Bio-active fibres for bone reconstruction in the medical field
The reconstruction of bones plays an important role in the medical field. Applications with fixing implants such as screws, plates, nails and external fixings to mechanically stabilise broken bones are made under the term of osteo synthesis
In most cases a fixing of the breaking point is sufficient to permit the re-joining of the bone. When there are complicated fractures or other deceases occur such as tumors leading to a massive damage of the bone it becomes necessary to apply bone substitute material, along with a reconstruction of the bone substance.
In the last few years more and more bio-active materials for such bone restruction were developed with the aim instead of a repair of defects these materials should also assist the healing process. With other words materials that enhance the re-growth of the bone.
Anorganic part of bones forms Calciumphophate – (foremost Hydoxapatit (Ca10(PO4)6 (OH); OHAp). Healing can be supported also by resorbable materials containing Calciumphophate. Apart from Hydrpoxyapartit they might be other Calciumphosphate such as a or b-Tricalciumphosphate Ca3(PO4).
At the phase of resorption Calcium and Phosphate-Ions are created and can be used for the re-building of bones. There are a series of R&D activities at universities and in companies to manufacture bio-materials for bone defect treatment (resorbable or permanent bio-compatible implants and bone cements). Some products are already successfully marketed. Calciumphosphate are applied as porous forming bodies or pulverised bone cements. However it is a recognised fact that besides the chemical formula of the filling material also the morphology and the mechanical character are important. In addition it is important that the materials can be applied by the surgeon easily into the defected bone, thus the qualities needed are forming and a defined porosity leading to a certain stability and elasticity to create the mechanical stimulus of the bone growth. For this reason there are can only a few materials be considered. In the framework of the competence network for bio-materials Baden-Württemberg foam structures and ceramic-filled nonwovens were examined. The results have provoked good initial ideas, but there is no through break achieved.
Ceramic fibre on the basis of Calciumphosphates would be ideal for the desired thought for application, because fibres with the needed qualities can be realised. From high temperature isolation are known aluminumoxide- and multi fibres and these are available in commercially large quantities, and they are capable to form porous and elastic nonwoven structures, and they are mechanically formable. However, so far there are no works published with the result that relevant fibres on the basis of Calciumphosphates are produced and tested for their use in bone reconstruction. Exactly this fact has been the subject of a multi-discipline research project by Textil- und Verfahrenstechnik Denkendorf (D) and the Institute for accident-surgical research and bio-mechanics at University Ulm (D). The research work has found a material system enabling the production of thread forming spinning systems (spinning mass) with sufficient stability. The spinning system with the best qualities is consisting of Calciumchloride, Phosphor-ester and Polyethylene oxide in a water/Ethanol mix.
The green fibres have been treated by a defined thermal process at temperatures up to max. 1300°C and were transformed into Calciumphosphate-fibres. All intermediate and end products have been analysed by various analytical methods and characterised.REM, EDX, XRD, IR, etc.). As a result it could be proved that with relevant base material stichiometry, the end product Hydroyapatit-fibres, respectively Chlorapatit-fibres can be had containing only a small amount of foreign fibres, however these fibres had only a light mechanical stability and further research work and development has been done as well as supplementary stages introduced. Research work was also done in view to the osteo-stimulating effect of the different fibre material. In conclusion, Hydroxyapatit/Aluminumoxid fibres as well as Tricalciumphophate fibres have been receptive to human, mesenchymal stem cells. There was no extension of cell growth into the inner test items noticeable. The insufficient mechanical stability did not allow the aim to create fibre cotton with reversible mechanical forming qualities.