A critical bone defect may be more frequently the consequence of a trauma, especially when a fracture occurs with wide exposure, but also of an infection, of a neoplasm or congenital deformities. This defect needs to be treated in order to restore the limb function. The treatments most commonly performed are represented by implantation of autologous or homologous bone, vascularized fibular grafting with autologous or use of external fixators; all these treatments are characterized by several limitations. Nowadays bone tissue engineering is looking forward new solutions: magnetic scaffolds have recently attracted significant attention. These scaffolds can improve bone formation by acting as a “fixed station” able to accumulate/release targeted growth factors and other soluble mediators in the defect area under the influence of an external magnetic field. Further, magnetic scaffolds are envisaged to improve implant fixation when compared to not-magnetic implants. We performed a series of experimental studies to evaluate bone regeneration in rabbit femoral condyle defect by implanting hydroxyapatite (HA), polycaprolactone (PCL) and collagen/HA hybrid scaffolds in combination with permanent magnets. Our results showed that ostetoconductive properties of the scaffolds are well preserved despite the presence of a magnetic component. Interestingly, we noticed that, using bio-resorbable collagen/HA magnetic scaffolds, under the effect of the static magnetic field generated by the permanent magnet, the reorganization of the magnetized collagen fibers produces a highly-peculiar bone pattern, with highly-interconnected trabeculae orthogonally oriented with respect to the magnetic field lines. Only partial healing of the defect was seen within the not magnetic control groups. Magnetic scaffolds developed open new perspectives on the possibility to exploiting magnetic forces to improve implant fixation, stimulate bone formation and control the bone morphology of regenerated bone by synergically combining static magnetic fields and magnetized biomaterials. Moreover magnetic forces can be exploited to guide targeted drug delivery of growth factors functionalized with nanoparticles.
Repetitive concavities threaded on the surface of bone implants have been already demonstrated to be effective on ectopic bone formation in vivo. The aim of this study was to investigate the effect of concavity on the mineralization process in vitro. The role of implant surface geometry in bone formation has been extensively investigated. Ripamonti and co. investigated the possibility to induce bone formation by threading concavities on the surface of calcium phosphate implants, without the need for exogenous osteogenic soluble factors. The underlying hypothesis was that this geometry, by resembling the hemi-osteon trench observable during osteoclastogenesis, was able to activate the ripple-like cascade of bone tissue induction and morphogenesis. Despite several studies indicating a positive effect of concavities on bone induction, so far no attempts have rationalised this phenomenon by means of in vitro tests. Consequently, this study aimed to evaluate the effect of surface concavities on the mineralization of hydroxyapatite (HA) and beta-tricalciumphosphate (b-TCP) ceramics in vitro. Our hypothesis was that concavities could effectively guide the mineralization process in vitro.Summary Statement
Introduction
