Intervertebral Spinal Fusion Using a RP-based PLGA/TCP/bBMP Biomimetic Grafting Material

Abstract

Three-dimensional highly porous poly(DL-lactic-co-glycolic acid)/tricalcium phosphate (PLGA/TCP) scaffolds were synthesized via a rapid prototyping (RP) technique. Bovine bone morphogenetic protein (bBMP) was loaded into the biopolymer scaffolds (PLGA/TCP/bBMP). Both the PLGA/TCP scaffolds and the PLGA/TCP/bBMP composites were evaluated by scanning electron microscopy. Lumbar intervertebral body fusion at L2~3 and L4~5 levels were performed on 15 goats using one of the following graft materials: RP synthesized PLGA/TCP scaffolds (group A), PLGA/TCP/bBMP composites (group B), and autogenous iliac bone graft (group C). All animals were sacrificed 24 weeks after surgery and the spine fusions evaluated by manual palpation tests, histological analyses, and radiography. In group A, the histological analyses showed that the PLGA/TCP scaffolds were biocompatible and biodegradable; however, no new bone was found. In group B, highly cellular bone marrow between the new trabecular bone was present in the fusion mass. In group C, there was a lesser amount of new bone. Twenty-four weeks after surgery, the fusion rate of lumbar intervertebral body fusion in group A, B, and C was 10% (1/10), 80% (8/10), and 50% (5/10), respectively. The fusion rate was significantly higher in group B compared with groups of A and C (p<0.01). Based on these results, extracted bBMP can be loaded in vitro into RP-based highly porous structural PLGA/TCP scaffolds to fabricate new graft composites that appear to be more effective for intervertebral spinal fusions. This biomimetic artificial grafting material holds promise as a tool for spine surgery.