Rabbit Femoral Defect Model Research Articles

Calcium Phosphate Cement (CPC): A Critical Development Path

The first generation of synthetic bone substitute materials (BSM) was initially investigated in the mid 1970s using hydroxyapatite (HA) as a biomaterial for remodeling of bone defects. The concepts established by CPC pioneers in the early 1980s were used as a platform to initiate a second generation of BSM for commercialization. Since then, advances have been made in composition, performance and manufacturing. A self-setting and injectable calcium phosphate cement (CPC) based on amorphous calcium phosphate (ACP) with calcium to phosphate (Ca/P) atomic ratio less than 1.5, combined with dicalcium phosphate dihydrate (DCPD or brushite, seeded with apatite), is proposed. Amorphization of raw material was observed following high energy mechano-chemical processing. Upon hydration, the cement hardened in less than 3 minutes at 37°C and reached a maximum compressive strength of about 50 MPa. The final product was a low crystalline calcium deficient carbonated apatite similar to the composition and structure of bone mineral. In vivo performance of this cement in mediating bone healing was compared to α-BSM® in a rabbit femoral defect model. Performance characteristics of some commercially available CPC products are compared. The concerns of CPC designers and the needs of product users (surgeons) are discussed.

A comparison of ProOsteon, DBX, and collagraft in a rabbit model

Many bone graft substitutes (BGSs) have been developed and are commercially available. These products differ in the tailoring of their properties, including size, form, osteoconductivity, osteoinductivity, and resorption kinetics. Differential enhancement of these properties may optimize the performance of these materials for varying applications. BGSs offer an opportunity to lessen morbidity of harvesting and use of autogenous and/or allograft bone. The purpose of this study is to quantitatively compare the magnitude of bony ingrowth and biodegradation of different commercially available BGS materials in a rabbit femoral defect model. BGSs from each of three classes (ceramic (ProOsteon), demineralized bone matrix (DBX), and composite (Collagraft)) were implanted in cylindrical defects in bilateral femoral condyles of 12 adult New Zealand White rabbits. Each of the three BGS materials and the empty controls were compared. The specimens were harvested at 3 months postimplantation for radiographic and histologic evaluation. Histomorphometry yielded resorption of graft material remaining in the index defect. Magnitude of bony ingrowth was assessed based on an 8-bit 256 densitometry model. Histomorphometric analysis of the data demonstrated statistical differences in the resorption and magnitude of bony ingrowth of the three BGS materials. The three BGS were significantly different for ingrowth (p = 0.046) when using the Wilcoxon Test. The ceramic graft material averaged 47% bony ingrowth. Rabbit-based DBX material showed extensive osseous ingrowth (35%) and the composite graft material demonstrated significant bony ingrowth (56%). The control, as anticipated, showed the least amount of bony ingrowth (29%). Fisher's Exact Test yielded statistical differences (p = 0.0003) when comparisons for resorption were conducted. An ideal BGS material should be biocompatible, be able to withstand the local load environment for a given application, degrade in concert with bony replacement, and be both osteoinductive and osteoconductive. This in-vivo, head-to-head comparison of three commercially available BGS materials in an animal model compares these characteristics and demonstrates differences between them, which may act as a guide in the use of these products in human applications.

Addition of fibrin sealant to ceramic promotes bone repair: long-term study in rabbit femoral defect model.

Despite their impact on the healing of soft connective tissue, fibrin sealants have not been shown conclusively to have an important role in the healing of bone defects. We report the positive influence of fibrin sealants on repair of cancellous bone cavities filled with a porous, resorbable ceramic. We studied two fibrin sealants: Autocolle and Tissucol. Autocolle is enriched in platelet factors during its preparation. Tissucol is a commercially available fibrin glue prepared from pooled human plasma that has no enrichment in platelet factors. Cavities 10 mm in depth and 5 mm in diameter were drilled in lateral condyles of 45 New Zealand rabbits. These defects were filled with either coral granules or a mixture of fibrin sealant (Autocolle or Tissucol) and coral granules or left empty. At 1 month addition of a fibrin sealant (Autocolle or Tissucol) to the coral led to a significant increase in bone formation in comparison to coral alone. At 2 months significant fibrin sealant mediated enhancement of bone repair was observed with Autocolle only. At 6 months bone formation was similar to the adult bone amount in nonoperated animals, whatever the initial material. Control cavities, on the other hand, were invaded with fibrous tissue only at each time period.