title: Effects of Cemented Hip Stem Pre-heating on Stem Push-out Strength.
abstract: 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: T24, ambient (24 °C); T37, body (37 °C); and T44, 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 Kruskal-Wallis with Dunn's test. A P value of less than 0.05 was considered statistically significant.
  
  
  RESULTS
  According to Kruskal-Wallis analysis, ultimate push-out load and surface shear strength differed significantly between the groups (P = 0.001). The T37 and T44 groups had higher ultimate push-out loads and surface shear strengths than the T24 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.
authors: Department of Orthopaedics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors: Vajara
authors: V
authors: Wilairatana
authors: Department of Orthopaedics, Hatyai Hospital, Songkla, Thailand.
authors: Chatchawan
authors: C
authors: Pirot
authors: Department of Orthopaedics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors: Noppachart
authors: N
authors: Limpaphayom
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation / Q000379:methods; D001843:Bone Cements; D002484:Cementation / Q000379:methods; D006361:Heating; D006622:Hip Prosthesis; D006801:Humans; D008422:Materials Testing / Q000379:methods; D011474:Prosthesis Design; D033081:Shear Strength; D013499:Surface Properties; D013696:Temperature; D014800:Vitallium
chemical_list: D001843:Bone Cements; D014800:Vitallium
keywords: Cobalt-Chromium-Molybdenum alloy; Hip arthroplasty; Pre-heated femoral stem; Push-out test; Surface shear strength