MINIMUM 13-YEAR MULTICENTRE STUDY OF THR WITH HIGHLY CROSS-LINKED POLYETHYLENE AND STANDARD DIAMETER FEMORAL HEADS

Introduction The first highly crosslinked and melted polyethylene acetabular component for use in total hip arthroplasty was implanted in 1998. Numerous publications have reported reduced wear rates and a reduction in particle induced peri-prosthetic osteolysis at short to mid-term follow-up. The purpose of this study was to re-assemble a previous multi-center patient cohort in order to evaluate the radiographic and wear analysis of patients receiving this form of highly crosslinked polyethylene articulating against 32mm femoral heads or less at a minimum of 13 years follow-up. Methods Inclusion criteria for patients was a primary THR with femoral heads 32mm or less and a minimum 13 year follow-up. 139 hips have been enrolled with an average follow-up of 13.7 years (13–16), 80 females (57%). Wear analysis was performed using the Martell Hip Analysis software. Radiographic grading was performed on the longest follow-up AP hip films. The extent of radiolucency in each zone greater than 0.5mm in thickness was recorded along with the presence of sclerotic lines and osteolysis. Results Wear analysis: Using the average of the slopes of the individual regression lines, the wear rate was 0.006±0.033mm/yr. Using the early to latest film method, the wear rate was 0.003±0.056mm/yr. Radiographic analysis: Acetabular side: the greatest incidence of radiolucency occurred in zone 1 at 21%; sclerotic lines had a less than 2% incidence in any of the 3 zones; there was no identified osteolysis. Femoral side: the incidence of radiolucencies was limited to zone 1, 2%; sclerotic lines were rare in any zone, maximum in zone 3, 4%; there was no identified osteolysis. Conclusion The wear of this form of irradiated and melted highly crosslinked polyethylene remained at levels lower than the detection limit of the software at minimum 13 year follow-up and there was no identified osteolysis.