Effect of the friction coefficient between bone cement and polished stem on subsidence of the stem in total hip arthroplasty.

The effect of the friction coefficient between bone cement and polished stems on stem subsidence was investigated in total hip arthroplasty (THA) using nonlinear finite element analysis. Stem subsidence results from both stem slip and shear deformation of the cement. On the lateral side, subsidence is mainly caused by stem slip, while on the medial side, cement deformation is involved. With low friction coefficients, "Reverse subsidence" occurs after load release, where the stem moves upward, and compressive stress is transmitted to the cement. On the other hand, with high friction coefficients, more significant shear deformation of the cement mantle occurs, and residual strain accumulates in the proximal region. The present study implies a trade-off relationship: high friction increases the risk of periprosthetic fractures (PPFs) in the proximal region, while low friction increases the risk in the distal region.