Femoral component revision using impacted morsellised cancellous graft. A biomechanical study of implant stability

We have tested the axial and torsional stability of femoral components after revision arthroplasty in a cadaver model, using impacted morsellised cancellous graft and cement. Each one of six matched pairs of fresh frozen human femora had either a primary or a revision prosthesis cemented in place. For the 'revision' experiments, all cancellous bone was removed from the proximal femur which was then over-reamed to create a smooth-walled cortical shell. An MTS servohydraulic test frame was used to apply axial and torsional loads to each specimen through the prosthetic femoral heads with the femur submerged in isotonic saline solution at 37 degrees C. The mean subsidence was 0.27 +/- 0.17 mm for the primary and 0.52 +/- 0.30 mm for the revision groups. The difference was statistically significant (p < 0.025), but the mean subsidence was <1 mm in both groups. The mean maximum torque before failure was 42.9 +/- 26.9 N-m for the primary and 34.8 +/- 20.7 N-m for the revision groups. This difference was not statistically significant (p > 0.015). Based on our results we suggest that revision of the femoral component using morsellised cancellous graft followed by cementing with a collarless prosthesis with a polished tapered stem restores the integrity of the proximal femur and provides immediate stability of the implant.