An Injectable Complex of β-tricalcium Phosphate Granules, Hyaluronate, and rhFGF-2 on Repair of Long-bone Fractures with Large Fragments

Bone Union Enhancement by bFGF-Containing HAp/Col in Prefabricated Vascularized Allo-Bone Grafts

BACKGROUND

 We have developed a prefabricated vascularized allo-bone graft (PVAG) by implanting the saphenous vascular bundles of recipient rats into transplanted donor bones in a flow-through manner. We previously demonstrated that the angiogenetic and bone formative abilities of the PVAG are stimulated by the addition of a basic fibroblast growth factor (bFGF)-containing hydroxyapatite/collagen (HAp/Col). This study aimed to demonstrate that the bone union ability of the PVAG is similarly stimulated by the bFGF-containing HAp/Col composite.

METHODS

 Sprague-Dawley donor rats (n = 32) and Wistar recipient rats (n = 32) were used in this study. The PVAG was fixed to the femur of the recipient rat using K-wire (dimeter: 0.7 mm) pinning, followed by suturing with a 4-0 nylon suture. Recipients were divided into four groups: with or without vascular bundles, and with or without bFGF-containing HAp/Col. Rats were sacrificed 6 weeks after transplantation, and bone union, bone resorption, and angiogenesis were radiologically and histologically evaluated.

RESULTS

 Radiological analysis revealed a significant increase in callus formation and union rate, while histological analysis showed a significant increase in bone formation and angiogenesis in the group treated with both vascular bundles and bFGF. Bone resorption did not significantly increase in any of the evaluated groups.

CONCLUSION

 Osteogenic cells, osteoconductive scaffolds, growth factors, and mechanical environment are known to be important factors in the process of fracture healing. The PVAG developed herein contains osteogenic cells, osteoconductive scaffolds, and growth factors. In addition, the PVAG is rigidly fixed to the fracture site, providing a stable mechanical environment. Together, these four factors contributed to a good bone union. Furthermore, this method did not promote bone resorption. Thus, the addition of a vascular bundle and bFGF-containing HAp/Col makes it possible to create an ideal vascularized allo-bone graft for the reconstruction of massive bone defects.

Augmentation of fracture healing by hydroxyapatite/collagen paste and bone morphogenetic protein-2 evaluated using a rat femur osteotomy model

In fracture treatment, biological bone union generally depends on the bone's natural fracture healing capacity, even in surgically treated cases. Hydroxyapatite/collagen composite (HAp/Col) has high osteoconductivity and stimulates osteogenic progenitors. Furthermore, it has the potent capacity to adsorb bone morphogenetic proteins (BMPs). In this study, we prepared an injectable HAp/Col paste and evaluated its augmentation of bone union. Furthermore, the effect of HAp/Col paste combined with BMP-2 was also evaluated. We used a rat femur osteotomy model with a defect size of 1 mm. Male Wistar rats were assigned to one of the following four groups; a control group without any implant, a HAp/Col implant group, a group that received an absorbable collagen sponge (ACS) implant impregnated with BMP-2 (1 μg), and a group that received a HAp/Col implant impregnated with BMP-2 implant. Micro-CT analysis, three-point bending tests, and histological evaluation were performed. Bone union was achieved in two of eight cases in the HAp/Col group, five of eight cases in the ACS + BMP-2 group, and all cases in the HAp/Col + BMP-2 group at 8 weeks post-surgery. The control group did not achieve bone union. In addition, in the HAp/Col + BMP-2 group, the biomechanical strength of the fused femurs was comparable to that of the contralateral intact femur; the ratio of the mechanical load at the breaking point of the osteotomy side relative to that of the contralateral side was 1.00 ± 0.151 (SD). These results indicate that HAp/Col paste with or without BMP-2 augments bone union. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:129-137, 2018.