Previous studies have shown that modification of cortical bone allografts by partial demineralization and laser-perforation may enhance their incorporation into host bone. However, these studies also showed that incorporation is commonly preceded by bone resorption which could result in premature mechanical failure. The purpose of this proposal is to investigate whether incorporation of these demineralized and perforated allografts can be accelerated by coating them with a bioresorbable polymer foam based on polypropylene fumarate (PPF) with the objective of promoting bony ingrowth into the porous foam coating. Pilot results suggest that PPF-foam coating of cortical bone can maintain strength over time and that the porosity of the scaffold supported bony ingrowth. This grant application will investigate (l) the preparation of scaffolds varying in porosity, (2) the effect of these scaffolds on the mechanical properties of polymer modified partially demineralized and perforated cortical allografts, and (3) the initial evaluation of scaffold coated cortical allografts in an orthotopic rat tibial transplantation model. The ultimate objective of these studies is to determine an optimum combination of porosity and thickness of the polymer coating so as to enable the manufacture of demineralized and perforated cortical allografts which retain sufficient mechanical properties to resist normal skeletal forces throughout the incorporation process.
Although the overall success rate for massive cortical bone allografts, implying return to work and engagement in relatively normal activities without crutches or braces, is approximately 75-85%, only 50% of these patients have an entirely uncomplicated postoperative course. About a quarter of the total group require reoperations such as autologous grafting or replating for stress fractures delayed unions. Some patients require excision of the graft because of infection, reimplantation, long-term bracing or in some cases amputation. If as successful as proposed, the clinical outcomes of our system will be uniquely successful commercially.
|Lewandrowski, Kai-Uwe; Bondre, Shrikar; Hile, David D et al. (2002) Porous poly(propylene fumarate) foam coating of orthotopic cortical bone grafts for improved osteoconduction. Tissue Eng 8:1017-27|