Femoral cement pressurization during total hip arthroplasty. The role of different femoral stems with reference to stem size and shape.

Aseptic loosening is the most common cause of femoral component failure following total hip arthroplasty (THA). Improvements have been made in cementing technique, but little attention has been directed toward the effect of different femoral components on bone cement pressurization. The effect of three different femoral stem sizes in one femoral canal and of eight different femoral stem designs on bone cement extrusion pressures was investigated on autopsy specimens. In a given femur significant increases in bone cement pressurization were achieved about the distal two-thirds of the femoral component in progressing from a small to a medium to a large stem. Similarly, femoral stems with rounded, rectangular cross sections generated greater bone cement pressurization about the distal two-thirds of the stems than stems trapezoidal and diamond-shaped in cross section due to their increased stem volume. The results of this study favor the use of the largest femoral component stem, preferably one with a rounded, rectangular cross section, that will fit comfortably in a given femoral canal and still allow a surrounding cement envelope such that bone cement pressurization will be enhanced with implant introduction.