Phase Transformation in Zirconia Heads after THA Myth or Reality?
From 1985 to 2001, about 400 000 zircon heads Prozyr™ had been implanted for total hip arthroplasties (THA). In FRANCE following an abnormal rate of ball fractures, concerning the introduction of the tunnel Furnace (TH), instead of the batch furnace method (BH) the manufacture of zircon heads was stopped in August 2001. Following the works of ALLAIN et al., another controversy arose regarding zircon heads, presenting an abnormal rate of polywear with osteolysis secondary according to the authors: “an increased roughness of the head by phase transformation with tearing off of grains”. This hypothesis was corroborated by HARAGUCHI et al. (2001) reporting on 2 explanted heads. We were prompted to verify this hypothesis.