Effects of Cemented Hip Stem Pre‐heating on Stem Push‐out Strength

Objective To determine the effect on ultimate push‐out load and cement–stem surface shear strength of thermally manipulating the cobalt‐chromium‐molybdenum ( CoCrMo ) alloy stems of bone cement–stem constructs. Methods Satin‐finished CoCrMo alloy stems were allocated to the following three groups with the predetermined temperatures: T 24, ambient (24 °C); T 37, body (37 °C); and T 44, pre‐heated stem (>44 °C). They were then inserted into hand‐mixed high viscosity bone cement. Ultimate push‐out load to failure was assessed with a servo hydraulic testing machine and the surface shear strength calculated. Data were compared among groups using the K ruskal– W allis with D unn's test. A P value of less than 0.05 was considered statistically significant. Results According to K ruskal– W allis analysis, ultimate push‐out load and surface shear strength differed significantly between the groups ( P = 0.001). The T 37 and T 44 groups had higher ultimate push‐out loads and surface shear strengths than the T 24 group ( P = 0.04 and 0.001, respectively). However, there was no statistically significant difference in these two variables between the T37 and T44 groups ( P = 0.08). Conclusions Pre‐heating CoCrMo alloy stems enhance the ultimate push‐out load and surface shear strength in vitro . The suggested temperature is 37 °C. This technique is recommended for hip arthroplasty procedures.