could significantly decrease polyethylene wear. This reduction will probably decrease the risk for osteolysis and implant loosening. Oxinium on HXLPE was associated with the lowest steady state penetration rate.