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

ObjectiveTo 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.MethodsSatin‐finished CoCrMo alloy stems were allocated to the following three groups with the predetermined temperatures:T24, ambient (24 °C);T37, body (37 °C); andT44, 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 theKruskal–Wallis withDunn's test. APvalue of less than 0.05 was considered statistically significant.ResultsAccording toKruskal–Wallis analysis, ultimate push‐out load and surface shear strength differed significantly between the groups (P= 0.001). TheT37 andT44 groups had higher ultimate push‐out loads and surface shear strengths than theT24 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).ConclusionsPre‐heatingCoCrMoalloy stems enhance the ultimate push‐out load and surface shear strengthin vitro. The suggested temperature is 37 °C. This technique is recommended for hip arthroplasty procedures.