25 февр. 2012 г.

Ceramic femoral heads generated less linear polyethylene cup wear over 20 years

German researchers concluded after two decades of investigation that ceramic femoral heads create less linear polyethylene cup wear over time compared with metal heads.

While the cobalt-chromium-molybdenum (CoCrMo) group showed a mean 0.190 mm/year wear rate in the long-term study – which examined long-term wear analysis of femoral heads over a 20-year period – the ceramic head group had a 0.107 mm/year wear rate, which caused “significantly less osteolysis and revisions of either component,” the authors wrote in the abstract. The paper was published in Seminars in Arthroscopy.

In 80 patients, surgeons performed 93 consecutive uncemented hip arthroplasties using a titanium-coated cup and cementless stem. Eighty ceramic and 13 CoCrMo 32-mm diameter femoral heads were used. On average, patients followed up for 19.3 years and no patient was lost during follow-up, according to the abstract.

CoCrMo revision rates were significantly higher, at 6 revisions over 13 cases, compared to the ceramic group, which had only 11 revisions in 80 cases. The authors noted that wear rate was positively correlated with cup revision, inclination, osteolysis as well as femoral head material and stem osteolysis.

Alumina head in total hip arthroplasty did better than metallic heads when sliding against polyethylene. This has been well-documented for 20 years even if laboratory studies were not totally confirmed by clinical experiences. In the laboratory, reduced wear is less by a factor of 4 times, while in clinical studies, Willert and Zichner (Clin Orthop Relat Res, 1992) showed a gain in time before revision of 25%. Some other factors could play a role, such as metal-backed polyethylene versus plain cemented ones and the quality of the polyethylene. Differences in surface roughness may explain the differences in abrasive wear, while fatigue or adhesive wear could be similar. Simulator studies are not perfect in reproducing natural stresses.

— Laurent Sedel, MD
Past President of the International Hip Society
Head of Department, Hõpital Lariboisiere
University Denis Diderot Paris
Disclosure: Sedel is a consultant for Ceraver Osteal.

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