Insertional femoral fracture: a biomechanical study of femoral component stability.

A Taperloc femoral component (Biomet Inc, Warsaw, IN) was implanted in seven fresh-frozen cadaver femora. In loads simulating single-leg stance and stair climbing, axial and rotational stability were tested before fracture, after fracture, and after fracture but with the addition of A-O cerclage wire fixation. All fractures were incomplete, began proximally at the anteromedial neck, and extended distally. More than 90% of the components showed decreased axial and rotational stability after fracture. The addition of cerclage wire fixation after femoral fracture provided acceptable axial stability in only three of seven femora and rotational stability in five of seven femora. In order to provide satisfactory initial implant stability after femoral fracture, improved methods of fixation and longer stemmed implants may be necessary.