Cement mantle defects and the role of distal femoral centralising devices

We performed an in vitro study to examine the effect of distal femoral centralising devices on the cement mantle after introduction of a tapered femoral prosthesis (Exeter no2 44 mm offset stem). This was assessed in relation to the timing of insertion (early, middle and late) and three different cement products (CMW 1, Simplex and Palamed). Forty-seven identical sawbone (R) femora model 1130 were examined after extraction of the stem. Each cement brand was divided into three groups (early, middle and late insertion times). A fourth group was added as a control, without a centraliser. Each of the femora was assessed using a 30 endoscope combined with VHS video analysis and 1 cm axial sectioning studies to examine the integrity of the cement mantle. The results were analysed statistically using the ANOVA method. These show that early insertion is important in preventing major cement mantle defects (P < 0.5). The addition of a centraliser to the stem and insertion in the late phase led to significantly greater defects in the cement mantle (P < 0.0001). This was independent of the cement type used. We conclude that there is a relationship between the late insertion of the femoral component with a distal centraliser and large cement mantle defects. We recommend insertion of the stem in the early phase of cement curing if a centraliser is used or removal of the centraliser if this stage has passed.