[The influence of reduced bone density on primary stability of cementless femoral stems. A biomechanical in vitro study].

OBJECTIVE

The aim of the present in vitro study is to examine the influence of bone density on the primary stability of cementless femoral stems in nine pairs of human cadaveric femurs.

METHOD

The human proximal femurs were evaluated with regard to their bone density by dual-energy X-ray absorptiometry. Two pairs of human cadaveric femurs had an osteoporotic and two pairs an osteopenic bone stock. After implantation of the cementless femoral stems, the prostheses were loaded in a physiological position. Subsidence, rotation and interface motion of the stems were measured with load cycles up to 2000 Newton.

RESULTS

There was no significant correlation between the bone density of the proximal femur and the primary stability of the femoral stem in subsidence (p=0.23) and rotation (p=0.79). Reduced bone density in the osteoporotic and osteopenic human femora did not increase the interface motion at the proximal or distal part of the prosthesis (p>0.05).

CONCLUSION

The initial stability of cementless femoral stems was not influenced by the bone density, at least in this biomechanical in vitro study. Thus, theoretical conditions exist that allow secondary osseointegration of femoral stems also in cases of reduced bone density.