EPIDURAL APPLICATION OF IONOMERIC CEMENT IMPLANTS - EXPERIMENTAL AND CLINICAL-RESULTS

During setting and hardening, the hybrid bone substitute ionomeric cem ent (Ionocem(R)) achieves a stable and durable bond with the apatite o f the adjacent bone without interpository soft tissue. Fluid contact d uring setting results in the release of aluminium ions which may reach critical levels as high as 3000 mu g/l. On epidural application it is , therefore, essential to prevent cement constituents from gaining acc ess to the intradural space. After the cement has hardened, the presen ce of aluminium is demonstrable in the adjacent bone to a maximum dept h of 20 mu m (EDX microanalysis). In rabbits, epidural placement of fr eshly mixed cement causes slight thickening of the dura. There is reas on to believe that human dura, with a thickness 10 times greater, is i mpermeable to components of the cement. After epidural application of the freshly mixed cement in the frontobasal and laterobasal regions an d at the skull cap and petrous apex, 76 patients in all have been foll owed for up to 6.5 years. During this period no complications have ari sen and functional (and cosmetic) results are promising. The availabil ity of preformed implants (Ionoroc(R), Ionocast(R)) permitted the peri dural placement of minimal quantities of freshly mixed cement. These i mplants were fixed to localized sites on the adjacent calvarial bone b y use of Ionocem(R). Notwithstanding the stringent manufacturer guidel ines, there have been reports in the literature that during the vulner able stage of setting neurotoxic aluminium ions were released into the dural space with a fatal outcome in two cases. In view of potential i ntradural complications, such as may occur in case of dural leaks, it was considered that further application of the material adjacent to th e dura was no longer warranted. The production of Ionocem(R) was disco ntinued in May 1995.