HYDROXYAPATITE CEMENT TO REPAIR SKULL BASE DEFECTS - RADIOLOGIC APPEARANCE

PURPOSE: To describe the radiologic appearance of hydroxyapatite cemen t (HAC), which, when mixed with liquid, forms a paste that can be cont oured to osseous defects and, over time, becomes ''osseointegrated'' ( native bone grows into the pores of the HAC and forms a strong chemica l bond with the substance). METHODS: Between March 1992 and June 1993, 24 adults (16 men, eight women) underwent skull base surgery that inc luded reconstruction or closure with HAC. Fourteen patients had HAC pl aced in the paranasal sinuses or facial bones, and 10 had HAC placed i n the mastoid cavity. RESULTS: HAC is homogeneously radiopaque on CT s cans and plain radiographs. Large amounts (ablating a frontal sinus or mastoid air cells) are readily seen; small amounts are inconspicuous. On MR images, HAC is a signal void. Infected HAC in one patient was s urrounded by enhancing soft tissue on MR images, separated from native bone by an irregular radiolucent cleft on CT scans. CONCLUSIONS: HAC is a valuable addition to the surgical armamentarium for the repair of skull base defects. More experience will determine the time course fo r normal osseointegration, as well as the typical appearance of infect ion.