Thermomechanical method for cement extraction in revision arthroplasty.

ABSTRACT

BACKGROUND: 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. METHODS: 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). RESULTS: 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). CONCLUSION: 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.