Alloplastic reconstruction of large cranio-orbital defects: a comparative evaluation

Norian CRS, Bone Cement (Synthes CMF), and Mimix (Lorenz) have been used to reconstruct large cranio-orbital defects in 85 patients. Resorbable mesh (Macropore), used in combination in selected patients, obviates dura pulsations that have been postulated to cause fragmentation of alloplastic material. Norian is composed of monocalcium phosphate, monohydrate, alpha-tricalcium phosphate, and calcium carbonate. Admixture with NaPO4 creates dahllite, which has a higher carbonate content (4%--6%) than hydroxyapatite (0%). CRS is soluble at low pH, facilitating its resorption and replacement by bone. In contradistinction, Mimix is converted to aqueous solution at 37 degrees C, supports fibrovascular ingrowth and bony interdigitation at the implant-material surface. Forty-five adults (mean age=42 years) and 40 children (mean age=8 years) were evaluated with respect to etiology of defect, size, location, gram usage of alloplast material, type of alloplast, postoperative clinical course, and complications. A minimum of 3-year follow-up is available; 22 adult patients additionally underwent resorbable mesh reconstruction. There were 7 (8%) complications, including infection, extrusion, a sterile loculated fluid collection and fragmentation. No difference in complication rate was noted between biomaterials. Two additional patients exhibited resorption (Norian), necessitating reaugmentation. Alloplastic replacement of cranio-orbital defects has recently advanced dramatically. Bivalved cranial bone grafting with its attached morbidity and sequelae can be avoided. Resorbable mesh allows for the placement of alloplast material in larger defects while avoiding dura pulsation causing alloplast fragmentation. In avoiding titanium type reconstruction, it obviates any interference with radiologic diagnosis and radiotherapeutic modalities. Long-term results are needed to assess bone growth within alloplast and to study bone growth in alloplastic reconstructed pediatric patients.