THERMAL EFFECTS OF ACRYLIC CEMENTATION AT BONE-TUMOR SITES

The use of acrylic bone cement as an adjunct to surgical excision of g iant cell tumour of bone appears to reduce the incidence of tumour rec urrence. Possible mechanisms for this apparent tumour inhibition inclu de cytotoxic effects from the methylmethacrylate monomer and tissue hy perthermia from the heat of polymerization of the cement. This work pr esents a method for the prediction of temperature fields and resulting tissue necrosis arising from the implantation of polymethylmethacryla te (PMMA) at the site of a curretted giant cell tumour of bone. This i s accomplished using a two-dimensional model based on geometry obtaine d from digitized MRI images of the distal femur. A general-coordinate, non-orthogonal grid generation technique is used and solutions are ob tained with an alternating-direction implicit (ADI) finite-difference scheme. The nodal temperature histories are then used to evaluate the effect of variable defect size on the zone of thermally induced cell n ecrosis. The results suggest the depth of the necrotic region is quite sensitive to the size of the implant. In at least some cases, the hea ting effect is sufficient to cause significant necrosis of tumorigenic cells. Implanting a large mass of acrylic may risk overkill, damaging substantial amounts of healthy tissue.