Measurement of transient and residual stresses during polymerization of bone cement for cemented hip implants.
The initial fixation of a cemented hip implant relies on the strength of the interface between the stem, bone cement and adjacent bone. Bone cement is used as grouting material to fix the prosthesis to the bone. The curing process of bone cement is an exothermic reaction where bone cement undergoes volumetric changes that will generate transient stresses resulting in residual stresses once polymerization is completed. However, the precise magnitude of these stresses is still not well documented in the literature. The objective of this study is to develop an experiment for the direct measurement of the transient and residual radial stresses at the stem-cement interface generated during cement polymerization. The idealized femoral-cemented implant consists of a stem placed inside a hollow cylindrical bone filled with bone cement. A sub-miniature load cell is inserted inside the stem to make a direct measurement of the radial compressive forces at the stem-cement interface, which are then converted to radial stresses. A thermocouple measures the temperature evolution during the polymerization process. The results show the evolution of stress generation corresponding to volumetric changes in the cement. The effect of initial temperature of the stem and bone as well as the cement-bone interface condition (adhesion or no adhesion) on residual radial stresses is investigated. A maximum peak temperature of 70 degrees C corresponds to a peak in transient stress during cement curing. Maximum radial residual stresses of 0.6 MPa in compression are measured for the preheated stem.
Nuño
N
N
Ecole de technologie supérieure, Laboratoire de recherche en imagerie et orthopédie, Département de génie de la production automatisée, Université du Québec, 1100 rue Notre-Dame Ouest, Montréal, Québec, Canada H3C 1K3. natalia.nuno@etsmtl.ca
Madrala
A
A
Plamondon
D
D
D000268:Adhesiveness; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D001843:Bone Cements / Q000737:chemistry*; D002484:Cementation / Q000379:methods*; D019245:Compressive Strength; D055119:Elastic Modulus; D006622:Hip Prosthesis; D008422:Materials Testing / Q000295:instrumentation* / Q000379:methods*; D011108:Polymers / Q000737:chemistry; D013314:Stress, Mechanical
D001843:Bone Cements; D011108:Polymers