Computational Modeling of Tissue Engineering Scaffolds as Delivery Devices for Mechanical and Mechanically Modulated Signals - Computational Modeling in Tissue Engineering - page 125

Fig. 2 Flow chart for design and optimization of tissue engineering scaffolds using CFD as a
predictive tool. CFD multiphysics methods demonstrate chemical transport and delivery of
mechanical signals within a given tissue engineering scaffold geometry, such as that shown in Fig. 3
where the primary flow direction is axial (along the length of the cylinder) and the secondary flow
direction is orthogonal (transverse, defined by secondary flow geometry). Adapted from [ 2 ], used
with permission. Please refer to online version of chapter for color version of the figure
current standard treatment option for such defects involves bone grafting,
where graft is obtained from the patient himself (autograft), a bone bank (allo-
graft), a graft substitute, or a structural implant or filler such as titanium or
poly-methylmethacrylate (PMMA). Autografts are the gold standard treatment for
CSDs due to their lack of immunogenicity; immune rejection is a critical compli-
cation associated with use of allograft. One complication associated with the use of
autograft for CSDs, particularly of the cranium, is poor vascularization, which
results in the need for reoperations and/or the removal of the implant [ 19 ]. In
addition, packing of CSD with morcellized bone graft has been shown recently to
retard the ingression of MSCs from the periosteum, when it is left in situ around the
defect zone [ 29 ]. Furthermore, success of the surgery depends highly on both the
size of the defect and the quality of its surrounding tissue [ 28 ]. Even with a suffi-
ciently small defect that is surrounded by a healthy tissue bed, autografting per se is
associated with risks including donor site morbidity and additional pains [ 19 , 38 ].
Over the past several decades, tissue engineering has been developed as an
alternative to tissue transplantation. For CSDs of long bone, a new surgical
technique referred to as the one-stage bone transport procedure has been developed