The effect of body weight on the choice of material for the bearing couple in artificial hip joints

The effect of body weight on the success of arthroplasty replacement of the hip joint is a controversial issue, particularly the question of whether the choice of bearing couple used should be adapted to individual patient characteristics. As part of this study, we carried out a literature-based meta-analysis of clinical results that referred to patient weight. The friction of various material combinations under different joint forces was also experimentally determined. Clinically, there are reports of unfavorable implant positioning, increased rate of dislocations, and increased noise developments for obese patients. The results of the friction measurements do not suggest a material choice adapted to body weight. For obese patients, therefore, the same argument applies as for patients with normal weight; provided a correct implantation situation can be ensured, ceramic-on-ceramic bearing couples should be favored from a tribological point of view. If the correct implant position—for example, based on the more complicated implant conditions in obese patients—cannot be achieved, a hard–soft bearing couple with a ceramic head appears to be preferable to a hard–hard bearing couple.