be concluded that elution occurs mainly from the surface of the disc and related to the porosity and other surface properties of the disc a female patient 68 years old having a previous total knee replacement and a below the knee amputation presented with latent infection in the knee a revision to remove the knee prosthesis was performed and the cut ends of the bone were treated with an anti bacterial bone cement to keep the bones spaced three weeks later the bone cement was removed and tissue samples were taken for laboratory analysis for signs of infection bone cement was temporarily applied to keep the bones spaced and aligned but this time the cement was howmedica bone cement containing 2 g of lidocaine xylocaine u00ae per 40 g package of cement the lidocaine laden cement was gas sterilized but not irradiated after recovery from anaesthesia the patient reported severe pain in the knee for a period of approximately 6 hours and thereafter no pain at all 24 hours post surgery the patient was sleeping without the aid of pain killers and was also able to receive physiotherapy without feeling undue discomfort from this example it appears that lidocaine is eluted from bone cement and within 6 hours of placement sufficient lidocaine has eluted to provide an analgesic effect which persists for at least 24 hours and probably at least several days before it metabolizes in the body the effects of lidocaine on the mechanical properties of cmw3 bone cement have also been evaluated and are summarized in table 1 below from the table it can be seen that addition of.