Thermomechanical method for cement extraction in revision arthroplasty.

Abstract

In joint revision surgery, bone cement extraction remains a major challenge which even today has not seen a satisfactory solution yet. We studied in an experimental setting the impact of heat sources on the mechanical properties and microstructure of bone cement and determined the glass transition temperature (T _G) of bone cement. As a result, it would be possible to establish a thermomechanical method which makes use of the structural and material-specific property changes inherent in bone cement at elevated temperatures. Prepared samples of polymerized bone cement were thermoanalyzed with a Netzsch STA 409 C thermal analyzer. Samples weighing approx. 55 mg were heated to 390 °C at a rate of 5 K/min. Both simultaneous differential thermal analysis and thermogravimetry were employed. The thermomechanically induced changes in the microstructure of the material were analyzed with a computed tomography scanner specifically developed for materials testing (3D-μXCT). The bone cement changed from a firm elastic state over entropy-plastic (air atmosphere 60-155 °C) to a plastic viscosity state (air atmosphere >155 °C). Between 290 and 390 °C, the molten mass disintegrated (decomposition temperature). Our study was able to determine the glass transition temperature (T _G) of bone cement which was about 60 and 65 °C under air and nitrogen, respectively. Heating the dry bone cement up to at least 65 °C would be more than halve the strength needed to detach it. Bone cement extraction would then be easy and swift.