A variable geometry turbine has an annular inlet passageway defined between a radial wall of a moveable wall member and a facing wall of the turbine housing. The liquid bituminous material is atomized by mixing it with a pressurized gas, such as compressed air, forming a mist comprising droplets of bituminous material having a diameter between 20 microns and 50 microns. The preparation that is injected into the joint cavity and subjected to an alternating electromagnetic field promises an excellent treatment outcome due to the high rate of phagocytosis and the trimodal combinatorial effect of thermotherapy, radiotherapy and chemotherapy.