Femoral cement pressurisation for hip arthroplasty in previously fixated hips: an experimental study.

INTRODUCTION

It is common to use a cemented total hip replacement following failed hip screw fixation of a fractured femoral neck; this solution, however, is complicated by the presence of the holes that are left in the femur when the screws are removed. These holes can allow cement to leak out while being pressurised. The aim of this study was to look at the cement femoral pressures proximally and distally in a sawbone model with pre-drilled holes to assess if the commonest surgical technique of occluding the holes with fingers could maintain the cement pressure high enough.

MATERIALS AND METHODS

We used eight synthetic proximal femurs, four with dynamic hip screw holes drilled in them on the lateral surface ("drilled femurs") and four with no holes ("undrilled femurs"). We used pressure sensors positioned in holes drilled in the proximal and distal parts of the medial surface to measure the pressure in the cement as it was being delivered and pressurised into the femur canal. The tests were conducted while the femur was clamped at its distal end and, in the case of the drilled femurs, while the screw holes were occluded manually.

RESULTS

We found that on the proximal side, the peak cement pressure in undrilled femurs was significantly greater than in drilled femurs (p=0.006). On the distal side, the difference in peak cement pressure between the two study groups was not significant (p=0.22). At both the proximal and distal positions, the time over which the cement pressure exceeded both 5 and 100 kPa was significantly longer in undrilled femurs than in drilled femurs (p<0.05).

CONCLUSION

Our results show that it is difficult to fully occlude the drill holes completely with finger tips, especially when using pressurised cement. There are significant differences in the peak cement pressures between drilled and undrilled femurs with possible consequences for patients undergoing total hip replacement.