Comparison of Stress Shielding between Straight and Curved Stems in Cementless Total Hip Arthroplasty-An in vitro Experimental Study

Adaptive bone remodelings in the proximal femur often occur following either cemented or uncemented total hip arthroplasty (THA). Stress shielding is one of the most significant determinants of this bone remodeling, and it results from changes in force distribution following prosthetic implantation. In order to evaluate the alteration of stress distribution after implantation of straight or curved femoral stem, this study was designed to compare the difference of stress shielding for straight and curved stems in cementless THA using in vitro experimental method. Uniaxial strain gauges and synthetic femora were used to perform the surface strain measurement of proximal femora. A total of eight synthetic femora were enrolled and assigned into C-Fit (Straight stem) and PCA (Curved stem) groups (four in each). Under 1,000-N axial loading, the surface strains of proximal femora were measured and compared between C-Fit and PCA implanted femora with press-fit fixation. The results revealed that the straight stem group got less stress shielding as compared to that of the curved stem group. We concluded that curved stem caused a more significant stress shielding as compared to those with straight stem.