title: Hydroxyapatite cement to repair skull base defects: radiologic appearance.
abstract: OBJECTIVE
  To describe the radiologic appearance of hydroxyapatite cement (HAC), which, when mixed with liquid, forms a paste that can be contoured to osseous defects and, over time, becomes "osseointegrated" (native bone grows into the pores of the HAC and forms a strong chemical bond with the substance).
  
  
  METHODS
  Between March 1992 and June 1993, 24 adults (16 men, eight women) underwent skull base surgery that included reconstruction or closure with HAC. Fourteen patients had HAC placed in the paranasal sinuses or facial bones, and 10 had HAC placed in the mastoid cavity.
  
  
  RESULTS
  HAC is homogeneously radiopaque on CT scans 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 surrounded be 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 for normal osseointegration, as well as the typical appearance of infection.
authors.affiliation: Department of Radiology, University of Pittsburgh (Pa) Medical Center 15213, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Weissman
authors.forename: C H
authors.initials: CH
authors.lastname: Snyderman
authors.forename: B E
authors.initials: BE
authors.lastname: Hirsch
mesh_terms: D000328:Adult; D000368:Aged; D001672:Biocompatible Materials / Q000009:adverse effects / Q000737:chemistry; D001843:Bone Cements / Q000009:adverse effects / Q000737:chemistry; D001847:Bone Diseases / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D003287:Contrast Media / Q000737:chemistry; D017886:Durapatite / Q000009:adverse effects / Q000737:chemistry; D005147:Facial Bones / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D005260:Female; D005626:Frontal Sinus / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008416:Mastoid / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D008875:Middle Aged; D009824:Ointments; D016348:Osseointegration; D010256:Paranasal Sinuses / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D019291:Skull Base / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D013530:Surgical Wound Infection / Q000175:diagnosis / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed
chemical_list: D001672:Biocompatible Materials; D001843:Bone Cements; D003287:Contrast Media; D009824:Ointments; D017886:Durapatite