PHASE TRANSFORMATION OF ZIRCONE HEADS AFTER TOTAL HIP ARTHROPLASTY: MYTH OR REALITY ?

Purpose: From 1985 to 2001, nearly 400,000 Zircone heads were implanted for total hip arthroplasty. In France, following an abnormally high rate of ruptures in two lots of heat-treated heads, production of Zircone heads was interrupted in 2001. Following work by Allain et al., another controversy developed concerning abnormal secondary wear of Zircone heads. According to certain authors, head roughness was increased by pitting phase transformation. This hypothesis was corroborated by Haraguchi (2001) who reported three explanted heads. We wanted to check the hypothesis.Material and methods: In 2002, we explanted three Prozyr 22.2 Zircone heads for recurrent dislocation. We compared the explanted heads with a new Zircone head, a 28-mm alumina head explanted after prosthesis loosening and a new alumina head, using the same protocol as Haraguchi.Results: On the explanted heads, the percentage of monoclinic Zircone was always less than 10% (3–10%). Roughness was also very minimal (Ra=0.01μm) for Zircone and c...