Effects of prosthetic acetabular replacement on strains in the pelvis

The effects of cemented acetabular components on the strains in the pelvis were determined experimentally. Four components were tested: A plain metal hemisphere; a metal hemisphere with a triflange; a hemisphere with an iliac peg; and a hemisphere with a complete flange and a peg. Loading was carried out in neutral, flexion, and extension directions. The subchondral bone was only slightly reamed, and components were cemented and tested successively. For the intact hip joint, the strains on the superior acetabular rim were much lower than those on the posterior rim. After placement of the components, the tensile strains on the rim decreased by 22-54% while the compressive strains increased by 0-25%. The bone on the medial inferior surface was subjected to 65% less tensile strain and 48% more compressive strain in neutral and extension loading. There were no great differences between the four styles of acetabular component.