Higher prevalence of periprosthetic fractures with ceramic on polyethylene hip bearing compared with ceramic on ceramic on the contralateral side: a forty year experience with hip osteonecrosis.

PURPOSE: It is unclear whether late THA periprosthetic femoral fractures are related to a mechanical mechanism that decreases strength of the femur (for example, loosening) or to a biological problem as osteolysis. It is also unknown if ceramic on ceramic bearing couples decrease the risk of late periprosthetic fractures as a result of the absence of wear and osteolysis.
MATERIAL AND METHODS: We therefore asked whether the cumulative long-term fractures were different according to the couple of friction ceramic on ceramic or ceramic on polyethylene in 327 patients (654 hips) with bilateral THA (one ceramic-ceramic, and the contralateral ceramic-polyethylene) who had THA with cemented stems performed between from 1978 to 2000 for osteonecrosis.
RESULTS: There were two intra-operative fractures (0.3%). The median follow-up was 22 years (range, 15-40 years), and at the most recent follow-up, the cumulative number of late (after 7 years of follow-up) post-operative fractures was 32 (5% of 654 hips). Fractures were unilateral, which means for the 327 patients, a 10% rate of fractures. Periprosthetic fractures increased in number with follow-up: seven fractures (1% of 654 hips) occurred within ten years of THA implantation, 20 (3%) within 20 years, 26 (4%) within 30 years, and 32 (5%) within 40 years. The risk of fracture was influenced (p < 0.001) by the bearing surfaces at the time of prosthetic implantation, low (0.3%) for ceramic on ceramic (1/32 fractures; 1/327 hips), high (10%) for ceramic on PE (31/32 fractures; 31/327 hips).
CONCLUSION: In summary, when the contralateral hip of the same patient is the control, after 40 years of follow-up, post-operative fractures occur 30 times more often on the side with PE cup than on the side with ceramic/ceramic bearing.