Some problems in using a polyvinylidene fluoride transducer for the intra-articular determination of joint contact stress

A piezoelectric transducer and associated instrumentation were developed and evaluated as a means of experimentally determining joint contact stress. Each transducer, fabricated from a polyvinylidene fluoride film, comprised four discrete sensing elements. Following dynamic calibration of all sensing elements, in vitro evaluations were performed with transducers positioned in canine tibio-femoral joints. Quantitative measurements of contact stress as a function of time were obtained using these transducers, the magnitudes of which ranged between 0.01 and 7.99 MPa. Limitations associated with the transducer material and its use in this specific application included calibration variability and temporal phase shift of the transducer output signal relative to the applied load.