title: Additive manufacturing for in situ repair of osteochondral defects.
abstract: Tissue engineering holds great promise for injury repair and replacement of defective body parts. While a number of techniques exist for creating living biological constructs in vitro, none have been demonstrated for in situ repair. Using novel geometric feedback-based approaches and through development of appropriate printing-material combinations, we demonstrate the in situ repair of both chondral and osteochondral defects that mimic naturally occurring pathologies. A calf femur was mounted in a custom jig and held within a robocasting-based additive manufacturing (AM) system. Two defects were induced: one a cartilage-only representation of a grade IV chondral lesion and the other a two-material bone and cartilage fracture of the femoral condyle. Alginate hydrogel was used for the repair of cartilage; a novel formulation of demineralized bone matrix was used for bone repair. Repair prints for both defects had mean surface errors less than 0.1 mm. For the chondral defect, 42.8+/-2.6% of the surface points had errors that were within a clinically acceptable error range; however, with 1 mm path planning shift, an estimated approximately 75% of surface points could likely fall within the benchmark envelope. For the osteochondral defect, 83.6+/-2.7% of surface points had errors that were within clinically acceptable limits. In addition to implications for minimally invasive AM-based clinical treatments, these proof-of-concept prints are some of the only in situ demonstrations to-date, wherein the substrate geometry was unknown a priori. The work presented herein demonstrates in situ AM, suggests potential biomedical applications and also explores in situ-specific issues, including geometric feedback, material selection and novel path planning techniques.
authors.affiliation: Cornell University, Mechanical and Aerospace Engineering, Ithaca, NY, USA. dlc44@cornell.edu
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Cohen
authors.forename: Jeffrey I
authors.initials: JI
authors.lastname: Lipton
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Bonassar
authors.forename: Hod
authors.initials: H
authors.lastname: Lipson
mesh_terms: D000464:Alginates; D000818:Animals; D001672:Biocompatible Materials; D001709:Biotechnology; D001847:Bone Diseases / Q000473:pathology / Q000628:therapy*; D018786:Bone Substitutes; D002357:Cartilage Diseases / Q000473:pathology / Q000628:therapy*; D002417:Cattle; D017076:Computer-Aided Design; D005269:Femur; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D007719:Knee Joint / Q000473:pathology; D008592:Menisci, Tibial / Q000033:anatomy & histology / Q000502:physiology; D008954:Models, Biological; D023822:Tissue Engineering / Q000295:instrumentation / Q000379:methods*; D054457:Tissue Scaffolds; D014057:Tomography, X-Ray Computed
chemical_list: D000464:Alginates; D001672:Biocompatible Materials; D018786:Bone Substitutes; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate