COMPARATIVE STUDY OF POLYETHYLENE WEAR IN THR: 28 MM DIAMETRE CERAMIC VERSUS METALLIC HEAD – A FIFTEEN YEARS RESULT

Abstract

Introduction: The aim of this prospective, randomized, monocentric study was to compare wear of polyethylene when using a 28 mm diametre ceramic head versus a metallic head.

Material and Method: 226 THR performed between 1988 and 1990 were evaluated in 2005: 111 patients had died, 28 were lost of follow up and in 17 cases radiological assessment was not possible. 74 arthroplasties have been analyzed. In all cases, a straight femoral stem in protasul 10 (Zimmer), and a polyethylene cup sterilized under gamma radiation were used. In 37 cases the bearing surface used a metal head and in 37 cases a ceramic head. Radiolucent lines were analysed on AP x-rays. Aseptic loosening was defined according to Hodgkinson and Harris criteria. The penetration of the femoral head was measured with a special software (M.P.H. Wear) on digitalised x-rays.

Results: The two groups were statistically comparable (p = 0.0857). For metallic heads, linear wear was 0,102 mm/year (62.8 mm3/year volumetric wear). For ceramic heads, linear wear was 0,058 mm/year (volumetric wear 35.7 mm3/year. It represents a significant reduction (p = 0.0004) 44% of penetration. There was a penetration higher than 0.1 mm per year in thirteen cases of metal heads and in only one case of ceramic head. It was noted four aseptic loosening. In these four cases penetration was greater than 0.2 mm per year. In three cases, it was a metal head and in one case, a ceramic head.

Discussion: Our results are comparable to those found in the literature when the follow up is more than ten years as reported by Schuller, Oonichi and Hernigou. For authors with follow up shortest than ten years, it is reported identical outcomes between ceramic head and metal head (as reported Jenni, Devane and Sychterz).

Conclusion: This is the first randomized prospective study with two identical populations, showing a statistical significant difference of wear of polyethylene between ceramic and metallic prosthesis head.