Comparison of diamond-like-carbon and alumina-oxide articulating with polyethylene in total hip arthroplasty

To reduce wear in joint bearings of total hip arthroplasty (THA) is the most important issue for improving long term results and implant survival. Due to low wear rates and excellent tribological features in simulator tests Diamond-Like-Carbon coating (DLC) of femoral balls is still discussed as an alternative articulation in THA. This clinical prospective study compares survivorship of DLC-coated femoral heads and of Aluminia-Oxide- (Al2O3) heads articulating with Polyethylene (PE). Over a period of two years 101 THA with DLC-coated heads and PE cups (DLC-group) and another 101 THA consisting of Al2O3 heads (Al2O3-group) and PE cups as well were implanted. Both articulations were based on the same type of cementless hip joint prosthesis. All hips were implanted by one surgeon in consecutive series consisting of 51 Al2O3 and 101 DLC-articulations and further 50 Al2O3. All perioperative and follow-up data was processed with SPSS(R). Survival of THA in both groups was evaluated according to Kaplan-Meier survivorship analysis with an intervall of 90 months (range:78-101). Qualitative surface analysis was performed in nineteen retrieved DLC-heads which were revised for aseptic loosening using field scanning electron microscopy (FE-SEM, XL 30 SFEG Philips, Eindoven NL). 178 patients (88.2%) were evaluated for follow-up. Fourteen patients died meantimes (nine DLC, five Al2O3) with the implant components not revised. Ten patients (five DLC, five Al2O3) were lost to follow-up. Both groups were comparable regarding patient age, weight and indications for THA with a normal distribution. Survivorship analysis for aseptic loosening 8.5 years following implantation resulted in a significant difference between both groups with a 54% survival for DLC/PE compared to 88% for Al2O3/PE bearings (p <0.001). No correlation to variables as age, gender or bodyweight could be detected. Surfaces of nineteen retrieved DLC-heads showed numerous smallest pits of the diamond-carbon layers in different quantity. SEM showed delamination of the carbon layer which caused excessive debris of polyethylene and in some cases even of the metallic substrate of the heads. Despite modern manufacturing technology and excellent experimental results for its tribochemical characteristics and wear, even new DLC-coating of femoral heads is to be considered critically due to very high rates of clinical failure.