Experimental Measurement and Numerical Validation of Bone Cement Mantle Strains of an In Vitro Hip Replacement Using Optical FBG Sensors

Experimental pre-clinical tests associated with numeric models of cemented implants are important for screening of new implants in the market. The aim of this study was to measure strain profiles and maximum temperature polymerization inside a cement mantle of an in vitro cemented hip reconstruction using optical fiber Bragg grating (FBG) sensors. For this purpose, a hip femoral prosthesis was instrumented with 12 FBG sensors, three in each aspect of the femur, anterior, posterior, medial and lateral. These were positioned at the proximal, middle and distal part of the cement mantle relatively to the stem. Another sensor was placed in the lateral-proximal region of the mantle to measure the maximum temperature of cement polymerization. The strains measured were compared with those obtained with a Finite Element model, both for quaistatic mechanical loading. The results show that the experimental technique used can measure strains inside the cement mantle with good correlation, R-2 = 0.970, with the numerical model results. The results present a maximum temperature of polymerization around 110 degrees C inside of cement at proximal region. It was also observed strain concentration in lateral aspect of the femur in polymerization process. The procedure hereby explained can be used to improve experimental pre-clinical tests to measure the strain distribution inside the cement mantle as well as residual strain and temperature variation along with time, as a result of the curing process of cement.