Biomechanical comparison of three cemented stem removal techniques in revision hip surgery

Background

There are various techniques available to remove a cemented femoral component and distal cement in the case of septic or aseptic loosening, periprosthetic or component fracture. The present study describes the mechanical effects of three techniques: the transfemoral approach (TFA), the distal fenestration technique (DF) and the retrograde stem removal technique (RSR). An experiment on cadaveric femora was performed to establish if there are any differences in the resistance to fracture in and between the various groups.

Methods

Twenty-two paired femora were recovered from human cadavers and were frozen. These were later subdivided into three groups to provide similar specimens in each group (TFA, DF, RSR). The femora were tested using an Instron 8874 biaxial testing system. The torque required to fracture was measured. Intra- and intergroup statistical analysis was performed.

Results

In the TFA group, the force required till fracture was significantly less than in controls. (p = 0.018). Similar results were found in the DF group (p = 0.048). There was no difference in the RSR group (p = 1). Intergroup analysis showed the following: Femora in the TFA group required significantly less force to fracture than specimens in the DF group (p = 0.018) or the RSR group (p = 0.0055). Femora in the DF group required significantly less force to fracture than specimens in the RSR (p = 0.037).

Conclusions

The TFA technique decreases the mechanical resistance of human cadaveric femora very significantly against rotational forces. The DF technique in the same setup also significantly decreases the resistance of bone, whilst no significant change is seen with the RSR technique.