Effect of removal and reinsertion of force-closed stems on deformation of total hip arthroplasty☆

OBJECTIVES This study investigated removal of a force-closed stem, done in order to improve acetabular exposure during revision, with reinsertion afterwards. It is unknown how much this procedure modifies the stem/cement interface. METHODS Three tapered stem models were implanted into composite femurs. Strain gauges were embedded in the medial aspect of the cement mantle and in several positions on the outer surface of the femurs. The deformation was measured during static loading, which was applied at two different times: after implantation and after one million loading cycles, followed by stem removal and reinsertion. The t test was performed. The differences in deformation were compared (at p ≤ 0.05) between the two static loading times and among the three stem designs. RESULTS No significant differences in deformation were found after the two loading times for the three models. No significant differences in the initial deformations of the three models were found for most of the gauges attached to the femurs. CONCLUSIONS Reinsertion of the force-closed stem does not alter the load transmission from the stem to the cement and to the surface of the femur, even after one million loading cycles.