Tissue Engineering: Growing Skull with In Situ Osteogenesis

Abstract

Introduction Acquired skull defects are common as a result of trauma infection and calvarial expansion among other causes. The techniques available to repair these defects have included a variety of foreign body implants or bone grafting from proximal or distant sites. Tissue engineering using bone morphogenetic protein (rBMP) and an absorbable mesh scaffold offers a unique opportunity to fill defects with in situ osteogenesis. Methods Bony calvarial defects in 19 children ranging in age from 11 months to 15 years were repaired using rBMP and a collagen scaffold plus a synthetic hydroxyapatite ceramic in a granular or matrix form. The construct is held with poly D,L-lactide acid resorbable mesh. The skull defects were a result of trauma (n = 5) craniotomy for tumor (n = 2), congenital absence (n = 1), infection (n = 4), and calvarial expansion for synostosis (n = 7). The reconstruction technique varied with the size and geometry of the defect. The defects repaired ranged from 10 to 60 cm2. Results of the repair were judged by physical exam and 3D computed tomography. Results In 18 patients followed for at least 6 months, the calvarium was completely ossified in 15 cases and had a small residual defect (2 cm2) in 3 from early in the series. Two surgeries were required to completely reconstruct a bifrontal bone flap. Conclusion BMP shows promise for repairing significant calvarial defects by promoting the growth of the patient's own bone in situ osteogenesis, thereby avoiding the need for foreign body implants or bone grafts from other sites.